Prof Ravi Silva


Director, Advanced Technology Institute (ATI) and Head of NanoElectronics Centre
+44 (0)1483 689825
20 ATI 01
Mrs. Lynn Tumilty
01483 686080

Academic and research departments

Advanced Technology Institute.

Biography

Biography

Ravi Silva is the Director of the Advanced Technology Institute (ATI) and Heads the Nano-Electronics Centre (NEC), which is an interdisciplinary research activity. The ATI has over 150 active researchers working on multidiscipline programmes with the NEC being a major research group within the institute. He joined Surrey in 1995. Ravi's secondary education was in Sri Lanka, after which he joined the Engineering Department at Cambridge University for his undergraduate and postgraduate work. He was a recipient of Cambridge Commonwealth Trust Fellowship while at Cambridge and member of Clare College.

His research has resulted in over 600 presentations at international conferences, and over 550 journal papers, Over 17,000 citations (Google Scholar), and a Google H-factor of 66. In 2002 he was awarded the Charles Vernon Boys Medal by the Institute of Physics, and in 2003 he was awarded the IEE Achievement Award.In 2003 he was also awarded the Albert Einstein Silver Medal and Javed Husain Prize by UNESCO for contributions to electronic devices.In 2003 the largest EPSRC Portfolio award for £6.68M was awarded to Prof. Silva and his team on Integrated Electronics which examined nanoscale design featrues on the optical and photonic device properties. In 2004 by a SRIF award for £4M to set up a Nano-Electronics Centre for multidisciplinary research was awarded and allowed the enhancement of nano-bio activities via the EU Sensation and EU Carbio programme.

In 2005, the Nano-Electronics Centre was a finalist in the Emerging Technologies category of the IEE 2005 Awards for Innovation in Engineering.In 2007, Prof. Silva was the runner-up of the "Times Higher Education Young Scientist of the Year", and "Most Entrepreneurial Scientist 2007, United Kingdom", by UKSEC and Science Alliance of the Netherlands. He was elected a Fellow of the Royal Society of Arts in 2007.In 2008 he was elected a Fellow of the Royal Academy of Engineering, UK.

Since 2005 he has worked with the National Science Foundation (NSF), Sri Lanka to establish nanotechnology as a vehicle from which to create wealth for the nation that will allow for poverty alleviation in the country. By introducing high technology in to the manufacturing base in Sri Lanka he has spearheaded a drive to introduce innovation and competitiveness in to the industrial sector within the country. Prof. Silva was on the advisory board of Imprimatur Ltd and the National Nanotechnology Initiative (NNI) of Sri Lanka. He spent the year 2008 acting as an Advisor to the Honourable Minister of Science and Technology in Sri Lanka, and helped set up the Sri Lanka Institute of NanoTechnology (SLINTec) and the Nano-Science Park NANCO (private) Ltd. He acts as an advisor to both these activities and sits on the director board. 

Prof. Silva was also a member of the Electrical and Electronic Panel (UoA24) for the Research Assessment Exercise (2003-2008) RAE2008, EPSRC Nanotechnology Task Force and sat (2007-2010) on the Engineering and Physical Sciences Research Council's (EPSRC) Technology Opportunities Panel (TOP). In 2009 he was elected as a Fellow of the National Academy of Sciences Sri Lanka. He is a panel member in Engineering for the REF2021.

He was awarded the Royal Society Clifford Patterson Award for 2011. The Clifford Patterson Prize lecture is for outstanding contribution in the fields of carbon nanoscience and nanotechnology. In 2013 he was elected a Distinguished Professor at Chonbuk National University. In 2014 he was awarded a premium medal by the Institute of Engineering and Technology (IET), the JJ Thompson Medal for contributions to Electrical and Electronic Engineering. In 2015, he won the Institute of Materials, Minerals & Mining (IOM3) premium award, the Platinum Medal for contributing to materials science, technology and industry.

In 2016, Government of Sri Lanka Presidential Award in recognition for many contributions in the field of nanotechnology. In 2016 he was also elected to a Visiting Professorship at Dalian Technology University, China. April 2017, Honarary president letter of appointment as Honarary Director to the Zengzhou Materials Genome Institute (ZMGI) in China.

In March 2018, he was elected the joint Editor-in-Chief of Wiley's Energy and Environmental Materials.

Research interests

His research interest encompass a wide range of activities with a focus in nanotechnology and renewables. A strong electronics background combined with materials science has enabled him and his team to produce bespoke nano-scale designer materials for specific applications. From examining the underlying feasibility of devices for specific applications, to specifically designed nanoscale structures and devices for technology solutions, the group looks to solve challenging problems with wide contributions to society. Technology associated within the group was put on show at the Pyeongchang Winter Olympics 2018 Hyundai pavilion.  Prof. Silva is passionate about enabling technology to provide free energy from the sun to society with a view of alleviating poverty and better quality of life. Areas in which he and his group contribute include: solar cells, nano-manufacturing, energy materials, carbon electronics, transistor designs & simulations, OPV, OLEDs, CNT, graphene, SGT, CFRP, DLC, nano-biotechnology, nano carbons, nanotechnology, water technology, large area electronics, electronic and photonic devices.

In addition to Nano-Electronics, the characterisation, growth and processing of novel semiconductor materials for large area electronic applications is central to the group activity. Novel device structures & the physics of carbon nanotubes, photovoltaics based on polymer/nanotube composites, electron field emission from amorphous materials and modelling of the emission, photovoltaics, electroluminescent cells, electronic doping of amorphous carbon, Excimer laser annealing and ablation, disordered (amorphous and n-C) GaN for optoelectronic applications, band gap modulated superlattice structures, diamond and SiC thin film deposition, the use of ion implantation for electronic doping and synthesis of novel materials are some of his other interests.

Research is progressing rapidly on growth kinetics of low temperature carbon nanotubes, which has now extended to CVD graphene growth over large areas & the synthesis of novel 2D materials.

Research collaborations

Research collaborations are in progress with national and international partners both from academia and industry. He has acted as advisor to many national and international organisations, including governments from USA, Korea, Japan, China, India, Sri Lanka, Singapore,Saudi Arabia, Israel, Hong Kong, Portugal, Canada, Brazil and Europe.

News

In the media

Media Contacts

Contact the press team

Email:

mediarelations@surrey.ac.uk

Phone: +44 (0)1483 684380 / 688914 / 684378
Out-of-hours: +44 (0)7773 479911
Senate House, University of Surrey
Guildford, Surrey GU2 7XH

My publications

Publications

Clowes SK, Silva SRP, Yahya I, Bonaccorso F, Ferrari A (2015) Temperature dependent separation of metallic and semiconducting carbon nanotubes using gel agarose chromatography, Carbon 93 pp. 574-594 Elsevier
Post-synthesis separation of metallic (m-SWNTs) and semiconducting (s-SWNTs) single-wall carbon nanotubes (SWNTs) remains a challenging process. Gel agarose chromatography is emerging as an efficient and large scale separation technique. However, the full (100%) separation has not been achieved yet, mainly due to the lack of understanding of the underlying mechanism. Here, we study the temperature effect on the SWNTs separation via gel agarose chromatography, for four different SWNT sources. Exploiting a gel agarose micro-beads filtration technique we achieve up to 70% m-SWNTs and over 90% s-SWNTs, independent of the source material. The process is temperature dependent, with yields up to 95% for s-SWNT (HiPco) at 6 °C. Temperature affects the sodium dodecyl sulfate surfactant-micelle distribution along the SWNT sidewalls, thus determining the effectiveness of the SWNTs sorting by electronic type. The sorted SWNTs are then used to fabricate transistors with very low OFF-currents (106) and charge carriers mobility
Miller AJ, Hatton RA, Chen GY, Silva SRP (2007) Carbon nanotubes grown on In2O3 : Sn glass as large area electrodes for organic photovoltaics, APPLIED PHYSICS LETTERS 90 (2) ARTN 023105 AMER INST PHYSICS
Zhang W, Tan YY, Wu C, Silva SRP (2012) Self-assembly of single walled carbon nanotubes onto cotton to make conductive yarn, Particuology 10 (4) pp. 517-521 Elsevier
A simple, economical and scalable technique is demonstrated to make conductiveyarn. Singlewalledcarbonnanotubes (SWCNTs) are non-covalently functionalized with dye (Acid Red 91) and dispersed in water; while cottonyarn is treated with poly (ethylene imine). When the resulting yarn is immersed in the SWCNT dispersion, SWCNTs self-assemble onto the yarn due to electrostatic forces between the functionalized nanotubes and yarn. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicate the assembly of carbonnanotubes. The SWCNT functionalized yarn exhibits reasonable electrical conduction behaviour and are then used to make chemiresistors. The electrical resistance of the chemiresistors used as sensors increases on exposure to ammonia gas, which can be explained in terms of electron transfer between gas molecules and SWCNTs.
Kang B, Tan LW, Silva SRP (2009) Ultraviolet-illuminated fluoropolymer indium-tin-oxide buffer layers for improved power conversion in organic photovoltaics, ORGANIC ELECTRONICS 10 (6) pp. 1178-1181 ELSEVIER SCIENCE BV
Nismy NA, Jayawardena KD, Adikaari AA, Silva SR (2011) Photoluminescence Quenching in Carbon Nanotube-Polymer/Fullerene Films: Carbon Nanotubes as Exciton Dissociation Centres in Organic Photovoltaics., Advanced Materials 23 (33) pp. 3796-3800 Wiley
Carey JD, Forrest RD, Silva SRP (2001) Origin of electric field enhancement in field emission from amorphous carbon thin films, APPLIED PHYSICS LETTERS 78 (16) pp. 2339-2341 AMER INST PHYSICS
Mureau N, Mendoza E, Silva SRP (2007) Dielectrophoretic manipulation of fluorescing single-walled carbon nanotubes, ELECTROPHORESIS 28 (10) pp. 1495-1498 WILEY-BLACKWELL
Young WT, Silva SRP, Benyoucef M, Kuball M, Anguita JV, Shannon JM, Homewood KP, Sealy BJ (1999) The growth of gallium nitride films produced by reactive sputtering at low temperature, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH 176 (1) pp. 319-322 WILEY-V C H VERLAG GMBH
Smith RC, Carey JD, Cox DC, Silva SRP (2007) In-situ field emission characterisation of multi walled carbon nanotubes, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 84-85 IEEE
Chong LC, Sloan J, Wagner G, Silva SRP, Curry RJ (2008) Controlled growth of true nanoscale single crystal fullerites for device applications, JOURNAL OF MATERIALS CHEMISTRY 18 (28) pp. 3319-3324 ROYAL SOC CHEMISTRY
Sporea RA, Shannon JM, Silva SRP (2010) Properties of source-gated transistors in polysilicon, 6th Conference on Ph.D. Research in Microelectronics and Electronics, PRIME 2010
This paper describes some of the performance characteristics of self-aligned polysilicon Schottky Source-Gated Transistors (SGTs) made on glass by laser annealing of amorphous silicon. The threshold and Schottky barrier height are tuned by varying the dose of dopants in the bulk and under the source respectively. These devices are well suited for analog applications owing to their low saturation voltage, low drain field dependence of the current and intrinsic gain which is in excess of 1000 for well designed structures. Double drain operation leads to fT H100MHz for non-optimized devices.
Alenezi MR, Henley SJ, Silva SRP (2015) On-chip Fabrication of High Performance Nanostructured ZnO UV Detectors, SCIENTIFIC REPORTS 5 ARTN 8516 NATURE PUBLISHING GROUP
Silva SRP (2012) Electron field emission from carbon nanotubes, Technical Digest - 25th International Vacuum Nanoelectronics Conference, IVNC 2012 pp. 102-103
Technological advances in microfabrication has resulted in a renewed interest in vacuum microelectronics. The potential scatter-free ballistic motion of electrons in vacuum out-performs solid state scatter-dominated electron transport in many applications. Carbon nanotubes has been identified as a suitable source for cold cathodes, and a second generation technology for Spindt metal tips. This is enabled by the high aspect ratios, mechanical robustness, high current carrying capability and chemical inertness. There is a long held belief that CNTs will be an ideal material structure for high resolution electron beam instruments that use point electron sources. In addition, there are a number of other applications that can utilise CNT for technologies that range from field emission displays to X-ray sources to microwave amplifiers. Before CNTs can be adopted for technologies, routes to manufacture, with suitable quality and appropriate characteristics must be realised. Furthermore, the key application that allows the science to move into a technology product must be identified. © 2012 IEEE.
Carey JD, Silva SRP (2004) Disorder, Clustering, and Localization Effects in Amorphous Carbon, Physical Review B 70 (23)

The nanostructure of amorphous carbon thin films is described in terms of a disordered nanometer-sized conductive sp(2) phase embedded in an electrically insulating sp(3) matrix. It is shown that the degree of clustering and disorder within the sp(2) phase plays a determining role in the electronic properties of these films. Clustering of the sp(2) phase is shown to be important in explaining several experimental results including the reduction of the electron spin resonance linewidth with increasing spin density and the dispersion associated with the width of the Raman active G band. The influence of structural disorder, associated with sp(2) clusters of similar size, and topological disorder, due to undistorted clusters of different sizes, on both spin density and Raman measurements, is discussed. An extension of this description to intercluster interactions to explain some of the electrical transport and electron field emission behavior is also presented.

Sporea RA, Trainor M, Young N, Shannon JM, Silva SRP (2015) Temperature Effects in Complementary Inverters Made With Polysilicon Source-Gated Transistors, Electron Devices, IEEE Transactions on PP (99) pp. 1-1
Through their high gain and low saturation voltage, source-gated transistors (SGTs) have applications in both analog and digital thin-film circuits. In this paper, we show how we can design SGT-based logic gates, which are practically unaffected by temperature variations. We discuss design characteristics, which ensure reliable operation in spite of SGT temperature dependence of drain current, and their implications for manufacturability and large signal operation.
Tang YF, Silva SRP, Boskovic BO, Shannon JM, Rose MJ (2002) Electron field emission from excimer laser crystallized amorphous silicon, Applied Physics Letters 80 (22) pp. 4154-4156
We show field emission from excimer laser crystallized (ELC) hydrogenated amorphous silicon (a-Si:H) at current densities and threshold fields suitable for display applications. The laser crystallized a-Si:H gives rise to a densely packed and relative sharp surface morphology that gives emission currents of the order of 10-5A (current densitiesH0.04A/cm2) at threshold fields less than 15 V/¼m in a diode configuration, without the need for a forming process. With the progress in utilizing ELC in flat panel driver electronics, a fully integrated field emission display on a single glass substrate can now be envisaged. © 2002 American Institute of Physics.
Pharr GM, Callahan DL, McAdams SD, Tsui TY, Anders S, Anders A, Ager JW, Brown IG, Bhatia CS, Silva SRP, Robertson J (1995) Hardness, elastic modulus, and structure of very hard carbon films produced by cathodic-arc deposition with substrate pulse biasing, Applied Physics Letters
The hardness, elastic modulus, and structure of several amorphous carbon films on silicon prepared by cathodic-arc deposition with substrate pulse biasing have been examined using nanoindentation, energy loss spectroscopy (EELS), and cross-sectional transmission electron microscopy. EELS analysis shows that the highest sp3 contents (85%) and densities (3.00 g/cm3) are achieved at incident ion energies of around 120 eV. The hardness and elastic modulus of the films with the highest sp3 contents are at least 59 and 400 GPa, respectively. These values are conservative lower estimates due to substrate influences on the nanoindentation measurements. The films are predominantly amorphous with a
Melios C, Centeno A, Zurutuza A, Panchal V, Giusca CE, Spencer S, Silva SRP, Kazakova O (2016) Effects of humidity on the electronic properties of graphene prepared by chemical vapour deposition, CARBON 103 pp. 273-280 PERGAMON-ELSEVIER SCIENCE LTD
Alshammari AS, Shkunov M, Silva SRP (2013) Inkjet printed PEDOT: PSS/MWCNT nano-composites with aligned carbon nanotubes and enhanced conductivity, Physica Status Solidi - Rapid Research Letters
Conductive patterns of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/multi-walled carbon nanotube (MWCNT) composites were deposited on glass substrates using a drop on demand (DOD) inkjet printer, with the concentration of CNT varied from 0.01 wt% to 0.05 wt%. We show that by increasing the concentration of the nanotubes in the ink, percolated networks of well distributed carbon nanotubes in the printed samples can be achieved. Moreover, the orientation of the nanotubes in the printed sample can be controlled using a novel simple approach. The impact of the nanotube alignment on the conduction properties of inkjet printed nano-hybrid materials is studied and shown in this Letter. Samples with aligned nanotubes show a 53% enhanced conductivity in comparison with the randomly oriented nanotubes. The results show that the electrical performance of the nano-composite can be improved further by controlling the dispersion and orientation of the nano-filler in the printed samples. Carbon nanotubes orientation control in the printed PEDOT:PSS/MWCNT nano-composite samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Burden AP, Anguita JV, Silva SRP (1998) Microstructural characterisation of carbonaceous dust generated during the deposition of diamond-like carbon coatings, THIN SOLID FILMS 332 (1-2) pp. 252-256 ELSEVIER SCIENCE SA
Neves V, Heister E, Costa S, Tilmaciu C, Borowiak-Palen E, Giusca CE, Flahaut E, Soula B, Coley HM, McFadden J, Silva SRP (2010) Uptake and Release of Double-Walled Carbon Nanotubes by Mammalian Cells, ADVANCED FUNCTIONAL MATERIALS 20 (19) pp. 3272-3279 WILEY-V C H VERLAG GMBH
Dissanayake DMNM, Hatton RA, Lutz T, Curry RJ, Silva SRP (2009) Charge transfer between acenes and PbS nanocrystals, NANOTECHNOLOGY 20 (19) ARTN 195205 IOP PUBLISHING LTD
Kench PJ, Shannon JM, Shao G, Tsakiropoulos P, Silva SRP (2001) Ion beam synthesis of gallium nitride, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 175 pp. 678-682 ELSEVIER SCIENCE BV
Adikaari AADT, Carey JD, Stolojan V, Keddie JL, Silva SRP (2006) Bandgap enhancement of layered nanocrystalline silicon from excimer laser crystallization, NANOTECHNOLOGY 17 (21) pp. 5412-5416 IOP PUBLISHING LTD
Marques FC, Lacerda RG, Champi A, Stolojan V, Cox DC, Silva SRP (2003) Thermal expansion coefficient of hydrogenated amorphous carbon, APPLIED PHYSICS LETTERS 83 (15) pp. 3099-3101 AMER INST PHYSICS
Anguita JV, Young WT, Khan RU, Silva SRP, Haq S, Sturland I, Pritchard A (2000) Photoluminescence in low defect density a-C : H and a-C : H : N, JOURNAL OF NON-CRYSTALLINE SOLIDS 266 pp. 821-824 ELSEVIER SCIENCE BV
SILVA SRP, KNOWLES KM, AMARATUNGA GAJ, PUTNIS A (1994) THE MICROSTRUCTURE OF INCLUSIONS IN NANOCRYSTALLINE CARBON-FILMS DEPOSITED AT LOW-TEMPERATURE, DIAMOND AND RELATED MATERIALS 3 (7) pp. 1048-1055 ELSEVIER SCIENCE SA LAUSANNE
Smith RC, Carey JD, Cox DC, Silva SRP (2007) In-situ field emission characterisation of multi walled carbon nanotubes, Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07 pp. 94-95
Mureau N, Watts PCP, Tison Y, Silva SRP (2008) Bulk electrical properties of single-walled carbon nanotubes immobilized by dielectrophoresis: Evidence of metallic or semiconductor behavior, ELECTROPHORESIS 29 (11) pp. 2266-2271 WILEY-V C H VERLAG GMBH
Li YH, Zhao YM, Zhu YQ, Rodriguez J, Morante JR, Mendoza E, Poa CHP, Silva SRP (2006) Mechanical and NH3 sensing properties of long multi-walled carbon nanotube ropes, CARBON 44 (9) pp. 1821-1825 PERGAMON-ELSEVIER SCIENCE LTD
Poa CHP, Lacerda RG, Silva SRP, Marques FC (2004) Influence of stress on the field emission properties of amorphous carbon thin films and multiwall carbon nanotube-polymer composites, TECHNICAL DIGEST OF THE 17TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 194-195 IEEE
Xu S, Flynn D, Tay BK, Prawer S, Nugent KW, Silva SRP, Lifshitz Y, Milne WI (1997) Mechanical properties and Raman spectra of tetrahedral amorphous carbon films with high sp(3) fraction deposited using a filtered cathodic arc, PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES 76 (3) pp. 351-361 TAYLOR & FRANCIS LTD
Lyth SM, Filip LD, Cox PC, Silva SRP (2007) Novel carbon nanotube based three terminal devices, Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07 pp. 241-242
Silva SRP, Carey JD (2003) Enhancing the electrical conduction in amorphous carbon and prospects for device applications, DIAMOND AND RELATED MATERIALS 12 (2) pp. 151-158 ELSEVIER SCIENCE SA
Kim SH, Kim JH, Silva SRP, Hahn YB (2013) Conjugated polymer/Sn-doped ZnO nanowires for heterojunction hybrid solar cells, Science of Advanced Materials 5 (5) pp. 499-504
Bulk heterojunction hybrid solar cells were fabricated on the ITO glass using the synthesized undoped ZnO and tin-doped ZnO (Sn:ZnO) nanowires (NWs) blending with poly(3-hexylthiophene). The NWs were synthesized by simple thermal evaporation using the metallic zinc and tin powders in the presence of oxygen, and their electrical properties were characterized by field effect transistors. The carrier mobilities of the undoped ZnO and Sn:ZnO NWs were 19.8 and 90.1 cm2/Vs, respectively. The conversion efficiency of the hybrid solar cells increased from 0.093% with undoped ZnO NWs/P3HT to 0.212% with Sn:ZnO NWs/P3HT. © 2013 by American Scientific Publishers. All rights reserved.
Poa CHP, Smith RC, Silva SRP, Watts PCP, Hsu WK, Kroto HW, Walton DRM (2003) Field emission from nonaligned carbon nanotube-polymer matrix cathodes, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 21 (4) pp. 1715-1719 A V S AMER INST PHYSICS
Guo XJ, Silva SRP (2005) Investigation on the current nonuniformity in current-mode TFT active-matrix display pixel circuitry, IEEE TRANSACTIONS ON ELECTRON DEVICES 52 (11) pp. 2379-2385 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Boskovic BO, Stolojan V, Khan RUA, Haq S, Silva SRP (2002) Large-area synthesis of carbon nanofibres at room temperature, NATURE MATERIALS 1 (3) pp. 165-168 NATURE PUBLISHING GROUP
Zhang W, Shiozawa H, Wu CW, Hamerton I, Cox DC, Silva SR (2012) The effect of pH on the functionalization of nylon fabric with carbon nanotubes., J Nanosci Nanotechnol 12 (1) pp. 84-90
Single walled carbon nanotubes (SWCNTs) were dispersed in water and attached to nylon fabrics by a dip-drying procedure; scanning electron microscopy and Raman spectroscopy suggest the attachment of the SWCNTs. The electrical resistance of the functionalized fabrics is found to be pH-dependent, which is correlated with the quantity of SWCNTs dispersed in water at different values of pH. This can be further ascribed to the influence of the pK(a) of the acid (e.g., acetic acid in this study) used to tune pH. The acid may affect the dispersion of SWCNTs through two different mechanisms: (1) the free protons may protonate the amine and/or sulfonate group in the dye molecules, resulting in a variety of interactions among the dye molecules, SWCNTs and water molecules and (2) the resulting ions may increase the ionic strength of the solution, compressing the electric double layers of SWCNT colloids and thus impairing their stability. The former possibility is ruled out by data obtained using X-ray photoelectron spectroscopy, Raman spectroscopy, and ultraviolet-visible-near infrared spectroscopy; thus the latter is proposed to account for the experimental results. The colour strength of the functionalized fabrics increases with increasing pH, which is in agreement with their measured electrical properties.
Lyth SM, Hatton RA, Silva SRP (2007) Li-salt functionalised carbon nanotubes as low work function field emitters, EIGHTH IEEE INTERNATIONAL VACUUM ELECTRONICS CONFERENCE pp. 195-196 IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP
Gateru RG, Shannon JM, Silva SRP (2003) Memory switching in ion bombarded amorphous silicon carbide thin film devices, SILICON CARBIDE 2002-MATERIALS, PROCESSING AND DEVICES 742 pp. 79-83 MATERIALS RESEARCH SOCIETY
Chen GY, Stolojan V, Silva SRP (2010) Top-Down Heating for Low Substrate Temperature Synthesis of Carbon Nanotubes, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 10 (6) pp. 3952-3958 AMER SCIENTIFIC PUBLISHERS
Silva SRP, Amaratunga GAJ (1995) Doping of rf plasma deposited diamond-like carbon films, THIN SOLID FILMS 270 (1-2) pp. 194-199 ELSEVIER SCIENCE SA LAUSANNE
Guo X, Silva SRP (2008) Engineering - High-performance transistors by design, SCIENCE 320 (5876) pp. 618-619 AMER ASSOC ADVANCEMENT SCIENCE
Guo X, Silva SRP (2005) Active-matrix addrsssing for carbon nanotube field emission displays, Proceedings of the Second Americas Display Engineering and Applications Conference, ADEAC 2005 pp. 366-368
In this paper, the current-mode active matrix (AM) addressing method is developed for carbon nanotube (CNT) based field emission displays (FEDs). Simulation results show that this method is very promising to be used to produce FEDs with good enough luminance uniformity. A simple SPICE model for the CNT field emission (FE) device, and a circuit model emulating the pixel circuit's behaviour in the true display matrix, is introduced for the simulation.
Stolojan V, Whiting MJ, Goringe MJ, Kelly MJ, Silva SRP (2003) Electron energy loss line spectral and TEM analysis of heterojunctions, MICROSCOPY OF SEMICONDUCTING MATERIALS 2003 (180) pp. 41-44 IOP PUBLISHING LTD
Silva SRP, Carey JD, Chen GY, Cox DC, Forrest RD, Poa CHP, Smith RC, Tang YF, Shannon JM (2004) Nanoengineering of materials for field emission display technologies, IEE PROCEEDINGS-CIRCUITS DEVICES AND SYSTEMS 151 (5) pp. 489-496 IEE-INST ELEC ENG
CHAN KK, SILVA SRP, AMARATUNGA GAJ (1992) ELECTRONIC-PROPERTIES OF SEMICONDUCTING DIAMOND-LIKE CARBON DIAMOND, THIN SOLID FILMS 212 (1-2) pp. 232-239 ELSEVIER SCIENCE SA LAUSANNE
Filip LD, Smith RC, Nicolaescu D, Carey JD, Silva SRP (2007) Modelling of electron transfer from a carbon nanotube cap into the vacuum under high extraction fields, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 42-43 IEEE
Barklie RC, Collins M, Cunniffe J, Silva SRP (1998) An EPR study of defects in hydrogenated amorphous carbon thin films, DIAMOND AND RELATED MATERIALS 7 (6) pp. 864-868 ELSEVIER SCIENCE SA
Schwan J, Ulrich S, Theel T, Roth H, Ehrhardt H, Becker P, Silva SRP (1997) Stress-induced formation of high-density amorphous carbon thin films, JOURNAL OF APPLIED PHYSICS 82 (12) pp. 6024-6030 AMER INST PHYSICS
Inigo AR, Henley SJ, Silva SRP (2011) Dispersive hole transport in polymer:carbon nanotube composites., Nanotechnology 22 (26)
The hole transport properties of poly(2-methoxy, 5-(2'-ethyl-hexoxy)-p-phenylene vinylene) (MEH-PPV) blended with acid oxidized multiwall carbon nanotubes (COOH-MWCNTs) were investigated in a diode configuration using the time-of-flight (TOF) photocurrent method. While the room temperature hole mobility in pure MEH-PPV films was non-dispersive with positive field dependent mobility, MEH-PPV:COOH-MWCNT blended devices exhibited dispersive transport and negative field dependent mobility. This indicates that the hole mobility in this composite is influenced by positional disorder caused by the presence of COOH-MWCNTs in the MEH-PPV matrix. These results strongly suggest that the distribution of COOH-MWCNTs optimising in the organic matrix is important for charge transport in the high mobility nanotube component to be activated, when used in hybrid material systems.
Silva SRP, Beliatis MJ, Jayawardena KDGI, Mills CA, Rhodes RW, Rozanski LJ (2014) Hybrid and nano-composite materials for flexible organic electronics applications, 3 Woodhead Publishing
Flexible organic electronics have recently progressed from ?organic-only? semiconductor devices, based on thin films of organic materials (small molecules and polymers), to hybrid and nano-composite materials - a family of truly advanced materials designed at the nanoscale which offer enhancements in device performance and a reduction in production costs over their traditional inorganic predecessors. These hybrid and nano-composite materials are attractive given the potentially wide range of available organic semiconductors (both small molecule and polymeric) and nanoparticle types (carbon allotropes, metal oxides, metal nanostructures etc.). Here, we emphasise the variety and potential of these materials and introduce some of the production methods, properties and limitations for their use in flexible electronics applications.
Fryar J, Jayawardena KDGI, Silva SRP, Henley SJ (2012) The origin of the metal enrichment of carbon nanostructures produced by laser ablation of a carbon-nickel target, Carbon
Compositional analysis of metal-containing carbon thin films and nanostructures produced by pulsed laser ablation of a carbon-nickel target revealed significantly higher fractions of nickel in the materials than in the target used to produce them. Ablation of mixed targets is used routinely in the synthesis of carbon nanotubes and to enhance the conductivity of amorphous carbon films by metal incorporation. In this extensive study we investigate the physical mechanisms underlying this metal-enrichment and relate changes in the dynamics of the ablation plumes with increasing background gas pressure to the composition of deposited materials. The failure to preserve the target atom ratios cannot, in this case, be attributed to conventional mechanisms for non-stoichiometric transfer. Instead, nickel-enrichment of the target surface by back-deposition, combined with significantly different propagation dynamics for C atoms, Ni atoms and alloy clusters through the background gas, appears to be the main cause of the high nickel fractions. © 2012 Elsevier Ltd. All rights reserved.
Blanchard NP, Hatton RA, Silva SRP (2007) Tuning the work function of surface oxidised multi-wall carbon nanotubes via cation exchange, CHEMICAL PHYSICS LETTERS 434 (1-3) pp. 92-95 ELSEVIER SCIENCE BV
Filip LD, Palumbo M, Carey JD, Silva SRP (2009) Sequential and resonant field emission from nano-structured cathodes, Technical Digest - 2009 22nd International Vacuum Nanoelectronics Conference, IVNC 2009 pp. 105-106
Yahya I, Stolojan V, Clowes S, Mustaza SM, Silva SRP (2010) Carbon nanotube field effect transistor measurements in vacuum, IEEE International Conference on Semiconductor Electronics, Proceedings, ICSE pp. 224-228
Three terminal measurements on a carbon nanotube field effect transistor (CNTFET) were carried out in high vacuum and the ambient, and its performance compared. The on-off current ratio, ION/IOFF, were 10 2 and 105 for devices operated in high vacuum and in ambient air, respectively. Here, we show that the conversion of p-type to ambipolar behavior may largely be attributed to the O2 in ambient doping the single walled carbon nanotubes (SWCNTs) in the active channel which consists of bundles of SWCNTs. Switching behaviour of these devices, with respect to constituent types of SWCNTs in the bundles will be discussed. © 2010 IEEE.
SILVA SRP, AMARATUNGA GAJ, CONSTANTINOU CP (1992) OPTICAL-PROPERTIES OF AMORPHOUS C/DIAMOND THIN-FILMS, JOURNAL OF APPLIED PHYSICS 72 (3) pp. 1149-1153 AMER INST PHYSICS
Smith RC, Carey JD, Murphy RJ, Blau WJ, Coleman JN, Silva SRP (2005) Charge transport effects in field emission from carbon nanotube-polymer composites, APPLIED PHYSICS LETTERS 87 (26) ARTN 263105 AMER INST PHYSICS
Carreno N, Escote M, Valentini A, McCafferty L, Stolojan V, Beliatis M, Mills C, Rhodes R, Smith C, Silva S (2015) Adsorbent 2D and 3D carbon matrices with protected magnetic iron nanoparticles, NANOSCALE 7 (41) pp. 17441-17449 ROYAL SOC CHEMISTRY
Alshammari AS, Shkunov M, Silva SRP (2013) Correlation between wetting properties and electrical performance of solution processed PEDOT:PSS/CNT nano-composite thin films, Colloid and Polymer Science pp. 1-8
Nano-composite thin films of poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS) with different loading concentrations of multi-walled carbon nanotubes (MWCNT) were deposited on glass substrates using inkjet printing and spin coating techniques. The surface energy of the substrate was modified using an oxygen plasma to achieve different degrees of wetting by the composite solution. We show that the electrical properties strongly depend on the wetting of the substrate and by controlling the wettability, the conductivity of the nano-composite samples can be improved. Based on polymer conductivity, the electrical conductivity of the composite film can be improved or degraded by orders of magnitude with the incorporation of the same concentration of MWCNT. Moreover, electrical measurements show strong correlation between the conductivity of the carbon nanotube network and the resulting nano-composite films. The dependence of electrical properties on the wettability and the conductivity of the composite components could explain the diversity in the electrical behaviour reported in the literature for PEDOT:PSS/MWCNT nano-composite thin films. [Figure not available: see fulltext.] © 2013 Springer-Verlag Berlin Heidelberg.
Balon F, Stolojan V, Silva SRP, Michalka M, Kromka A (2005) Diamond-like carbon thin films for high-temperature applications prepared by filtered pulsed laser deposition, VACUUM 80 (1-3) pp. 163-167 PERGAMON-ELSEVIER SCIENCE LTD
McKenzie DR, Muller DA, Kravtchinskaia E, Segal D, Cockayne DJH, Amaratunga G, Silva R (1991) Synthesis, structure and applications of amorphous diamond, Thin Solid Films 206 (1-2) pp. 198-203 Elsevier
The relation was investigated between the compressive stress, the substrate
temperature and the microstructure of amorphous carbon films deposited from the plasma
stream of a cathodic vacuum arc with a curved magnetic filter. A pressure-temperature
phase diagram is presented in which the results of a number of depositions at various
substrate bias levels and temperatures are plotted. The microstructure of each film was
determined by electron energy loss spectroscopy and electron diffraction.
Melios C, Panchal V, Giusca CE, Strupinski W, Silva SRP, Kazakova O (2015) Carrier type inversion in quasi-free standing graphene: studies of local electronic and structural properties, SCIENTIFIC REPORTS 5 ARTN 10505 NATURE PUBLISHING GROUP
Shiozawa H, Kramberger C, Pfeiffer R, Kuzmany H, Pichler T, Liu Z, Suenaga K, Kataura H, Silva SRP (2010) Catalyst and Chirality Dependent Growth of Carbon Nanotubes Determined Through Nano-Test Tube Chemistry, ADVANCED MATERIALS 22 (33) pp. 3685-+ WILEY-V C H VERLAG GMBH
Jeynes JCG, Mendoza E, Chow DCS, Watts PCR, McFadden J, Silva SRP (2006) Generation of chemically unmodified pure single-walled carbon nanotubes by solubilizing with RNA and treatment with ribonuclease A, ADVANCED MATERIALS 18 (12) pp. 1598-+ WILEY-V C H VERLAG GMBH
Mollah S, Henley SJ, Silva SRP (2008) Continuous-flow laser synthesis of large quantities of iron oxide nanowires in solution, NANOTECHNOLOGY 19 (20) ARTN 205604 IOP PUBLISHING LTD
Hatton RA, Blanchard NP, Stolojan V, Miller AJ, Silva SRP (2007) Nanostructured copper phthalocyanine-sensitized multiwall carbon nanotube films, LANGMUIR 23 (11) pp. 6424-6430 AMER CHEMICAL SOC
Palumbo M, Henley SJ, Lutz T, Stolojan V, Cox D, Silva SRP (2008) Engineering the shape of zinc oxide crystals via sonochemical or hydrothermal solution-based methods, Materials Research Society Symposium Proceedings 1087 pp. 59-65
Recent results in the use of Zinc Oxide (ZnO) nano/submicron crystals in fields as diverse as sensors, UV lasers, solar cells, piezoelectric nanogenerators and light emitting devices have reinvigorated the interest of the scientific community in this material. To fully exploit the wide range of properties offered by ZnO, a good understanding of the crystal growth mechanism and related defects chemistry is necessary. However, a full picture of the interrelation between defects, processing and properties has not yet been completed, especially for the ZnO nanostructures that are now being synthesized. Furthermore, achieving good control in the shape of the crystal is also a very desirable feature based on the strong correlation there is between shape and properties in nanoscale materials. In this paper, the synthesis of ZnO nanostructures via two alternative aqueous solution methods - sonochemical and hydrothermal - will be presented, together with the influence that the addition of citric anions or variations in the concentration of the initial reactants have on the ZnO crystals shape. Foreseen applications might be in the field of sensors, transparent conductors and large area electronics possibly via ink-jet printing techniques or self-assembly methods. © 2008 Materials Research Society.
Inigo AR, Underwood JM, Silva SRP (2011) Carbon nanotube modified electrodes for enhanced brightness in organic light emitting devices, CARBON 49 (13) pp. 4211-4217 PERGAMON-ELSEVIER SCIENCE LTD
kutsarov DI, New E, Bausi F, Zoladek-Lemanczyk A, Castro FA, Silva SRP Fabrication of air-stable, large-area, PCDTBT:PC70BM polymer solar cell modules using a custom built slot-die coater Solar Energy Materials and Solar Cells, University of Surrey
Robertson J, Silva SRP, Amaratunga GAJ, Milne WI (1996) Electron field emission from diamond-like carbon, III-NITRIDE, SIC AND DIAMOND MATERIALS FOR ELECTRONIC DEVICES 423 pp. 777-782 MATERIALS RESEARCH SOC
Zhang W, Ravi S, Silva P (2011) Application of carbon nanotubes in polymer electrolyte based fuel cells, Reviews on Advanced Materials Science 29 (1) pp. 1-14
Polymer electrolyte based fuel cells (PEFCs) are always in the forefront of fuel cell revolution. Recently a wide variety of application of carbon nanotubes (CNTs) in PEFC components has been exploited. The impetus is to improve the PEFC performance by taking advantages of CNTs' extraordinary physical, chemical and electronic properties. Herein, we briefly review these efforts with an attempt to obtain a better understanding on the role of CNTs in PEFCs, and this article is structured as the following: the contribution of CNTs is first addressed in terms of improving the mechanical strength and proton conductivity of polymer electrolyte membrane; their role in electrocatalysis is then discussed with respect to facilitating the utilization of noble metal catalysts (platinum) and exploring the platinum-free catalysts; the consideration of CNTs as hydrogen storage materials is also highlighted. Based on the literatures studied, CNTs demonstrate great potential as multifunctional materials in improving PEFC performance.
Gao C, Jin YZ, Kong H, Whitby RLD, Acquah SFA, Chen GY, Qian H, Hartschuh A, Silva SRP, Henley S, Fearon P, Kroto HW, Walton DRM (2005) Polyurea-functionalized multiwalled carbon nanotubes: Synthesis, morphology, and Raman spectroscopy, Journal of Physical Chemistry B 109 (24) pp. 11925-11932
An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloridefunctionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl 2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH:). In the presence of MWNT-NH 2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,42- methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flator flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs. © 2005 American Chemical Society.
Amaratunga GAJ, Silva SRP (1996) Nitrogen containing hydrogenated amorphous carbon for thin-film field emission cathodes, APPLIED PHYSICS LETTERS 68 (18) pp. 2529-2531 AMER INST PHYSICS
Chen GY, Poa PCH, Henley SJ, Stolojan V, Silva SRP (2005) Carbon nanotubes and nanostructures grown at low temperatures below 400°C, Materials Research Society Symposium Proceedings 901 pp. 511-522
In this paper, we report clear evidence for the growth of carbon nanotubes and nanostructures at low substrate temperatures, using direct-current plasma-enhanced chemical vapour deposition. The catalyst particles are mounted on a titanium layer which acts as a thermal barrier, and allows for a larger temperature gradient between the Ni catalyst surface and the substrate. A simple thermodynamic simulation shows that the temperature differential between the substrate growth surface and the growth electrode is determined by the thickness of the titanium layer. This facilitates the growth of nanotubes, as opposed to nanofibres with herring-bone or amorphous structures. The growth properties are discussed as a function of the bias voltage and hydrocarbon concentration. The heating during growth provided solely by the plasma is below 400°C and is dependent on the process conditions and the electrode configuration in the growth chamber. These conditions need to be taken into account when comparing processes across different growth methods and instruments. The novel approach based on the use of a thermal barrier ensures the synthesis of carbon nanotubes at room temperature substrate conditions, which can be attained with a suitable cooling scheme. © 2006 Materials Research Society.
Silva SRP, Amaratunga GAJ, Okano K (1998) Modelling of the electron field emission process in polycrystalline diamond-like carbon thin films, Proceedings of the IEEE International Vacuum Microelectronics Conference, IVMC pp. 176-177
A model based on space charge band bending at the back junction is proposed to account for the electron emission at low electric fields from amorphous carbon. In this space charge interlayer model, the real cathode is the substrate from which hot electrons are created due to fully depleted diamond-like carbon the electrons encounter before reaching the front surface of the film. The model is extended to the incorporation of the emission of electrons from polycrystalline diamond thin films.
Forrest RD, Burden AP, Khan RUA, Silva SRP (1998) Electron field emission from amorphous carbon thin films as a function of annealing, SURFACE & COATINGS TECHNOLOGY 108 (1-3) pp. 577-582 ELSEVIER SCIENCE SA
Bhattacharyya S, Silva SRP (2007) Demonstration of an amorphous carbon tunnel diode, APPLIED PHYSICS LETTERS 90 (8) ARTN 082105 AMER INST PHYSICS
Ramli MM, Zhang W, Silva SRP, Henley SJ (2012) Dye-assisted dispersion of single-walled carbon nanotubes for solution fabrication of NO2 sensors, AIP ADVANCES 2 (3) ARTN 032165 AMER INST PHYSICS
Adikaari AADT, Dissanayake DMNM, Mudugamuwa NK, Silva SRP (2009) Nano engineered organic-inorganic material systems for photovoltaics, Advanced Materials Research 67 pp. 1-6
RUSLI, SILVA SRP, AMARATUNGA GAJ (1994) THE OPTICAL-PROPERTIES OF BAND-GAP-MODULATED DIAMOND-LIKE CARBON THIN-FILMS, DIAMOND AND RELATED MATERIALS 3 (4-6) pp. 817-820 ELSEVIER SCIENCE SA LAUSANNE
Chen GY, Stolojan V, Silva SRP, Herman H, Haq S (2005) Carbon spheres generated in 'dusty plasmas', CARBON 43 (4) pp. 704-708 PERGAMON-ELSEVIER SCIENCE LTD
Silva SRP, Rafferty B, Amaratunga GAJ, Schwan J, Franceschini DF, Brown LM (1996) Nitrogenated amorphous carbon as a semiconductor, DIAMOND AND RELATED MATERIALS 5 (3-5) pp. 401-404 ELSEVIER SCIENCE SA LAUSANNE
Silva SRP, Rusli, Homewood KP, Amaratunga GAJ (1998) Superlattice structures based on amorphous carbon, JOURNAL OF NON-CRYSTALLINE SOLIDS 227 pp. 1137-1141 ELSEVIER SCIENCE BV
Filip LD, Carey DJ, Silva SRP (2010) P2-29: Electron tunneling from a 3D nano-sphere, 23rd International Vacuum Nanoelectronics Conference pp. 179-180
A study of the 3D electron transfer from a spherical nano-particle in vacuum is presented as a continuation of a similar 1D analysis. The 3D confinement of the electronic states is analyzed and the emission current in vacuum is obtained as a function of the applied voltage on a distant anode.
Borowiak-Palen E, Mendoza E, Bachmatiuk A, Rummeli MH, Gemming T, Nogues J, Skumryev V, Kalenczuk RJ, Pichler T, Silva SRP (2006) Iron filled single-wall carbon nanotubes - A novel ferromagnetic medium, CHEMICAL PHYSICS LETTERS 421 (1-3) pp. 129-133 ELSEVIER SCIENCE BV
Gao C, Jin YZ, Kong H, Whitby RLD, Acquah SFA, Chen GY, Qian HH, Hartschuh A, Silva SRP, Henley S, Fearon P, Kroto HW, Walton DRM (2005) Polyurea-functionalized multiwalled carbon nanotubes: Synthesis, morphology, and Raman spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY B 109 (24) pp. 11925-11932 AMER CHEMICAL SOC
kutsarov DI, New E, Bausi F, Zoladek-Lemanczyk A, Castro FA, Silva SRP Fabrication of air-stable, large-area, PCDTBT:PC70BM polymer solar cell modules using a custom built slot-die coater Solar Energy Materials and Solar Cells, University of Surrey
Sanz V, Borowiak E, Lukanov P, Galibert AM, Flahaut E, Coley HM, Silva SRP, McFadden J (2011) Optimising DNA binding to carbon nanotubes by non-covalent methods, Carbon 49 (5) pp. 1775-1781 Elsevier
The use of carbon nanotubes as a gene delivery system has been extensively studied in recent years owing to its potential advantages over viral vectors. To achieve this goal, carbon nanotubes have to be functionalized to become compatible with aqueous media and to bind the genetic material. To establish the best conditions for plasmid DNA binding, we compare the dispersion properties of single-, double- and multi-walled carbon nanotubes (SWCNTs, DWCNTs and MWCNTs, respectively) functionalized with a variety of surfactants by non-covalent attachment. The DNA binding properties of the functionalized carbon nanotubes were studied and compared by electrophoresis. Furthermore, a bilayer functionalization method for DNA binding on SWCNTs was developed that utilized RNA-wrapping to solubilize the nanotubes and cationic polymers as a bridge between nanotubes and DNA.
Smith RC, Carey JD, Silva SRP (2004) Simulation of field enhancement effects in carbon nanotubes, TECHNICAL DIGEST OF THE 17TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 176-177 IEEE
Dabera GDMR, Prabhath MRR, Lai KT, Jayawardena KDGI, Sam FLM, Rozanski LJ, Adikaari AADT, Silva SRP (2015) Does Electronic Type Matter when Single-Walled Carbon Nanotubes are Used for Electrode Applications?, Advanced Functional Materials 25 (28) pp. 4520-4530
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Single-walled carbon nanotube (SWNT) electrodes that are chemically and mechanically robust are fabricated using a simple drop cast method with thermal annealing and acid treatment. An electronic-type selective decrease in sheet resistance of SWNT electrodes with HNO3 treatment is shown. Semiconducting SWNTs show a significantly higher affinity toward hole doping in comparison to metallic SWNTs; a H12-fold and a Hfivefold drop in sheet resistance, respectively. The results suggest the insignificance of the electronic type of the SWNTs for the film conductivity after hole doping. The SWNT films have been employed as transparent hole extracting electrodes in bulk heterojunction (BHJ) organic photovoltaics. Performances of the devices enlighten the fact that the electrode film morphology dominates over the electronic type of the doped SWNTs with similar sheet resistance and optical transmission. The power conversion efficiency (PCE) of 4.4% for the best performing device is the best carbon nanotube transparent electrode incorporated large area BHJ solar cell reported to date. This PCE is 90% in terms of PCEs achieved using indium tin oxide (ITO) based reference devices with identical film fabrication parameters indicating the potential of the SWNT electrodes as an ITO replacement toward realization of all carbon solar cells.
Almeida SA, Silva SRP (1997) Stoichiometric limitations of RF plasma deposited amorphous silicon-nitrogen alloys, THIN SOLID FILMS 311 (1-2) pp. 133-137 ELSEVIER SCIENCE SA
Sporea RA, Trainor MJ, Young ND, Shannon JM, Silva SRP (2012) Field plate optimization in low-power high-gain source-gated transistors, IEEE Transactions on Electron Devices 59 (8) pp. 2180-2186
Source-gated transistors (SGTs) have potentially very high output impedance and low saturation voltages, which make them ideal as building blocks for high-performance analog circuits fabricated in thin-film technologies. The quality of saturation is greatly influenced by the design of the field-relief structure incorporated into the source electrode. Starting from measurements on self-aligned polysilicon structures, we show through numerical simulations how the field plate (FP) design can be improved. A simple source FP around 1 ¼m long situated several tens of nanometers above the semiconductor can increase the low-voltage intrinsic gain by more than two orders of magnitude and offers adequate tolerance to process variations in a moderately scaled thin-film SGT. © 2012 IEEE.
Latini G, Tan LW, Cacialli F, Silva SRP (2012) Superficial fluoropolymer layers for efficient light-emitting diodes, Organic Electronics 13 (6) pp. 992-998 Elsevier
Fluoropolymers are characterized by high chemical inertness and, when in solid state, by superficial dipoles due to the C?F bond where the charge density is strongly displaced. These two characteristics are exploited here for fine control of charge balance in organic light-emitting devices and for preventing electrochemical interaction between heterogeneous layers. The insertion of a thin layer of polytetrafluoroethylene, PTFE, at the interface between poly(ethylene dioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, and an electroluminescent polymer leads to improved device efficiency and longevity. The presence of the superficial dipole increases the effective work function of the anode and improves the charge balance which enhances the external quantum efficiency, EQE, of the devices by up to a factor of two without significant effects on the luminance levels. The insertion of the PTFE layer reduces the photoluminescence quenching at the PEDOT:PSS/polymer interface, however we show that the EQE enhancement is mainly due to a better confinement of minority carrier electrons in the active layer. The lifetime of the devices shows a remarkable increase correlated with the insertion of the PTFE layer. Such improvements are ascribed to the reduced electrochemical interaction between the electroluminescent polymer and PEDOT:PSS due to the chemically inert nature of PTFE. The PTFE acts as a chemical zipper of two heterogeneous media with the added functionality of control over the charge balance.
Burden AP, Silva SRP (1998) Fullerene-like carbon nanoparticles generated by radio-frequency plasma-enhanced chemical vapour deposition, PHILOSOPHICAL MAGAZINE LETTERS 78 (1) pp. 15-19 TAYLOR & FRANCIS LTD
Mudugamuwa NK, Adikaari AADT, Dissanayake DMNM, Stolojan V, Silva SRP (2008) Reversible increase of photocurrents in excimer laser-crystallized silicon solar cells, SOLAR ENERGY MATERIALS AND SOLAR CELLS 92 (11) pp. 1378-1381 ELSEVIER SCIENCE BV
Henley SJ, Silva SRP (2007) Laser direct write of silver nanoparticles from solution onto glass substrates for surface-enhanced Raman spectroscopy, APPLIED PHYSICS LETTERS 91 (2) ARTN 023107 AMER INST PHYSICS
Prabhath MR, Romanova J, Curry RJ, Silva SR, Jarowski PD (2015) The Role of Substituent Effects in Tuning Metallophilic Interactions and Emission Energy of Bis-4-(2-pyridyl)-1,2,3-triazolatoplatinum(II) Complexes., Angew Chem Int Ed Engl 54 (27) pp. 7949-7953
The photoluminescence spectra of a series of 5-substituted pyridyl-1,2,3-triazolato Pt(II) homoleptic complexes show weak emission tunability (ranging from »=397-408?nm) in dilute (10(-6) M) ethanolic solutions at the monomer level and strong tunability in concentrated solutions (10(-4) M) and thin films (ranging from »=487-625?nm) from dimeric excited states (excimers). The results of density functional calculations (PBE0) attribute this "turn-on" sensitivity and intensity in the excimer to strong Pt-Pt metallophilic interactions and a change in the excited-state character from singlet metal-to-ligand charge transfer ((1)MLCT) to singlet metal-metal-to-ligand charge transfer ((1)MMLCT) emissions in agreement with lifetime measurements.
OBrien P, Walsh JR, Watson IM, Hart L, Silva SRP (1996) Properties of cadmium sulphide films grown by single-source metalorganic chemical vapour deposition with dithiocarbamate precursors, JOURNAL OF CRYSTAL GROWTH 167 (1-2) pp. 133-142 ELSEVIER SCIENCE BV
Anguita JV, Silva SRP, Burden AP, Sealy BJ, Haq S, Hebbron M, Sturland I, Pritchard A (1999) Thermal stability of plasma deposited thin films of hydrogenated carbon-nitrogen alloys, JOURNAL OF APPLIED PHYSICS 86 (11) pp. 6276-6281 AMER INST PHYSICS
Tsang WM, Wong SP, Lindner JKN, Silva SRP (2005) Improving electron emission properties of SiC layers by introducing electrically conductive clusters using ion implantation, Technical Digest of the 18th International Vacuum Nanoelectronics Conference, IVNC 2005 2005 pp. 54-55
Kang B, Tan LW, Silva SRP (2008) Fluoropolymer indium-tin-oxide buffer layers for improved power conversion in organic photovoltaics, APPLIED PHYSICS LETTERS 93 (13) ARTN 133302 AMER INST PHYSICS
Beliatis MJ, Martin NA, Leming EJ, Silva SR, Henley SJ (2011) Laser ablation direct writing of metal nanoparticles for hydrogen and humidity sensors., Langmuir 27 (3) pp. 1241-1244 American Chemical Society
A UV pulsed laser writing technique to fabricate metal nanoparticle patterns on low-cost substrates is demonstrated. We use this process to directly write nanoparticle gas sensors, which operate via quantum tunnelling of electrons at room temperature across the device. The advantages of this method are no lithography requirements, high precision nanoparticle placement, and room temperature processing in atmospheric conditions. Palladium-based nanoparticle sensors are tested for the detection of water vapor and hydrogen within controlled environmental chambers. The electrical conduction mechanism responsible for the very high sensitivity of the devices is discussed with regard to the interparticle capacitance and the tunnelling resistance.
Miyajima Y, Adamopoulos G, Henley SJ, Stolojan V, Tison Y, Garcia-Caurel E, Drevillon B, Shannon JM, Silva SRP (2008) Electronic state modification in laser deposited amorphous carbon films by the inclusion of nitrogen, JOURNAL OF APPLIED PHYSICS 104 (6) ARTN 063701 AMER INST PHYSICS
Anguita JV, Silva SRP (2000) Semiconducting hydrogenated carbon-nitrogen alloys with low defect densities, DIAMOND AND RELATED MATERIALS 9 (3-6) pp. 777-780 ELSEVIER SCIENCE SA
Jayawardena KDGI, Amarasinghe KMP, Nismy NA, Mills CA, Mills CA, Silva SRP (2015) Effect of solution processed and thermally evaporated interlayers on the performance of backgrated polymer solar cells, Thin Solid Films
© 2015 Elsevier B.V. Polymer solar cells are fast gaining momentum as a potential solution towards low cost sustainable energy generation. However, the performance of architectures is known to be limited by the thin film nature of the active layer which, although required due to low charge carrier mobilities, limits the optical coupling to the active layer. The formation of periodic backgratings has been proposed as a solution to this problem. Here, we investigate the effect of solution processed and thermally evaporated interlayers on the performance of backgrated polymer solar cells. Analysis of device performance under standard conditions indicates higher power conversion efficiencies with the incorporation of the evaporated interlayer (5.7%) over a sol-gel processed interlayer (4.9%). This is driven by a more conformal coating as evidenced through two orders of magnitude higher electron mobilities (10-5 versus 10-7 cm2 V-1 s-1) as well as the balanced electron and hole transport observed for the former architecture. It is believed that these results will catalyse further development of such device engineering concepts for improved optical coupling in thin film photovoltaics.
AMARATUNGA GAJ, SILVA SRP, MCKENZIE DR (1991) INFLUENCE OF DC BIAS VOLTAGE ON THE REFRACTIVE-INDEX AND STRESS OF CARBON-DIAMOND FILMS DEPOSITED FROM A CH4/AR RF PLASMA, JOURNAL OF APPLIED PHYSICS 70 (10) pp. 5374-5379 AMER INST PHYSICS
Prabhath MRR, Romanova J, Curry RJ, Silva SRP, Jarowski PD (2015) The Role of Substituent Effects in Tuning Metallophilic Interactions and Emission Energy of Bis-4-(2-pyridyl)-1,2,3-triazolatoplatinum(II) Complexes, Angewandte Chemie - International Edition
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.The photoluminescence spectra of a series of 5-substituted pyridyl-1,2,3-triazolato PtII homoleptic complexes show weak emission tunability (ranging from »=397-408 nm) in dilute (10-6M) ethanolic solutions at the monomer level and strong tunability in concentrated solutions (10-4M) and thin films (ranging from »=487-625 nm) from dimeric excited states (excimers). The results of density functional calculations (PBE0) attribute this "turn-on" sensitivity and intensity in the excimer to strong Pt-Pt metallophilic interactions and a change in the excited-state character from singlet metal-to-ligand charge transfer (1MLCT) to singlet metal-metal-to-ligand charge transfer (1MMLCT) emissions in agreement with lifetime measurements.
Mureau N, Mendoza E, Hoettges KF, Silva SRP, Hughes MP (2006) Determination of relative concentrations of metallic and semi-conducting SWNTs in suspension via dielectrophoresis, 2006 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2006 Technical Proceedings 1 pp. 110-112
Dielectrophoresis (DEP) is a phemomenon of induced particle motion in non-uniform electric fields. The effect is frequency dependent; by monitoring the motion of particles in AC fields and ananlysing the change in motion with frequency, it is possible to determine the electrical properties of nanoparticles in lab-on-a-chip systems. In this paper, we demonstrate how DEP can be used to determine the ratio of semiconducting and metallic carbon nanotubes in solution, by monitoring the frequency-dependent impedance change between two electrodes as a function of energising frequency.
SILVA SRP, AMARATUNGA GAJ, RUSLI, HAQ S, SALJE EK (1994) OPTICAL QUANTUM-SIZE EFFECTS IN DIAMOND-LIKE CARBON SUPERLATTICE STRUCTURES, THIN SOLID FILMS 253 (1-2) pp. 20-24 ELSEVIER SCIENCE SA LAUSANNE
Lyth SM, Silva SRP (2007) Field emission from multiwall carbon nanotubes on flexible paper substrates, EIGHTH IEEE INTERNATIONAL VACUUM ELECTRONICS CONFERENCE pp. 395-396 IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP
Sloan J, Carter R, Vlandas A, Meyer RR, Liu Z, Suenaga K, Lindan PJD, Lin G, Harding J, Flahaut E, Giusca C, Silva SRP, Hutchison JL, Kirkland AI (2008) Band-Gap Modification Induced in HgTe by Dimensional Constraint in Carbon Nanotubes: Effect of Nanotube Diameter on Microstructure, MICROSCOPY OF SEMICONDUCTING MATERIALS 2007 120 pp. 213-216 SPRINGER-VERLAG BERLIN
Zeze DA, Silva SRP, Brown NMD, Joyce AM, Anderson CA (2002) Targeting mass-selected cluster ions for the deposition of advanced carbonaceous materials using an inductively coupled plasma, JOURNAL OF APPLIED PHYSICS 91 (4) pp. 1819-1827 AMER INST PHYSICS
Guo X, Silva SRP (2007) A simple and effective approach to improve the output linearity of switched-current AMOLED pixel circuitry, IEEE ELECTRON DEVICE LETTERS 28 (10) pp. 887-889 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Tan LW, Hatten RA, Giusca CE, Silva SRP (2010) Interfacial energy level alignment at acid oxidised carbon nanotube - Triphenyldiamine contacts, MRS Proceedings 1258 pp. 253-259 Cambridge University Press
Jayawardena KDGI, Opoku C, Fryar J, Silva SRP, Henley SJ (2011) Excimer laser accelerated hydrothermal synthesis of ZnO nanocrystals & their electrical properties, Applied Surface Science 257 (12) pp. 5274-5277
Filip LD, Nicolaescu D, Silva SRP (2006) Quantum size dependence of electron distribution on carbon nanotubes and its influence on field emission, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 24 (2) pp. 874-880 A V S AMER INST PHYSICS
Shiozawa H, Silva SRP, Liu Z, Suenaga K, Kataura H, Kramberger C, Pfeiffer R, Kuzmany H, Pichler T (2010) Low-temperature growth of single-wall carbon nanotubes inside nano test tubes, Physica Status Solidi (B) Basic Research 247 (11-12) pp. 2730-2733
Gopee V, Thomas O, Hunt C, Stolojan V, Allam J, Silva SRP (2016) Carbon Nanotube Interconnects Realized through Functionalization and Sintered Silver Attachment, ACS Applied Materials and Interfaces 8 (8) pp. 5563-5570 American Chemical Society
Carbon nanotubes (CNTs) in the form of interconnects have many potential applications, and their ability to perform at high temperatures gives them a unique capability. We show the development of a novel transfer process using CNTs and sintered silver that offers a unique high-temperature, high-conductivity, and potentially flexible interconnect solution. Arrays of vertically aligned multiwalled carbon nanotubes of approximately 200 ¼m in length were grown on silicon substrates, using low-temperature photothermal chemical vapor deposition. Oxygen plasma treatment was used to introduce defects, in the form of hydroxyl, carbonyl, and carboxyl groups, on the walls of the carbon nanotubes so that they could bond to palladium (Pd). Nanoparticle silver was then used to bind the Pd-coated multiwalled CNTs to a copper substrate. The silver?CNT?silver interconnects were found to be ohmic conductors, with resistivity of 6.2 × 10?4 ©m; the interconnects were heated to temperatures exceeding 300 °C (where common solders fail) and were found to maintain their electrical performance.
Miller AJ, Hatton RA, Silva SRP (2006) Water-soluble multiwall-carbon-nanotube-polythiophene composite for bilayer photovoltaics, APPLIED PHYSICS LETTERS 89 (12) ARTN 123115 AMER INST PHYSICS
Ahmad M, Anguita JV, Stolojan V, Carey JD, Silva SRP (2013) Efficient coupling of optical energy for rapid catalyzed nanomaterial growth: High-quality carbon nanotube synthesis at low substrate temperatures, ACS Applied Materials and Interfaces 5 (9) pp. 3861-3866
The synthesis of high-quality nanomaterials depends on the efficiency of the catalyst and the growth temperature. To produce high-quality material, high-growth temperatures (often up to 1000 C) are regularly required and this can limit possible applications, especially where temperature sensitive substrates or tight thermal budgets are present. In this study, we show that high-quality catalyzed nanomaterial growth at low substrate temperatures is possible by efficient coupling of energy directly into the catalyst particles by an optical method. We demonstrate that using this photothermal-based chemical vapor deposition method that rapid growth (under 4 min, which includes catalyst pretreatment time) of high-density carbon nanotubes can be grown at substrate temperatures as low as 415 C with proper catalyst heat treatment. The growth process results in nanotubes that are high quality, as judged by a range of structural, Raman, and electrical characterization techniques, and are compatible with the requirements for interconnect technology. © 2013 American Chemical Society.
Stolojan V, Moreau P, Henley SJ, Goringe MJ, Silva SRP (2006) Energy loss spectroscopic profiling across linear interfaces: The example of amorphous carbon superlattices, ULTRAMICROSCOPY 106 (4-5) pp. 346-355 ELSEVIER SCIENCE BV
Zhang W, Lei MK, Zhang W, Silva SRP, Johnson L (2012) The effect of plasma modification on the sheet resistance of nylon fabrics coated with carbon nanotubes, Applied Surface Science
Low-pressure oxygen and argon plasmas were used to pre-treat nylon fabrics, and the modified fabrics, together with the raw fabrics, were subsequently coated with single walled carbon nanotubes (SWCNTs) by a dip-drying process. Scanning electron microscopy (SEM) and Raman spectroscopy analyses indicated the attachment of SWCNTs onto nylon fabrics. After the coating with SWCNTs, the plasma modified fabrics exhibited sheet resistance of as low as 2.0 k©/sq. with respect to 4.9 k©/sq. of the raw fabrics, presumably owing to the increase of fibre surface roughness incurred by the plasma modification, which is evidenced by SEM analyses. Fourier transform infrared spectroscopy (FTIR) analysis indicates the incorporation of oxygen functionalities on fibre surfaces in the plasma modification. This is responsible for the variation of the electrical conductance of SWCNT-coated fabrics with the type of plasma and the duration of plasma ablation. © 2012 Elsevier B.V. All rights reserved.
Sporea RA, Georgakopoulos S, Shkunov M, Shannon JM, Silva SRP, Xu X, Guo X (2013) Leveraging contact effects for field-effect transistor technologies with reduced complexity and superior current uniformity, MRS Online Proceedings Library 1553
In order to achieve high performance, the design of devices for large-area electronics needs to be optimized despite material or fabrication shortcomings. In numerous emerging technologies thin-film transistor (TFT) performance is hindered by contact effects. Here, we show that contact effects can be used constructively to create devices with performance characteristics unachievable by conventional transistor designs. Source-gated transistors (SGTs) are not designed with increasing transistor speed, mobility or sub-threshold slope in mind, but rather with improving certain aspects critical for real-world large area electronics such as stability, uniformity, power efficiency and gain. SGTs can achieve considerably lower saturation voltage and power dissipation compared to conventional devices driven at the same current; higher output impedance for over two orders of magnitude higher intrinsic gain; improved bias stress stability in amorphous materials; higher resilience to processing variations; current virtually independent of source-drain gap, source-gate overlap and semiconductor thickness variations. Applications such as amplifiers and drivers for sensors and actuators, low cost large area analog or digital circuits could greatly benefit from incorporating the SGT architecture.
Borowiak-Palen E, Ruemmeli MH, Mendoza E, Henley SJ, Cox DC, Poa CHP, Stolojan V, Gemming T, Pichler T, Silva SRP (2005) Silver intercalated carbon nanotubes, AIP Conference Proceedings 786 pp. 236-239
The intercalation of metals within carbon nanotube structures has extended the potential applications of these materials to possible quantum memory elements as well as high density magnetic storage media. In our study we use methodologies based on wet chemistry and solid state physical (excimer laser) processes to incorporate silver nanoparticles in single and multiwall carbon nanotubes. We show high resolution TEM as evidence for the formation of very long (
Nismy NA, Jayawardena KDGI, Adikaari AADT, Silva SRP (2015) Nano-engineering of hybrid organic heterojunctions with carbon nanotubes to improve photovoltaic performance, Organic Electronics: physics, materials, applications 22 pp. 35-39
© 2015 Elsevier B.V. All rights reserved.Organic-inorganic hybrid photovoltaics are beginning to show significant promise as a low cost highly efficient route towards renewable energy generation. Of the hybrid architectures available, carbon nanotube incorporated organic photovoltaics is considered to be among the most promising. Herein, the optical and electronic effects of localizing multiwalled carbon nanotubes in the donor polymer is investigated in comparison to its incorporation into the bulk heterojunction architecture (triple heterojunction scheme) through photoluminescence quenching and dark diode characteristics analysis. A significant improvement in photoluminescence quenching is observed when the nanotubes are localized in the donor polymer where the active layer is formed through a sequential deposition route in comparison to the triple heterojunction scheme. However, the former architecture also leads to a higher recombination of carriers due to the introduction of trap states as observed through space charge limited conduction analysis. In comparison, the triple heterojunction scheme shows a lower dark current and hence a significantly improved photovoltaic device performance (3.8% in comparison to 2.6% for the sequentially deposited architecture). This indicates that the formation of the triple heterojunction is the more ideal scheme for improving device performances in organic-inorganic hybrid architectures.
SILVA SRP, KAPOOR A, AMARATUNGA GAJ (1995) TRIBOLOGICAL PROPERTIES OF DIAMOND-LIKE CARBON-FILMS DEPOSITED ON SILICON USING RF PLASMA-ENHANCED CVD, SURFACE & COATINGS TECHNOLOGY 73 (1-2) pp. 132-136 ELSEVIER SCIENCE SA LAUSANNE
Cox DC, Forrest RD, Smith PR, Stolojan V, Silva SRP (2005) Study of the current stressing in nanomanipulated three-dimensional carbon nanotube structures, APPLIED PHYSICS LETTERS 87 (3) ARTN 033102 AMER INST PHYSICS
Mills CA, Sam FLM, Alshammari AS, Rozanski LJ, Emerson NG, Silva SRP (2013) Storage Lifetime of Polymer-Carbon Nanotube Inks for Use as Charge Transport Layers in Organic Light Emitting Diodes, IEEE/OSA Journal of display technology 10 (2) pp. 125-131 IEEE
The long-term stability of multi-wall carbon nanotubes (MWCNT) mixed with the hole-transport polymer Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been examined. These surfactant stabilised solutions, used as transport layers in organic light emitting diodes (OLEDs), are shown to be stable for periods of up to fifteen months, and show no signs of degrading soon after this time. In comparison, non-stabilised aqueous MWCNT solutions have been shown to aggregate within 30 minutes of production, and, although these aggregates can be re-dispersed, the solution displays an increase in smaller aggregates over time which cannot subsequently be re-dispersed by manual agitation. The stable MWCNT/PEDOT:PSS solutions have been used in ink-jet printing and as composite MWCNT/PEDOT:PSS films suitable as charge transport layers in spin coated organic light emitting diodes.
SILVA SRP, AMARATUNGA GAJ (1994) USE OF SPACE-CHARGE-LIMITED CURRENT TO EVALUATE THE ELECTRONIC DENSITY-OF-STATES IN DIAMOND-LIKE CARBON THIN-FILMS, THIN SOLID FILMS 253 (1-2) pp. 146-150 ELSEVIER SCIENCE SA LAUSANNE
Dissanayake N, Hatton RA, Giusca C, Lutz T, Curry R, Silva R (2008) Organic:PbS-nanocrystal:fullerene hybrid photovoltaics, MRS Proceedings 1102 pp. 59-65 Cambridge University Press
Alenezi MR, Alzanki TH, Almeshal AM, Alshammari AS, Beliatis MJ, Henley SJ, Silva SRP (2014) Hierarchically designed ZnO nanostructure based high performance gas sensors, RSC Advances 4 (90) pp. 49521-49528
© the Partner Organisations 2014.Rationally controlled multistage hydrothermal methods have been developed to prepare different types of hierarchical zinc oxide (ZnO) nanostructures with high surface-to-volume ratios and more exposed polar facets. Four types of hierarchical ZnO nanostructures, i.e. nanobrushes (ZNBs), nanoleaves (ZNLs), hierarchical nanodisks (HNDs) and nanoflakes (ZNFs), assembled from initial mono-morphological nanostructures, i.e. nanowires (ZNWs) and nanodisks (ZNDs), were produced from sequential nucleation and growth after a hydrothermal process. Hierarchical nanostructures with 1D nanowire and 2D nanodisk building blocks were realized using zinc nitrate and zinc sulphate as the source of zinc ions, respectively. Compared to their initial mono-morphological counterparts, the grown hierarchical nanostructures demonstrated superior gas sensing properties. ZNLs and ZNFs showed a significant improvement in the sensitivity and fast response to acetone. In addition to the high surface-to-volume ratio, due to the ultrathin sheet building blocks, the enhanced gas sensing properties of the ZNLs and ZNFs are chiefly ascribed to the increased proportion of exposed (0001) polar facets. The current study offers a path for the structure induced development of gas sensing properties by designing a necessary nanostructure, which could be used to fabricate high performance nanostructured gas sensors based on other metal oxides.
Khan RUA, Silva SRP (2003) Electrical transport within polymeric amorphous carbon thin films and the effects of ion implantation, JOURNAL OF APPLIED PHYSICS 94 (7) pp. 4470-4476 AMER INST PHYSICS
Kerr GL, Cox DC, Stolojan V, Silva SRP (2008) Characterisation of electron-beam deposited tungsten interconnects, EMAG: ELECTRON MICROSCOPY AND ANALYSIS GROUP CONFERENCE 2007 126 IOP PUBLISHING LTD
Sanz V, Coley HM, Silva SRP, McFadden J (2012) Modeling the binding of peptides on carbon nanotubes and their use as protein and DNA carriers, Journal of Nanoparticle Research 14 (2) Springer
An in-depth study of a novel functionalization
of carbon nanotubes for their application as
protein and DNA carriers is presented. First, the
optimum conditions for the dispersion of singlewalled
carbon nanotubes (SWCNTs) with amphiphilic
polypeptides were obtained, and the SWCNT?polypeptide
complexes were characterized by different
techniques (UV?Vis-NIR, CD, and AFM). Based on
the properties of the SWCNT?polypeptide complexes,
a model that characterizes the adsorption of natural
proteins onto SWCNT was described for the first time.
This model predicts the adsorption of natural proteins
on SWCNTs based on the protein structure and
composition, and therefore, allows the design of
methods for the preparation of SWCNT?protein
complexes. Besides, the use of cationic-designed
amphiphilic polypeptides to disperse SWCNTs is
applied for subsequent and efficient binding of DNA
to carbon nanotubes by a bilayer approach. Therefore,
in this article, we develop procedures for the use of
SWCNTs as protein and DNA carriers. The systems
were delivered into cells showing that the efficiency of
delivery is affected by the charge of the complexes,
which has important implications in the use of
SWCNT as platforms for protein and DNA binding
and subsequent use as delivery systems.
Almeida SA, Silva SRP, Sealy BJ, Watts JF (1999) Bond formation in ion beam synthesised amorphous gallium nitride, THIN SOLID FILMS 343 pp. 632-636 ELSEVIER SCIENCE SA
Henley SJ, Hatton RA, Chen GY, Gao C, Zeng H, Kroto HW, Silva SRP (2007) Enhancement of polymer luminescence by excitation-energy transfer from mufti-walled carbon nanotubes, SMALL 3 (11) pp. 1927-1933 WILEY-V C H VERLAG GMBH
Silva SRP, Forrest RD, Munindradasa DA, Amaratunga GAJ (1998) Electron field emission studies from amorphous carbon thin films, DIAMOND AND RELATED MATERIALS 7 (2-5) pp. 645-650 ELSEVIER SCIENCE SA
Chen GY, Jensen B, Stolojan V, Silva SRP (2011) Growth of carbon nanotubes at temperatures compatible with integrated circuit technologies, CARBON 49 (1) pp. 280-285 PERGAMON-ELSEVIER SCIENCE LTD
Clark J, Chen Y, Silva SRP (2016) Low Impedance Functionalised Carbon Nanotube Electrode Arrays for Electrochemical Detection, ELECTROANALYSIS 28 (1) pp. 58-62 WILEY-V C H VERLAG GMBH
Shiozawa H, Skeldon AC, Lloyd DJ, Stolojan V, Cox DC, Silva SR (2011) Spontaneous emergence of long-range shape symmetry, Nano Letters 11 (1) pp. 160-163
Self-organization of matter is essential for natural pattern formation, chemical synthesis, as well as modern material science. Here we show that isovolumetric reactions of a single organometallic precursor allow symmetry breaking events from iron nuclei to the creation of different symmetric carbon structures: microspheres, nanotubes, and mirrored spiraling microcones. A mathematical model, based on mass conservation and chemical composition, quantitatively explains the shape growth. The genesis of such could have significant implications for material design.
Chong LC, Stolojan V, Wagner G, Silva SRP, Curry RJ (2008) One-pot rapid low-cost synthesis of Pd-fullerite catalysts, JOURNAL OF MATERIALS CHEMISTRY 18 (40) pp. 4808-4813 ROYAL SOC CHEMISTRY
Lacerda RG, Stolojan V, Cox DC, Silva SRP, Marques FC (2002) Structural characterization of hard a-C : H films as a function of the methane pressure, DIAMOND AND RELATED MATERIALS 11 (3-6) pp. 980-984 ELSEVIER SCIENCE SA
Chen GY, Poa CHP, Stolojan V, Henley S, Silva SRP (2004) Growth kinetics changes of vertically aligned carbon nanostructures syntheslsed at low substrate temperatures, Materials Research Society Symposium Proceedings 858 pp. 91-96
Carbon nanotubes and nanofibres are typically synthesised under substrate temperatures above 600°C. Here we investigate the influence of the substrate temperature and the plasma conditions on the growth of vertically aligned carbon nanostructures using Direct Current plasma Chemical Vapour Deposition, at temperatures below 550°C. These nanostructures are produced using a C 2H2 based plasma and nickel thin film as the catalyst. We found that preferential deposition of amorphous carbon takes place as the synthesis temperature is lowered below 500°C. However, lowering the carbon concentration in the gas feedstock (
Sporea RA, Guo X, Shannon JM, Silva SRP (2011) Source-Gated Transistors for Versatile Large Area Electronic Circuit Design and Fabrication, ECS Transactions 37 (1) pp. 57-63 The Electrochemical Society
Source-gated transistors (SGTs) comprise a blocking contact or potential barrier at the source, which control the current. The paper describes how SGTs can be optimized for particular applications and for specific semiconductor material systems. It is shown how the saturation voltage can be designed to be an order of magnitude smaller than in equivalent FETs to give power savings of over 50% for the same current output. The SGT also achieves a better saturation regime, with lower output conductance over a larger range of drain voltages. Flat-panel lighting, remote sensing and signal processing and large-area circuits made using inexpensive but imprecise patterning techniques are some of the applications which could benefit from incorporating these devices.
Hamerton I, Tang W, Anguita JV, Silva SRP, Stute T (2016) Using Molecular Simulation to Explore Unusually Low Moisture Uptake in Amine-Cured Epoxy Carbon Fiber Reinforced Nanocomposites, MACROMOLECULAR CHEMISTRY AND PHYSICS 217 (11) pp. 1282-1292 WILEY-V C H VERLAG GMBH
Guo X, Silva SRP (2007) Analysis of self-heating in poly-Si thin-film transistors and circuits by a self-consistent electro-thermal simulation approach, ICSICT-2006: 2006 8th International Conference on Solid-State and Integrated Circuit Technology, Proceedings pp. 1398-1400
This paper investigated the self-heating effects in poly-Si thin-film transistors (TFTs) and circuits) by using a self-consistent electro-thermal simulation approach. The analysis indicates that, for the poly-Si technology, self-heating may lead to a significant degradation of the device's characteristics, and severely impact the circuit performance; therefore, reinforce the need for effective cooling strategies and also accurate device/circuit level models, including electro-thermal coupling effects, for reliable poly-Si TFT circuit design and integration. © 2006 IEEE.
Khan RUA, Silva SRP (2000) Electronic conduction in ion implanted amorphous carbon thin films, INTERNATIONAL JOURNAL OF MODERN PHYSICS B 14 (2-3) pp. 195-205 WORLD SCIENTIFIC PUBL CO PTE LTD
Henley SJ, Silva SRP, Fuge GM, Ashfold MNR (2007) Radiation trapping in LiF ablation plumes, COLA'05: 8TH INTERNATIONAL CONFERENCE ON LASER ABLATION 59 pp. 745-748 IOP PUBLISHING LTD
Lyth SM, Oyeleye F, Curry RJ, Davis J, Silva SRP (2006) Field emission from multiwall carbon nanotubes prepared by electrodeposition without the use of a dispersant, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 24 (3) pp. 1362-1364 A V S AMER INST PHYSICS
Tang YF, Silva SRP, Rose MJ (2001) Super sequential lateral growth of Nd : YAG laser crystallized hydrogenated amorphous silicon, APPLIED PHYSICS LETTERS 78 (2) pp. 186-188 AMER INST PHYSICS
Sanz V, Coley HM, McFadden J, Sanz V, Silva SRP (2012) Protamine and chloroquine enhance gene delivery and expression mediated by RNA-wrapped single walled carbon nanotubes, Journal of Nanoscience and Nanotechnology 12 (3) pp. 1739-1747 AMER SCIENTIFIC PUBLISHERS
The use of non-viral vectors as delivery systems in gene therapy has been extensively studied recently owing to their advantages over viral vectors. Here, we propose a new gene delivery system based on the use of RNA-wrapped single-walled carbon nanotubes (SWCNTs) complexed with the cationic protein, protamine and the drug chloroquine. Protamine was selected as a cationic protein acting as bridge between negatively charged RNA-wrapped SWCNTs and plasmid DNA. Protamine also contains a nuclear localization signal which enhances the expression of the transfected gene. The drug chloroquine, a lysosomotropic compound which has been reported to increase the transfection efficiency, was attached to RNA-wrapped SWNTs by ionic interactions. The simultaneous delivery of the drug chloroquine with plasmid DNA clearly showed an enhanced gene delivery and expression. The levels of gene expression were quantified using the luciferase reporter gene as model. Optimal conditions for transfection and gene expression were obtained and cytoxicity of the carbon nanotube complexes measured. The optimal complexes were shown to efficiently deliver plasmid DNA for efficient gene expression and may thereby be useful as gene delivery systems for gene therapy. Copyright © 2012 American Scientific Publishers.
Haq S, Hebbron MC, Anguita JV, Silva SRP High Emissivity Radiator, WO/2006/038040
(EN)This invention relates to a radiator 10 and to a method of making a radiator. In particular, this invention relates to a radiator 10 having thin-film 5 coatings that serve to increase the thermal emissivity of the entire structure. A radiator 10 is provided comprising a substrate 12, an amorphous carbon layer 16 and the metallic carbide forming layer 14 interposed between the substrate 12 and amorphous carbon layer 16. In addition, a method of making a radiator is provided comprising the steps of forming the metallic carbide-forming layer on 10 a substrate and forming an amorphous carbon layer on the metallic carbide- forming layer.
Silva SRP, Carey JD, Guo X, Tsang WM, Poa CHP (2005) Electron field emission from carbon-based materials, THIN SOLID FILMS 482 (1-2) pp. 79-85 ELSEVIER SCIENCE SA
Mahmoudi T, Rho WY, Yang HY, Silva SRP, Hahn YB (2014) Highly conductive and dispersible graphene and its application in P3HT-based solar cells, Chemical Communications 50 (63) pp. 8705-8708
A simple reduction method without the need for high-temperature annealing is proposed for highly conductive and dispersible graphene sheets. This method consists of the grafting of graphene oxide (GO) with 1-pyrenecarboxylic acid (PCA) and the exothermic reduction of the PCA-grafted GO, followed by an endothermic decarboxylation with refluxing hot water. The PCA-grafted reduced graphene oxide (PCA-rGO) has a high conductivity of
Katsuno T, Nitta S, Habuchi H, Stolojan V, Silva SRP (2004) Highly photoconductive amorphous carbon nitride films prepared by cyclic nitrogen radical sputtering, APPLIED PHYSICS LETTERS 85 (14) pp. 2803-2805 AMER INST PHYSICS
Kim C-H, Beliatis MJ, Gandhi KK, Rozanski LJ, Bonnassieux Y, Horowitz G, Silva SRP (2015) Equivalent Circuit Modeling for a High-Performance Large-Area Organic Photovoltaic Module, IEEE JOURNAL OF PHOTOVOLTAICS 5 (4) pp. 1100-1105 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Adikaari AADT, Silva SRP (2008) EXCIMER LASER CRYSTALLIZATION AND NANOSTRUCTURING OF AMORPHOUS SILICON FOR PHOTOVOLTAIC APPLICATIONS, NANO 3 (3) pp. 117-126 WORLD SCIENTIFIC PUBL CO PTE LTD
Henley SJ, Woolger NEP, Carey JD, Silva SRP, Fuge GM, Ashfold MNR (2005) Metal incorporation into nanoporous carbon, Materials Research Society Symposium Proceedings 876 pp. 256-261
Nanoporous carbon films were deposited by 248 nm pulsed laser ablation of a graphite target in different background pressures of argon (PAr). The morphology changed from smooth, high-density amorphous carbon films at PAr = 20 mTorr to ultra-low density nanoporous material at P Ar = 380 mTorr. Subsequently, the nanostructural, chemical and electrical properties of metal containing nanoporous carbon samples were investigated by ablating graphite targets containing known contents of Ni and Co. We demonstrate how the ablation plume dynamics affect both the nanostructure of the material and the incorporation of metal atoms. The suitability of these functionalised ultra-low density materials for gas sensing applications is discussed. © 2005 Materials Research Society.
Webb RP, Jimenez-Rodriguez JJ, Kerford M, Silva SRP (1998) The formation of diamond-like carbon films due to molecular impacts on graphite, DIAMOND AND RELATED MATERIALS 7 (8) pp. 1163-1166 ELSEVIER SCIENCE SA
Silva SRP, Xu S, Tay BK, Tan HS, Scheibe HJ, Chhowalla M, Milne WI (1996) The structure of tetrahedral amorphous carbon thin films, THIN SOLID FILMS 290 pp. 317-322 ELSEVIER SCIENCE SA
Miyajima Y, Henley SJ, Silva SRP (2011) Hydrogenated amorphous carbon and carbon nitride films deposited at low pressure by plasma enhanced chemical vapor deposition, THIN SOLID FILMS 519 (19) pp. 6374-6380 Elsevier
Bourdakos KN, Dissanayake DMNM, Lutz T, Silva SRP, Curry RJ (2008) Highly efficient near-infrared hybrid organic-inorganic nanocrystal electroluminescence device, APPLIED PHYSICS LETTERS 92 (15) ARTN 153311 AMER INST PHYSICS
Jin Y, Curry RJ, Sloan J, Hatton RA, Chong LC, Blanchard N, Stolojan V, Kroto HW, Silva SRP (2006) Structural and optoelectronic properties of C-60 rods obtained via a rapid synthesis route, JOURNAL OF MATERIALS CHEMISTRY 16 (37) pp. 3715-3720 ROYAL SOC CHEMISTRY
Sporea RA, Trainor MJ, Young ND, Guo X, Shannon JM, Silva SRP (2011) Performance trade-offs in polysilicon source-gated transistors, Solid-State Electronics 65-66 (1) pp. 246-249 Elsevier
Self-aligned Schottky-source source-gated transistors (SGTs) have been
made in polysilicon. The structures enable a direct comparison to be made between
a SGT and a standard thin-film field-effect transistor (FET) on the same device.
SGTs having excellent characteristics have been fabricated, with intrinsic gains
approaching 10,000. The effects of bulk doping in the polysilicon and of the source
barrier modification implant are considered in the context of the electrical output
characteristics. It is shown that the choice of source length is a tradeoff between
device speed and variations in current output due to variability during fabrication.
Alshammari AS, Shkunov M, Silva SRP (2014) Correlation between wetting properties and electrical performance of solution processed PEDOT:PSS/CNT nano-composite thin films, Colloid and Polymer Science 292 (3) pp. 661-668
Nano-composite thin films of poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS) with different loading concentrations of multi-walled carbon nanotubes (MWCNT) were deposited on glass substrates using inkjet printing and spin coating techniques. The surface energy of the substrate was modified using an oxygen plasma to achieve different degrees of wetting by the composite solution. We show that the electrical properties strongly depend on the wetting of the substrate and by controlling the wettability, the conductivity of the nano-composite samples can be improved. Based on polymer conductivity, the electrical conductivity of the composite film can be improved or degraded by orders of magnitude with the incorporation of the same concentration of MWCNT. Moreover, electrical measurements show strong correlation between the conductivity of the carbon nanotube network and the resulting nano-composite films. The dependence of electrical properties on the wettability and the conductivity of the composite components could explain the diversity in the electrical behaviour reported in the literature for PEDOT:PSS/MWCNT nano-composite thin films. © 2013 Springer-Verlag.
Sadhu V, Nismy NA, Adikaari AA, Henley SJ, Shkunov M, Silva SRP (2011) The incorporation of mono- and bi-functionalized multiwall carbon nanotubes in organic photovoltaic cells., Nanotechnology 22 (26)
We have successfully prepared mono- and bi-functionalized multiwall carbon nanotubes (MWCNT) with thiophene, amine and thiophene-amine groups. The dispersion of nanotubes has been enhanced and stable optimized dispersions in organic solvents were obtained. These functionalized nanotubes have been successfully incorporated into bulk heterojunction (BHJ) organic photovoltaic (OPV) cells with a poly (3-hexyl thiophene) (P3HT) and [6, 6]-phenyl-C(61)-butyric acid methyl ester (PCBM) photoactive blended layer. The incorporation of MWCNT with different functional groups, in the active layer, results in different cell performance with respect to a reference cell. A maximum power conversion efficiency of 2.5% is achieved with the inclusion of thiophene functionalized nanotubes. This improvement in the device performance is attributed to an extension of the exciton dissociation volume and charge transport properties through the nanotube percolation network in P3HT/CNT, PCBM/CNT or both phases. This is believed to be due to more efficient dispersion of the functionalized nanotubes within the photoactive composite layer.
Adikaari AADT, Mudugamuwa NK, Silva SRP (2007) Use of an asymmetric pulse profile for higher crystalline volumes from excimer laser crystallization of amorphous silicon, APPLIED PHYSICS LETTERS 90 (17) ARTN 171912 AMER INST PHYSICS
Zhang W, Wu CW, Tan YY, Silva SRP (2012) Functionalisation of nylon with carbon nanotubes to make thermally stable fabric and wearable capacitor, MICRO & NANO LETTERS 7 (3) pp. 193-195 INST ENGINEERING TECHNOLOGY-IET
Poa CHP, Smith RC, Silva SRP, Sun CQ (2005) Influence of mechanical stress on electron field emission of multiwalled carbon nanotube-polymer composites, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 23 (2) pp. 698-701 A V S AMER INST PHYSICS
Anguita JV, Sharma P, Henley SJ, Silva SRP (2009) Room temperature photoluminescence in the visible range from silicon nanowires grown by a solid-state reaction, SEMICONDUCTOR NANOSTRUCTURES TOWARDS ELECTRONIC AND OPTOELECTRONIC DEVICE APPLICATIONS II (SYMPOSIUM K, E-MRS 2009 SPRING MEETING) 6 IOP PUBLISHING LTD
Guo X, Sporea R, Shannon JM, Silva SRP (2009) Down-scaling of thin-film transistors: Opportunities and design challenges, ECS Transactions 22 (1) pp. 227-238
With the ever-increasing demands for integration of advanced electronic functions into large-area electronics, down-scaling of thin-film transistors (TFTs) becomes very necessary. The key device operational issues associated with TFT scaling, including short-channel effects (SCEs) and self-heating, are considered in this paper. Device structure engineering approaches are introduced to suppress the SCEs for designing short-channel TFTs with excellent digital and analog performance. And electro-thermal simulation results show that the self-heating in TFTs will be much more significant than that in silicon metal-oxide-semiconductor field-effect transistors (MOSFETs) due to the substrate of poor thermal conductivity. Enhancing the heat dissipation by placement of metal heat pipe in the cap dielectric layers is proved to be an effective way to deal with the heating issues.
Guo X, Silva SRP (2007) Analysis and management of the electro-thermal effects in analog poly-Si TFTs for SoP integration, AD'07: Proceedings of Asia Display 2007, Vols 1 and 2 pp. 579-582 EAST CHINA NORMAL UNIVERSITY
Sporea RA, Shannon JM, Silva SRP (2012) Modes of operation and optimum design for application of source-gated transistors, ECS Transactions 50 (8) pp. 65-70
We show that the source-gated transistor has two distinct modes of operation. In the low-field mode, the current from the reversebiased source barrier is restricted by the depleted semiconductor at the drain end of the source. In the high-field mode, the current depends on field-dependent barrier lowering in the same region of the source. In practice, both these modes usually occur: the former at low VG, the latter at high VG. It is shown that this understanding enables us to design devices in which the current is insensitive to large changes in structure and geometry. © The Electrochemical Society.
Shang NG, Tan YY, Stolojan V, Papakonstantinou P, Silva SRP (2010) High-rate low-temperature growth of vertically aligned carbon nanotubes, NANOTECHNOLOGY 21 (50) ARTN 505604 IOP PUBLISHING LTD
Stolojan V, Moreau P, Goringe MJ, Silva SRP (2006) Subnanometer-resolved measurement of the tunneling effective mass using bulk plasmons, APPLIED PHYSICS LETTERS 88 (12) ARTN 122109 AMER INST PHYSICS
Silva SRP, Forbes RG (1998) Controlling mechanisms for field-induced electron emission from diamond-like carbon films, ULTRAMICROSCOPY 73 (1-4) pp. 51-57 ELSEVIER SCIENCE BV
Jayawardena KDGI, Rhodes R, Gandhi KK, Prabhath MRR, Dabera GDMR, Beliatis MJ, Rozanski LJ, Henley SJ, Silva SRP (2013) Solution processed reduced graphene oxide/metal oxide hybrid electron transport layers for highly efficient polymer solar cells, Journal of Materials Chemistry A 1 (34) pp. 9922-9927 Royal Society of Chemistry
We report new solution processable electron transport layers for organic photovoltaic devices based on composites of metal oxides and reduced graphene oxides. Low bandgap polymer cells fabricated using these nanohybrid transport layers display power conversion efficiencies in the range of 7.4-7.5% which is observed to be an improvement over conventional metal oxide or thermally evaporated electron transport layers. This efficiency enhancement is driven mainly by improvements in the short circuit current (from
Palumbo M, Henley SJ, Lutz T, Stolojan V, Silva SRP (2008) A fast sonochemical approach for the synthesis of solution processable ZnO rods, JOURNAL OF APPLIED PHYSICS 104 (7) ARTN 074906 AMER INST PHYSICS
Silva R (2006) Highs and lows in nanotubes, Physics World 19 (6)
The development of a NanoGrowth tool to synthesize nanotubes at low temperatures is discussed. growing future prospects of carbon nanotubes to form the basis of a variety of applications, from semiconductor interconnects to solid-state lighting and solar cells is discussed. CEVP Ltd and the Advanced Technology Institute (ATI) has developed a NanoGrowth tool for producing carbon nanotubes at lower temperatures. The NanoGrowth tool uses careful tailoring of the plasma and a unique thermal control system to maintain the substrate at room temperature. This change in the processing concept allows the tool to be extended to the synthesis of other nanomaterials, such as silicon and metal-oxide nanowires, at low substrate temperatures. The tool also aims to spur the commercialization of carbon-nanotube-related applications through its reliable output and enhanced control over the growth process.
Amaratunga GAJ, Silva SRP (1995) Nitrogen containing hydrogenated amorphous carbon for thin-film field emission cathodes, Applied Physics Letters
Field emission measurements using 0.3 ¼m thick nitrogen containing hydrogenated amorphous carbon films (a-C:H:N) on n++-Si cathodes are reported. Onset emission fields as low as 4 V ¼m-1 have been obtained using a flat plate anode configuration. Uniform emission is observed over the entire cathode area at current densities below 7×10-2 mA cm-2. At higher current density preferential emission from spots is observed. The spot emission is imaged using the ITO coated plate anode. A model based on the a-C:H:N acting as a space charge interlayer on the n ++-Si is proposed to explain the emission at low electric fields. © 1996 American Institute of Physics.
Roy SS, McCann R, Papakonstantinou P, McLaughlin JA, Kirkman IW, Bhattacharyya S, Silva SRP (2006) Near edge x-ray absorption fine structure study of aligned pi-bonded carbon structures in nitrogenated ta-C films, JOURNAL OF APPLIED PHYSICS 99 (4) ARTN 043511 AMER INST PHYSICS
Mollah S, Henley SJ, Giusca CE, Silva SRP (2010) Photo-Chemical Synthesis of Iron Oxide Nanowires Induced by Pulsed Laser Ablation of Iron Powder in Liquid Media, INTEGRATED FERROELECTRICS 119 pp. 45-54 TAYLOR & FRANCIS LTD
Tsang WM, Stolojan V, Sealy BJ, Wong SP, Silva SRP (2007) Electron field emission properties of co quantum dots in SiO2 matrix synthesised by ion implantation, IVNC and IFES 2006 - Technical Digest - l9th International Vacuum Nanoelectronics Conference and 50th International Field Emission Symposium pp. 47-48
SILVA SRP, AMARATUNGA GAJ, MILNE WI (1995) The microstructure of plasma deposited diamond-like carbon thin films, ELECTRONIC, OPTOELECTRONIC AND MAGNETIC THIN FILMS 1 pp. 495-498 RESEARCH STUDIES PRESS
Cox DC, Forrest RD, Smith PR, Silva SRP (2004) Thermionic emission from defective carbon nanotubes, APPLIED PHYSICS LETTERS 85 (11) pp. 2065-2067 AMER INST PHYSICS
Amaratunga GAJ, Silva SRP (1996) Field emission from a-C:H and a-C:H:N, JOURNAL OF NON-CRYSTALLINE SOLIDS 198 pp. 611-614 ELSEVIER SCIENCE BV
Tsang WM, Stolojan V, Wong SP, Sealy BJ, Silva SRP (2005) The electron field emission properties of ion beam synthesised metal-dielectric nanocomposite layers on silicon substrates, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 124 pp. 453-457 ELSEVIER SCIENCE SA
Carey JD, Silva SRP (2001) Conditioning of hydrogenated amorphous carbon thin films for field emission via current stressing, Applied Physics Letters 78 pp. 347-349 http://apl.aip.org/resource/1/applab/v78/i3/p347_s1
The effects of electrical current stressing on the field emission characteristics of hydrogenated amorphous carbon (a-C:H) thin films are reported. In these a-C:H films an initial conditioning treatment of the film is often required before the onset of stable emission and only after several voltage cycles do the values of the threshold field tend to converge. By stressing of the film by applying a pre-determined current through the film, the initial conditioning treatment can be removed and stable and reproducible emission observed. Retesting of the current stressed films shows that the films remain fully conditioned provided a sufficiently high stress current was initially used.
Guo X, Silva SRP (2006) Capacitive compensation to suppress sample-and-hold non-idealities in switched-current AMOLED pixel circuits, IDW '06: PROCEEDINGS OF THE 13TH INTERNATIONAL DISPLAY WORKSHOPS, VOLS 1-3 pp. 829-832 INST IMAGE INFORMATION & TELEVISION ENGINEERS
Mendoza E, Henley SJ, Poa CHP, Chen GY, Giusca CE, Adikaari AADT, Carey JD, Silva SRP (2005) Large area growth of carbon nanotube arrays for sensing platforms, SENSORS AND ACTUATORS B-CHEMICAL 109 (1) pp. 75-80 ELSEVIER SCIENCE SA
Saaverda MS, Sims GD, McCartney LN, Stolojan V, Anguita JV, Tan YY, Ogin SL, Smith PA, Silva SRP (2012) Catalysing the production of multiple arm carbon octupi nanostructures, Carbon 50 (6) pp. 2141-2146 Elsevier
Octopus-like carbon nanofibres with leg diameters as small as 9 nm are reported, with a high yield over large areas, using a unique photo-thermal chemical vapour deposition system. The branched nature of these nanostructures leads to geometries ideal for increasing the surface area of contacts for many electronic and electrochemical devices. The manufacture of these structures involves a combination of a polyacrylonitrile/polysiloxane film covering the surface of cupronickel catalysts, supported on silicon. Acetylene is used as the carbon feedstock. High-resolution electron microscopy revealed a relationship between the geometry of the nanoparticles and the catalytic growth process, which can be tuned to maximise geometries (and therefore the surface area) and was obtained with a catalyst size of 125 nm. The technique proposed for growing these carbon octopi nanostructures is ideal to facilitate a new in situ transfer film process to place high-density carbon structures on secondary surfaces to produce high capacitance all-carbon contacts.
Rusli, Amaratunga GAJ, Silva SRP (1996) Highly luminescent hydrogenated amorphous carbon (a-C:H) thin films, OPTICAL MATERIALS 6 (1-2) pp. 93-98 ELSEVIER SCIENCE BV
Shiozawa H, Pichler T, Kramberger C, Ruemmeli M, Batchelor D, Liu Z, Suenaga K, Kataura H, Silva SRP (2009) Screening the Missing Electron: Nanochemistry in Action, PHYSICAL REVIEW LETTERS 102 (4) ARTN 046804 AMER PHYSICAL SOC
Thirimanne HM, Jayawardena KDGI, Anguita JV, Stolojan V, Mills CA, Silva SRP (2016) Charge Funneling through Metal Electrode Structuring for High-Efficiency Gains in Polymer Solar Cells, ADVANCED ELECTRONIC MATERIALS 2 (9) ARTN 1600049 WILEY-BLACKWELL
Adikaari AADT, Briscoe J, Dunn S, Carey JD, Silva SRP (2011) Effect of transparent electrode on the performance of bulk heterojunction solar cells, 1270 MRS
We present a performance comparison of polythiophene/fullerene derivative bulk heterojunction solar cells fabricated on fluorinated tin oxide (FTO) and indium tin oxide (ITO) in the presence and absence of the commonly used poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hole extraction layer. From a potential commercial perspective the performance of cheaper and more readily available FTO compares well with the more expensive ITO in terms of measured device efficiency (FTO:2.8 % and ITO:3.1%). The devices show similar fill factors (FTO:63% and ITO:64%) with the same open circuit voltage of 0.6 V. The short circuit current density is lower for FTO devices at 7.5 mA/cm2 which compares with 8.0 mA/cm2 for ITO; a behaviour that is mainly attributed to the reduced optical transmission of the FTO layer. Importantly, these devices were part fabricated and wholly characterized under atmospheric conditions. The quoted device performance is the best reported for FTO based bulk heterojunction systems in the absence of the highly acidic PEDOT:PSS hole extraction layer, which is believed to degrade conductive oxides.
Smith RC, Carey JD, Forrest RD, Silva SRP (2005) Effect of aspect ratio and anode location on the field emission properties of a single tip based emitter, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 23 (2) pp. 632-635 A V S AMER INST PHYSICS
Heister E, Neves V, Lamprecht C, Silva SRP, Coley HM, McFadden J (2012) Drug loading, dispersion stability, and therapeutic efficacy in targeted drug delivery with carbon nanotubes, Carbon 50 (2) pp. 622-632 Elsevier
We have designed a drug delivery system for the anti-cancer drugs doxorubicin and mitoxantrone based on carbon nanotubes, which is stable under biological conditions, allows for sustained release, and promotes selectivity through an active targeting scheme. Carbon nanotubes are particularly promising for this area of application due to their high surface area, allowing for high drug loading, and their unique interaction with cellular membranes. We have taken a systematic approach to PEG conjugation in order to create a formulation of stable and therapeutically effective CNTs. The presented drug delivery system may be a means of improving cancer treatment modalities by reducing drug-related side effects.
DAVIS CA, SILVA SRP, DUNINBORKOWSKI RE, AMARATUNGA GAJ, KNOWLES KM, STOBBS WM (1995) DIRECT OBSERVATION OF COMPOSITIONALLY HOMOGENEOUS A-C-H BAND-GAP-MODULATED SUPERLATTICES, PHYSICAL REVIEW LETTERS 75 (23) pp. 4258-4261 AMERICAN PHYSICAL SOC
Watts PCP, Lyth SM, Mendoza E, Silva SRP (2006) Polymer supported carbon nanotube arrays for field emission and sensor devices, APPLIED PHYSICS LETTERS 89 (10) ARTN 103113 AMER INST PHYSICS
Guo X, Silva SRP, Ishii T (2008) Current percolation in ultrathin channel nanocrystalline silicon transistors, APPLIED PHYSICS LETTERS 93 (4) ARTN 042105 AMER INST PHYSICS
Giusca CE, Stolojan V, Sloan J, Shiozawa H, Silva SRP (2010) GeTe-filled carbon nanotubes for data storage applications, MRS Proceedings 1251 pp. 19-24 Cambridge University Press
By virtue of their unique electronic properties, nanometer-diameter sized single-walled carbon nanotubes represent ideal candidates to function as active parts of nanoelectronic memory storage devices. We show for the first time that GeTe, a phase change material, currently considered to be one of the most promising materials for data-storage applications, can efficiently be encapsulated within single-walled carbon nanontubes of 1.4 nm diameter. Structural investigations on the encapsulated GeTe nanowires have been carried out by high resolution transmission electron microscopy. The electronic interactions between the filling material and the host nanotube have been examined using ultraviolet photoelectron spectroscopy experiments and show that the electronic structure of the encapsulating nanotube and that of the encased filling are not perturbed by the presence of each of the other component.
The newly formed hybrids offer potential to operate as active elements in non-volatile electronic memory storage devices.
Burden AP, Forrest R, Silva SRP, Sealy BJ, Amaratunga GAJ (1998) Field emission study of the critical parameters of amorphous carbon films deposited ion a variety of carbonaceous substrates, COVALENTLY BONDED DISORDERED THIN-FILM MATERIALS 498 pp. 221-226 MATERIALS RESEARCH SOCIETY
Khan RUA, Silva SRP (2001) Switching phenomena in boron-implanted amorphous carbon films, DIAMOND AND RELATED MATERIALS 10 (3-7) pp. 1036-1039 ELSEVIER SCIENCE SA
Stolojan V, Silva SRP, Goringe MJ, Whitby RLD, Hsu WK, Walton DRM, Kroto HW (2005) Dielectric properties of WS2-coated multiwalled carbon nanotubes studied by energy-loss spectroscopic profiling, APPLIED PHYSICS LETTERS 86 (6) ARTN 063112 AMER INST PHYSICS
Sporea RA, Guo X, Shannon JM, Silva SRP (2009) Effects of process variations on the current in Schottky Barrier Source-Gated Transistors, Proceedings of the International Semiconductor Conference (CAS) 2 pp. 413-416 IEEE
The sensitivity of the drain current in Schottky barrier source-gated transistors to process variation is studied using computer simulations. It is shown that provided the device is designed correctly, the current is independent of source-drain separation and is insensitive to source length variations. However, uniform insulator thickness and precise control of the source barrier is needed if good current uniformity is to be obtained.
Shang N, Chen GY, Tan YY, Stolojan V, Papakonstantinou P, Silva SRP (2010) Direct catalytic growth of high-density carbon nanotubes on nanoclusters at low temperatures, Proceedings - 2010 8th International Vacuum Electron Sources Conference and Nanocarbon, IVESC 2010 and NANOcarbon 2010
Carbon nanotubes (CNTs) have received extensive attention due to their one-dimensional structure and ability to demonstrate many novel physical and chemical phenomena in the quantum scale. However, the application of CNTs in electronics is hindered due to their higher growth temperatures which are usually in excess of 500 °C, which is not compatible with current semiconductor technology in industry. Low temperature growth is necessary for integrating CNTs into standard semiconductor devices such as CMOS and large-scale integrated circuits. © 2010 IEEE.
Bhattacharyya S, Henley SJ, Blanchard NP, Silva SRP (2007) Novel semiconducting phase of amorphous carbon nickel composite films, Amorphous and Polycrystalline Thin-Film Silicon Science and Technology 2006 910 pp. 285-290 MATERIALS RESEARCH SOCIETY
Han S, Fei Z, Jayawardena KDGI, Beliatis MJ, Hahn YB, Adikaari AADT, Heeney MJ, Silva SRP (2015) ZnO hybrid photovoltaics with variable side-chain lengths of thienothiophene polymer, Thin Solid Films 576 pp. 38-41
© 2014 Elsevier B.V. All rights reserved.The effect of the side-chain length of poly(3,6-dialkylthieno[3,2-b]thiophene-co-bithiophene) (pATBT) on the performance of hybrid polymer-metal oxide photovoltaics (PVs) utilizing zinc oxide (ZnO) acceptor is investigated. The pATBT attached with a dodecyl side chain (pATBT-C12) in hybrid photovoltaics with ZnO was compared to pATBT with a hexadecyl side chain (pATBT-C16). Atomic force microscopic analysis reveals a smoother surface for the pATBT-C16 photoactive layer compared to the pATBT-C12. For hybrid PVs using pATBT-C16, the relative intensity of the external quantum efficiency (EQE) increased particularly in wavelength region associated with the ZnO. Furthermore, the EQE spectrum shows a red shift for pATBT-C16 indicating better structural ordering compared to hybrid PVs with pATBT-C12. As a result, the hybrid PV utilizing pATBT-C16:ZnO blend layer is observed to display a better performance with a power conversion efficiency of 1.02% compared to 0.672% of pATBT-C12:ZnO PV.
Carey JD, Poa CH, Forrest RD, Burden AP, Silva SRP (2000) Modification of electron field emission properties from surface treated amorphous carbon thin films, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 18 (2) pp. 1051-1053 AMER INST PHYSICS
Gomez-Rojas L, Bhattacharyya S, Mendoza E, Cox DC, Rosolen JM, Silva SRP (2007) RF response of single-walled carbon nanotubes, NANO LETTERS 7 (9) pp. 2672-2675 AMER CHEMICAL SOC
Hurley RE, Gamble HS, Jin M-H, Armstrong BM, Ghita M, McCullough RW, Adikaari AADT, Henley SJ, Silva SRP (2007) Laser annealing of sputtered silicon for wafer-bonding applications, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS 9 (1) pp. 121-126 NATL INST OPTOELECTRONICS
Beliatis MJ, Gandhi KK, Rozanski LJ, Rhodes R, McCafferty L, Alenezi MR, Alshammari AS, Mills CA, Jayawardena KD, Henley SJ, Silva SR (2014) Hybrid graphene-metal oxide solution processed electron transport layers for large area high-performance organic photovoltaics., Adv Mater 26 (13) pp. 2078-2083
Solution processed core-shell nano-structures of metal oxide-reduced graphene oxide (RGO) are used as improved electron transport layers (ETL), leading to an enhancement in photocurrent charge transport in PCDTBT:PC70 BM for both single cell and module photovoltaic devices. As a result, the power conversion efficiency for the devices with RGO-metal oxides for ETL increases 8% in single cells and 20% in module devices.
Shi S, Sadhu V, Moubah R, Schmerber G, Bao Q, Silva SRP (2013) Solution-processable graphene oxide as an efficient hole injection layer for high luminance organic light-emitting diodes, JOURNAL OF MATERIALS CHEMISTRY C 1 (9) pp. 1708-1712 ROYAL SOC CHEMISTRY
Carey D, Smith R, Silva R, Murphy R, Blau W, Coleman J (2007) Transport and field emission in carbon nanotube - Polymer composite cathodes, Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07 pp. 187-188
Jeynes JCG, Mendoza E, Chow DCS, Watts PCP, McFadden J, Silva SRP (2006) Generation of chemically unmodified pure single-walled carbon nanotubes by solubilizing with RNA and treatment with ribonuclease A, Advanced Materials 18 (12) pp. 1598-1602
A simple, two-step method for using RNA to purify carbon nanotubes (CNT) without the use of a time-intensive process or harsh chemical or physical treatments was illustrated. The purity of RNA-purified CNTs by a variety of physical methods was demonstrated and the treatment of the RNA-wrapped CNTs with the enzyme ribonuclease (RNase) was shown to be very effective in removing the RNA allowing subsequent recovery of pure CNTs. The importance of using RNA over DNA oligonucleotides in this process is that RNA is a very liable molecule and is easily digested by RNase A, one of the most robust enzymes in biology. CNTs were treated with a variety of solublizing agents including total cellular RNA (tcRNA). RNA-wrapped CNTs were treated with the enzyme RNase A to remove the RNA and thereby precipitate the CNTs. The atomic force microscopy (AFM) images show the existence of tcRNA-CNTs and RNase treated CNTs deposited on mica.
Burden AP, Mendoza E, Silva SRP, Amaratunga GAJ (1998) The stability of nitrogen-containing amorphous carbon films after annealing at moderate temperatures, DIAMOND AND RELATED MATERIALS 7 (2-5) pp. 495-498 ELSEVIER SCIENCE SA
Sporea RA, Trainor MJ, Young ND, Shannon JM, Silva SRP (2010) Intrinsic Gain in Self-Aligned Polysilicon Source-Gated Transistors, IEEE TRANSACTIONS ON ELECTRON DEVICES 57 (10) pp. 2434-2439 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Nismy NA, Adikaari AADT, Silva SRP (2010) Enhanced performance from acid functionalized multiwall carbon nanotubes in the active layer of organic bulk heterojunction solar cells, Materials Research Society Symposium Proceedings 1270 pp. 61-66
Solution-processable organic bulk-heterojunction photovoltaic devices have made great advances over the past decade. The concept, ultrafast photo induced electron transfer from a conjugated polymer to fullerene derivative molecules in bulk-heterojunction systems, leads to device efficiencies as high as 6%. Light absorption, charge separation and charge transport to electrodes are the most important steps in organic photovoltaic devices. The enhanced light absorption through thicker active layers results in more exciton creation, however, leads to increased recombination due to the relatively short exciton diffusion length. We fabricated poly(3-hexylthiophene)/ [6,6]-phenyl C61 butyric acid methyl ester bulk-heterojunction devices with multiwall carbon nanotubes in the active layer in a bid to address this deficiency. Functionalization of carbon nanotubes allows better dispersion in aromatic solvents, 1,2-dichlorobenzene in this study, and pristine multiwall nanotubes result in poorer dispersions. Organic photovoltaic devices fabricated with pristine multiwall carbon nanotubes in the active layer result in power conversion efficiencies -1.4%, which show localized nanotube-rich areas in the active layer. Alternatively, acid functionalized nanotubes in the active layer results in efficiencies as high as 2.2 % with no distinct nanotube-rich sectors. The open circuit voltages of the devices show a dependency on the loading of nanotubes in the active layer. Further, the shunt resistances of the devices with carbon nanotubes decrease, which needs careful selection of the tubes depending on active layer thickness. This work compares the device performances in detail and identifies further improvements to conjugated polymer/fullerene derivative/multiwall carbon nanotubes hybrid photovoltaic systems. © 2010 Materials Research Society.
Khan RUA, Silva SRP (2001) A review of the effects of carbon self-implantation into amorphous carbon, DIAMOND AND RELATED MATERIALS 10 (2) pp. 224-229 ELSEVIER SCIENCE SA
Jeynes JCG, Mendoza E, Chow D, McFadden J, Silva SRP (2005) DNA/RNA purified single walled carbon nanotubes on self-assembled networks, 2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005 Technical Proceedings pp. 250-253
Single walled carbon nanotubes (SWCNT) have attracted a great interest due their extraordinary properties that envisage their use for a wide range of applications [reference physical properties]. However, these properties are controlled by the chirality of the SWC-NTs. Unfortunately, the growth processes available to-date produce SWCNTs with different chiralities. Also, the SWCNTs are produced together with a relatively high quantities of impurities such as amorphous carbon and metallic catalyst particles. Indeed, the purification and manipulation remains problematic, hindering some of the possible applications of these materials. In this paper, the purification of SWCNTs with biological polymers is presented. The results shown that DNA and UNA effectively purify SWCNT from the "soot" obtained during the growth process. The results show how effectively total genomic UNA (tgRNA) purifies SWCNT. Atomic force microscopy (AFM) studies reveal how nucleic acids wrap around SWCNTs forming RNA-CNT composites. Moreover, when a RNA-CNT solution is dried on a hydrophilic surface, SWCNTs are found lying or embedded on a self assembled two dimensional UNA network. Using tgRNA is not only a cheap and effective method of solubilising and purifying CNTs but offers a first step towards the self-assembly of CNTs from solution. Furthermore, tgRNA networks could be a convenient method of electrically linking individual RNA functionalised CNTs over a surface which could prove useful for RNA or DNA biosensors.
Hayashi Y, Fujita T, Tokunaga T, Kaneko K, Butler T, Rupesinghe N, Carey JD, Silva SRP, Amaratunga GAJ (2007) Encapsluation of Co and Pd multi-metal nanowires inside multiwalled carbon nanotubes by microwave plasma chemical vapor deposition, DIAMOND AND RELATED MATERIALS 16 (4-7) pp. 1200-1203 ELSEVIER SCIENCE SA
Han S, Adikaari AADT, Jayawardena KDGI, Nismy NA, Silva SRP (2012) Control of nanocrystal surface defects for efficient charge extraction in polymer-ZnO photovoltaic systems, Journal of Applied Physics 112 (6) AIP
Factors determining the photovoltaic device performance of blends of regioregular poly(3-hexylthiophene) (rr-P3HT) and ZnO nanostructures are reported. A decrease in the crystallinity of rr-P3HT upon the formation of ZnO (through hydrolysis) is observed through optical absorption spectroscopy. Increasing the humidity level for the ZnO formation leads to a decrease in the photoluminescence of the rr-P3HT:ZnO blend together with improved photovoltaic device performance. This is attributed to more efficient charge extraction due to a decrease in the radiative trap sites on the ZnO surface as a result of decreasing ZnO surface area with increasing humidity level. © 2012 American Institute of Physics.
Prabhath MRR, Curry RJ, Silva SRP, Jarowski PD (2014) Role of metallophilic interactions in "turning on" substituent effects and emission tunability of novel bis-4-(2-pyridyl)-1,2,3-triazolatoplatinum(II) complexes, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 248 AMER CHEMICAL SOC
Orwa JO, Silva SRP, Shannon JM (2005) Forming in hydrogenated amorphous silicon metal-semiconductor-metal devices using bipolar pulse stressing, ELECTRONICS LETTERS 41 (2) pp. 98-100 IEE-INST ELEC ENG
Schwan J, Batori V, Ulrich S, Ehrhardt H, Silva SRP (1998) Nitrogen doping of amorphous carbon thin films, JOURNAL OF APPLIED PHYSICS 84 (4) pp. 2071-2081 AMER INST PHYSICS
Guo X, Silva SRP (2006) A macro-modeling approach to integrate carbon nanotube field emission triode devices into circuit Simulations, IDW '06: PROCEEDINGS OF THE 13TH INTERNATIONAL DISPLAY WORKSHOPS, VOLS 1-3 pp. 1871-1874 INST IMAGE INFORMATION & TELEVISION ENGINEERS
Pharr GM, Callahan DL, McAdams SD, Tsui TY, Anders S, Anders A, Ager JW, Brown IG, Bhatia CS, Silva SRP, Robertson J (1996) Hardness, elastic modulus, and structure of very hard carbon films produced by cathodic-arc deposition with substrate pulse biasing, APPLIED PHYSICS LETTERS 68 (6) pp. 779-781 AMER INST PHYSICS
Konchits AA, Valakh MY, Shanina BD, Kolesnik SP, Yanchuk IB, Carey JD, Silva SRP (2003) Effects of ion implantation on electron centers in hydrogenated amorphous carbon films, JOURNAL OF APPLIED PHYSICS 93 (10) pp. 5905-5910 AMER INST PHYSICS
Barradas NP, Almeida SA, Jeynes C, Knights AP, Silva SRP, Sealy BJ (1999) RBS and ERDA study of ion beam synthesised amorphous gallium nitride, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 148 (1-4) pp. 463-467 ELSEVIER SCIENCE BV
Lyth SM, Silva SRP (2007) A study of field emission from glass spheres, coated with carbon nanotubes, EIGHTH IEEE INTERNATIONAL VACUUM ELECTRONICS CONFERENCE pp. 327-328 IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP
Zeze DA, Forrest RD, Carey JD, Cox DC, Robertson ID, Weiss BL, Silva SRP (2002) Reactive ion etching of quartz and Pyrex for microelectronic applications, JOURNAL OF APPLIED PHYSICS 92 (7) pp. 3624-3629 AMER INST PHYSICS
Tsang WM, Stolojan V, Giusca C, Poa CHP, Sealy B, Silva SRP, Wong SP (2005) The electron field emission properties of Ag-SiO2 nanocomposite layers, Technical Digest of the 18th International Vacuum Nanoelectronics Conference, IVNC 2005 2005 pp. 206-207
W. T. Young, S. R. P. silva, Anguita JV, shannon J, k. p. homewood, b. j. sealy (2000) Low temperature growth of gallium nitride, Diamond and Related Materials
W.T. Young, S.R.P. Silva, J.V. Anguita, J.M. Shannon, K.P. Homewood, B.J. Sealy
Stolojan V, Tsang W, Silva SRP (2008) The Dielectric Properties of Co-Implanted SiO(2) Investigated Using Spatially-Resolved EELS, MICROSCOPY OF SEMICONDUCTING MATERIALS 2007 120 pp. 341-344 SPRINGER-VERLAG BERLIN
Khan RUA, Carey JD, Silva SRP, Jones BJ, Barklie RC (2001) Electron delocalization in amorphous carbon by ion implantation, PHYSICAL REVIEW B 63 (12) ARTN 121201 AMER PHYSICAL SOC
Alenezi MR, Alzanki TH, Almeshal AM, Alshammari AS, Beliatis MJ, Henley SJ, Silva SRP (2015) A model for the impact of the nanostructure size on its gas sensing properties, RSC ADVANCES 5 (125) pp. 103195-103202 ROYAL SOC CHEMISTRY
Jayawardena KDGI, Rozanski LJ, Mills CA, Silva SRP (2015) The true status of solar cell technology, Nature Photonics 9 (4) pp. 207-208
Giusca CE, Silva SRP (2010) Influence of Structural Defects on the Electronic Properties of Carbon Nanotubes Examined by Scanning Tunnelling Microscopy, Semiconductor Nanowires - Growth, Physics, Devices, and Applications Volume 1258, 1258-R05-21
Palumbo M, Lutz T, Giusca CE, Shiozawa H, Stolojan V, Cox DC, Wilson RM, Henley SJ, Silva SRP (2009) From Stems (and Stars) to Roses: Shape-Controlled Synthesis of Zinc Oxide Crystals, CRYSTAL GROWTH & DESIGN 9 (8) pp. 3432-3437 AMER CHEMICAL SOC
Jayawardena KDGI, Fryar J, Ravi S, Silva P, Henley SJ (2010) Morphology Control of Zinc Oxide Nanocrystals via Hybrid Laser/Hydrothermal Synthesis, JOURNAL OF PHYSICAL CHEMISTRY C 114 (30) pp. 12931-12937 AMER CHEMICAL SOC
Zeze DA, Carey JD, Stolojan V, Weiss BL, Silva SRP (2006) Damage effects in Pyrex by CF4 reactive ion etching in dual RF-microwave plasmas, MICRO & NANO LETTERS 1 (2) pp. 103-107 INST ENGINEERING TECHNOLOGY-IET
Kerr GL, Smith PR, Carey JD, Silva SRP (2008) In-situ electrical characterisation of suspended multiwalled carbon nanotubes, EMAG: ELECTRON MICROSCOPY AND ANALYSIS GROUP CONFERENCE 2007 126 IOP PUBLISHING LTD
Rummeli MH, Borowiak-Palen E, Gemming T, Pichler T, Knupfer M, Kalbac M, Dunsch L, Jost O, Silva SRP, Pompe W, Buchner B (2005) Novel catalysts, room temperature, and the importance of oxygen for the synthesis of single-walled carbon nanotubes, NANO LETTERS 5 (7) pp. 1209-1215 AMER CHEMICAL SOC
Tsang WM, Adikaari AADT, Stolojan V, Silva SRP (2008) Improving the electron emission properties of ion-beam-synthesized Ag-SiO2 nanocomposites by pulsed laser annealing, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 26 (2) pp. 860-863 A V S AMER INST PHYSICS
Poa CH, Lacerda RG, Cox DC, Silva SRP, Marques FC (2002) Stress-induced electron emission from nanocomposite amorphous carbon thin films, APPLIED PHYSICS LETTERS 81 (5) pp. 853-855 AMER INST PHYSICS
Silva SRP High efficiency air stable organic photovoltaics with an aqueous inorganic contact, University of Surrey
Imalka Jayawardena K, Li S, Sam L, Smith C, Beliatis M, Gandhi K, Ranga Prabhath M, Pozegic T, Chen S, Xu X, Dabera D, Rozanski L, Sporea R, Mills C, Guo X, Silva S (2015) High efficiency air stable organic photovoltaics with an aqueous inorganic contact, Nanoscale (34) pp. 14241-14247 The Royal Society of Chemistry
We report a ZnO interfacial layer based on an environmentally friendly aqueous precursor for organic photovoltaics. Inverted PCDTBT devices based on this precursor show power conversion efficiencies of 6.8?7%. Unencapsulated devices stored in air display prolonged lifetimes extending over 200 hours with less than 20% drop in efficiency compared to devices based on the standard architecture.
Poa CH, Silva SRP, Watts PCP, Hsu WK, Kroto HW, Walton DRM (2002) Field emission from nonaligned carbon nanotubes embedded in a polystyrene matrix, APPLIED PHYSICS LETTERS 80 (17) pp. 3189-3191 AMER INST PHYSICS
Khan RUA, Burden AP, Silva SRP, Shannon JM, Sealy BJ (1999) A study of the effects of nitrogen incorporation and annealing on the properties of hydrogenated amorphous carbon films, CARBON 37 (5) pp. 777-780 PERGAMON-ELSEVIER SCIENCE LTD
Sporea RA, Shannon JM, Silva SRP, Trainor MJ, Young ND (2010) Performance trade-offs in polysilicon source-gated transistors, 2010 Proceedings of the European Solid State Device Research Conference, ESSDERC 2010 pp. 222-225
Self-aligned Schottky-source source-gated transistors (SGTs) have been made in polysilicon. The structures enable a direct comparison to be made between a SGT and a standard thin-film field-effect transistor (FET) on the same device. SGTs having excellent characteristics have been fabricated, with intrinsic gains approaching 10,000. The effects of bulk doping in the polysilicon and of the source barrier modification implant are considered in the context of the electrical output characteristics. It is shown that the choice of source length is a tradeoff between device speed and current uniformity. ©2010 IEEE.
Rozanski L, Smith C, Gandhi K, Beliatis M, Dabera G, Jayawardena K, Adikaari A, Kearney M, Silva S (2014) A critical look at organic photovoltaic fabrication methodology: Defining performance enhancement parameters relative to active area, SOLAR ENERGY MATERIALS AND SOLAR CELLS 130 pp. 513-520 ELSEVIER SCIENCE BV
With the ever-increasing focus on obtaining higher device power conversion efficiencies (PCEs) for organic photovoltaics (OPV), there is a need to ensure samples are measured accurately. Reproducible results are required to compare data across different research institutions and countries and translate these improvements to real-world production. In order to report accurate results, and additionally find the best-practice methodology for obtaining and reporting these, we show that careful analysis of large data sets can identify the best fabrication methodology. We demonstrate which OPV outputs are most affected by different fabrication or measurement methods, and identify that masking effects can result in artificially-boosted PCEs by increasing fill factor and current densities, requiring care when selecting which mask to use. For example, our best performing devices (>6% efficiency) show that the smallest mask areas have not produced a surfeit of the highest performers, with only 11% of the top performing devices measured using a 0.032 cm2 mask area, while 44% used the largest mask (0.64 cm2). This trend holds true for efficiencies going down to 5%, showing that effective fabrication conditions are reproducible with increasing mask areas, and can be translated to even larger device areas. Finally, we emphasise the necessity for reporting the best PCE along with the average value in order to implement changes in real-world production. © 2014 Elsevier B.V.
Bhattacharyya S, Silva SRP (2005) Transport properties of low-dimensional amorphous carbon films, THIN SOLID FILMS 482 (1-2) pp. 94-98 ELSEVIER SCIENCE SA
Adikaari AADT, Dissanayake DMNM, Mudugamuwa NK, Silva SRP (2009) Nano Engineered Organic-Inorganic Material Systems for Photovoltaics, NANOMATERIALS AND DEVICES: PROCESSING AND APPLICATIONS 67 pp. 1-6 TRANS TECH PUBLICATIONS LTD
Mohammad M, Khan MB, Khan ZM, Cavalli G, Adhikari D, Silva R (2011) Horizontal patterns of single wall carbon nanotubes by simple filtration method, Advanced Materials Research 326 pp. 121-126 Trans Tech Publications
This work demonstrates the horizontal patterning/alignment of single wall nano tubes (SWNTs) using simple filtration method. In the quest of vertical alignment of SWNTs to fabricate the vertically aligned CNT-membrane, this horizontal patterns as observed by simple filtration technique has been achieved. These horizontal patterns are key arrangements sought in the electronic field and fabrication of CNT-nano composites of required characteristics. In this work SWNTs purified/oxidized treatment with nitric acid at 120-122oC. Oxidized SWNTs further reacted with Octadecyl amine at same temperature to make them significantly dispersible/soluble in solvents especially in Tetrahydrofuran (THF). These modified SWNTs dissolved in THF by sonication and uniform black color solution was obtained that did not settle upon prolonged time of standing. This solution is subsequently filtered through 0.2 micro porous PTFE filter using long neck sintered funnel for horizontal alignment. The inter tube gap between CNTs is initially filled by the precursor reactive vapor stream that is consolidated as a solid polymer through insitu polymerization. Transform Infrared (FTIR) analysis was performed to find the attached functional groups. Alignment of functionalized SWNTs collected on PTFE filter was analyzed by Field-emission scanning electron microscopy (FE-SEM). Ordered horizontal patterns were observed. The contemporary horizontal alignment techniques being used are tedious and need very special facilities. The current method is comparatively quite simple and large quantities of CNTs can be aligned to advantage.
Silva SRP, Almeida SA, Sealy BJ (1999) Thin amorphous gallium nitride films formed by ion beam synthesis, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 147 (1-4) pp. 388-392 ELSEVIER SCIENCE BV
Rümmeli M, Jost O, Gemming T, Knupfer M, Borowiak-Palen E, Pichler T, Silva SRP, Büchner B (2005) Metal oxides and low temperature SWCNT synthesis via laser evaporation, AIP Conference Proceedings 786 pp. 77-80
Studies using metal oxides show they are active as catalysts for single wall carbon nanotubes synthesis in laser ablation, even at room temperature. In addition when combined with Ni and Co, large diameter SWCNT can be synthesized at temperatures below those required when only using Ni and Co as a binary catalyst. The results suggest a nucleation mechanism previously not identified. © 2005 American Institute of Physics.
Mendoza E, Borowiak-Palen E, Sharpe K, De Silva SGM, Mureau N, Henley SH, Silva SRP (2005) Multiwalled Carbon Nanotubes as platforms for the design of Biosensors, 2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005 Technical Proceedings pp. 426-429
Carbon Nanotubes (CNT) have attracted a huge interest in the research community due to their unique properties: good electrical conductivity, excellent mechanical properties and chemical stability. An interesting phenomena is the fact that CNT change their electrical properties depending on the absorbates on the surface. This is being exploited for the use of CNT as sensor platforms. In this work, the growth and chemical functionalisation of aligned CNT arrays for the development of electrochemical sensors is presented. The CNT growth process and surface has been tailored to maximise the interaction of the CNTs with the electrolyte. The possible use of the active bio-nano-sensors for mobile monitoring will be discussed in the context of a remote wireless sensors suitable to be integrated for long term patient monitoring, as well as long-haul driver/pilot situations.
Sanz V, Tilmacîu C, Soula B, Flahaut E, Coley HM, Silva SRP, McFadden J (2011) Chloroquine-enhanced gene delivery mediated by carbon nanotubes, Carbon 49 (15) pp. 5348-5358 Elsevier
Polyethyleneimine-coated double-walled carbon nanotubes (DWCNTs) were used for dual gene and drug delivery, after loading the DWCNTs with the drug chloroquine, a lysosomotropic compound that is able to promote escape from the lysosomal compartment. Different forms of functionalization of the DWCNTs were examined in order to optimize this system. They included the testing of different treatments on DWCNTs to optimize the loading and delivery of chloroquine and the selection of a cationic polymer for coating the DWCNTs for optimum DNA binding and delivery. An acid oxidation treatment of DWCNTs was selected for optimum chloroquine loading together with polyethyleneimine as optimum cationic coating agent for plasmid DNA binding. Optimization of the conditions for choroquine-enhanced gene delivery were developed using luciferase expression as a model system. We have demonstrated that chloroquine-loading increases the ability of polyethyleneimine-coated DWCNTs to deliver functional nucleic acid to human cells. Cell viability tests have shown no cytotoxicity of the functionalized DWCNTs at the concentrations needed for optimum gene delivery. These results support the potential applications of this methodology in gene therapy.
Tan LW, Hatton RA, Latini G, Shannon JM, Silva SRP (2008) Modification of charge transport in triphenyldiamine films induced by acid oxidized single-walled carbon nanotube interlayers, NANOTECHNOLOGY 19 (48) ARTN 485706 IOP PUBLISHING LTD
Tsang WM, Stolojan V, Wong S, Linder JKN, Sealy BJ, Silva SRR (2007) The structural and electron field emission properties of ion-beam-synthesised metallic-dielectric nanocomposites, REVIEWS ON ADVANCED MATERIALS SCIENCE 15 (3) pp. 179-184 INST PROBLEMS MECHANICAL ENGINEERING-RUSSIAN ACAD SCIENCES
Cheah LK, Shi X, Shi JR, Liu EJ, Silva SRP (1998) Properties of nitrogen doped tetrahedral amorphous carbon films prepared by filtered cathodic vacuum are technique, JOURNAL OF NON-CRYSTALLINE SOLIDS 242 (1) pp. 40-48 ELSEVIER SCIENCE BV
Zeze DA, Cox DC, Weiss BL, Silva SRP (2004) Lithography-free high aspect ratio submicron quartz columns by reactive ion etching, APPLIED PHYSICS LETTERS 84 (8) pp. 1362-1364 AMER INST PHYSICS
Jayawardena KDGI, Rozanski LJ, Mills CA, Beliatis MJ, Nismy NA, Silva SRP (2013) ?Inorganics - in - Organics?: Recent Developments and Outlook for 4G Polymer Solar Cells, Nanoscale 5 (18) pp. 8411-8427 Royal Society of Chemistry
Recent developments in solution processable single junction polymer solar cells have led to a significant improvement in power conversion efficiencies from ~5% to beyond 9%. While much of the initial efficiency improvements were driven through judicious design of donor polymers, it is the engineering of device architectures through the incorporation of inorganic nanostructures and better processing that has continued the efficiency gains. Inorganic nano-components such as carbon nanotubes, graphene and its derivatives, metal nanoparticles and metal oxides that have been central role in improving device performance and longevity beyond those achieved by conventional 3G polymer solar cells. The present work aims to summarise the diverse roles played by the nanosystems and features in state of the art next generation (4G) polymer solar cells. The challenges associated with the engineering of such devices for future deployment are also discussed.
Guo X, Silva SRP (2007) An efficient macromodeling approach for simulating carbon-nanotube field-emission triode devices in display applications, IEEE ELECTRON DEVICE LETTERS 28 (8) pp. 710-712 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Orwa JO, Shannon JM, Gateru RG, Silva SRP (2005) Effect of ion bombardment and annealing on the electrical properties of hydrogenated amorphous silicon metal-semiconductor-metal structures, JOURNAL OF APPLIED PHYSICS 97 (2) ARTN 023519 AMER INST PHYSICS
Misra SK, Ohashi F, Valappil SP, Knowles JC, Roy I, Silva SRP, Salih V, Boccaccini AR (2010) Characterization of carbon nanotube (MWCNT) containing P(3HB)/bioactive glass composites for tissue engineering applications, ACTA BIOMATERIALIA 6 (3) pp. 735-742 ELSEVIER SCI LTD
Tan YY, Tan LW, Jayawardena KDGI, Anguita JV, Carey JD, Silva SRP (2011) Field effect in chemical vapour deposited graphene incorporating a polymeric gate dielectric, Synthetic Metals 161 (21-22) pp. 2249-2252
We have investigated the room temperature long channel field effect characteristics of a single graphene layer transistor incorporating a poly-4-vinyl-phenol (PVP) organic insulating layer, as an alternative to conventional oxide gate dielectric materials. High purity copper foils were used in the chemical vapour growth of the graphene layer and visible Raman analysis confirmed the presence of a high quality mono-layer carbon film. Using a channel length of 50 ¼m, a field effect hole mobility of 37 cm2/Vs was calculated, which demonstrates the possibility of an all carbon graphene based large area transistor with carrier mobilities above those found in conventional long channel all organic electronic transistors.
Ohashi F, Chen GY, Stolojan V, Silva SRP (2008) The role of the gas species on the formation of carbon nanotubes during thermal chemical vapour deposition, NANOTECHNOLOGY 19 (44) ARTN 445605 IOP PUBLISHING LTD
Poa CHP, Lacerda RG, Cox DC, Marques FC, Silva SRP (2003) Effects of stress on electron emission from nanostructured carbon materials, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 21 (4) pp. 1710-1714 A V S AMER INST PHYSICS
Chhowalla M, Robertson J, Chen CW, Silva SRP, Davis CA, Amaratunga GAJ, Milne WI (1997) Influence of ion energy and substrate temperature on the optical and electronic properties of tetrahedral amorphous carbon (ta-C) films, JOURNAL OF APPLIED PHYSICS 81 (1) pp. 139-145 AMER INST PHYSICS
Rosolen JM, Poa CHP, Tronto S, Marchesin MS, Silva SRP (2006) Electron field emission of carbon nanotubes on carbon felt, CHEMICAL PHYSICS LETTERS 424 (1-3) pp. 151-155 ELSEVIER SCIENCE BV
Mendoza E, Rodriguez J, Li Y, Zhu YQ, Poa CHP, Henley SJ, Romano-Rodriguez A, Morante JR, Silva SRP (2007) Effect of the nanostructure and surface chemistry on the gas adsorption properties of macroscopic multiwalled carbon nanotube ropes, CARBON 45 (1) pp. 83-88 PERGAMON-ELSEVIER SCIENCE LTD
Guo X, Ishii T, Silva SRP (2007) Electrical properties and carrier transport mechanisms of nanometer-scale ultra-thin channel poly-Si transistors, ICSICT-2006: 2006 8th International Conference on Solid-State and Integrated Circuit Technology, Proceedings pp. 194-196
This paper investigates the electrical properties and the carrier transport mechanisms of nanometer-scale ultra-thin channel (d3.0nm) poly-Si transistors to be guidelines for future process on device optimization and modeling. Devices used for the study are fabricated with a precise control over the film thickness down to sub-nanometer scale. © 2006 IEEE.
Dissanayake DMNM, Lutz T, Curry RJ, Silva SRP (2008) Measurement and validation of PbS nanocrystal energy levels, APPLIED PHYSICS LETTERS 93 (4) ARTN 043501 AMER INST PHYSICS
Dissanayake DMNM, Hatton RA, Lutz T, Giusca CE, Curry RJ, Silva SRP (2007) A PbS nanocrystal-C-60 photovoltaic device for infrared light harvesting, APPLIED PHYSICS LETTERS 91 (13) ARTN 133506 AMER INST PHYSICS
Nanditha DM, Dissanayake M, Hatton RA, Curry RJ, Silva SRP (2007) Operation of a reversed pentacene-fullerene discrete heterojunction photovoltaic device 10.1063/1.2713345, APPLIED PHYSICS LETTERS 90 (11) ARTN 113505 AMER INST PHYSICS
Henley SJ, Poa CHP, Adikaari AADT, Giusca CE, Carey JD, Silva SRP (2004) Excimer laser nanostructuring of nickel thin films for the catalytic growth of carbon nanotubes, APPLIED PHYSICS LETTERS 84 (20) pp. 4035-4037 AMER INST PHYSICS
Chen GY, Poa CHP, Henley SJ, Stolojan V, Silva SRP, Haq S (2005) Deployment of titanium thermal barrier for low-temperature carbon nanotube growth, APPLIED PHYSICS LETTERS 87 (25) ARTN 253115 AMER INST PHYSICS
Tison V, Stolojan V, Watts PCP, Cox DC, Chen GY, Silva SRP (2008) Gas Sensing Properties of Vapour-Deposited Tungsten Oxide Nanostructures, MICROSCOPY OF SEMICONDUCTING MATERIALS 2007 120 pp. 281-284 SPRINGER-VERLAG BERLIN
Kerr GL, Smith PR, Carey JD, Silva SRP (2008) In-situ electrical characterisation of suspended multiwalled carbon nanotubes, Journal of Physics: Conference Series 126
Room temperature electrical transport measurements have been made on suspended multi-walled carbon nanotubes (MWNTs) using a remote controlled manipulation system within a scanning electron microscope. It is shown that the current-voltage characteristics of the MWNTs are symmetric with respect to voltage and that the conductance improves with multiple cycling of the voltage. Estimations of the semiconducting sub-bands and the contact transmission coefficients of the MWNTs have also been made. © 2008 IOP Publishing Ltd.
Miyajima Y, Nitta S, Silva SRP, Zeze DA (2005) Surface induced bulk modifications of amorphous carbon nitride films by post-deposition oxygen and hydrogen plasma treatment, THIN SOLID FILMS 491 (1-2) pp. 161-167 ELSEVIER SCIENCE SA
Burden AP, Silva SRP (1998) Fullerene and nanotube formation in cool terrestrial "dusty plasmas", APPLIED PHYSICS LETTERS 73 (21) pp. 3082-3084 AMER INST PHYSICS
Shiozawa H, Kramberger C, Ruemmeli M, Batchelor D, Kataura H, Pichler T, Silva SRP (2009) Electronic properties of single-walled carbon nanotubes encapsulating a cerium organometallic compound, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 246 (11-12) pp. 2626-2630 WILEY-V C H VERLAG GMBH
Yahya I, Bonaccorso F, Clowes SK, Ferrari AC, Silva SRP Temperature dependent separation of metallic and semiconducting carbon nanotubes using gel agarose chromatography, Elsevier
Adikaari AADT, Mudugamuwa NK, Silva SRP (2008) Nanocrystalline silicon solar cells from excimer laser crystallization of amorphous silicon, SOLAR ENERGY MATERIALS AND SOLAR CELLS 92 (6) pp. 634-638 ELSEVIER SCIENCE BV
Cronin HM, Imalka Jayawardena KDG, Stoeva Z, Shkunov M, Silva SRP (2016) Effects of Ambient Humidity on the Optimum Annealing Time of Mixed-Halide Perovskite Solar Cells, Nanotechnology
Mixed halide Perovskite solar cells are commonly produced by depositing PbCl2 and CH3NH3I from a common solvent followed by thermal annealing, which in an up-scaled manufacturing process is likely to take place under ambient conditions. However, it has been reported that, similar to the effects of thermal annealing, ambient humidity also affects the crystallisation behaviour and subsequent growth of the Perovskite films. This implies that both of these factors must be accounted for in solar cell production. In this work, we report for the first time the correlation between the annealing time, relative humidity and device performance for inverted, mixed halide CH3NH3PbI(3-x)Clx Perovskite solar cells with active area H1 cm2. We find a trade-off between ambient humidity and the required annealing time to produce efficient solar cells, with low humidities needing longer annealing times and vice-versa. At around 20% RH, device performance depends relatively weakly on annealing time, but at higher (30 - 40% RH) or lower (0 - 15 % RH) humidities it is very sensitive. Processing in humid environments is shown to lead to the growth of both larger Perovskite grains and larger voids; similar to the effect of thermal annealing, which also leads to grain growth. Therefore, samples which are annealed for too long under high humidity show loss of performance due to low open circuit voltage caused by an increased number of shunt paths. Based on these results it is clear that humidity and annealing time are closely interrelated and both are important factors affecting the performance of Perovskite solar cells. The findings of this work opens a route for reduced annealing times to be employed by control of humidity; critical in roll-to-roll manufacture where low manufacturing time is preferred for cost reductions.
Khan AA, Dabera GDMR, Butt H, Qasim MM, Amaratunga GAJ, Silva SRP, Wilkinson TD (2015) Tunable scattering from liquid crystal devices using carbon nanotubes network electrodes, Nanoscale 7 (1) pp. 330-336
© The Royal Society of Chemistry.Liquid crystals are of technological interest as they allow for optical effects which can be electrically controlled. In this paper we present an electro-optical device consisting of nematic liquid crystals addressed by an electrode structure consisting of thin films of polymer wrapped single walled carbon nanotubes (nanohybrids). Thin films of nanohybrids display excellent optical transmission and electrical conduction properties. Due to the randomly organised nanohybrids these composite films produce interesting director profile arrangements within the liquid crystal layers. As a result, enhanced scattering of laser and white light was observed from these liquid crystal cells which bend themselves as electrically controllable optical diffusers and beam shapers. This journal is
Papworth AJ, Kiely CJ, Burden AP, Silva SRP, Amaratunga GAJ (2000) Electron-energy-loss spectroscopy characterization of the sp(2) bonding fraction within carbon thin films, PHYSICAL REVIEW B 62 (19) pp. 12628-12631 AMER PHYSICAL SOC
Silva SRP, Carey JD, Forrest RD (2000) Amorphous semiconductors for cold cathodes: a route to large-area flat-panel displays, Journal of the Society for Information Display 8 (1) pp. 17-21
The field-emission-display (FED) technology examined in the early sixties used metal tips or Spindt cathodes in order to extract electron beams to excite phosphors. The tips were necessitated by the large work function the electrons needed to overcome in order to be released into the vacuum. In the early nineties it was noticed that 'flat' diamond surfaces emitted electrons at relatively low electric fields. Just as its crystalline counterparts, amorphous-carbon thin films also showed that this class of materials were also capable of electron emission at low threshold fields. By using flat emitters, technologist can remove a number of fabrication steps that otherwise would have been required to produce large-area arrays of field emitters and therefore reduce the cost of production significantly. This paper will review the progress of the use of flat amorphous semiconductors as cold cathodes. New results that appear to point towards a space-charge-controlled emission mechanism as opposed to a purely surface emission process based upon Fowler-Nordheim tunneling will be introduced, which have implications on the type of device structure that will ultimately be needed for electron field-emission devices. Two possible cold-cathode materials, namely, amorphous-carbon and amorphous silicon, will be examined.
Silva SRP, Amaratunga GAJ, Barnes JR (1997) Self-texturing of nitrogenated amorphous carbon thin films for electron field emission, APPLIED PHYSICS LETTERS 71 (11) pp. 1477-1479 AMER INST PHYSICS
Sporea RA, Trainor MJ, Young ND, Shannon JM, Silva SRP (2012) Field plate optimization in low-power high-gain source-gated transistors, IEEE Transactions on Electron Devices 59 (8) IEEE
Source-gated transistors (SGTs) have potentially very high output impedance and low saturation voltages, which make them ideal as building blocks for high performance analog circuits fabricated in thin-film technologies. The quality of the saturation is greatly influenced by the design of the field-relief structure incorporated into the source electrode. Starting from measurements on self-aligned polysilicon structures, we show through numerical simulations how the field plate design can be improved. A simple source field plate around 1µm long situated several tens of nm above the semiconductor can increase the low-voltage intrinsic gain by more than two orders of magnitude and offers adequate tolerance to process variations in a moderately scaled thin-film SGT.
AMARATUNGA GAJ, VEERASAMY VS, MILNE WI, DAVIS CA, SILVA SRP, MACKENZIE HS (1993) PHOTOCONDUCTIVITY IN HIGHLY TETRAHEDRAL DIAMOND-LIKE AMORPHOUS-CARBON, APPLIED PHYSICS LETTERS 63 (3) pp. 370-372 AMER INST PHYSICS
Matsubara EY, Rosolen JM, Silva SRP (2008) Composite electrode of carbon nanotubes and vitreous carbon for electron field emission, JOURNAL OF APPLIED PHYSICS 104 (5) ARTN 054303 AMER INST PHYSICS
Smith RC, Silva SRP (2009) Interpretation of the field enhancement factor for electron emission from carbon nanotubes, JOURNAL OF APPLIED PHYSICS 106 (1) ARTN 014314 AMER INST PHYSICS
Bhattacharyya S, Henley SJ, Mendoza E, Gomez-Rojas L, Allam J, Silva SRP (2006) Resonant tunnelling and fast switching in amorphous-carbon quantum-well structures, NATURE MATERIALS 5 (1) pp. 19-22 NATURE PUBLISHING GROUP
Stolojan V, Tison Y, Chen GY, Silva R (2006) Controlled growth-reversal of catalytic carbon nanotubes under electron-beam irradiation., Nano Lett 6 (9) pp. 1837-1841
The growth of carbon nanotubes from Ni catalysts is reversed and observed in real time in a transmission electron microscope, at room temperature. The Ni catalyst is found to be Ni3C and remains attached to the nanotube throughout the irradiation sequence, indicating that C most likely diffuses on the surface of the catalyst to form nanotubes. We calculate the energy barrier for saturating the Ni3C (2-13) surface with C to be 0.14 eV, thus providing a low-energy surface for the formation of graphene planes.
SILVA SRP, AMARATUNGA GAJ, SALJE EKH, KNOWLES KM (1994) EVIDENCE OF HEXAGONAL DIAMOND IN PLASMA-DEPOSITED CARBON-FILMS, JOURNAL OF MATERIALS SCIENCE 29 (19) pp. 4962-4966 KLUWER ACADEMIC PUBL
Zeze DA, Silva SRP, Haq S, Harris SJ (2003) Comparison of the X-ray photoelectron and electron-energy-loss spectra of the nitrogen-doped hydrogenated amorphous carbon bond, PHILOSOPHICAL MAGAZINE 83 (16) pp. 1937-1947 TAYLOR & FRANCIS LTD
Clark J, Anguita JV, Chen Y, Silva SRP Optical nanostructures in 2D for wide-diameter and broadband beam collimation, NATURE PUBLISHING GROUP
Ruffini G, Dunne S, Fuentemilla L, Grau C, Farres E, Marco-Pallares J, Watts PCP, Silva SRP (2008) First human trials of a dry electrophysiology sensor using a carbon nanotube array interface, SENSORS AND ACTUATORS A-PHYSICAL 144 (2) pp. 275-279 ELSEVIER SCIENCE SA
Bhattacharyya S, Henley SJ, Lock D, Blanchard NP, Silva SRP (2006) Semiconducting phase of amorphous carbon-nickel composite films, APPLIED PHYSICS LETTERS 89 (2) ARTN 022113 AMER INST PHYSICS
Gandhi KK, Nejim A, Beliatis MJ, Mills CA, Henley S, Silva SRP (2015) Simultaneous Optical and Electrical Modeling of Plasmonic Light Trapping in Thin-Film Amorphous Silicon Photovoltaic Devices, Journal of Photonics for Energy 5 (1) 057007 SPIE
Rapid prototyping of photovoltaic (PV) cells requires a method for the simultaneous simulation of the optical and electrical characteristics of the device. The development of nanomaterial enabled PV cells only increases the complexity of such simulations. Here, we use a commercial technology-computer-aided-design (TCAD) software, Silvaco Atlas, to design and model plasmonic gold nanoparticles integrated in optoelectronic device models of thin film amorphous silicon (a-Si:H) PV cells. Upon illumination with incident light, we simulate the optical and electrical properties of the cell simultaneously, and use the simulation to produce current-voltage (J-V) and external quantum efficiency (EQE) plots. Light trapping due to light scattering and localized surface plasmon resonance interactions by the nanoparticles has resulted in the enhancement of both the optical and electrical properties due to the reduction in the recombination rates in the photoactive layer. We show that the device performance of the modeled plasmonic a-Si:H PV cells depends significantly on the position and size of the gold nanoparticles, which leads to improvements either in optical properties only, or in both optical and electrical properties. The model provides a route to optimize the device architecture, by simultaneously optimizing the optical and electrical characteristics, which leads to a detailed understanding of plasmonic PV cells from a design perspective and offers an advanced tool for rapid device prototyping.
Silva SRP, Forrest RD, Shannon JM (1998) Electron field emission from amorphous silicon, Proceedings of the IEEE International Vacuum Microelectronics Conference, IVMC pp. 285-286
Hydrogenated amorphous silicon thin films were grown by plasma enhanced chemical vapor deposition onto coated glass substrates or n-Si wafers and were investigated for their electron field emission. The observed emission current did not fit a Fowler-Nordheim type tunneling current, but was closer to a space charge limited current which would be expected if the current limiting process was due to space charge. The observed decrease and turning off of the emission current with time can be addressed by pulsed mode operation and surface charge extraction via a gate electrode. Multilayer structures that contain Schottky and ohmic back contacts as well as thin 15 nm n+ surface layers used to control the potential of the front surface of the emitting device.
Sharma P, Stolojan V, Silva SRP (2011) Raman analysis of oxide cladded silicon core nanowires grown with solid silicon feed stock, JOURNAL OF NANOPARTICLE RESEARCH 13 (7) pp. 2697-2703 SPRINGER
Carey JD, Silva SRP (2006) Effects of nanoscale clustering in amorphous carbon, CARBON: THE FUTURE MATERIAL FOR ADVANCED TECHNOLOGY APPLICATIONS 100 pp. 137-152 SPRINGER-VERLAG BERLIN
Carey JD, Forrest RD, Poa CH, Silva SRP (2003) Role of nanostructure on electron field emission from amorphous carbon thin films, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 21 (4) pp. 1633-1639 A V S AMER INST PHYSICS
Nagavolu C, Susmitha K, Raghavender M, Giribabu L, Rao K, Smith C, Mills C, Silva S, Srikanth V (2016) Pt-free spray coated reduced graphene oxide counter electrodes for dye sensitized solar cells, SOLAR ENERGY 137 pp. 143-147 PERGAMON-ELSEVIER SCIENCE LTD
Watts PCP, Mureau N, Tang Z, Miyajima Y, Carey JD, Silva SRP (2007) The importance of oxygen-containing defects on carbon nanotubes for the detection of polar and non-polar vapours through hydrogen bond formation, NANOTECHNOLOGY 18 (17) ARTN 175701 IOP PUBLISHING LTD
Khan RUA, Grambole D, Silva SRP (2000) Studies of carbon ion self-implantation into hydrogenated amorphous carbon films, DIAMOND AND RELATED MATERIALS 9 (3-6) pp. 675-679 ELSEVIER SCIENCE SA
Silva SRP, Amaratunga GAJ, Okano K (1999) Modeling of the electron field emission process in polycrystalline diamond and diamond-like carbon thin films, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 17 (2) pp. 557-561 AMER INST PHYSICS
Beliatis MJ, Henley SJ, Han S, Gandi K, Adikaari D, Stratakis E, Kymakis E, Silva SRP (2013) Organic solar cells with plasmonic layers formed by laser nanofabrication, Physical Chemistry Chemical Physics (PCCP) RSC Publishing
Sporea RA, Burridge T, Silva SRP (2015) Self-Heating Effects In Polysilicon Source Gated Transistors, SCIENTIFIC REPORTS 5 ARTN 14058 NATURE PUBLISHING GROUP
Lyth SM, Henley SJ, Silva SRP (2009) Improved field emission via laser processing of carbon nanotubes on paper substrates, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 27 (3) pp. 1068-1071 A V S AMER INST PHYSICS
Sporea RA, Wright W, Shannon JM, Silva SRP (2015) Bulk barrier source-gated transistors with improved drain current dynamic range and temperature coefficient, ECS Transactions 67 (1) pp. 91-96
© The Electrochemical Society.Source-gated thin-film transistors (SGTs) have remarkable properties related to low-voltage amplification, tolerance to process variation and electrical stability. They rely on a potential barrier at the source in their operation, and usually this barrier is realized through a Schottky contact. Here, we study SGTs with source barriers made by doping the source region of the semiconductor to form bulk unipolar diodes (BUD). A BUSGT can have much higher drain current with a lower activation energy, resulting in higher switching speed and improved transconductance. Barriers made via doping also provide a wider range of barrier heights compared with Schottky contacts. We discuss design parameters for BUSGTs and compare these devices with SBSGTs.
Adikaari AADT, Mudugamuwa NK, Silva SRP (2008) Higher crystalline volume yields from excimer laser crystallization of amorphous silicon with an asymmetrical peak pulse profile, SEMICONDUCTOR PHOTONICS: NANO-STRUCTURED MATERIALS AND DEVICES 31 pp. 185-188 TRANS TECH PUBLICATIONS LTD
Adikaari AADT, Dissanayake DMNM, Hatton RA, Silva SRP (2007) Efficient laser textured nanocrystalline silicon-polymer bilayer solar cells, APPLIED PHYSICS LETTERS 90 (20) ARTN 203514 AMER INST PHYSICS
Adikaari AADT, Silva SRP (2005) Thickness dependence of properties of excimer laser crystallized nano-polycrystalline silicon, JOURNAL OF APPLIED PHYSICS 97 (11) ARTN 114305 AMER INST PHYSICS
Carey D, Smith R, Silva R, Murphy R, Blau W, Coleman J, IEEE (2007) Transport and field emission in carbon nanotube - polymer composite cathodes, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 165-166
Pozegic TR, Anguita JV, Hamerton I, Jayawardena KDGI, Chen J-S, Stolojan V, Ballocchi P, Walsh R, Silva SRP (2016) Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing, Scientific Reports 6 37334
Carbon fibre reinforced polymers (CFRP) were introduced to the aerospace, automobile and civil engineering industries for their high strength and low weight. A key feature of CFRP is the polymer sizing - a coating applied to the surface of the carbon fibres to assist handling, improve the interfacial adhesion between fibre and polymer matrix and allow this matrix to wet-out the carbon fibres. In this paper, we introduce an alternative material to the polymer sizing, namely carbon nanotubes (CNTs) on the carbon fibres, which in addition imparts electrical and thermal functionality. High quality CNTs are grown at a high density as a result of a 35 nm aluminium interlayer which has previously been shown to minimise diffusion of the catalyst in the carbon fibre substrate. A CNT modified-CFRP show 300%, 450% and 230% improvements in the electrical conductivity on the ?surface?, ?through-thickness? and ?volume? directions, respectively. Furthermore, through-thickness thermal conductivity calculations reveal a 107% increase. These improvements suggest the potential of a direct replacement for lightning strike solutions and to enhance the efficiency of current de-icing solutions employed in the aerospace industry.
Stolojan V, McCafferty L, King S, Zhang W, Haq S, Silva S (2015) Decoration of multiwalled carbon nanotubes with protected iron nanoparticles, Carbon 84 pp. 47-55 Elsevier
A method to simultaneously synthesize carbon-encapsulated magnetic iron nanoparticles (Fe-NPs) and attach these particles to multi-walled carbon nanotubes (MWCNT) is presented. Thermal decomposition of cyclopentadienyliron dicarbonyl dimer [(C5H5)(2)Fe-2(CO)(4)], over a range of temperatures from 250 degrees C to 1200 degrees C, results in the formation of Fe-NPs attached to MWCNT. At the same time, a protective carbon shell is produced and surrounds the Fe-NPs, covalently attaching the particles to the MWCNT and leading to resistance to acid dissolution. The carbon coating varies in degree of graphitisation, with higher synthesis temperatures leading to a higher degree of graphitisation. The growth model of the nanoparticles and subsequent mechanism of MWCNT attachment is discussed. Adsorption potential of the hybrid material towards organic dyes (Rhodamine B) has been displayed, an indication of potential uses as a material for water treatment. The material has also been electrospun into aligned nanocomposite fibres to produce a soft magnetic composite (SMC) with future applications in sensors and fast switching solenoids.
Barradas NP, Almeida SA, Jeynes C, Knights AP, Silva SRP, Sealy BJ (1999) RBS and ERDA study of ion beam synthesised amorphous gallium nitride, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 148 (1-4) pp. 463-467
Amorphous GaN was synthesised by Ga implantation into N-rich PECVD a-SiNx:H films after annealing between 200°C and 500°C. Similar implantation into Si-rich films did not form GaN. X-ray Photoelectron Spectroscopy (XPS) demonstrated the presence of GaN bonds in the former, but not the latter, case. Rutherford backscattering (RBS) and Elastic Recoil Detection Analysis (ERDA) demonstrated that implanted Ga substituted for Si in the N-rich films but not in the Si-rich ones. The RBS/ERDA analysis used self-consistent fitting of multiple spectra using the combinatorial optimisation Simulated Annealing algorithm, followed by a determination of the confidence limits on the depth profiles obtained using Bayesian Inference. © 1999 Elsevier Science B.V. All rights reserved.
Knox-Davies EC, Henley SJ, Shannon JM, Silva SRP (2006) Improved optical and electrical properties of low-temperature sputtered GaN by hydrogenation, JOURNAL OF APPLIED PHYSICS 99 (3) ARTN 036108 AMER INST PHYSICS
Tison Y, Giusca CE, Sloan J, Silva SRP (2008) Registry-Induced Electronic Superstructure in Double-Walled Carbon Nanotubes, Associated with the Interaction between Two Graphene-Like Monolayers, ACS NANO 2 (10) pp. 2113-2120 AMER CHEMICAL SOC
Franceschini DF, Freire FL, Silva SRP (1995) Influence of precursor gases on the structure of plasma deposited amorphous hydrogenated carbon-nitrogen films, Applied Physics Letters
The atomic structure of amorphous hydrogenated carbon-nitrogen films was studied by electron energy loss spectroscopy (EELS). The films were deposited onto Si(100) substrates by rf plasma decomposition of CH4-NH 3 and CH4-N2 mixtures, with substrates placed on the powered electrode of a diode glow-discharge system. The sp2 fraction of C and N atoms as a function of the nitrogen content in the films was obtained by EELS analysis. An increase of the carbon sp2 fraction with increasing fraction of NH3 and N2 feed gases was observed. The variation in the atomic structure of the a-C(N):H thin films is correlated to the internal compressive stress. © 1996 American Institute of Physics.
Watts PCP, Lyth SM, Henley SJ, Silva SRP (2008) Secondary nanotube growth on aligned carbon nanofibre arrays or superior field emission, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 8 (4) pp. 2147-2150 AMER SCIENTIFIC PUBLISHERS
Cheah LK, Shi X, Tay BK, Silva SRP, Sun Z (1998) Field emission from undoped and nitrogen-doped tetrahedral amorphous carbon film prepared by filtered cathodic vacuum arc technique, DIAMOND AND RELATED MATERIALS 7 (2-5) pp. 640-644 ELSEVIER SCIENCE SA
Henley SJ, Carey JD, Silva SRP (2006) Silver-nanoparticle-decorated carbon nanoscaffolds: Application as a sensing platform, APPLIED PHYSICS LETTERS 89 (18) ARTN 183120 AMER INST PHYSICS
Carey JD, Silva SRP (2001) Conditioning of hydrogenated amorphous carbon thin films for field emission via current stressing, APPLIED PHYSICS LETTERS 78 (3) pp. 347-349 AMER INST PHYSICS
Sporea RA, Alshammari AS, Georgakopoulos S, Underwood J, Shkunov M, Silva SRP (2013) Micron-scale inkjet-assisted digital lithography for large-area flexible electronics, European Solid-State Device Research Conference pp. 280-283
Large-area electronics require cost-effective yet precise patterning of electrodes. We demonstrate a simple electrode patterning technique capable of micron-scale gap formation, that allows the patterning of a larger variety of metals than the current portfolio of jettable metallic ink comprises and does not require a high-temperature sintering step. However, this method can produce large variations in gap size resulting in inconsistent and irreproducible transistor drain current. We propose that source-gated transistors (SGTs) are well suited to this technique, as they have a saturated drain current independent of source-drain separation, thus leading to improved current uniformity despite inconsistencies in gap size. © 2013 IEEE.
Jayawardena KDGI, Tan YY, Fryar J, Shiozawa H, Silva SRP, Henley SJ, Fuge GM, Truscott BS, Ashfold MNR (2011) Highly conductive nanoclustered carbon:nickel films grown by pulsed laser deposition, Carbon 49 (12) pp. 3781-3788 Elsevier
An enhancement by 5 orders of magnitude of the electrical conductivity of nanoclustered carbon films is reported by incorporation of metallic atoms, but without significant morphological changes. Films were deposited by 248 nm pulsed laser ablation of both a pyrolytic graphite target and a mixed carbon?nickel (C:Ni) target, and structural analysis revealed that similar film morphologies were obtained when deposition was carried out using either target. Compositional analysis demonstrated a preferential incorporation of nickel over carbon in the resulting films (cf. the composition of the target). This non-stoichiometric transfer was also observed for films grown by 193 nm laser ablation of the C:Ni target, for which the enhancement was more pronounced, indicating that the ablation mechanism and the subsequent transfer are important in determining the eventual film composition.
Chen JS, Stolojan V, Silva SRP (2015) Towards type-selective carbon nanotube growth at low substrate temperature via photo-thermal chemical vapour deposition, Carbon 84 (1) pp. 409-418
© 2014 Elsevier Ltd. All rights reserved.Carbon nanotubes have been intensively researched for electronic applications, driven by their excellent electronic properties, where the goals are control and reproducibility of growth, semiconducting/metallic type selectivity and maintaining high quality of carbon nanotubes, in a process that is temperature-compatible with the electronics. Photo-thermal chemical vapour deposition can achieve these goals and, through a thorough investigation of the parameter space, we achieve very high nanotube-quality and growth rates, and produce a phase-diagram that reveals distinct regions for growing semiconducting and metallic single-walled nanotubes, as well as multi-walled. Correlation with the carbon-catalyst phase diagram allows for the development of a novel growth model. We propose that the temperature-gradient induces carbon diffusivity-gradient across the catalyst to yield the high growth rate. This is attributed to the increase of a-iron of catalyst. The growth control demonstrated here allows for integration of the nanotube growth process by photo-thermal deposition into mainstream electronics manufacture.
Gibson I, Silva SRP (2008) Harnessing the full potential of nanotechnology for wealth creation, Nanotechnology Perceptions 4 (2) pp. 87-92
Hatton RA, Blanchard NP, Tan LW, Latini G, Cacialli F, Silva SRP (2009) Oxidised carbon nanotubes as solution processable, high work function hole-extraction layers for organic solar cells, ORGANIC ELECTRONICS 10 (3) pp. 388-395 ELSEVIER SCIENCE BV
Young WT, Silva SRP, Shannon JM (2001) Laser annealing of low temperature grown gallium nitride, DIAMOND AND RELATED MATERIALS 10 (3-7) pp. 1311-1313 ELSEVIER SCIENCE SA
Neves V, Gerondopoulos A, Heister E, Tîlmaciu C, Flahaut E, Soula B, Silva SRP, McFadden J, Coley HM (2012) Cellular localization, accumulation and trafficking of double-walled carbon nanotubes in human prostate cancer cells, Nano Research 5 (4) pp. 223-234 Springer
Carbon nanotubes (CNTs) are at present being considered as potential nanovectors with the ability to deliver therapeutic cargoes into living cells. Previous studies established the ability of CNTs to enter cells and their therapeutic utility, but an appreciation of global intracellular trafficking associated with their cellular distribution has yet to be described. Despite the many aspects of the uptake mechanism of CNTs being studied, only a few studies have investigated internalization and fate of CNTs inside cells in detail. In the present study, intracellular localization and trafficking of RNA-wrapped, oxidized double-walled CNTs (oxDWNT-RNA) is presented. Fixed cells, previously exposed to oxDWNT-RNA, were subjected to immunocytochemical analysis using antibodies specific to proteins implicated in endocytosis; moreover cell compartment markers and pharmacological inhibitory conditions were also employed in this study. Our results revealed that an endocytic pathway is involved in the internalization of oxDWNT-RNA. The nanotubes were found in clathrin-coated vesicles, after which they appear to be sorted in early endosomes, followed by vesicular maturation, become located in lysosomes. Furthermore, we observed co-localization of oxDWNT-RNA with the small GTP-binding protein (Rab 11), involved in their recycling back to the plasma membrane via endosomes from the trans-golgi network.
Tsang WM, Stolojan V, Adikaari AADT, Wong SP, Silva SRP (2005) Ion-beam-synthesized Ag-SiO2 nanocomposite layers for electron field emission devices, Materials Research Society Symposium Proceedings 908 pp. 81-86
Ag-SiO2 nanocomposite layers were synthesised by Ag+ implantation into thermally oxidised SiO2 layers and demonstrated to have excellent field emission (FE) properties. These nanocomposite layers can give an emission current of 1 nA at electric fields less than 20 V/¼m, compared to several thousand volts per micrometre of pure metal surfaces. Their fabrication processes are fully compatible with existing integrated circuit technology. By correlating the FE results with other characterisation techniques including atomic force microscopy, Rutherford backscattering spectroscopy and transmission electron microscopy, it is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the excellent FE properties of these cathodes. Firstly, the electrically conductive Ag nano-clusters embedded in the insulating SiO2 matrix give rise to a local electric field enhancement due to an electrical inhomogeneity effect and secondly, the dense surface protrusions provide a geometric local electric field enhancement. The FE properties of these layers are critically dependent on the size and distribution of the Ag clusters, which can be controlled by the Ag dose and modified by the post-implantation pulse annealing with a high power KrF Excimer laser operating at 248 nm. © 2006 Materials Research Society.
Tsang WM, Stolojan V, Sealy BJ, Wong SP, Silva SRP (2007) Electron field emission properties of Co quantum dots in SiO2 matrix synthesised by ion implantation, ULTRAMICROSCOPY 107 (9) pp. 819-824 ELSEVIER SCIENCE BV
Silva SRP (2007) Large area electron field emission cathodes, AD'07: Proceedings of Asia Display 2007, Vols 1 and 2 pp. 628-628 EAST CHINA NORMAL UNIVERSITY
Munindradasa DAI, Chhowalla M, Amaratunga GAJ, Silva SRP (1998) Electronic behaviour and field emission of a-C : H : N/Si heterojunctions, JOURNAL OF NON-CRYSTALLINE SOLIDS 227 pp. 1106-1112 ELSEVIER SCIENCE BV
Dabera GD, Jayawardena KD, Prabhath MR, Yahya I, Tan YY, Nismy NA, Shiozawa H, Sauer M, Ruiz-Soria G, Ayala P, Stolojan V, Adikaari AA, Jarowski PD, Pichler T, Silva SR (2013) Hybrid carbon nanotube networks as efficient hole extraction layers for organic photovoltaics., ACS Nano 7 (1) pp. 556-565
Transparent, highly percolated networks of regioregular poly(3-hexylthiophene) (rr-P3HT)-wrapped semiconducting single-walled carbon nanotubes (s-SWNTs) are deposited, and the charge transfer processes of these nanohybrids are studied using spectroscopic and electrical measurements. The data disclose hole doping of s-SWNTs by the polymer, challenging the prevalent electron-doping hypothesis. Through controlled fabrication, high- to low-density nanohybrid networks are achieved, with low-density hybrid carbon nanotube networks tested as hole transport layers (HTLs) for bulk heterojunction (BHJ) organic photovoltaics (OPV). OPVs incorporating these rr-P3HT/s-SWNT networks as the HTL demonstrate the best large area (70 mm(2)) carbon nanotube incorporated organic solar cells to date with a power conversion efficiency of 7.6%. This signifies the strong capability of nanohybrids as an efficient hole extraction layer, and we believe that dense nanohybrid networks have the potential to replace expensive and material scarce inorganic transparent electrodes in large area electronics toward the realization of low-cost flexible electronics.
Watts PCP, Henley SJ, Mendoza E, Silva SRP, Irvine JK, McAdams ET (2007) Core-shell silver/silver chloride nanoparticles on carbon nanofibre arrays for bio-potential monitoring, NANOTECHNOLOGY 18 (20) ARTN 205502 IOP PUBLISHING LTD
Forrest RD, Khan RUA, Silva SRP (2000) Tailoring of the field emission properties of hydrogenated amorphous carbon thin films by nitrogen incorporation and thermal annealing, DIAMOND AND RELATED MATERIALS 9 (3-6) pp. 1205-1208 ELSEVIER SCIENCE SA
Jones BJ, Barklie RC, Khan RUA, Carey JD, Silva SRP (2001) Electron paramagnetic resonance study of ion implantation induced defects in amorphous hydrogenated carbon, DIAMOND AND RELATED MATERIALS 10 (3-7) pp. 993-997 ELSEVIER SCIENCE SA
Hamerton I, Tang W, Anguita JV, Silva SRP (2015) Dramatic reductions in water uptake observed in novel POSS nanocomposites based on anhydride-cured epoxy matrix resins, Materials Today Communications 4 pp. 186-198
© 2015.A methylnadic anhydride-cured diglycidylether of bisphenol A, is prepared and characterised and a mono-epoxy POSS reagent added (0.5-4wt-%) to produce a series of nanocomposites. Two reaction mechanisms are observed involving esterification at lower temperatures (60-180°C) and etherification at temperatures above 180°C. Using the Ozawa and Kissinger methods, the activation energy for the first reaction was found to be 87-90kJ/mol and 122-124kJ/mol for the second reaction. Incorporation of POSS into the epoxy-anhydride network increases the Tg and cross-link density, indicating a more rigid network, but the values do not follow a trend based solely on POSS content. The char yield increases with POSS content with very little change in the degradation temperature. Incorporation of POSS (1wt-%) can reduce the moisture uptake in the cured resin by ~25% at 75% relative humidity. This is accompanied by a lower impact on glass transition temperature: the Tg is reduced by 10K at saturation, compared with 31K for the unmodified epoxy.
Giusca CE, Tison Y, Silva SRP (2007) Atomic and electronic structure in collapsed carbon nanotubes evidenced by scanning tunneling microscopy, PHYSICAL REVIEW B 76 (3) ARTN 035429 AMER PHYSICAL SOC
Lyth SM, Silva SRP (2009) Resonant behavior observed in electron field emission from acid functionalized multiwall carbon nanotubes, APPLIED PHYSICS LETTERS 94 (12) ARTN 123102 AMER INST PHYSICS
Acid functionalized multiwall carbon nanotube ink was deposited onto carbon fiber fabric via dip coating. Repeatable staircaselike current-field curves were observed in the field emission data. These atypical curves are attributed to resonant tunneling through localized surface states in a quantum well structure, which arises due to the presence of the surface carboxylic functional group.
Shiozawa H, Puchegger S, Pichler T, Silva SRP (2013) Structural properties of mirrored carbon spirals as revealed by scanning electron microscopy and micro-raman spectroscopy, Physica Status Solidi (B) Basic Research 250 (12) pp. 2737-2740
A novel type of iron-carbon composite nano-structures has been synthesised from a pressurized ferrocene vapor. Scanning electron microscopy shows that the nano-structures are produced in large yield and high purity. Their unique morphology is manifested by high reflectional symmetry, composed of two conical arms spiralling out of an almost spherical core. The size extends to 40¼m in length with the arm's tips as thin as 100nm. In the micrograph, the core area shows brighter contrasts than the arms, indicating its iron richness. Micro-Raman spectroscopy across the sample surface unravels that the graphitic arms encapsulate the iron core entirely. Such unique encapsulated nano-composites with defined shapes could be useful in many applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zhang W, Silva SRP (2010) Reversible functionalization of multi-walled carbon nanotubes with organic dyes, SCRIPTA MATERIALIA 63 (6) pp. 645-648 PERGAMON-ELSEVIER SCIENCE LTD
Hamerton I, Tang W, Anguita JV, Silva SRP (2013) Towards the rational design of polymers using molecular simulation: predicting the effects of cure schedule on thermomechanical properties for a cycloaliphatic amine-cured epoxy resin, Elsevier
Shang NG, Silva SRP, Jiang X, Papakonstantinou P (2011) Directly observable G band splitting in Raman spectra from individual tubular graphite cones, CARBON 49 (9) pp. 3048-3054 PERGAMON-ELSEVIER SCIENCE LTD
Almeida SA, Silva SRP, Sealy BJ, Watts JF (1998) Ion-beam synthesis of amorphous gallium nitride, PHILOSOPHICAL MAGAZINE LETTERS 78 (4) pp. 319-324 TAYLOR & FRANCIS LTD
Lyth SM, Silva SRP (2015) Electron Field Emission from Water-Based Carbon Nanotube Inks, ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 4 (4) pp. P3034-P3043 ELECTROCHEMICAL SOC INC
Sam FLM, Razali MA, Jayawardena KDGI, Mills CA, Rozanski LJ, Beliatis MJ, Silva SRP (2014) Silver Grid Transparent Conducting Electrodes for Organic Light Emitting Diodes, Organic Electronics 15 (12) pp. 3492-3500 Elsevier
Polymer organic light emitting diodes (OLEDs) were fabricated using thin silver hexagonal grids replacing indium tin oxide (ITO) as the transparent conducting electrodes (TCE). Previous literature has assumed that thick metal grids (several hundred nanometres thick) with a lower sheet resistance ( 80 %) compared to thinner grids would lead to OLEDs with better performance than when thinner metal grid lines are used. This assumption is critically examined using OLEDs on various metal grids with different thicknesses and studying their performances. The experimental results show that a 20 nm thick silver grid TCE resulted in more efficient OLEDs with higher luminance (10 cd/A and 1460 cd/m2 at 6.5 V) than a 111 nm thick silver grid TCE (5 cd/A and 159 cd/m2 at 6.5 V). Furthermore, the 20 nm thick silver grid OLED has a higher luminous efficiency than the ITO OLED (6 cd/A and 1540 cd/m2 at 6.5 V) at low voltages. The data shows that thinner metal grid TCEs (about 20 nm) make the most efficient OLEDs, contrary to previous expectations.
Shiozawa H, Giusca CE, Silva SRP, Kataura H, Pichler T (2008) Capillary filling of single-walled carbon nanotubes with ferrocene in an organic solvent, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 245 (10) pp. 1983-1985 WILEY-V C H VERLAG GMBH
Pozegic TR, Anguita JV, Tang W, Silva SRP, Hamerton I, Ballocchi P, Jenkins P (2014) Low temperature growth of carbon nanotubes on carbon fibre to create a highly networked fuzzy fibre reinforced composite with superior electrical conductivity, Carbon
We report a method for the growth of carbon nanotubes on carbon fibre using a low temperature growth technique which is infused using a standard industrial process, to create a fuzzy fibre composite with enhanced electrical characteristics. Conductivity tests reveal improvements of 510% in the out-of-plane and 330% in the in-plane direction for the nanocomposite compared to the reference composite. Further analysis of current-voltage (I-V) curves confirm a transformation in the electron transport mechanism from charge - hopping in the conventional material, to an Ohmic diffusive mechanism for the carbon nanotube modified composite. Single fibre tensile tests reveal a tensile performance decrease of only 9.7% after subjecting it to our low temperature carbon nanotube growth process, which is significantly smaller than previous reports. Our low-temperature growth process uses substrate water-cooling to maintain the bulk of the fibre material at lower temperatures, whilst the catalyst on the surface of the carbon fibre is at optimally higher temperatures required for carbon nanotube growth. The process is large-area production compatible with bulk-manufacturing of carbon fibre polymer composites. © 2014 Elsevier Ltd. All rights reserved.
Watts PCP, Mureau N, Tang Z, Miyajima Y, David Carey J, Silva SRP (2007) The importance of oxygen-containing defects on carbon nanotubes for the detection of polar and non-polar vapours through hydrogen bond formation, Nanotechnology 18 (17)
We report the electrical responses of water vapour and O2 adsorption onto macroscopic multi-walled carbon nanotube (MWCNT) ropes, and compare the results with mats of acid-treated MWCNTs on SiO2 substrates in order to investigate the importance of oxygen-containing defects on CNTs. In the outgassed state both carbon nanotube (CNT) materials exhibit rapid changes in electrical resistance when exposed to dry air, humid air or water vapour at standard temperature and pressure (STP). The measured electrical responses are highly reversible at STP when cycled between humid air, vacuum and dry air. We report a decrease in resistance for the CNT materials in dry air, attributed to O2 p-type doping of the CNTs, whereas there is an increase in resistance when exposed to a humid environment. This latter effect is attributed to the formation of hydrogen bonding from the polar water molecules with the oxygen-containing defects on the CNTs. Our observations indicate that the increase in electrical resistance upon water absorption affects a reduction of the electron-withdrawing power of the oxygen-containing defect groups, thus leading to a reduced hole carrier concentration in the p-type nanotubes. © IOP Publishing Ltd.
Barklie RC, Collins M, Silva SRP (2000) EPR linewidth variation, spin relaxation times, and exchange in amorphous hydrogenated carbon, Physical Review B - Condensed Matter and Materials Physics 61 (5) pp. 3546-3554
Electron paramagnetic resonance (EPR) measurements have been made of amorphous hydrogenated carbon (a-C:H) films grown by plasma enhanced chemical vapor deposition (PECVD) with negative self-bias voltages Vb in the approximate range 10-540 V. For Vb100 V the linewidth is shown to be dominated by the dipolar interactions and exchange and it decreases as Vb increases; the change is shown to arise primarily from a change in the exchange interaction. Evidence for this comes from measurements which show that the spin-lattice relaxation time appreciably shortens and the spin-spin relaxation time lengthens as the bias voltage is increased. The magnitude and variation with bias of the linewidth are consistent with the EPR signal originating from the À-type radicals. ©2000 The American Physical Society.
Alenezi MR, Alshammari AS, Alzanki TH, Jarowski P, Henley SJ, Silva SRP (2014) ZnO nanodisk based UV detectors with printed electrodes, Langmuir 30 (13) pp. 3913-3921
The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 104), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface. © 2014 American Chemical Society.
Lucyszyn S, Silva SRP, Robertson ID, Collier RJ, Jastrzebski AK, Thayne IG, Beaumont SP (1998) Terahertz multi-chip module (T-MCM) technology for the 21 st century?, IEE Colloquium (Digest) (231)
This paper describes a new philosophy for realising terahertz MCMs, that can operate within the frequency range of approximately 75 to 300 GHz, which are not only manufacturable but can also provide state-of-the-art performance. To this end, a consortium of four leading UK universities has recently been formed to demonstrate this T-MCM technology. Some of the techniques that will be under investigation within this ambitious three-year research programme are presented here. The ultimate goal is to provide industry with a technology that will allow them, for the first time, to realise complete terahertz sub-systems without the need for bulky and expensive superconducting and machined waveguide components.
King S, McCafferty L, Stolojan V, Silva S (2015) Highly aligned arrays of super resilient carbon nanotubes by steam purification, Carbon 84 (1) pp. 130-137
Steam treatment has been applied to our prefabricated highly aligned areas of electrospun carbon nanotube composite nano-fibres, leading to controlled and targeted removal of polymeric and amorphous carbon materials, resulting in areas of highly aligned, highly crystalline, pure nanotubes. Raman analysis shows how the ID to IG intensity ratio was reduced to 0.03, and the radial breathing mode peak intensity, used for nanotube diameter calculation, changes. Therefore, suggesting that some carbon nanotubes are more resistant to steam assisted oxidation, meaning that specific carbon nanotube diameters are preferentially oxidised. The remaining carbon nanotubes have displayed a significant improvement in both quality, with respect to defect density, and in crystallinity, resulting in an increased resistance to oxidation. These steam treated super resilient carbon nanotubes are shown to withstand temperatures of above 900 °C under ambient conditions. Applying this purification method to electrospun nano-fibres leads the way for the next generation of composite materials which can be used in high temperature extreme environments.
Franceschini DF, Freire FL, Silva SRP (1996) Influence of precursor gases on the structure of plasma deposited amorphous hydrogenated carbon-nitrogen films, APPLIED PHYSICS LETTERS 68 (19) pp. 2645-2647 AMER INST PHYSICS
Mureau N, Mendoza E, Silva SRP, Hoettges KF, Hughes MP (2006) In situ and real time determination of metallic and semiconducting single-walled carbon nanotubes in suspension via dielectrophoresis, APPLIED PHYSICS LETTERS 88 (24) ARTN 243109 AMER INST PHYSICS
Smith C, Rhodes R, Beliatis M, Jayawardena K, Rozanski L, Mills C, Silva S (2014) Graphene oxide hole transport layers for large area, high efficiency organic solar cells, Applied Physics Letters 105 (7) 073304 American Institute of Physics
Graphene oxide (GO) is becoming increasingly popular for organic electronic applications. We present large active area (0.64 cm^2), solution processable, poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:[6,6]-Phenyl C71 butyric acid methyl ester (PCDTBT:PC70BM) organic photovoltaic (OPV) solar cells, incorporating GO hole transport layers (HTL). The power conversion efficiency (PCE) of ~5% is the highest reported for OPV using this architecture. A comparative study of solution-processable devices has been undertaken to benchmark GO OPV performance with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) HTL devices, confirming the viability of GO devices, with comparable PCEs, suitable as high chemical and thermal stability replacements for PEDOT:PSS in OPV.
Giusca CE, Tison Y, Stolojan V, Borowiak-Palen E, Silva SRP (2007) Inner-tube chirality determination for double-walled carbon nanotubes by scanning tunneling microscopy, NANO LETTERS 7 (5) pp. 1232-1239 AMER CHEMICAL SOC
Ruffini G, Dunne S, Farres E, Marco-Pallares J, Ray C, Mendoza E, Silva R, Grau C (2006) A dry electrophysiology electrode using CNT arrays, SENSORS AND ACTUATORS A-PHYSICAL 132 (1) pp. 34-41
Cox DC, Forrest RD, Smith PR, Silva SRP (2004) Bespoke carbon nanotube devices and structures, NANOENGINEERED NANOFIBROUS MATERIALS 169 pp. 323-328 SPRINGER
Shi S, Silva SRP (2012) High luminance organic light-emitting diodes with efficient multi-walled carbon nanotube hole injectors, Carbon 50 (11) pp. 4163-4170
We report on high luminance organic light-emitting diodes using acid functionalized multi-walled carbon nanotube (o-MWCNTs) as efficient hole injector electrodes, using a simple, solution processable device structure. At only 10 V, the luminance approaches 50,000 cd/m 2 with an external quantum efficiency over 2% and a current efficiency greater than 21 cd/A. The investigation of hole-only devices shows that the mechanism for hole injection changes from injection limited to bulk limited because of the higher effective work function of the anode modified by the o-MWCNTs. We expect the enhancement of the local electric field, brought about by both the dielectric inhomogeneities within the o-MWCNT containing anode and the high aspect ratio carbon nanotubes, improves hole injection from the anode to the organic active layer at much lower applied voltage. © 2012 Elsevier Ltd. All rights reserved.
Silva SRP, Khan RUA, Burden AP, Anguita JV, Shannon JM, Sealy BJ, Papworth AJ, Kiely CJ, Amaratunga GAJ (1998) The microstructural dependence of the opto-electronic properties of nitrogenated hydrogenated amorphous carbon thin films, THIN SOLID FILMS 332 (1-2) pp. 118-123 ELSEVIER SCIENCE SA
Silva SRP, Robertson J, Amaratunga GAJ, Rafferty B, Brown LM, Schwan J, Franceschini DF, Mariotto G (1997) Nitrogen modification of hydrogenated amorphous carbon films, JOURNAL OF APPLIED PHYSICS 81 (6) pp. 2626-2634 AMER INST PHYSICS
Khan RUA, Anguita JV, Silva SRP (2000) Ion-implantation into amorphous hydrogenated carbon films, JOURNAL OF NON-CRYSTALLINE SOLIDS 276 (1-3) pp. 201-205 ELSEVIER SCIENCE BV
Tang YF, Silva SRP, Boskovic BO, Shannon JM, Rose MJ (2002) Electron field emission from excimer laser crystallized amorphous silicon, APPLIED PHYSICS LETTERS 80 (22) pp. 4154-4156 AMER INST PHYSICS
Tsang WM, Stolojan V, Giusca C, Poa CHP, Sealy B, Silva SRP, Wong SP (2006) Electron field-emission properties of Ag-SiO2 nanocomposite layers, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 24 (2) pp. 958-961 A V S AMER INST PHYSICS
Tokunaga T, Hayashi Y, Fujita T, Silva SRP, Amaratunga GAJ (2006) Demixing of solid-soluted Co-Pd binary alloy induced by microwave plasma hydrogen irradiation technique, JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 45 (29-32) pp. L860-L863 INST PURE APPLIED PHYSICS
Stolojan V, Moreau P, Goringe MJ, Silva SRP (2005) Quantum effects in band gap-modulated amorphous carbon superlattices, Microscopy of Semiconducting Materials 107 pp. 307-310 SPRINGER-VERLAG BERLIN
Giusca CE, Stolojan V, Sloan J, Börrnert F, Shiozawa H, Sader K, Rümmeli MH, Büchner B, Silva SR (2013) Confined crystals of the smallest phase-change material., Nano Lett 13 (9) pp. 4020-4027
The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales.
Henley SJ, Mollah S, Giusca CE, Silva SRP (2009) Laser-induced self-assembly of iron oxide nanostructures with controllable dimensionality, JOURNAL OF APPLIED PHYSICS 106 (6) ARTN 064309 AMER INST PHYSICS
Carey JD, Ong LL, Silva SRP (2003) Formation of low-temperature self-organized nanoscale nickel metal islands, NANOTECHNOLOGY 14 (11) PII S0957-4484(03)66225-2 pp. 1223-1227 IOP PUBLISHING LTD
Beliatis MJ, Henley SJ, Silva SRP (2011) Engineering the plasmon resonance of large area bimetallic nanoparticle films by laser nanostructuring for chemical sensors, OPT LETT 36 (8) pp. 1362-1364 OPTICAL SOC AMER
Large area fabrication of metal alloy nanoparticles with tunable surface plasmon resonances on low-cost substrates is reported. A UV excimer laser was used to anneal 5 nm thick Ag Au bilayer films deposited with different composition ratios to create alloy nanoparticles. These engineered surfaces are used to investigate how the wavelength of the surface plasmon resonance affects the optical detection capability of chemical species by surface-enhanced Raman spectroscopy. (c) 2011 Optical Society of America
Filip LD, Palumbo M, Carey JD, Silva SRP (2009) Two-step electron tunneling from confined electronic states in a nanoparticle, PHYSICAL REVIEW B 79 (24) ARTN 245429 AMER PHYSICAL SOC
Carey JD, Ahmad M, Anguita JV, Stolojan V, Corless T, Silva SRP High Quality Carbon Nanotubes on Conductive Substrates Grown at Low Temperatures, University of Surrey
Ayala P, Miyata Y, De Blauwe K, Shiozawa H, Feng Y, Yanagi K, Kramberger C, Silva SRP, Follath R, Kataura H, Pichler T (2009) Disentanglement of the electronic properties of metallicity-selected single-walled carbon nanotubes, PHYSICAL REVIEW B 80 (20) ARTN 205427 AMER PHYSICAL SOC
Sporea RA, Trainor MJ, Young ND, Shannon JM, Silva SRP (2010) Performance improvements in polysilicon source-gated transistors, DRC Conference Digest pp. 245-246 IEEE
The source-gated transistor (SGT) is a new type of transistor in which the current is controlled by a potential barrier at the source and by a gate which modulates the effective height of the source barrier. It is an ideal device architecture to be used with the low mobility materials typically applied to large area electronics, as it provides low saturation voltages and high output impedances. Furthermore, the high internal fields and low concentration of excess carriers lead to higher speed and better stability compared with FETs, particularly in disordered, low mobility semiconductors. As such, the SGT is especially well suited to thin-film analog circuits.
Silva SRP, Amaratunga GAJ, Constantinou CP, McKenzie DR (1992) Smooth thin film C/diamond membranes with controllable optical band gaps, Diamond and Related Materials 1 (5-6) pp. 612-618
Mixed phase carbon-diamond films which consist of small grain diamond in an a:C matrix were deposited on polished Si using a radio frequency CH4 Ar plasma CVD deposition process. Ellipsometry, surface profilometry, scanning electron microscopy (SEM) and spectrophotometry were used to analyse these films. Film thicknesses were typically 50-100 nm with a surface roughness of ± 30 A
over centimetre length scans. SEM analysis showed the films were smooth and pinhole free. The Si substrate was etched using backside masking and a directional etch to give taut carbon-diamond membranes on a Si grid. Spectrophotometry was used to analyse the optical properties of these membranes. Band gap control was achieved by varying the dc bias of the deposition process. Band gaps of 1.2 eV to 4.0 eV were achieved in these membranes. A technique for controlling the compressive stress in the films, which can range from 0.02 to 7.5 GPa has been employed. This has allowed the fabrication of thin, low stress, high band gap membranes that are extremely tough and chemically inert. Such carbon-diamond membranes seem promising for applications as windows in analytical instruments. © 1992.
Henley SJ, Carey JD, Silva SRP (2006) Laser-nanostructured Ag films as substrates for surface-enhanced Raman spectroscopy, APPLIED PHYSICS LETTERS 88 (8) ARTN 081904 AMER INST PHYSICS
Feng L, Anguita JV, Tang W, Zhao J, Guo X, Silva SRP (2016) Room Temperature Grown High-Quality Polymer-Like Carbon Gate Dielectric for Organic Thin-Film Transistors, ADVANCED ELECTRONIC MATERIALS 2 (3) ARTN 1500374 WILEY-BLACKWELL
Silva SRP, Forrest RD, Shannon JM, Sealy BJ (1999) Electron field emission from amorphous silicon, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 17 (2) pp. 596-600 AMER INST PHYSICS
Silva SRP, Blanchard N, Lyth S (2006) Nanotechnology: The science and engineering of tomorrow, Journal of the National Science Foundation of Sri Lanka 34 (1) pp. 3-5
Forrest RD, Burden AP, Silva SRP, Cheah LK, Shi X (1998) A study of electron field emission as a function of film thickness from amorphous carbon films, APPLIED PHYSICS LETTERS 73 (25) pp. 3784-3786 AMER INST PHYSICS
Heister E, Lamprecht C, Neves V, Tilmaciu C, Datas L, Flahaut E, Soula B, Hinterdorfer P, Coley HM, Silva SRP, McFadden J (2010) Higher Dispersion Efficacy of Functionalized Carbon Nanotubes in Chemical and Biological Environments, ACS NANO 4 (5) pp. 2615-2626 AMER CHEMICAL SOC
Sporea RA, Shannon JM, Silva SRP (2011) High-resolution temperature sensing with source-gated transistors, Device Research Conference (DRC), 2011 69th Annual pp. 61-62 IEEE
Source-gated transistors (SGTs) are three-terminal devices in which the current is controlled by a potential barrier at the source. The gate voltage is used primarily to modulate the effective height of the source barrier. These devices have a number of operational advantages over conventional field-effect transistors, including a potentially much smaller saturation voltage and very low output conductance in saturation, which lead to low power operation and high intrinsic gain.
Smith PR, Carey JD, Cox DC, Forrest RD, Silva SRP (2009) On the importance of the electrostatic environment for the transport properties of freestanding multiwall carbon nanotubes, NANOTECHNOLOGY 20 (14) ARTN 145202 IOP PUBLISHING LTD
Rajkumar RK, Cox DC, Tzalenchuk A, Kazakova O, Silva SRP, Manzin A (2013) 3-D mapping of sensitivity of graphene hall devices to local magnetic and electrical fields, IEEE Transactions on Magnetics 49 (7) pp. 3445-3448
We report the response of sub-micron epitaxial graphene Hall devices to localized and inhomogeneous magnetic field produced by an MFM tip. We analyze the magneto-transport properties of epitaxial graphene and report the independent contribution of magnetic and electric fields in the measured transverse voltage maps with respect to the lateral and vertical position of the tip. A finite element model has also been developed to support the experimental results. © 2013 IEEE.
Miyajima Y, Henley SJ, Adamopoulos G, Stolojan V, Garcia-Caurel E, Drevillon B, Shannon JM, Silva SRP (2009) Pulsed laser deposited tetrahedral amorphous carbon with high sp(3) fractions and low optical bandgaps, JOURNAL OF APPLIED PHYSICS 105 (7) ARTN 073521 AMER INST PHYSICS
Adikaari AADT, Dissanayake DMNM, Silva SRP (2008) Organic-Inorganic Solar Cells: Recent Developments and Outlook, IEEE Journal on Selected Topics in Quantum Electronics 16 (6) pp. 1595-1606 IEEE
Solution-processed photovoltaic devices are an attractive alternative to costly inorganic semiconductor-based conventional photovoltaics. Solution-processable organic photovoltaic systems are affected by low carrier mobility, lifetime issues under ambient conditions, and limited optical absorption due to the high bandgaps of organic materials. Nanostructured inorganic materials promise to alleviate some of these drawbacks, by enabling the systems to perform better in a commercial perspective. This paper examines four key areas of hybrid organic-inorganic photovoltaic systems. These are metal oxide-organic, carbon nanotube-organic, semiconductor nanowire-organic, and semiconductor nanocrystal-organic systems, which are showing growing importance and potential in the literature. Recent advances in terms of device performance for these respective topics are reviewed, along with an outlook for each system.
Forrest RD, Chen GY, Silva SRP (2001) Electron field emission from amorphous carbon films as a function of deposition self bias, nitrogen content and substrate resistivity - experiment and simulation, MATERIALS CHEMISTRY AND PHYSICS 72 (2) pp. 204-209 ELSEVIER SCIENCE SA
Shannon JM, Sporea RA, Georgakopoulos S, Shkunov M, Silva SRP (2013) Low-Field Behavior of Source-Gated Transistors, IEEE Transactions on Electron Devices 60 (8) pp. 2444-2449 IEEE
A physical description of low-field behavior of a Schottky source-gated transistor (SGT) is outlined where carriers crossing the source barrier by thermionic emission are restricted by JFET action in the pinch-off region at the drain end of the source. This mode of operation leads to transistor characteristics with low saturation voltage and high output impedance without the need for field relief at the edge of the Schottky source barrier and explains many characteristics of SGT observed experimentally. 2-D device simulations with and without barrier lowering due to the Schottky effect show that the transistors can be designed so that the current is independent of source length and thickness variations in the semiconductor. This feature together with the fact that the current in an SGT is independent of source-drain separation hypothesizes the fabrication of uniform current sources and other large-area analog circuit blocks with repeatable performance even in imprecise technologies such as high-speed printing.
Bhattacharyya S, Rojas LG, Henley SJ, Silva SRP (2007) Switching behaviour and high frequency response of amorphous carbon double-barrier structures, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS 27 (5-8) pp. 957-960 ELSEVIER SCIENCE BV
Saavedra MS, Sims GD, McCartney LN, Stolojan V, Anguita JV, Tan YY, Ogin SL, Smith PA, Silva SRP (2012) Catalysing the production of multiple arm carbon octopi nanostructures, Carbon 50 (6) pp. 2141-2146 Elsevier
Octopus-like carbon nanofibres with leg diameters as small as 9 nm are reported, with a high yield over large areas, using a unique photo-thermal chemical vapour deposition system. The branched nature of these nanostructures leads to geometries ideal for increasing the surface area of contacts for many electronic and electrochemical devices. The manufacture of these structures involves a combination of a polyacrylonitrile/polysiloxane film covering the surface of cupronickel catalysts, supported on silicon. Acetylene is used as the carbon feedstock. High-resolution electron microscopy revealed a relationship between the geometry of the nanoparticles and the catalytic growth process, which can be tuned to maximise geometries (and therefore the surface area) and was obtained with a catalyst size of 125 nm. The technique proposed for growing these carbon octopi nanostructures is ideal to facilitate a new in situ transfer film process to place high-density carbon structures on secondary surfaces to produce high capacitance all-carbon contacts.
Poa CHP, Henley SJ, Chen GY, Adikaari AADT, Giusca CE, Silva SRP (2005) Growth and field emission properties of vertically aligned carbon nanofibers, JOURNAL OF APPLIED PHYSICS 97 (11) ARTN 114308 AMER INST PHYSICS
Sporea RA, Georgakopoulos S, Xu X, Guo X, Shkunov M, Shannon JM, Silva SRP (2013) Leveraging contact effects for field-effect transistor technologies with reduced complexity and superior current uniformity, Materials Research Society Symposium Proceedings 1553
In order to achieve high performance, the design of devices for large-area electronics needs to be optimized despite material or fabrication shortcomings. In numerous emerging technologies thin-film transistor (TFT) performance is hindered by contact effects. Here, we show that contact effects can be used constructively to create devices with performance characteristics unachievable by conventional transistor designs. Source-gated transistors (SGTs) are not designed with increasing transistor speed, mobility or sub-threshold slope in mind, but rather with improving certain aspects critical for real-world large area electronics such as stability, uniformity, power efficiency and gain. SGTs can achieve considerably lower saturation voltage and power dissipation compared to conventional devices driven at the same current; higher output impedance for over two orders of magnitude higher intrinsic gain; improved bias stress stability in amorphous materials; higher resilience to processing variations; current virtually independent of source-drain gap, source-gate overlap and semiconductor thickness variations. Applications such as amplifiers and drivers for sensors and actuators, low cost large area analog or digital circuits could greatly benefit from incorporating the SGT architecture. Copyright © Materials Research Society 2013.
Zhang W, Silva SRP (2010) Raman and FT-IR studies on dye-assisted dispersion and flocculation of single walled carbon nanotubes, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 77 (1) pp. 175-178 PERGAMON-ELSEVIER SCIENCE LTD
Curry RJ, adikaari, silva S, etchart I, Guering P, Berard M, cheetham A (2012) Near infrared up-conversion in organic photovoltaic devices using an efficient Yb3+:Ho3+ Co-doped Ln2BaZnO5 (Ln = Y, Gd) phosphor, Journal of Applied Physics 111 (9) 094502 American Institute of Physics
The first detailed study that combines the use of a new generation of high-efficiency Yb3+:Ho3+
co-doped Y2BaZnO5 near-infrared up-converting phosphors with organic photovoltaic devices
is reported. We show that it is possible to obtain a Jsc of 16 µA / cm2 under 986 nm illumination (~390 mW / cm2 corresponding to ~37 suns) leading to an up-conversion external quantum efficiency (UC EQE) of 0.0052%. Through modification of the organic photovoltaic devices to incorporate
transparent electrodes we show that UC EQE could be increased to 0.031 %, matching that achieved in amorphous-Si:H PV cells. Accounting for the full spectral range that may be absorbed by the phosphor(~870?1030 nm) yields an up-conversion power conversion efficiency (UC PCE) of 0.073% which again could be improved to 0.45% using transparent electrodes. This technique for utilizing the near-infrared spectral region may therefore offer a potential route to improving the performance of organic photovoltaic devices as research into discovering high-efficiency up-converting phosphors continues to provide improved materials.
Poa CHP, Silva SRP (2004) Effect of conductive filaments on the electron emission properties in cathodes, TECHNICAL DIGEST OF THE 17TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 76-77 IEEE
Forrest RD, Cox DC, Tang YF, Shannon JM, Silva SRP (2003) Fabrication of a self-aligned microtip field emission array, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 21 (4) pp. 1560-1565 A V S AMER INST PHYSICS
Kerr GL, Smith PR, Carey JD, Silva SRP (2007) Electrical conduction and transmission coefficients of suspended multiwalled carbon nanotubes, NANOTECHNOLOGY 18 (29) ARTN 295203 IOP PUBLISHING LTD
Smith RC, Forrest RD, Carey JD, Hsu WK, Silva SRP (2005) Interpretation of enhancement factor in nonplanar field emitters, APPLIED PHYSICS LETTERS 87 (1) ARTN 013111 AMER INST PHYSICS
Sporea RA, Guo X, Shannon JM, Silva SRP (2010) Polysilicon source-gated transistors for mixed-signal systems-on-panel, ECS Transactions 33 (5) pp. 419-424 Electrochemical Society
The performance benefits of using source-gated transistors (SGTs)
in analog large-area electronic circuits are examined practically
and via numerical simulations. In current mirror circuits made
using thin-film technology, significant advantages are observed for
SGT implementations. A comparison of current mirrors
implemented with standard field effect transistors (FETs) and
SGTs shows that the SGT version can operate at a lower voltage
and has larger output dynamic range for a given device geometry.
The results are explained in relation to the saturation mechanisms
of the SGT and are supported by experimental measurements of
polysilicon devices.
Borowiak-Palen E, Ruemmeli MH, Gemming T, Pichler T, Kalenczuk RJ, Silva SRP (2006) Silver filled single-wall carbon nanotubes - synthesis, structural and electronic properties, NANOTECHNOLOGY 17 (9) pp. 2415-2419 IOP PUBLISHING LTD
Burden AP, Forrest RD, Silva SRP (1999) Enhancing the field emission properties of amorphous carbon films by thermal annealing, THIN SOLID FILMS 337 (1-2) pp. 257-260 ELSEVIER SCIENCE SA
Guo X, Silva SRP (2004) Circuit simulation of current-modulated field emission display pixel driver based on carbon nanotubes, ELECTRONICS LETTERS 40 (18) pp. 1113-1115 IEE-INST ELEC ENG
SILVA SRP, AMARATUNGA GAJ, WOODBURN CN, WELLAND ME, HAQ S (1994) QUANTUM SIZE EFFECTS IN AMORPHOUS DIAMOND-LIKE CARBON SUPERLATTICES, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 33 (12A) pp. 6458-6465 JAPAN J APPLIED PHYSICS
Okano K, Koizumi S, Silva SRP, Amaratunga GAJ (1996) Low-threshold cold cathodes made of nitrogen-doped chemical-vapour-deposited diamond, NATURE 381 (6578) pp. 140-141 MACMILLAN MAGAZINES LTD
Sharma P, Anguita JV, Stolojan V, Henley SJ, Silva SRP (2010) The growth of silica and silica-clad nanowires using a solid-state reaction mechanism on Ti, Ni and SiO2 layers, NANOTECHNOLOGY 21 (29) ARTN 295603 IOP PUBLISHING LTD
Ruffini G, Dunne S, Farrés E, Watts PCP, Mendoza E, Silva SRP, Grau C, Marco-Pallarés J, Fuentemilla L, Vandecasteele B (2006) ENOBIO - First tests of a dry electrophysiology electrode using carbon nanotubes, Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings pp. 1826-1829
We describe the development and first tests of ENOBIO, a dry electrode sensor concept for biopotential applications. In the proposed electrodes the tip of the electrode is covered with a forest of multi-walled Carbon Nanotubes (CNTs) that can be coated with Ag/AgCl to provide ionic-electronic transduction. The CNT brush-like structure is to penetrate the outer layers of the skin improving electrical contact as well as increase the contact surface area. In this paper we report the results of the first tests of this concept-immersion on saline solution and pig skin signal detection. These indicate performance on a par with state of the art research-oriented wet electrodes. © 2006 IEEE.
Miller AJ, Hatton RA, Silva SRP (2006) Interpenetrating multiwall carbon nanotube electrodes for organic solar cells, APPLIED PHYSICS LETTERS 89 (13) ARTN 133117 AMER INST PHYSICS
Zhang W, Silva SRP (2010) The effects of phenolic hydrogens and methyl substitute groups in organic dyes on their dispersion of multiple-walled carbon nanotubes, CARBON 48 (7) pp. 2063-2071 PERGAMON-ELSEVIER SCIENCE LTD
Zhang W, Stolojan V, Silva SR, Wu CW (2013) Raman, EELS and XPS studies of maghemite decorated multi-walled carbon nanotubes., Spectrochim Acta A Mol Biomol Spectrosc 121 pp. 715-718
Iron oxide particles with the diameter being 5-10 nm were attached onto the sidewalls of multi-walled carbon nanotubes (MWCNTs) by the thermal decomposition of cyclopentadieny iron (II) dicarbonyl dimmer. The red shift of G-mode from 1579 cm(-1) to 1571 cm(-1) in the Raman profile of the decorated MWCNTs is indicative of the attachment of nanoparticles. Electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses reveals that the attached nanoparticles are composed of a maghemite phase. Transmission electron microscopy suggests the maghemite particles are covered with amorphous carbon materials and form a core-shell structure.
Miyajima Y, Shkunov M, Silva SRP (2009) Amorphous carbon and carbon nitride bottom gate thin film transistors, APPLIED PHYSICS LETTERS 95 (10) ARTN 102102 AMER INST PHYSICS
Henley SJ, Watts PCP, Mureau N, Silva SRP (2008) Laser-induced decoration of carbon nanotubes with metal nanoparticles, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING 93 (4) pp. 875-879 SPRINGER
Silva SRP, Xu S, Tay BX, Tan HS, Milne WI, Ravi S (1996) Nanocrystallites in tetrahedral amorphous carbon films (vol 69, pg 491, 1996), APPLIED PHYSICS LETTERS 69 (4) pp. 491-493 AMER INST PHYSICS
The microstructure of filtered cathodic vacuum arc deposited tetrahedral amorphous carbon films is studied as a function of ion energy. An optimum energy window in the density and C?C sp 3 content at an ion energy of
Tsang WM, Henley SJ, Stolojan V, Silva SRP (2006) Negative differential conductance observed in electron field emission from band gap modulated amorphous-carbon nanolayers, APPLIED PHYSICS LETTERS 89 (19) ARTN 193103 AMER INST PHYSICS
Smith RC, Silva SRP (2008) Design of carbon nanotubes for large-area electron field-emission cathodes, JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY 16 (5) pp. 615-624 SOC INFORMATION DISPLAY
Haberer D, Giusca CE, Wang Y, Sachdev H, Fedorov AV, Farjam M, Jafari SA, Vyalikh DV, Usachov D, Liu X, Treske U, Grobosch M, Vilkov O, Adamchuk VK, Irle S, Silva SRP, Knupfer M, Buechner B, Grueneis A (2011) Evidence for a New Two-Dimensional C4H-Type Polymer Based on Hydrogenated Graphene, ADVANCED MATERIALS 23 (39) pp. 4497-+
Zhang W, Silva SRP (2012) Alter the sheet resistance of carbon nanotube-coated cellulose fabric with argon plasma pretreatment, MICRO & NANO LETTERS 7 (8) pp. 850-853 INST ENGINEERING TECHNOLOGY-IET
Tsang WM, Adikaari AADT, Stolojan V, Sealy B, Wong SP, Silva SRP (2007) Improving the electron emission properties of ion-beam-synthesized Ag-SiO2 nanocomposites by pulsed laser annealing, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 91-92 IEEE
Smith RC, Carey JD, Poa CHP, Cox DC, Silva SRP (2004) Electron field emission from room temperature grown carbon nanofibers, JOURNAL OF APPLIED PHYSICS 95 (6) pp. 3153-3157 AMER INST PHYSICS
Beliatis MJ, Rozanski LJ, Jayawardena KDGI, Rhodes RW, Anguita JV, Mills CA, Silva SRP (2014) Hybrid and Nano-composite Carbon
Sensing Platforms,
5 pp. 105-132 Springer International Publishing Switzerland
Carbon nanomaterials offer a number of possibilities for sensing
platforms. The ability to chemically functionalize the surfaces of the
nano-carbon, using hybrid or nano-composite structures, can further
enhance the material properties. Complementary to the addition of
any requisite chemical or biochemical functionality, such
enhancements can take the form of improved electrical, optical or
morphological properties which improve the transduction capabilities
of the carbon nano-material, or facilitate detection of the transduced
signal, for example by improving charge transfer to detection
electronics. Here we review the methods of producing hybrid and
nano-composite carbon structures for sensing systems, highlighting
the advantages of the functionalization in each case and benchmark
their performance against existing carbon-only devices. Finally, we
detail some of the recent applications of hybrid and nano-composite
carbon technologies in a wide variety of sensor technologies.
Barradas NP, Khan RUA, Anguita JV, Silva SRP, Kreissig U, Grotzschel R, Moller W (2000) Growth and characterisation of amorphous carbon films doped with nitrogen, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 161 pp. 969-974 ELSEVIER SCIENCE BV
Lyth SM, Silva SRP (2007) Field emission from multiwall carbon nanotubes on paper substrates, APPLIED PHYSICS LETTERS 90 (17) ARTN 173124 AMER INST PHYSICS
Schwan J, Ulrich S, Batori V, Ehrhardt H, Silva SRP (1996) Raman spectroscopy on amorphous carbon films, JOURNAL OF APPLIED PHYSICS 80 (1) pp. 440-447 AMER INST PHYSICS
Henley SJ, Carey JD, Silva SRP, Fuge GM, Ashfold MNR, Anglos D (2005) Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite, Physical Review B - Condensed Matter and Materials Physics 72 (20)
The optical emission from electronically excited C species in the ablation plume following the short (ns) and ultrashort (fs) UV pulsed laser ablation of graphite is studied. Wavelength, time and spatially resolved imaging of the plume, in background pressures of inert gases such as argon and helium, is performed. Analysis of images of optical emission from C+* ions and C2* radicals, yielded estimates of the apparent velocity of emitting species, which appear to arise both from the initial ablation event and, in the presence of background gas, mainly from impact excitation. At elevated background pressures of argon (PAr), the formation and propagation of a shock wave is observed for ns pulses, whereas for fs pulses, the propagation of two shock waves is observed. During fs ablation, the first shock wave we associate with an initial burst of highly energetic/electronically excited ablated components, indicative of an enhanced fraction of non-thermal ejection mechanisms when compared with ns ablation. The second shock wave we associate with subsequently ejected, slower moving, material. Concurrent with the plume dynamics investigations, nanostructured amorphous carbon materials were deposited by collecting the ablated material. By varying PAr from 5 to 340 mTorr, the film morphology could be changed from mirror smooth, through a rough nanostructured phase and, at the highest background pressures for ns pulses, to a low density cluster-assembled material. The evident correlations between the film structure, the mean velocities of the emitting C species, and their respective dependences upon PAr are discussed for both pulse durations. In addition, we comment on the effect of observed initial plume dynamics on the subsequent C cluster formation in the expanding plume. © 2005 The American Physical Society.
Shang N, Papakonstantinou P, Wang P, Silva SRP (2010) Platinum integrated graphene for methanol fuel cells, Journal of Physical Chemistry C 114 (37) pp. 15837-15841 American Chemical Society
Uniform and porous graphene nanoflake films (GNFs) have been investigated as a support for catalytic Pt nanoclusters in direct methanol electro-oxidation. Pt nanoclusters of varying thickness are deposited on GNFs using magnetron sputtering, and their effects on the electrocatalytic activity for oxidizing methanol are systemically studied. GNF supported Pt nanoclusters with ultralow catalyst loading exhibit high performance for methanol electrocatalytic oxidation with a large mass-specific peak current density and a ratio of forward to backward peak currents up to 1.4. These characteristics compare favorably to the majority of Pt?C based electrodes, except for those of carbon nanotubes with Pt decoration on both the inner and the outer wall surfaces. The results obtained are ascribed to a highly coupled network made of high-density 2?4 nm Pt monolayer nanoclusters on both the basal and edge planes of each nanoflakes of graphene. GNFs are a promising support material for developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy.
Nanditha DM, Dissanayake M, Adikaari AADT, Curry RJ, Hatton RA, Silva SRP (2007) Nanoimprinted large area heterojunction pentacene-C-60 photovoltaic device, APPLIED PHYSICS LETTERS 90 (25) ARTN 253502 AMER INST PHYSICS
Ohashi F, Chen GY, Stolojan V, Silva SRP (2008) Influences of hydrogen gas on carbon nanotube growth, Materials Research Society Symposium Proceedings 1081 pp. 87-93
For practical deployment of carbon nanotubes for real world applications, an understanding of their growth mechanism is required in order to obtain better control over their crystallinity, chirality and other structural properties. In this study, we focus on the influences of gas species on carbon nanotube synthesis using thermal chemical vapour deposition. The influences of methane, hydrogen and helium gases were investigated from the viewpoint of gas chemistry in relation to structural changes in the resulting nanotubes, by varying the growth pressure, the gas-flow ratio and the growth temperature. Simple changes in the hydrogen gas concentration during different growth stages have been found to induce surprising changes to the nanotube structure, varying from amorphous to graphitic as the growth temperature and the concentration of hydrogen in the initial periods of growth decreased. The excess hydrogen tends to give rise to poor crystalline carbon nanofibres but has the effect of increasing the yield. Hydrogen gas is typically used in reducing the metal catalyst particles during the pre-treatment and the carbon nanotube growth periods. We show that while hydrogen species can improve yield, it can also result in the degradation of the nanotube's crystallinity. The use of hydrogen in the growth process is one of the key parameters for enhanced control of carbon nanotube/nanofibre growth and their resulting crystallinity. © 2008 Materials Research Society.
Lyth SM, Hatton RA, Silva SRP (2007) Efficient field emission from Li-salt functionalized multiwall carbon nanotubes on flexible substrates, APPLIED PHYSICS LETTERS 90 (1) ARTN 013120 AMER INST PHYSICS
Tison Y, Giusca CE, Stolojan V, Hayashi Y, Silva SRP (2008) The inner shell influence on the electronic structure of double-walled carbon nanotubes, ADVANCED MATERIALS 20 (1) pp. 189-+ WILEY-V C H VERLAG GMBH
Ruffini G, Dunne S, Farrés E, Cester I, Watts PCP, Silva SRP, Grau C, Fuentemilla L, Marco-Pallares J, Vandecasteele B (2007) ENOBIO dry electrophysiology electrode; first human trial plus wireless electrode system, Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings pp. 6689-6693
This paper presents the results of the first human trials with the ENOBIO electrophysiology electrode prototype plus the initial results of a new wireless prototype with flexible electrodes based on the same platform. The results indicate that a dry active electrode that employs a CNT array as the electrode interface can perform on a par with traditional "wet" electrodes for the recording of EEG, ECG, EOG and EMG. We also demonstrate a new platform combining wireless technology plus flexible electrodes for improved comfort for applications that take advantage of the dry electrode concept. © 2007 IEEE.
Hatton RA, Miller AJ, Silva SRP (2008) Carbon nanotubes: a multi-functional material for organic optoelectronics, JOURNAL OF MATERIALS CHEMISTRY 18 (11) pp. 1183-1192 ROYAL SOC CHEMISTRY
Nismy NA, Adikaari AADT, Silva SRP (2010) Functionalized multiwall carbon nanotubes incorporated polymer/fullerene hybrid photovoltaics, APPLIED PHYSICS LETTERS 97 (3) ARTN 033105 AMER INST PHYSICS
Xu S, Tay BK, Tan HS, Zhong L, Tu YQ, Silva SRP, Milne WI (1996) Properties of carbon ion deposited tetrahedral amorphous carbon films as a function of ion energy, JOURNAL OF APPLIED PHYSICS 79 (9) pp. 7234-7240 AMER INST PHYSICS
Heister E, Neves V, Tilmaciu C, Lipert K, Beltran VS, Coley HM, Silva SRP, McFadden J (2009) Triple functionalisation of single-walled carbon nanotubes with doxorubicin, a monoclonal antibody, and a fluorescent marker for targeted cancer therapy, CARBON 47 (9) pp. 2152-2160 PERGAMON-ELSEVIER SCIENCE LTD
Schwan J, Ulrich S, Roth H, Ehrhardt H, Silva SRP, Robertson J, Samlenski R, Brenn R (1996) Tetrahedral amorphous carbon films prepared by magnetron sputtering and dc ion plating, JOURNAL OF APPLIED PHYSICS 79 (3) pp. 1416-1422 AMER INST PHYSICS
Filip LD, Smith RC, Carey JD, Silva SRP (2009) Electron transfer from a carbon nanotube into vacuum under high electric fields, JOURNAL OF PHYSICS-CONDENSED MATTER 21 (19) ARTN 195302 IOP PUBLISHING LTD
Kurzyp M, Mills C, Rhodes R, Pozegic T, Smith C, Beliatis M, Rozanski L, Werbowy A, Silva S (2015) Filtration properties of hierarchical carbon nanostructures deposited on carbon fibre fabrics, JOURNAL OF PHYSICS D-APPLIED PHYSICS 48 (11) ARTN 11530 IOP PUBLISHING LTD
© 2015 IOP Publishing Ltd.Hierarchical carbon nanostructures have been produced and examined for their use in liquid filtration experiments. The nanostructures are based on carbon nanotube growth and graphite oxide sponge deposition on the surface of commercially available carbon fibre fabrics. The hierarchical nanomaterial construction on the carbon fibre fabric is made possible due to the chemical vapour deposited carbon nanotubes which act as anchoring sites for the solution deposited sponge nanomaterial. The nanomaterials show a high capacity for Rhodamine B filtration, with the carbon fibre - carbon nanotube - graphite oxide sponge fabric showing filtering performance comparable to a commercial activated carbon filter. After 40 successive filtrations of 10 mg ml-1 Rhodamine B solution, the filtrate of dual modified fabrics returned an increase in transparency of 94% when measured at approx. 550 nm compared to 72% for the commercial carbon filter. When normalised with respect to the areal density of the commercial filter, the increase in optical transparency of the filtrate from the dual modified fabrics reduces to 65%. The Rhodamine B is found to deposit in the carbon nanomaterials via a nucleation, growth and saturation mechanism.
Miyajima Y, Tison Y, Giusca CE, Stolojan V, Watanabe H, Habuchi H, Henley SJ, Shannon JM, Silva SRP (2011) Probing the band structure of hydrogen-free amorphous carbon and the effect of nitrogen incorporation, CARBON 49 (15) pp. 5229-5238 PERGAMON-ELSEVIER SCIENCE LTD
Dissanayake DMNM, Adikaari AADT, Silva SRP (2008) Enhanced photovoltaic performance in nanoimprinted pentacene-PbS nanocrystal hybrid device, APPLIED PHYSICS LETTERS 92 (9) ARTN 093308 AMER INST PHYSICS
Filip LD, Nicolaescu D, Silva SRP (2005) Quantum size dependence of electron distribution on carbon nanotubes and its influence on field emission, Technical Digest of the 18th International Vacuum Nanoelectronics Conference, IVNC 2005 2005 pp. 87-88
Smith RC, Carey JD, Cox DC, Silva SRP (2006) In situ electrode manipulation for three terminal field emission characterization of individual carbon nanotubes, APPLIED PHYSICS LETTERS 89 (6) ARTN 063111 AMER INST PHYSICS
Silva SRP, Robertson J, Rusli, Amaratunga GAJ, Schwan J (1996) Structure and luminescence properties of an amorphous hydrogenated carbon, PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES 74 (4) pp. 369-386 TAYLOR & FRANCIS LTD
Khan RUA, Silva SRP, van Swaaij RACMM (2003) Polymeric amorphous carbon as p-type window within amorphous silicon solar cells, APPLIED PHYSICS LETTERS 82 (22) pp. 3979-3981 AMER INST PHYSICS
Sporea RA, Trainor MJ, Young ND, Shannon JM, Silva SR (2014) Source-gated transistors for order-of-magnitude performance improvements in thin-film digital circuits., Sci Rep 4
Ultra-large-scale integrated (ULSI) circuits have benefited from successive refinements in device architecture for enormous improvements in speed, power efficiency and areal density. In large-area electronics (LAE), however, the basic building-block, the thin-film field-effect transistor (TFT) has largely remained static. Now, a device concept with fundamentally different operation, the source-gated transistor (SGT) opens the possibility of unprecedented functionality in future low-cost LAE. With its simple structure and operational characteristics of low saturation voltage, stability under electrical stress and large intrinsic gain, the SGT is ideally suited for LAE analog applications. Here, we show using measurements on polysilicon devices that these characteristics lead to substantial improvements in gain, noise margin, power-delay product and overall circuit robustness in digital SGT-based designs. These findings have far-reaching consequences, as LAE will form the technological basis for a variety of future developments in the biomedical, civil engineering, remote sensing, artificial skin areas, as well as wearable and ubiquitous computing, or lightweight applications for space exploration.
Rosolen JM, Tronto S, Marchesin MS, Almeida EC, Ferreira NG, Poa CHP, Silva SRP (2006) Electron field emission from composite electrodes of carbon nanotubes-boron-doped diamond and carbon felts, APPLIED PHYSICS LETTERS 88 (8) ARTN 083116 AMER INST PHYSICS
Damitha AA, Adikaari T, Silva SRP, Kearney MJ, Shannon JM (2005) Improved efficiency in hydrogenated amorphous silicon solar cells irradiated by excimer laser, Materials for Photovoltaics 836 pp. 279-284 MATERIALS RESEARCH SOCIETY
Neves V, Heister E, Costa S, Tîlmaciu C, Flahaut E, Soula B, Coley HM, McFadden J, Silva SR (2012) Design of double-walled carbon nanotubes for biomedical applications., Nanotechnology 23 (36) Institute of Physics
Double-walled carbon nanotubes (DWNTs) prepared by catalytic chemical vapour deposition were functionalized in such a way that they were optimally designed as a nano-vector for the delivery of small interfering RNA (siRNA), which is of great interest for biomedical research and drug development. DWNTs were initially oxidized and coated with a polypeptide (Poly(Lys:Phe)), which was then conjugated to thiol-modified siRNA using a heterobifunctional cross-linker. The obtained oxDWNT-siRNA was characterized by Raman spectroscopy inside and outside a biological environment (mammalian cells). Uptake of the custom-designed nanotubes was not associated with detectable biochemical perturbations in cultured cells, but transfection of cells with DWNTs loaded with siRNA targeting the green fluorescent protein (GFP) gene, serving as a model system, as well as with therapeutic siRNA targeting the survivin gene, led to a significant gene silencing effect, and in the latter case a resulting apoptotic effect in cancer cells.
Alshammari AS, Shkunov M, Silva SRP (2014) Inkjet printed PEDOT: PSS/MWCNT nano-composites with aligned carbon nanotubes and enhanced conductivity, Physica Status Solidi - Rapid Research Letters 8 (2) pp. 150-153
Conductive patterns of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/multi-walled carbon nanotube (MWCNT) composites were deposited on glass substrates using a drop on demand (DOD) inkjet printer, with the concentration of CNT varied from 0.01 wt% to 0.05 wt%. We show that by increasing the concentration of the nanotubes in the ink, percolated networks of well distributed carbon nanotubes in the printed samples can be achieved. Moreover, the orientation of the nanotubes in the printed sample can be controlled using a novel simple approach. The impact of the nanotube alignment on the conduction properties of inkjet printed nano-hybrid materials is studied and shown in this Letter. Samples with aligned nanotubes show a 53% enhanced conductivity in comparison with the randomly oriented nanotubes. The results show that the electrical performance of the nano-composite can be improved further by controlling the dispersion and orientation of the nano-filler in the printed samples. Carbon nanotubes orientation control in the printed PEDOT:PSS/MWCNT nano-composite samples. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Poa CHP, Silva SRP, Lacerda RG, Amaratunga GAJ, Milne WI, Marques FC (2005) Effects of applying stress on the electron field emission properties in amorphous carbon thin films, APPLIED PHYSICS LETTERS 86 (23) ARTN 232102 AMER INST PHYSICS
Shang N, Kumar A, Sun N, Sharma S, Papakonstantinou P, Li M, Blackley RA, Zhou W, Karlsson LS, Silva SRP (2012) Vertical graphene nanoflakes for the immobilization, electrocatalytic oxidation and quantitative detection of DNA, Electrochemistry Communications 25 (1) pp. 140-143
Vertical graphene nanoflake integrated films having a high density of edge planes have been used as an electrochemical platform to systematically investigate the immobilization, electrochemical oxidation kinetics and direct quantitative determination of native DNA. Consistently, both transmission electron microscopy and atomic force microscopy observations demonstrate the presence of a self-assembled monolayer of native DNA, immobilized on the graphene nanoflakes. Graphene shows excellent electrocatalytic activity for the electrooxidation of double stranded DNA, better than carbon nanotubes and glassy carbon, due to the abundance of electrocatalytic graphene edges present not only at the top but also along the sides of each graphene nanoflake. © 2012 Elsevier B.V.
Collins M, Barklie RC, Anguita JV, Carey JD, Silva SRP (2000) Characterisation of defects in thin films of hydrogenated amorphous carbon, DIAMOND AND RELATED MATERIALS 9 (3-6) pp. 781-785 ELSEVIER SCIENCE SA
Henley SJ, Silva SRP, Carey JD (2007) Surface morphology and evolution of amorphous carbon thin films, DIAMOND AND RELATED MATERIALS 16 (10) pp. 1777-1781 ELSEVIER SCIENCE SA
Quo X, Adikaari AADT, Silva SRP (2006) Performance evaluation and design guidelines of sub-100-nm source/drain unilateral-crystallized poly-Si TFTs for SoP applications, IDW '06: PROCEEDINGS OF THE 13TH INTERNATIONAL DISPLAY WORKSHOPS, VOLS 1-3 pp. 1667-1670 INST IMAGE INFORMATION & TELEVISION ENGINEERS
Henley SJ, Carey JD, Silva SRP (2007) Metal nanoparticle production by pulsed laser nanostructuring of thin metal films, APPLIED SURFACE SCIENCE 253 (19) pp. 8080-8085 ELSEVIER SCIENCE BV
Champi A, Ferlauto AS, Alvarez F, Silva SRP, Marques FC (2008) On the elastic constants of amorphous carbon nitride, DIAMOND AND RELATED MATERIALS 17 (11) pp. 1850-1852 ELSEVIER SCIENCE SA
Misra SK, Watts PCP, Valappil SP, Silva SRP, Roy I, Boccaccini AR (2007) Poly(3-hydroxybutyrate)/Bioglass (R) composite films containing carbon nanotubes, NANOTECHNOLOGY 18 (7) ARTN 075701 IOP PUBLISHING LTD
Kerr L, Cox C, Stolojan V, Silva P (2008) Characterisation of electron-beam deposited tungsten interconnects, Journal of Physics: Conference Series 126 (1) 012073
Silva SRP, Forrest RD, Shannon JM (1998) Electron emission from amorphous silicon thin films, JOURNAL OF NON-CRYSTALLINE SOLIDS 227 pp. 1101-1105 ELSEVIER SCIENCE BV
Jeynes JCG, Jeynes C, Kirkby KJ, Ruemmeli A, Silva SRP (2008) RBS/EBS/PIXE measurement of single-walled carbon nanotube modification by nitric acid purification treatment, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 266 (8) pp. 1569-1573 ELSEVIER SCIENCE BV
Sporea RA, Georgakopoulos S, Shkunov M, Shannon JM, Silva SRP, Xu X, Guo X (2013) Leveraging contact effects for field-effect transistor technologies with reduced complexity and superior current uniformity, International Review of the Red Cross 1553 (888)
In order to achieve high performance, the design of devices for large-area electronics needs to be optimized despite material or fabrication shortcomings. In numerous emerging technologies thin-film transistor (TFT) performance is hindered by contact effects. Here, we show that contact effects can be used constructively to create devices with performance characteristics unachievable by conventional transistor designs. Source-gated transistors (SGTs) are not designed with increasing transistor speed, mobility or sub-threshold slope in mind, but rather with improving certain aspects critical for real-world large area electronics such as stability, uniformity, power efficiency and gain. SGTs can achieve considerably lower saturation voltage and power dissipation compared to conventional devices driven at the same current; higher output impedance for over two orders of magnitude higher intrinsic gain; improved bias stress stability in amorphous materials; higher resilience to processing variations; current virtually independent of source-drain gap, source-gate overlap and semiconductor thickness variations. Applications such as amplifiers and drivers for sensors and actuators, low cost large area analog or digital circuits could greatly benefit from incorporating the SGT architecture.
Tsang WM, Adikaari AADT, Stolojan V, Sealy B, Wong SP, Silva SRP (2007) Improving the electron emission properties of ion-beam-synthesized Ag-SiO2 nanocomposites by pulsed laser annealing, Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07 pp. 102-103
Carey JD, Silva SRP (2001) Current-induced conditioning of hydrogenated amorphous carbon thin films for field emission, DIAMOND AND RELATED MATERIALS 10 (3-7) pp. 873-877 ELSEVIER SCIENCE SA
Li Y-H, Zhao YM, Roe M, Furniss D, Zhu YQ, Silva SRP, Wei JQ, Wu DH, Poa CHP (2006) In-plane large single-walled carbon nanotube films: In situ synthesis and field-emission properties, SMALL 2 (8-9) pp. 1026-1030 WILEY-V C H VERLAG GMBH
Shi X, Cheah LK, Tay BK, Silva SRP (1999) Electron field emission from surface treated tetrahedral amorphous carbon films, APPLIED PHYSICS LETTERS 74 (6) pp. 833-835 AMER INST PHYSICS
Silva SRP, Anguita JV (2011) Material having a Low Dielectric Constant and Method of Making the Same,
Rozanski LJ, Castaldelli E, Sam FLM, Mills CA, Demets GJ-F, Silva SRP (2013) Solution processed naphthalene diimide derivative as electron transport layers for enhanced brightness and efficient polymer light emitting diodes, Journal of Materials Chemistry C 1 (20) pp. 3347-3352 Royal Society of Chemistry
Increasing the efficiency and lifetime of polymer light emitting diodes (PLEDs) requires a balanced injection
and flow of charges through the device, driving demand for cheap and effective electron transport/hole
blocking layers. Some materials, such as conjugated polyelectrolytes, have been identified as potential
candidates but the production of these materials requires complex, and hence costly, synthesis routes.
We have utilized a soluble small molecule naphthalene diimide derivative (DC18) as a novel electron
transport/hole blocking layer in common PLED architectures, and compared its electronic properties to
those of the electron transport/hole blocking small molecule bathocuproine (BCP). PLEDs incorporating
DC18 as the electron transport layer reduce turn on voltage by 25%; increase brightness over three and
a half times; and provide a full five-fold enhancement in efficiencies compared to reference devices.
While DC18 has similar properties to the effective conjugated polyelectrolytes used as electron transport
layers, it is simpler to synthesise, reducing cost while retaining favourable electron transport properties,
and producing a greater degree of efficiency enhancement. The impact on device lifetime is
hypothesized to be significant as well, due to the air-stability seen in many naphthalene diimide derivatives.
Young WT, Silva SRP, Anguita JV, Shannon JM, Homewood KP, Sealy BJ (2000) Low temperature growth of gallium nitride, DIAMOND AND RELATED MATERIALS 9 (3-6) pp. 456-459 ELSEVIER SCIENCE SA
Filip LD, Carey JD, Silva SRP (2011) Exact equipotential profile mapping: A self-validating method, JOURNAL OF APPLIED PHYSICS 109 (8) ARTN 084527 AMER INST PHYSICS
Tsang WM, Henley SJ, Stolojan V, Silva SRP (2006) Negative differential conductance observed in electron field emission from band gap modulated A-C nanolayers, IVNC and IFES 2006 - Technical Digest - l9th International Vacuum Nanoelectronics Conference and 50th International Field Emission Symposium pp. 199-200
Carey JD, Silva SRP (2001) Field emission from amorphous semiconductors, SOLID-STATE ELECTRONICS 45 (6) pp. 1017-1024 PERGAMON-ELSEVIER SCIENCE LTD
Alenezi MR, Alshammari AS, Jayawardena KDGI, Beliatis MJ, Henley SJ, Silva SRP (2013) Role of the exposed polar facets in the performance of thermally and UV activated ZnO nanostructured gas sensors, Journal of Physical Chemistry C 117 (34) pp. 17850-17858
ZnO nanostructures with different morphologies (nanowires, nanodisks, and nanostars) were synthesized hydrothermally. Gas sensing properties of the as-grown nanostructures were investigated under thermal and UV activation. The performance of the ZnO nanodisk gas sensor was found to be superior to that of other nanostructures (Sg
Carey JD, Forrest RD, Khan RUA, Silva SRP (2000) Influence of sp(2) clusters on the field emission properties of amorphous carbon thin films, APPLIED PHYSICS LETTERS 77 (13) PII [S0003-6951(00)01639-9] pp. 2006-2008 AMER INST PHYSICS
Giusca CE, Tison Y, Silva SRP (2008) INTER-LAYER INTERACTION IN DOUBLE-WALLED CARBON NANOTUBES EVIDENCED BY SCANNING TUNNELING MICROSCOPY AND SPECTROSCOPY, NANO 3 (2) pp. 65-73 WORLD SCIENTIFIC PUBL CO PTE LTD
Alenezi MR, Henley SJ, Emerson NG, Silva SR (2013) From 1D and 2D ZnO nanostructures to 3D hierarchical structures with enhanced gas sensing properties., Nanoscale 6 (1) pp. 235-247
Facile and low cost hydrothermal routes are developed to fabricate three-dimensional (3D) hierarchical ZnO structures with high surface-to-volume ratios and an increased fraction of (0001) polar surfaces. Hierarchical ZnO nanowires (ZNWs) and nanodisks (ZNDs) assembled from initial ZnO nanostructures are prepared from sequential nucleation and growth following a hydrothermal process. These hierarchical ZnO structures display an enhancement of gas sensing performance and exhibit significantly improved sensitivity and fast response to acetone in comparison to other mono-morphological ZnO, such as nanoparticles, NWs, or NDs. In addition to the high surface-to-volume ratio due to its small size, the nanowire building blocks show the enhanced gas sensing properties mainly ascribed to the increased proportion of exposed active (0001) planes, and the formation of many nanojunctions at the interface between the initial ZnO nanostructure and secondary NWs. This work provides the route for structure induced enhancement of gas sensing performance by designing a desirable nanostructure, which could also be extended to synthesize other metal oxide nanostructures with superior gas sensing performance.
SILVA SRP, CLAY KJ, SPEAKMAN SP, AMARATUNGA GAJ (1995) DIAMOND-LIKE CARBON THIN-FILM DEPOSITION USING A MAGNETICALLY CONFINED RF PECVD SYSTEM, DIAMOND AND RELATED MATERIALS 4 (7) pp. 977-983 ELSEVIER SCIENCE SA LAUSANNE
Dissanayake DMNM, Hatton RA, Lutz T, Curry RJ, Silva SRP (2009) The fabrication and analysis of a PbS nanocrystal:C-60 bilayer hybrid photovoltaic system, NANOTECHNOLOGY 20 (24) ARTN 245202 IOP PUBLISHING LTD
Henley SJ, Carey JD, Silva SRP (2004) Room temperature photoluminescence from nanostructured amorphous carbon, Applied Physics Letters 85 (25) pp. 6236-6238
Visible room-temperature photoluminescence (PL) was observed from hydrogen-free nanostructured amorphous carbon films deposited by pulsed laser ablation in different background pressures of argon (PAr). By varying PAr from 5 to 340 mTorr, the film morphology changed from smooth to rough and at the highest pressures, low-density filamentary growth was observed. Over the same pressure regime an increase in the ordering of s p2 bonded C content was observed using visible Raman spectroscopy. The origin of the PL is discussed in terms of improved carrier localization within an increased s p2 rich phase. © 2004 American Institute of Physics.
Miyajima Y, Shannon JM, Henley SJ, Stolejan V, Cox DC, Silva SRP (2007) Electrical conduction mechanism in laser deposited amorphous carbon, THIN SOLID FILMS 516 (2-4) pp. 257-261 ELSEVIER SCIENCE SA
Jones BJ, Barklie RC, Smith G, El Mkami H, Carey JD, Silva SRP (2003) An EPR study at X- and W-band of defects in a-C : H films in the temperature range 5-300 K, DIAMOND AND RELATED MATERIALS 12 (2) pp. 116-123 ELSEVIER SCIENCE SA
Guo X, Silva SRP (2005) Active-matrix addressing for carbon nanotube field emission displays, PROCEEDINGS OF THE TWENTY-FIFTH INTERNATIONAL DISPLAY RESEARCH CONFERENCE - EURODISPLAY 2005 pp. 366-368 SOC INFORMATION DISPLAY
Lyth SM, Filip LD, Cox DC, Silva SRP (2007) Novel carbon nanotube based three terminal devices, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 214-215 IEEE
Melios C, Spencer S, Shard A, Strupinski W, Silva SRP, Kazakova O (2016) Surface and interface structure of quasi-free standing graphene on SiC, 2D MATERIALS 3 (2) ARTN 025023 IOP PUBLISHING LTD
Smith RC, Filip LD, Carey JD, Silva SRP (2007) Calculation of field enhancement factor and screening effects in carbon nanotube arrays, 2007 IEEE 20TH INTERNATIONAL VACUUM NANOELECTRONICS CONFERENCE pp. 155-156 IEEE
Carey JD, Smith RC, Silva SRP (2006) Carbon based electronic materials: applications in electron field emission, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 17 (6) pp. 405-412 SPRINGER
Tan YY, Jayawardena KDGI, Adikaari AADT, Tan LW, Anguita JV, Henley SJ, Stolojan V, Carey JD, Silva SRP (2012) Photo-thermal chemical vapor deposition growth of graphene, Carbon 50 (2) pp. 668-673 Elsevier
The growth of graphene on Ni using a photo-thermal chemical vapor deposition (PT-CVD) technique is reported. The non-thermal equilibrium nature of PT-CVD process resulted in a much shorter duration in both heating up and cooling down stages, thus allowing for a reduction in the overall growth time. Despite the reduced time for synthesis compared to standard thermal chemical vapor deposition (T-CVD), there was no decrease in the quality of the graphene film produced. Furthermore, the graphene formation under PT-CVD is much less sensitive to cooling rate than that observed for T-CVD process. Growth on Ni also allows for the alleviation of hydrogen blister damage that is commonly encountered during growth on Cu substrates and a lower processing temperature. To characterize the film?s electrical and optical properties, we further report the use of pristine PT-CVD grown graphene as the transparent electrode material in an organic photovoltaic device (OPV) with poly(3-hexyl)thiophene (P3HT)/phenyl-C61-butyric acid methyl ester (PCBM) as the active layer where the power conversion efficiency of the OPV cell is found to be comparable to that reported using pristine graphene prepared by conventional CVD.
Zhang W, Zuo X, Zhang D, Wu C, Silva SRP (2016) Cr3+ substituted spinel ferrite nanoparticles with high coercivity, NANOTECHNOLOGY 27 (24) ARTN 245707 IOP PUBLISHING LTD
Sam FLM, Dabera GDMR, Lai KT, Mills CA, Rozanski LJ, Silva SRP (2014) Hybrid metal grid-polymer-carbon nanotubes electrodes for high luminance organic light emitting diodes, Nanotechnology 25 (34) 345202 Institute of Physics
Organic light emitting diodes (OLEDs) incorporating grid transparent conducting electrodes (TCEs) with wide grid line spacing suffer from an inability to transfer charge carriers across the gaps in the grids to promote light emission in these areas. High luminance OLEDs fabricated using a hybrid transparent conducting electrode (TCE) composed of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS PH1000) or regioregular poly(3-hexylthiophene)-wrapped semiconducting single-walled carbon nanotubes (rrP3HT-SWCNT) in combination with a nanometre thin gold grid are reported here. OLEDs fabricated using the hybrid gold grid/PH1000 TCE have a luminance of 18,000 cd/m2 at 9 V; the same as the reference indium tin oxide (ITO) OLED. The gold grid/rrP3HT-SWCNT OLEDs have a lower luminance of 8,260 cd/m2 at 9 V, which is likely due to a rougher rrP3HT-SWCNT surface. These results demonstrate that the hybrid gold grid/PH1000 TCE is a promising replacement for ITO in future plastic electronics applications including OLEDs and organic photovoltaics (OPVs). For applications where surface roughness is not critical, e.g. electrochromic devices or discharge of static electricity, the gold grid/rrP3HT-SWCNT hybrid TCE can be employed.
Sporea RA, Overy M, Shannon JM, Silva SRP (2015) Temperature dependence of the current in Schottky-barrier source-gated transistors, Journal of Applied Physics 117 (18)
© 2015 AIP Publishing LLC.The temperature dependence of the drain current is an important parameter in thin-film transistors. In this paper, we propose that in source-gated transistors (SGTs), this temperature dependence can be controlled and tuned by varying the length of the source electrode. SGTs comprise a reverse biased potential barrier at the source which controls the current. As a result, a large activation energy for the drain current may be present which, although useful in specific temperature sensing applications, is in general deleterious in many circuit functions. With support from numerical simulations with Silvaco Atlas, we describe how increasing the length of the source electrode can be used to reduce the activation energy of SGT drain current, while maintaining the defining characteristics of SGTs: low saturation voltage, high output impedance in saturation, and tolerance to geometry variations. In this study, we apply the dual current injection modes to obtain drain currents with high and low activation energies and propose mechanisms for their exploitation in future large-area integrated circuit designs.
Knox-Davies EC, Shannon JM, Silva SRP (2006) The properties and deposition process of GaN films grown by reactive sputtering at low temperatures, JOURNAL OF APPLIED PHYSICS 99 (7) ARTN 073503 AMER INST PHYSICS
Anguita JV, Silva SRP, Young W (2000) Photoluminescence from polymer-like hydrogenated and nitrogenated amorphous carbon films, JOURNAL OF APPLIED PHYSICS 88 (9) PII [S0021-8979(00)01122-1] pp. 5175-5179 AMER INST PHYSICS
Zeze DA, Silva SRP, Brown NMD, Joyce AM, Anderson CA (2002) Targeting mass-selected cluster ions for the deposition of advanced carbonaceous materials using an inductively coupled plasma, Journal of Applied Physics 91 (3) pp. 1819-1827
Study has been initiated of the deposition of thin films using cluster ions in differing abundances generated in a pulsed inductively coupled plasma. A pulse unit controlling the "on" and "off" timing ratio of a 13.56 MHz rf power supply is used to alter systematically the composition of the contents of the plasma. Adamantane (C10H16) vapor, in argon or nitrogen, was selected as precursor for the deposition of CxHy or CxNyHz thin films using this pulsed source. The effect of varying the relative abundances of the cluster ions present in the resultant plasmas on the films produced, by changing driving power on/off ratio, is investigated. The mass-energy diagnostic data recorded under 50/150 and 150/50 ¼s on/off pulse sequences showed that fragmentation of C10H16 is a function of the switching ratio selected, i.e., clusters of different sizes and abundances are thus produced. Langmuir probe data also suggest that the electrical characteristics of the plasma generated under these regimes can be monitored. Postdeposition x-ray photoelectron spectroscopy (XPS) analysis of specimen films deposited under the same on/off regimes, within a 200 ¼s cycle, indicate clear differences are present in these films in terms of the atomic concentration, the C1s envelope bandwidths, and profiles. Contact angle measurements and optical data performed were found to reflect the variations in the differently deposited films already indicated in the XPS data. For example, specimens deposited under a 50/150 on/off ratio show a high contact angle (low surface energy) and lower refractive index, whereas those deposited under a 150/50 ratio exhibit a low contact angle (high surface energy). Films prepared using the same precursor streams but with the further on/off ratios, 20/180, 100/100, and 20/180 ¼s, were also considered. Postdeposition analyses confirmed the same tends in the fragmentation behavior of C10H16. Finally, the significance of such a cluster ions selection technique is discussed. © 2002 American Institute of Physics.
Henley SJ, Fryar J, Jayawardena KDGI, Silva SRP (2010) Laser-assisted hydrothermal growth of size-controlled ZnO nanorods for sensing applications, NANOTECHNOLOGY 21 (36) ARTN 365502 IOP PUBLISHING LTD
Miyajima Y, Adikaari A, Henley SJ, Shannon JM, Silva SRP (2008) Electrical properties of pulsed UV laser irradiated amorphous carbon, APPLIED PHYSICS LETTERS 92 (15) ARTN 1 AMER INST PHYSICS

Amorphous carbon films containing no hydrogen were irradiated with a pulsed UV laser in vacuum. Raman spectroscopy indicates an increase in the quantity of sp(2) clustering with the highest laser energy density and a commensurate reduction in resistivity. The reduction of resistivity is explained to be associated with thermally induced graphitization of amorphous carbon films. The high field transport is consistent with a Poole-Frenkel type transport mechanism via neutral trapping centers related to sp(2) sites which are activated under high fields. Decreasing the resistivity is an important feature for use of carbon as an electronic material. (C) 2008 American Institute of Physics.

Gopee V, Thomas O, Hunt C, Stolojan V, Allam J, Silva SRP Carbon Nanotube Interconnects Realized through Functionalization and Sintered Silver Attachment, AMER CHEMICAL SOC
Tsang WM, Henley SJ, Blanchard N, Silva SRP (2006) Pulsed laser deposited Ag-Sio2 nanocomposite thin films for vacuum microelectronic applications, IVNC and IFES 2006 - Technical Digest - l9th International Vacuum Nanoelectronics Conference and 50th International Field Emission Symposium pp. 377-378
Sporea RA, Shannon JM, Silva SRP, Guo X (2011) Source-gated transistors for improved current-mode pixel drivers,
Emissive displays require high-efficiency linear drivers which are stable under electrical stress and can deliver uniform performance across a large area. Owing to their low saturation voltage and flat saturation characteristic, source-gated transistors (SGTs) are ideally suited to act as power-efficient driving transistors in active matrix backplanes for lighting, low-power signage and display screens. It is shown that SGTs are also very stable during electrical stress. The technology is compatible with standard TFT fabrication allowing FET and SGT devices to be integrated in the same design and fabrication run.
Shiozawa H, Bachmatiuk A, Stangl A, Cox DC, Silva SRP, Ruemmeli MH, Pichler T (2013) Microscopic insight into the bilateral formation of carbon spirals from a symmetric iron core, SCIENTIFIC REPORTS 3 ARTN 1840 NATURE PUBLISHING GROUP
Mirrored carbon-spirals have been produced from pressured ferrocene via the bilateral extrusion of the spiral pairs from an iron core. A parametric plot of the surface geometry displays the fractal growth of the conical helix made with the logarithmic spiral. Electron microscopy studies show the core is a crystalline cementite which grows and transforms its shape from spherical to biconical as it extrudes two spiralling carbon arms. In a cross section along the arms we observe graphitic flakes arranged in a herringbone structure, normal to which defects propagate. Local-wave-pattern analysis reveals nanoscale defect patterns of two-fold symmetry around the core. The data suggest that the bilateral growth originates from a globular cementite crystal with molten surfaces and the nano-defects shape emerging hexagonal carbon into a fractal structure. Understanding and knowledge obtained provide a basis for the controlled production of advanced carbon materials with designed geometries.
Hatton RA, Blanchard NP, Miller AJ, Silva SRP (2007) A multi-wall carbon nanotube-molecular semiconductor composite for bi-layer organic solar cells, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 37 (1-2) pp. 124-127 ELSEVIER SCIENCE BV
Clay KJ, Speakman SP, Amaratunga GAJ, Silva SRP (1996) Characterization of C:H:N deposition from CH4/N-2 rf plasmas using optical emission spectroscopy, JOURNAL OF APPLIED PHYSICS 79 (9) pp. 7227-7233 AMER INST PHYSICS
Boskovic BO, Stolojan V, Zeze DA, Forrest RD, Silva SRP, Haq S (2004) Branched carbon nanofiber network synthesis at room temperature using radio frequency supported microwave plasmas, JOURNAL OF APPLIED PHYSICS 96 (6) pp. 3443-3446 AMER INST PHYSICS
Henley SJ, Beliatis MJ, Stolojan V, Silva SR (2012) Laser implantation of plasmonic nanostructures into glass., Nanoscale
A laser direct-writing method producing high-resolution patterns of gold, silver and alloy plasmonic nanoparticles implanted into the surface of glass substrates is demonstrated, by scanning a pulsed UV laser beam across selected areas of ultra-thin metal films. The nanoparticles are incorporated beneath the surface of the glass and hence the patterns are scratch-resistant. The physical mechanisms controlling the process are investigated and we demonstrate that this technique can be used to fabricate a wide range of plasmonic optical structures such as wavelength selected diffraction gratings and high-density substrates for lab-on-chip surface-enhanced Raman spectroscopy.
Han SJ, Adikaari AADT, Jayawardena KDGI, Nismy NA, Hak Kim Y, Won Kim J, Hahn YB, Silva SRP (2013) Band alignment effects at the metal electrode interface of poly(3-hexylthiophene):zinc oxide hybrid photovoltaics, Applied Physics Letters 102 (8)
Photoelectron spectroscopy is used to investigate the role of titanium oxide as an interfacial layer between a hybrid regioregular poly(3- hexylthiophene):zinc oxide photoactive layer and the Al back contact. The inspection of chemical bonds through X-ray photoemission spectroscopy core peaks indicates that the inner structure of the rr-P3HT:ZnO photo-active layer is preserved, subsequent to the deposition of the TiOx layer. Furthermore, the band alignment of rr-P3HT:ZnO/TiOx and TiO x/Al interfaces gives rise to the enhancement in device efficiency from 1.08% to 1.22% upon incorporating the TiOx layer, which is associated with the additional open circuit voltage obtained in the interface of P3HT:ZnO/TiOx. © 2013 American Institute of Physics.
Giusca CE, Tison Y, Silva SRP (2008) Evidence for Metal-Semiconductor Transitions in Twisted and Collapsed Double-Walled Carbon Nanotubes by Scanning Tunneling Microscopy, NANO LETTERS 8 (10) pp. 3350-3356 AMER CHEMICAL SOC
Silva SRP, Stolojan V (2005) Electron energy loss spectroscopy of carbonaceous rnaterials, THIN SOLID FILMS 488 (1-2) pp. 283-290 ELSEVIER SCIENCE SA
Hayashi Y, Fujita T, Tokunaga T, Kaneko K, Tanemura M, Butler T, Rupesinghe N, Carey JD, Silva SRP, Teo KBK, Amaratunga GAJ (2008) Microstructure and local magnetic induction of segmented and alloyed Pd/Co nanocomposites encapsulated inside vertically aligned multiwalled carbon nanotubes, DIAMOND AND RELATED MATERIALS 17 (7-10) pp. 1525-1528 ELSEVIER SCIENCE SA
Mendoza E, Henley SJ, Poa CHP, Stolojan V, Chen GY, Giusca CE, Carey JD, Silva SRP (2005) Dendrimer assisted catalytic growth of mats of multiwall carbon nanofibers, CARBON 43 (10) pp. 2229-2231 PERGAMON-ELSEVIER SCIENCE LTD
Bourdakos KN, Dissanayake DMNM, Lutz T, Silva SRP, Curry RJ (2008) Erratum: "Highly efficient near-infrared hybrid organic-inorganic nanocrystal electroluminescence device" [Appl. Phys. Lett.92, 153311 (2008)], Applied Physics Letters 92 (20) 209903 American Institute of Physics
Knox-Davies EC, Silva SRP, Shannon JM (2003) Properties of nanocrystalline GaN films deposited by reactive sputtering, DIAMOND AND RELATED MATERIALS 12 (8) pp. 1417-1421 ELSEVIER SCIENCE SA
Beliatis MJ, Gandhi KK, Rozanski LJ, Rhodes R, McCafferty L, Alenezi MR, Alshammari AS, Mills CA, Jayawardena KDGI, Henley SJ, Silva SRP (2014) Hybrid graphene-metal oxide solution processed electron transport layers for large area high-performance organic photovoltaics, Advanced Materials 26 (13) pp. 2078-2083
Solution processed core-shell nano-structures of metal oxide-reduced graphene oxide (RGO) are used as improved electron transport layers (ETL), leading to an enhancement in photocurrent charge transport in PCDTBT:PC 70BM for both single cell and module photovoltaic devices. As a result, the power conversion efficiency for the devices with RGO-metal oxides for ETL increases 8% in single cells and 20% in module devices. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Smith RC, Silva SRP (2009) Maximizing the electron field emission performance of carbon nanotube arrays, APPLIED PHYSICS LETTERS 94 (13) ARTN 133104 AMER INST PHYSICS
Opoku C, Hoettges KF, Hughes MP, Stolojan V, Silva SRP, Shkunov M (2013) Solution processable multi-channel ZnO nanowire field-effect transistors with organic gate dielectric, Nanotechnology 24 (40) pp. 405203-4(7pp)
The present work focuses on nanowire (NW) applications as semiconducting elements in solution processable field-effect transistors (FETs) targeting large-area low-cost electronics. We address one of the main challenges related to NW deposition and alignment by using dielectrophoresis (DEP) to select multiple ZnO nanowires with the correct length, and to attract, orientate and position them in predefined substrate locations. High-performance top-gate ZnO NW FETs are demonstrated on glass substrates with organic gate dielectric layers and surround source-drain contacts. Such devices are hybrids, in which inorganic multiple single-crystal ZnO NWs and organic gate dielectric are synergic in a single system. Current-voltage (I-V) measurements of a representative hybrid device demonstrate excellent device performance with high on/off ratio of 10^7, steep subthreshold swing (s-s) of 400 mV/dec and high electron mobility of 35 cm2 V-1 s-1 in N2 ambient. Stable device operation is demonstrated after 3 months of air exposure, where similar device parameters are extracted including on/off ratio of 4x10^6, s-s 500 mV/dec and field-effect mobility of 28 cm2 V-1 s-1. These results demonstrate that DEP can be used to assemble multiples of NWs from solvent formulations to enable low-temperature hybrid transistor fabrication for large-area inexpensive electronics.
Shi S, Silva SRP (2012) High luminance organic light-emitting diodes with efficient multi-walled carbon nanotube hole injectors, CARBON 50 (11) pp. 4163-4170 PERGAMON-ELSEVIER SCIENCE LTD
Rusli, Amaratunga GAJ, Silva SRP (1995) Photoluminescence in amorphous carbon thin films and its relation to the microscopic properties, THIN SOLID FILMS 270 (1-2) pp. 160-164 ELSEVIER SCIENCE SA LAUSANNE
Anguita JV, Ahmad M, Haq S, Allam J, Silva SR Ultra-broadband light trapping using nanotextured decoupled graphene multilayers.,
Liang H, Smith C, Mills C, Silva S (2015) The band structure of graphene oxide examined using photoluminescence spectroscopy, Journal of Materials Chemistry C 3 (48) pp. 12484-12491 The Royal Society of Chemistry
Photoluminescence (PL) spectra have been used to elucidate the band structure of graphene oxide (GO) reduced in aqueous solution. The GO reduction is measured in situ via the identification of four PL peaks produced from GO solutions with different concentrations. Using corresponding UV-visible and photoluminescence excitation (PLE) spectroscopy, and on progressing from high energy to low energy transitions, the four PL peaks are identified as Ã?Ã* and À?À* transitions, a À band tail due to oxygen localized states, and a À band tail due to trapped water, respectively. The labeling of the band structure has been used to challenge the prevailing assignation of the low energy transitions, reported in the literature, to molecular Ã?Ã* and À?À* transitions alone.
Shi X, Lutz T, Giannakidis A, Goulianos A, Watts P, Yaici K, Evans B, Kondoz A, Petrou M, Silva SRP, de Silva S (2008) The Guardian Angel Project: Using an unobtrusive Wireless Sensor Network System to Improve Health and Well-being in the 21st Century,
Smith RC, Cox DC, Silva SRP (2008) In situ field emission characterization of multiwalled carbon nanotubes, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 26 (2) pp. 842-846 A V S AMER INST PHYSICS
Carey JD, Silva SRP (2004) Disorder, clustering, and localization effects in amorphous carbon, Physical Review B 70 (235417)

The nanostructure of amorphous carbon thin films is described in terms of a disordered nanometer-sized conductive sp2 phase embedded in an electrically insulating sp3 matrix. It is shown that the degree of clustering and disorder within the sp2 phase plays a determining role in the electronic properties of these films. Clustering of the sp2 phase is shown to be important in explaining several experimental results including the reduction of the electron spin resonance linewidth with increasing spin density and the dispersion associated with the width of the Raman active G band. The influence of structural disorder, associated with sp2 clusters of similar size, and topological disorder, due to undistorted clusters of different sizes, on both spin density and Raman measurements, is discussed. An extension of this description to intercluster interactions to explain some of the electrical transport and electron field emission behavior is also presented.

Smith R, Cox DC, Silva SRP (2005) Electron field emission from a single carbon nanotube: Effects of anode location, APPLIED PHYSICS LETTERS 87 (10) 103112 AMER INST PHYSICS

Electron field emission from an isolated carbon nanotube (CNT) was performed in situ in a modified scanning electron microscope, over a range of anode to CNT tip separations, D, of 1-60 mu m. The threshold field required for an emission current of 100 nA was seen to decrease from a value of 42 V mu m(-1) at an anode to CNT tip separation of 1 mu m, asymptotically, to approach 4 V mu m(-1) at a separation of 60 mu m. It is proposed that at low D, the electric field enhancement factor (beta) reduces as the anode electrode approaches the CNT mimicking a parallel plate configuration. Under "far field" conditions, where D > 3 h, where h is the CNT height, the CNT enhancement factor is no longer dependant on D, as shown by the asymptotic behavior of the threshold field, and is purely a factor of the CNT height and radius. For each CNT to tip separation, measured emission current data together with the threshold field and enhancement, are consistent with a Fowler-Nordheim analysis for the far field conditions, and dispels the need for a novel emission mechanism to explain the results as has been proposed recently. (c) 2005 American Institute of Physics.

Smith R, Tsang W, Cox D, Silva SRP (2005) Electron field emission from a single carbon nanotube: Effects of anode location, Technical Digest of the 18th International Vacuum Nanoelectronics Conference, IVNC 2005 2005 pp. 264-265
Dabera G, Prabhath M, Lai K, Jayawardena K, Sam F, Rozanski L, Adikaari A, Silva SRP (2015) Does Electronic Type Matter when Single-Walled Carbon Nanotubes are Used for Electrode Applications?, Advanced Functional Materials 25 (28) pp. 4520-4530 Wiley
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Single-walled carbon nanotube (SWNT) electrodes that are chemically and mechanically robust are fabricated using a simple drop cast method with thermal annealing and acid treatment. An electronic-type selective decrease in sheet resistance of SWNT electrodes with HNO3 treatment is shown. Semiconducting SWNTs show a significantly higher affinity toward hole doping in comparison to metallic SWNTs; a H12-fold and a Hfivefold drop in sheet resistance, respectively. The results suggest the insignificance of the electronic type of the SWNTs for the film conductivity after hole doping. The SWNT films have been employed as transparent hole extracting electrodes in bulk heterojunction (BHJ) organic photovoltaics. Performances of the devices enlighten the fact that the electrode film morphology dominates over the electronic type of the doped SWNTs with similar sheet resistance and optical transmission. The power conversion efficiency (PCE) of 4.4% for the best performing device is the best carbon nanotube transparent electrode incorporated large area BHJ solar cell reported to date. This PCE is 90% in terms of PCEs achieved using indium tin oxide (ITO) based reference devices with identical film fabrication parameters indicating the potential of the SWNT electrodes as an ITO replacement toward realization of all carbon solar cells. Fabrication of electronic-type separated single-walled carbon nanotube (SWNT) electrodes for organic solar cells, using a simple drop cast method followed by thermal and acid treatment. The thermal and acid treatment processes significantly enhance the conductivity of the SWNT films, enabling the use of the conductivity-enhanced SWNT layers as hole extracting, transparent electrodes in organic bulk heterojunction solar cells.
Dharmasena R, Jayawardena I, Mills C, Deane J, Anguita J, Dorey R, Silva S (2017) Triboelectric Nanogenerators: Providing a Fundamental Framework, Energy & Environmental Science 10 (8) pp. 1801-1811 Royal Society of Chemistry
A new model which comprehensively explains the working principles of contact-mode Triboelectric Nanogenerators (TENGs) based on Maxwell?s equations is presented. Unlike previous models which are restricted to known simple geometries and derived using the parallel plate capacitor model, this model is generic and can be modified to a wide range of geometries and surface topographies. We introduce the concept of a distance-dependent electric field, a factor not taken in to account in previous models, to calculate the current, voltage, charge, and power output under different experimental conditions. The versatality of the model is demonstrated for non-planar geometry consisting of a covex-conave surface. The theoretical results show excellent agreement with experimental TENGs. Our model provides a complete understanding of the working principles of TENGs, and accurately predicts the output trends, which enables the design of more efficient TENG structures.
Lyth S, Oyeleye F, Curry RJ, Silva SRP, Davis J (2005) Field emission from multiwall carbon nanotubes prepared by electrodeposition without the use of a dispersant, Technical Digest of the 18th International Vacuum Nanoelectronics Conference, IVNC 2005 2005 pp. 304-305
Carbon nanotubes (CNTs) are ideal candidates to be used as field emission sources. Electrodeposition could provide a viable method to deposit CNTs over large areas as part of an industrialized process. It has been shown that CNTs can be co-deposited with nickel onto various substrates, using a suitable CNT dispersant. In the present study, a multiwall carbon nanotube (MWNT): nickel (Ni) composite has been electrodeposited without the use of a dispersant. The field emission properties of the resulting electrodeposits were studied. Unpurified MWNTs grown by CVD were added to a Ni plating bath comprising of IM NiSO·6HO, 0.2M NiCl and 0.5M HBO. Due to their hydrophobic nature, MWNTs did not disperse naturally, so the plating solution was placed in a sonic bath for 15 minutes before electrodeposition. Electrochemical measurements were conducted using a ¼Autolab computer controlled potentiostat with a three-electrode configuration and typical cell volume of 10 cm. A spiral wound platinum wire served as the counter electrode with a Ag:AgCl wire reference electrode. Cu plates were used as cathodes, with an exposed surface area of 2 cm. After deposition, samples were thoroughly rinsed in deionised water to remove Ni salts. The resulting electrodeposits were imaged using a scanning electron microscope (FIG.1) Importantly, these deposits were observed after the samples were thoroughly rinsed in deionised water, suggesting that there is a strong adhesion between the nickel coated nanotubes and the substrate surface. FIG.1 (a) shows MWNTs (0.013 mg/ml) electrodeposited directly after sonication. Note that a thick Ni coating is not observed (see inset), and that uniform MWNT deposition is observed over a relatively large area. FIG.1(b) shows MWNTs deposited with the same solution after five minutes. A much thicker Ni coating indicates that a relatively higher concentration of Ni to MWNT was present. This was probably due to a rebundling of MWNTs over time, after the sonication process. FIG.1(c) and (d) show MWNTs deposited with a much lower concentration (0.005 mg/ml), and therefore relatively higher concentration of Ni, resulting in thicker Ni coating. Beads of Ni (visible in FIG.1(d)), approximately one micron in diameter completely encased the MWNTs, previously observed by Aria et al., using a poly(acrylic acid) dispersant. Subsequently, the substrates were subjected to field emission characterisation using a 5 mm spherical stainless steel anode. The emission current
Carey JD, Henley SJ, Mendoza E, Giusca C, Adikaari A, Silva SRP (2004) Formation of three dimensional Ni nanostructures for large area catalysts, NANOENGINEERED ASSEMBLIES AND ADVANCED MICRO/NANOSYSTEMS 820 pp. 357-362

The formation of Ni nanostructures to act as catalysts in the growth of carbon nanotubes is reported. The changes in the surface morphology of Ni produced by three methods - thermal
evaporation and annealing of thin films, pulsed laser ablation and annealing of Ni, and the use of metal containing macromolecules - have been investigated by atomic force microscopy and scanning electron microscopy. In the case of thermal annealing of thin metal films in the temperature range 300-500oC we observe an increase in the mean diameter of the islands formed, accompanied by a reduction in the mean island density with increasing temperature. We
attribute this effect to mass transport of weakly bound individual Ni atoms and/or small island clusters across the surface to form larger isolated islands, in a process similar to Ostwald ripening. Using a pulsed KrF excimer laser for ablation of a Ni target we show that nanometre smooth Ni thin films can be produced provided a sufficient number of laser shots is used. The surface morphology of these smooth films can then be altered by laser annealing to form Ni droplets. It is found that the mean diameter of the Ni droplets depends not only on the initial Ni thickness but also the laser fluence. It is also found that the nanostructuring of the film depends
on the presence of an oxide under layer, with a higher fluence required on thinner oxides and no nanostructuring observed on bare Si. Finally, we show that Ni nanostructuring can be formed by suitable annealing of a Ni containing aqueous dendrimer solutions.

Chen G, Stolojan V, Cox DC, Giusca C, Silva SRP (2006) Growth of tungsten oxide nanowires using simple thermal heating, 2006 IEEE Conference on Emerging Technologies - Nanoelectronics pp. 376-378

Tungsten oxide nanowires are grown directly on tungsten wires and plates using thermal heating in an acetylene and nitrogen mixture. By heating the tungsten in nitrogen ambient, single crystal tungsten oxide nanowires can be synthesized via a self-assembly mechanism. It was found that the yield can be significantly increased with the addition of acetylene, which also results in thinner nanowires, as compared to nanowires synthesized in an oxidizing ambient. The tungsten oxide nanowires are 5 to 15 nm in diameter and hundreds of nanometers in length. In some cases, the use of acetylene and nitrogen process gas would result in tungsten oxide nanowires samples that appear visually,transparent. Comparison of the growth using the acetylene/nitrogen or then air/nitrogen mixtures is carried out. A possible synthesis mechanism, taking into account the effect of hydrocarbon addition is proposed.

Ahmad M, Anguita JV, Stolojan V, Corless T, Chen J, Carey JD, Silva SRP (2015) High Quality Carbon Nanotubes on Conductive Substrates Grown at Low Temperatures, Advanced Functional Materials 25 (28) pp. 4419-4429 Wiley
For carbon nanotubes (CNTs) to be exploited in electronic applications, the growth of high quality material on conductive substrates at low temperatures (
Anguita JV, Cox DC, Ahmad M, Tan Y, Allam J, Silva SRP (2013) Highly transmissive carbon nanotube forests grown at low substrate temperature, Advanced Functional Materials 23 (44) pp. 5502-5509 Wiley
Despite the "darker than black" association attributed to carbon nanotube forests, here is shown that it is also possible to grow these structures, over heat-sensitive substrates, featuring highly transmissive characteristics from the UV to infrared wavelengths, for forest heights as high as 20 ¼m. The optical transmission is interpreted in terms of light propagation along channels that are self-generated by localized bundling of tubes, acting as waveguides. A good correlation is shown between the distribution of diameter sizes of these sub-wavelength voids and the transmission spectrum of the forests. For the shorter visible and near-UV wavelengths, this model shows that light propagates by channeling along individual vertical voids in the forests, which elucidates the origin for the widely-reported near-zero reflectance values observed in forests. For the longer infrared wavelengths, the mode spreads over many nanotubes and voids, and propagates along a "homogeneous effective medium". The strong absorption of the forest at the shorter wavelengths is correlated in terms of the stronger attenuation inside a waveguide cavity, according to the » attenuation dependency of standard waveguide theory. The realization of this material can lead to novel avenues in new optoelectronic device design, where the carbon nanotube forests can be used as highly conducting "scaffolds" for optically active materials, whilst also allowing light to penetrate to significant depths into the structure, in excess of 20 ¼m, enabling optical functionality. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Guo X, Ishii T, Silva SRP (2008) Improving switching performance of thin-film transistors in disordered silicon, IEEE ELECTRON DEVICE LETTERS 29 (6) pp. 588-591 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

The silicon integrated electronics on glass or plastic substrates attracts wide interests. The design, however, depends critically on the switching performance of transistors, which is limited by the quality of silicon films due to the materials and substrate process constraints. Here, the ultrathin channel device structure is proposed to address this problem. In a previous work, the ultrathin channel transistor was demonstrated as an excellent candidate for ultralow power memory design. In this letter, theoretical analysis shows that, for an ultrathin channel transistor, as the channel becomes thinner, stronger quantum confinement can induce a marked reduction of OFF-state leakage current (I-OFF), and the subthreshold swing (S) is also decreased due to stronger control of channel from the gate. Experimental results based on the fabricated nanocrystalline silicon thin-film transistors prove the theoretical analysis. For the 2.0-nm-thick channel devices, I-ON/I-OFF ratio of more than 10(11) can be achieved, which can never be obtained for normal thick channel transistors in disordered silicon.

Lyth S, Henley SJ, Silva SRP (2007) Laser ablation of thin carbon nanotube films on glass substrates as transparent field emitters, EIGHTH IEEE INTERNATIONAL VACUUM ELECTRONICS CONFERENCE pp. 329-330 IEEE

This paper reports the transparent field-emitters, produced by spin-coating acid-oxidised multiwall carbon nanotubes (o-MWNT) onto indium tin oxide (ITO)-coated glass slides via an o-MWNT ink. We report substantial changes in the morphology of the o-MWNT layer and an improvement in the FE properties after exposing the films to laser pulses of differing intensity. It is envisaged that this technique could be scaled up as an industrial process for producing truly large area, transparent and cheap FE substrates.

Hayashi Y, Tokunaga T, Kaneko K, Henley SJ, Stolojan V, Carey JD, Silva SRP (2006) Microstructure analyses of metal-filled carbon nanotubes synthesized by microwave plasma-enhanced chemical vapor deposition, IEEE TRANSACTIONS ON NANOTECHNOLOGY 5 (5) pp. 485-490 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Pd/Co-based metal-filled carbon nanotubes (MF-CNTs) were synthesized by a microwave plasma-enhanced chemical vapor deposition method using a bias-enhanced growth technique. Pd/Co-based MF-CNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) electron energy loss spectroscopy (EELS), and Raman spectroscopy. MF-CNTs were well-aligned and uniform in size on a Si substrate. Both multiwall nanotube carbon nanotubes (CNTs) and herringbone (or stacked cups structure) structures were observed. High-resolution TEM revealed that MF-CNTs were composed of highly ordered graphite layers, and the elemental maps of EELS indicate that both Co and Pd metals are present inside the nanotubes. TEM results clearly showed that both Pd and Co metals were successfully encapsulated into the CNTs. We observed a low value for the Raman intensity ratio between D (1355 cm(-1)) and G (1590 cm(-1)) bands with no shift of the G-peak position and no broadening of the G-peak, indicative of high-quality Pd/Co-based MF-CNTs. Based on TEM characterization, we propose a description for the encapsulating mechanisms.

Emah J, Curry RJ, Silva SRP (2008) Low cost patterning of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) films to increase organic photovoltaic device efficiency, Applied Physics Letters 93 103301 American Institute of Physics

A low-cost lithographic technique to pattern poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) films with 10 nm deep features of 700 nm periodicity is demonstrated. The use of these patterned films in poly (3-hexylthiophene) : [6,6]-phenylC(61)-butyric acid methyl ester organic photovoltaic devices leads to an increase in short circuit current (J(sc)), fill factor, and power conversion efficiency (PCE) with only a slight reduction in open circuit voltage. Patterning the PEDOT: PSS at 150 degrees C increases Jsc from 2.44 to 3.03 mA/cm(2) improving the PCE from 0.63% to 0.81% with similar increases due to patterning also being obtained at other temperatures.

Hayashi Y, Tokunaga T, Kaneko K, Henley SJ, Stolojan V, Carey JD, Silva SRP (2006) Microstructure analyses of metal-filled carbon nanotubes synthesized by microwave plasma-enhanced chemical vapour deposition, 2006 IEEE Conference on Emerging Technologies - Nanoelectronics pp. 93-98
Filip L, Smith R, Carev J, Silva SRP, Nicolaescu D (2007) Modelling of electron transfer from a carbon nanotube cap into the vacuum under high extraction fields, Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07 pp. 48-49
Adikaari A, Dissanayake D, Silva SRP (2010) Organic-Inorganic solar cells: Recent developments and outlook, IEEE Journal on Selected Topics in Quantum Electronics 16 (6) pp. 1595-1606 IEEE
Solution-processed photovoltaic devices are an attractive alternative to costly inorganic semiconductor-based conventional photovoltaics. Solution-processable organic photovoltaic systems are affected by low carrier mobility, lifetime issues under ambient conditions, and limited optical absorption due to the high bandgaps of organic materials. Nanostructured inorganic materials promise to alleviate some of these drawbacks, by enabling the systems to perform better in a commercial perspective. This paper examines four key areas of hybrid organic-inorganic photovoltaic systems. These are metal oxide-organic, carbon nanotube-organic, semiconductor nanowire-organic, and semiconductor nanocrystal-organic systems, which are showing growing importance and potential in the literature. Recent advances in terms of device performance for these respective topics are reviewed, along with an outlook for each system.
Chen G, Poa C, Stolojan V, Silva SRP (2006) Novel approach to low substrate temperature synthesis of carbon nanotubes, 2006 IEEE Conference on Emerging Technologies - Nanoelectronics pp. 254-257

We present a novel approach, which will potentially allow for low-temperature-substrate synthesis of carbon nanotubes using direct-current plasma-enhanced chemical vapour deposition. The approach utilizes top-down plasma heating rather than conventional heating from a conventional substrate heater under the electrode. In this work, a relatively thick titanium layer is used as a thermal barrier to create a temperature gradient between the Ni catalyst surface and the substrate. We describe the growth properties as a function of the bias voltage and the hydrocarbon concentrations. The heating during growth is provided solely by the plasma, which is dependent only on the process conditions, which dictate the power density and the cooling of the substrate, plus now the thermal properties of the "barrier layer". This novel approach of using plasma heating and thermal barrier allows for the synthesis of carbon nanotubes at low substrate temperature conditions to be attained with suitable cooling schemes.

Zhang W, Lei M, Silva SRP, Johnson L (2012) The effect of plasma modification on the sheet resistance of nylon fabrics coated with carbon nanotubes, Applied Surface Science 258 (20) pp. 8209-8213 Elsevier
Low-pressure oxygen and argon plasmas were used to pre-treat nylon fabrics, and the modified fabrics, together with the raw fabrics, were subsequently coated with single walled carbon nanotubes (SWCNTs) by a dip-drying process. Scanning electron microscopy (SEM) and Raman spectroscopy analyses indicated the attachment of SWCNTs onto nylon fabrics. After the coating with SWCNTs, the plasma modified fabrics exhibited sheet resistance of as low as 2.0 k©/sq. with respect to 4.9 k©/sq. of the raw fabrics, presumably owing to the increase of fibre surface roughness incurred by the plasma modification, which is evidenced by SEM analyses. Fourier transform infrared spectroscopy (FTIR) analysis indicates the incorporation of oxygen functionalities on fibre surfaces in the plasma modification. This is responsible for the variation of the electrical conductance of SWCNT-coated fabrics with the type of plasma and the duration of plasma ablation. © 2012 Elsevier B.V. All rights reserved.
Fryar J, Jayawardena K, Silva SRP, Henley SJ (2012) The origin of the metal enrichment of carbon nanostructures produced by laser ablation of a carbon-nickel target, Carbon 50 (15) pp. 5505-5520 Elsevier
Compositional analysis of metal-containing carbon thin films and nanostructures produced by pulsed laser ablation of a carbon-nickel target revealed significantly higher fractions of nickel in the materials than in the target used to produce them. Ablation of mixed targets is used routinely in the synthesis of carbon nanotubes and to enhance the conductivity of amorphous carbon films by metal incorporation. In this extensive study we investigate the physical mechanisms underlying this metal-enrichment and relate changes in the dynamics of the ablation plumes with increasing background gas pressure to the composition of deposited materials. The failure to preserve the target atom ratios cannot, in this case, be attributed to conventional mechanisms for non-stoichiometric transfer. Instead, nickel-enrichment of the target surface by back-deposition, combined with significantly different propagation dynamics for C atoms, Ni atoms and alloy clusters through the background gas, appears to be the main cause of the high nickel fractions. © 2012 Elsevier Ltd. All rights reserved.
Hamerton I, Tang W, Anguita JV, Silva SRP (2013) Towards the rational design of polymers using molecular simulation: Predicting the effect of cure schedule on thermo-mechanical properties for a cycloaliphatic amine-cured epoxy resin, REACTIVE & FUNCTIONAL POLYMERS 74 pp. 1-15 ELSEVIER SCIENCE BV
We report prediction of selected physical properties (e.g. glass transition temperature, moduli and thermal
degradation temperature) using molecular dynamics simulations for a difunctional epoxy monomer
(the diglycidyl ether of bisphenol A) when cured with p-3,30
-dimethylcyclohexylamine to form a dielectric
polymer suitable for microelectronic applications. Plots of density versus temperature show decreases
in density within the same temperature range as experimental values for the thermal degradation and
other thermal events determined using e.g. dynamic mechanical thermal analysis. Empirical characterisation
data for a commercial example of the same polymer are presented to validate the network constructed.
Extremely close agreement with empirical data is obtained: the simulated value for the glass
transition temperature for the 60 C cured epoxy resin (simulated conversion a = 0.70; experimentally
determined a = 0.67 using Raman spectroscopy) is ca. 70?85 C, in line with the experimental temperature
range of 60?105 C (peak maximum 85 C). The simulation is also able to mimic the change in processing
temperature: the simulated value for the glass transition temperature for the 130 C cured epoxy
resin (simulated a = 0.81; experimentally determined a = 0.73 using Raman and a = 0.85 using DSC) is ca.
105?130 C, in line with the experimental temperature range of 110?155 C (peak maximum 128 C).
This offers the possibility of optimising the processing parameters in silico to achieve the best final properties,
reducing labour- and material-intensive empirical testing.
Hamerton I, Anguita JV, Silva SRP (2013) Towards the rational design of polymers using molecular simulation: predicting the effect of cure schedule on thermo-mechanical properties for a cycloaliphatic amine-cured epoxy resin, Proceedings of the Aristotelian Society 1 (1) pp. 235-238
We report prediction of selected physical properties (e.g. glass transition temperature, moduli and thermal
degradation temperature) using molecular dynamics simulations for a difunctional epoxy monomer
(the diglycidyl ether of bisphenol A) when cured with p-3,30
-dimethylcyclohexylamine to form a dielectric
polymer suitable for microelectronic applications. Plots of density versus temperature show decreases
in density within the same temperature range as experimental values for the thermal degradation and
other thermal events determined using e.g. dynamic mechanical thermal analysis. Empirical characterisation
data for a commercial example of the same polymer are presented to validate the network constructed.
Extremely close agreement with empirical data is obtained: the simulated value for the glass
transition temperature for the 60 C cured epoxy resin (simulated conversion a = 0.70; experimentally
determined a = 0.67 using Raman spectroscopy) is ca. 70?85 C, in line with the experimental temperature
range of 60?105 C (peak maximum 85 C). The simulation is also able to mimic the change in processing
temperature: the simulated value for the glass transition temperature for the 130 C cured epoxy
resin (simulated a = 0.81; experimentally determined a = 0.73 using Raman and a = 0.85 using DSC) is ca.
105?130 C, in line with the experimental temperature range of 110?155 C (peak maximum 128 C).
This offers the possibility of optimising the processing parameters in silico to achieve the best final properties,
reducing labour- and material-intensive empirical testing.
2013
Anguita JV, Ahmad M, Haq S, Allam J, Silva SRP (2016) Ultra-broadband light trapping using nanotextured decoupled graphene multilayers, Science Advances 2 (2) e1501238 American Association for the Advancement of Science
The ability to engineer a thin two-dimensional surface for light trapping across an ultra-broad spectral range is central for an increasing number of applications including energy, optoelectronics, and spectroscopy. Although broadband light trapping has been obtained in tall structures of carbon nanotubes with millimeter-tall dimensions, obtaining such broadband light?trapping behavior from nanometer-scale absorbers remains elusive. We report a method for trapping the optical field coincident with few-layer decoupled graphene using field localization within a disordered distribution of subwavelength-sized nanotexturing metal particles. We show that the combination of the broadband light?coupling effect from the disordered nanotexture combined with the natural thinness and remarkably high and wavelength-independent absorption of graphene results in an ultrathin (15 nm thin) yet ultra-broadband blackbody absorber, featuring 99% absorption spanning from the mid-infrared to the ultraviolet. We demonstrate the utility of our approach to produce the blackbody absorber on delicate opto-microelectromechanical infrared emitters, using a low-temperature, noncontact fabrication method, which is also large-area compatible. This development may pave a way to new fabrication methodologies for optical devices requiring light management at the nanoscale.
Kutsarov D (2017) Large-area slot-die coated organic
photovoltaics with high ef?ciencies.,
Commercially available organic photovoltaics (OPV) are commonly fabricated using printing and coating techniques that allow for low-cost, high throughput processing of large-area OPV devices. However, the power conversion e?ciency (PCE) of scaled-up OPVs is often lower than that of small-area ones. This is because the deposition techniques typically being used in industry are di?erent to those used in research laboratories (printing/coating vs. spin-coating). Thus, detailed studies of functional materials are required to tailor the characteristics of photoactive D/A blends of OPVs in order to preserve high PCE values for scaled-up device sizes. Therefore, the aims of this thesis were to enhance the PCEs of OPV cells made using a well-known donor material (P3HT), and to develop a structured approach to fabricating large-area OPVs thus easing the transfer of fabrication procedures from laboratory to industry.

To achieve the ?rst goal, indene-C70-bis-adduct (IC70BA) was chosen as an acceptor material for a photoactive blend with P3HT. A review of P3HT:ICBA-based solar cells indicated a signi?cant variation of reported device PCE values (average of 4.66±1.45%). The majority of reported device e?ciencies were measured for OPVs with photoactive areas rarely exceeding 0.1 cm2. Therefore, a detailed study of the intrinsic characteristics of the IC70BA molecule and the morphology of the P3HT:IC70BA blends was carried out in order to design the optimal fabrication conditions for achieving higher PCEs and up-scaled device areas. Record PCEs approaching 7% were accomplished in this thesis for OPVs with photoactive areas of 0.43 cm2. This was achieved by understanding the correlation between the isomeric properties of the IC70BA molecule and the resulting D/A blend morphology depending on the fabrication conditions used.

The second goal of this thesis was accomplished by designing a slot-die coating equipment that allows for the deposition of functional materials over large-areas. Di?erent solubilised materials were deposited in ambient conditions on glass and plastic substrates in order to fabricate OPV devices. Two di?erent photoactive D/A systems were used: P3HT:IC70BA and PCDTBT:PC70BM. OPV cell and module PCEs approaching 4% were achieved for devices with photoactive areas of about 35 cm2. The quality of the slot-die coated layers was investigated using LBIC, PL, and Raman mapping. This will allow for future improvements in the coating process and, therefore, in

Zhang W, Zuo X, Niu Y, Wu C, Wang S, Guan S, Silva S (2017) Novel nanoparticles with Cr3+ substituted ferrite for self-regulating temperature hyperthermia, Nanoscale 9 (37) pp. 13929-13937 Royal Society of Chemistry
For hyperthermia to be used under clinical conditions for cancer therapeutics the temperature regulation needs to be precise and accurately controllable. In the case of the metal nanoparticles used for such activities, a high coercivity is a prerequisite in order to couple more energy in a single heating cycle for efficient and faster differential heating. The chemically stable Co?Zn ferrite nanoparticles have typically not been used in such self-regulating hyperthermia temperature applications to date due to their low Curie temperature usually accompanied by a poor coercivity. The latter physical property limitation under clinically applied magnetic field conditions (frequency: 100 kHz, intensity: 200 Oe) restricts the transfer of a reasonable heat energy, and thus limits the hyperthermia efficiency. Here, we report a novel Cr3+ substituted Co?Zn ferrite (Zn0.54Co0.46Cr0.6Fe1.4O4), whose Curie temperature and coercivity values are 45.7 °C and 174 Oe, respectively. Under clinically acceptable magnetic field conditions, the temperature of these nanoparticle suspensions can be self-regulated to 44.0 °C and, most importantly with a specific absorption rate (SAR) of 774 W kg?1, which is two-fold higher than the SAR standard for magnetic nanoparticles used in hyperthermia (300 W kg?1). The evaluation of the in vitro cytotoxicity of the nanoparticles reports a low toxicity, which points to a novel set of magnetic nanoparticles for use in self-regulating hyperthermia.
Fisher B (2017) Nanoscale light manipulation for improved organic solar cells.,
Organic Solar Cells can be made to be flexible, semi-transparent, and low-cost making them ideal for novel energy harvesting applications such as in greenhouses. However, the main disadvantage of this technology is its low energy conversion efficiency ( high recombination rates, compared with other higher performing technologies, such as thinfilm GaAs (>30% Efficiency), and Si-based (>20% Efficiency), solar cells, where recombination within these technologies is much less than Organic Solar Cells. There are still many challenges to overcome to improve the efficiency of Organic Solar Cells. Some of these challenges include: Maximising the absorption of the solar spectrum; improving the charge
dynamics; and increasing the lifetime of the devices.

One method to address some of these challenges is to include plasmonic nanoparticles into the devices, which has been shown to increase the absorption through scattering, and improve the charge dynamic through localised surface plasmon resonance effects. However, including nanoparticles into Organic Solar Cells has shown to adversely affect the performance of the devices in other ways, such as increasing the recombination of excitons. To address this, an additional (insulating) coating around the nanoparticles supresses this increase, and has shown to be able to increase the performance of the solar cells.

In this work, we demonstrate the use of our all-inclusive optical model in the design and optimisation of bespoke colour-specific windows (i.e. Red, Green, and Blue), where the solar cells can be made to have a specific transparency and colour, whilst maximizing their efficiency. For example, we could specify that we wish the colour to be red, with 50% transmissivity; the model will then maximise the Power Conversion Efficiency. We also demonstrate how our extension to Mie theory can simulate nanoparticle systems and can be used to tune the plasmon resonance utilising different coatings, and configurations thereof.

Melios C (2017) Graphene metrology : substrate and environmental effects on graphene.,
Graphene, a single layer of sp2-bonded carbon atoms, has received significant attention due to its exceptional opto-electronic properties and potentially scalable production processes. However, scalable graphene requires an underlying substrate, which is often a source of strain, doping and carrier scattering, limiting the mobility and quality of graphene. It was shown that by intercalating graphene on SiC by hydrogen, the interfacial layer, associated with n-doping and mobility degradation, is de-coupled from the substrate. The transformations of the H2-intercalation were demonstrated using Raman spectroscopy, while the SiC/interface changes were probed using surface enhanced Raman scattering. The H2-intercalation resulted in carrier type inversion, where the decoupled graphene change from n- to p-type, as well as showing mobility enhancement, up to more than four times, compared to as-grown graphene. Using calibrated Kelvin probe force microscopy, local work function maps were generated, demonstrating the changes in local electronic properties with nanoscale resolution. Furthermore, the layer structure, doping and strain induced by the underlying substrate are compared to CVD grown graphene transferred onto Si/SiO2.
In addition to the substrate effects, the electronic properties of graphene are also significantly affected due to the direct exposure of À electrons to the environment. For the investigation of the environmental effects on graphene (i.e. H2O and NO2), a custom-built environmental transport properties measurement system was designed and developed, allowing magneto-transport measurements to be conducted in highly controlled environments. Using this system and calibrated local work function mapping, it is demonstrated that water withdraws electrons from graphene on SiC and SiO2 substrates, as well as acting as a source of impurity scattering. However, the sensitivity of graphene to water depends highly on the underlying substrate and substrate-induced doping. Moreover, it is shown that epitaxial graphene can successfully be used as the sensing material with detection down to 10 parts-per-billion molecules. Considering the environmental effects on the electronic properties of graphene, the importance of clearly reporting the measurement environmental conditions is high-lighted, whenever a routine characterisation for carrier concentration and mobility is reported.
Castaldelli E, Jayawardena K, Cox D, Clarkson G, Walton R, Le-Quang L, Chauvin J, Silva S, Demets G (2017) Electrical conduction modulated by light in a cobalt and naphthalene diimide metal-organic framework, Nature Communications 8 2139 Nature Publishing Group
Metal-organic frameworks (MOFs) have emerged as an exciting class of porous materials that can
be structurally designed by choosing particular components according to desired applications. De-
spite the wide interest in and many potential applications of MOFs, such as in gas storage, catal-
ysis, sensing and drug delivery, electrical semiconductivity and its control is still rare. The use
and fabrication of electronic devices with MOF-based components has not been widely explored,
despite the significant progress of these components made in recent years. Here we report the syn-
thesis and properties of a new highly crystalline, electrochemically active, cobalt and naphthalene
diimide-based MOF that is an efficient electrical semiconductor and has a broad absorption spec-
trum, from 300 nm to 2500 nm. Its semiconductivity was determined by direct voltage bias using
a four-point device, and it features a wavelength dependant photoconductive-photoresistive dual
behaviour, with a very high responsivity of 2.5×105 A W?1.
Cronin H (2018) Manufacturability aspects of printable electronics and halide perovskite photovoltaics.,
Manufacturing electronic devices by printing or coating is a key emerging technology, promising low cost and high throughput. Halide perovskites have emerged as high efficiency, solution processable photovoltaic materials, and within this thesis some of the issues relevant to their up-scaling are explored. Additionally, photo-curing ? a post-processing technique with a wide range of applications in printed electronics ? is investigated.

Aqueous silver flake inks are a promising material for printed conductive applications, combining low cost and high conductivity. Within this thesis, photo-curing of these inks to further improve their conductivity is investigated. Photo-cured samples showed an 11x conductivity improvement compared with thermally cured samples. Furthermore, the manufacturing yield was doubled following photo-curing. These novel observations are explained, by recourse to percolation theory, by an increase in mean particle size. These results enable lower cost and increased yield in future manufacturing.

Halide perovskite materials show great promise for solution processable photovoltaics. Within this thesis, the effects of ambient conditions during device processing are measured, in order to inform future up-scaled manufacturing. The chemical and morphological effects of ambient humidity in perovskite films are correlated with the annealing time used and final device performance. This work led to new insights into the combined effects of these two parameters, and a suggestion is made for reducing the annealing time.

Finally, a barrier to commercialisation of perovskite solar cells is the use of toxic solvents in their fabrication. Within this thesis, a novel deposition technique is proposed, based on the synthesis of perovskite material in particulate form followed by re-dispersal in non-toxic solvents. This mitigates solvent toxicity, reduces sensitivity to ambient conditions, and in some cases enhances stability. Devices are fabricated based on this technique, and though performance remains low, a marked improvement is observed by the addition of conductive graphene flakes to the inks.

King S, Stolojan V, Silva S (2017) Large area uniform electrospun polymer nanofibres by balancing of the electrostatic field, Reactive and Functional Polymers Elsevier
As a technique, electrospinning has been increasingly utilised for polymer nanofibre production, which has a growing list of advanced applications to which they are being applied. However, commercially scaling the process is challenging, especially when the uniformity of the nanofibres across the bulk of the material is important for the required application. At present, most commercially-scalable systems tend to rely on a drum or cylindrical-style electrode, where a multitude of electrospinning jets are formed with no specific controlled distribution or uniformity over its surface. These electrospinning systems also have the drawback of possessing a varying electrostatic field across the length of the electrode, resulting in a range of spinning conditions which result in an inconsistency in the produced nanofibres. Due to the high centrifugal stresses exerted on the polymer during electrospinning, controlling the electrostatic field is crucial for consistent nanofibre production, which forms the basis for applications such as cellular scaffolds and smart materials. In the work reported here, we utilise computational simulation to explore a range of electrode designs to achieve a large area electrospinning system with a balanced electrostatic field across its entire active surface. We demonstrate the output by producing a high-throughput of nanofibres with comparable properties to that of a traditional single spinneret system, but at a processing rate two orders of magnitude faster.
Dharmasena R, Jayawardena K, Mills C, Dorey R, Silva S (2018) A unified theoretical model for Triboelectric Nanogenerators, Nano Energy 48 pp. 391-400 Elsevier
A unified theoretical model applicable to different types of Triboelectric Nanogenerators (TENGs) is presented based on Maxwell?s equations, which fully explains the working principles of a majority of TENG types. This new model utilizes the distance-dependent electric field (DDEF) concept to derive a universal theoretical platform for all vertical charge polarization TENG types which overcomes the inaccuracies of the classical theoretical models as well as the limitations of the existing electric field-based model. The theoretical results show excellent agreement with experimental TENGs for all working modes, providing an improved capability of predicting the influence of different device parameters on the output behaviour. Finally, the output performances of different TENG types are compared. This work, for the first time, presents a unified framework of analytical equations for different TENG working modes, leading to an in-depth understanding of their working principles, which in turn enables more precise design and construction of efficient energy harvesters.