Direct analyte-probed nano-extraction (DAPNe) is a method of extracting material from a microscale region of a sample and provides the opportunity for detailed mass spectrometry analysis of extracted analytes from a small area. The technique has been shown to provide enhanced sensitivity compared with bulk analysis by selectively removing analytes from their matrix and has been applied for selective analysis of single cells and even single organelles. However, the quantitative capabilities of the technique are yet to be fully evaluated. In this study, various normalisation techniques were investigated in order to improve the quantitative capabilities of the technique. Two methods of internal standard incorporation were applied to test substrates, which were designed to replicate biological sample matrices. Additionally, normalisation to the extraction spot area and matrix compounds were investigated for suitability in situations when an internal standard is not available. The variability observed can be significantly reduced by using a sprayed internal standard, and in some cases, by normalising to the extracted area.
Holly-May Lewis, Roger Webb, Guido F Verbeck, Josephine Bunch, Janella De Jesus, Catia Costa, Vladimir Palitsin, John G. Swales, Richard J. A. Goodwin, Patrick Sears, Melanie Jane Bailey (2019)Nanoextraction coupled to liquid chromatography mass spectrometry delivers improved spatially resolved analysis, In: Analytical Chemistry91(24)pp. 15411-15417
American Chemical Society
Direct analyte probed nanoextraction (DAPNe) is a technique that allows extraction of drug and endogenous compounds from a discrete location on a tissue sample using a nano capillary filled with solvent. Samples can be extracted from a spot diameters as low as 6 µm. Studies previously undertaken by our group have shown that the technique can provide good precision (5%) for analysing drug molecules in 150 µm diameter areas of homogenised tissue, provided an internal standard is sprayed on to the tissue prior to analysis. However, without an isotopically labelled standard, the repeatability is poor, even after normalisation to and the spot area or matrix compounds. By application to tissue homogenates spiked with drug compounds, we can demonstrate that it is possible to significantly improve the repeatability of the technique by incorporating a liquid chromatography separation step. Liquid chromatography is a technique for separating compounds prior to mass spectrometry (LC-MS) which enables separation of isomeric compounds that cannot be discriminated using mass spectrometry alone, as well as reducing matrix interferences. Conventionally, LC-MS is carried out on bulk or homogenised samples, which means analysis is essentially an average of the sample and does not take into account discrete areas. This work opens a new opportunity for spatially resolved liquid chromatography mass spectrometry with precision better than 20%.
The space industry is continuing to use commercial off the shelf (COTS) devices in satellites where the ionising radiation environment poses a threat. For device qualification, their single event effects (SEE) and total ionising dose (TID) performances are normally assessed separately. However, it has been shown that there can be a synergistic relationship in static random-access memory (SRAM) between TID and SEEs, where by the single event upset (SEU) cross section increases with dose, with some devices showing a significant increase for doses less than those seen by low earth orbit (LEO) satellites. The mechanism behind this effect in older SRAM technologies is believed to be due to threshold voltage shift imbalances of the nMOS transistors of the cross coupled inverter within the cell. This is due to variations in the build up of trapped charge in the nMOS transistors when they are ON or OFF. This degrades the noise threshold of the cell making it more susceptible to upsets when holding the opposite state to which it was irradiated in. For more modern devices the gate oxide is too thin to hold enough trapped charge to cause a significant change in threshold voltage. The mechanism for these modern SRAMs is based on the potential between the gate of the ON nMOS transistor and its substrate, in this situation fringing fields are at their strongest ushering the charge created by ionising radiation towards the boundary of the field oxide and the gate channel. It is at this boundary that a significant amount of trapped charge can create a parasitic leakage current between the transistor's source and drain. This parasitic leakage current then reduces the voltage seen at its drain and hence degrades the cell's noise threshold. The main goal of this work is to determine if these mechanisms behind synergy still have a significant affect on the SEU cross section of modern six transistor (6T) SRAMs built on the 180 and 130 nm fabrication processes. Other non-volatile memory devices have also been tested to see if their memory cell or complex CMOS peripheral circuitry suffer any synergistic effects such as an increase in single event functional interrupt (SEFI) or single event latchup (SEL) with increasing dose. To do this test boards containing the devices were irradiated with Co-60 gamma-rays to 5, 10, 15, 25 krads. These boards, as well as the control group test boards, were then taken to be tested with 23.5, 60.9, 151 and 230 MeV protons to determine the SEE response of the various parts. To help assess these devices a highly adaptable test system was developed consisting of high level control software and a control board. The high level software offers an over-view of key data such as the device under test's (DUT) current consumption, SEFI and SEL notifications and a preview of the incoming results. The control board is based around Texas Instrument's microcontroller, the TMS570, and is capable of testing both serial and parallel devices while offering latchup protection via a selectable current limit. From the testing run carried out in this work it was found that the modern SRAM's tested did not exhibit any significant signs of synergy. However there are concerns over the accuracy of some of the data due to the SRAM's SEL response dominating behaviour. These results would benefit from further testing at lower proton energies and flux to ensure any synergy effect was not obscured by the SRAM's SEL response or being close to saturation at 23.5 MeV. The 110 and 65 nm NOR flash memories tested did not show any SEUs in their main memory sectors, while the 110 nm SONOS flash functionally failed at less than 25 krad. The serial ferroelectric random-access memory (FeRAM) suffered a few SEFI events at both 10 and 15 krad resulting in the device being non-responsive, while the device suffered a transient error where by two groups of four addresses were reported to contain errors. Lastly a new method for determining if a device is susceptible to synergy has been suggested, in addition to recommendations for improving the test methodology used in this work.
Ion beam analysis comprises of a group of analytical techniques tackling the elemental composition of thin films by probing them with MeV ions. These techniques exploit information from photons and particles that come from the interaction of the MeV ions with the sample surface. Secondary ions, yet another species ensuing from such interactions can also be analysed providing information on molecular composition. The only ion beam analysis technique addressing the molecular composition is MeV SIMS, enabling detection and imaging of organic matter. The molecular detection and imaging of organic material is dominated by other surface sensitive techniques, such as TOF SIMS, providing a strong competition to MeV SIMS. In a pursuit to fully exploit the advantages of MeV SIMS in the field, the possibility to extract MeV ions into the air can also be utilised, thus offering the potential for application of ambient based MeV SIMS. In this work, a fully ambient MeV SIMS setup is introduced and commissioned at the University of Surrey Ion Beam Centre, and termed “Ambient Pressure MeV SIMS”. The aims of this thesis are to optimise AP MeV SIMS for detection and imaging of organic species, as well as to explore potential applications for the technique. The complex optimisation of AP MeV SIMS described in this work encounters many parameters influencing either the electronic sputtering or gas dynamic of secondary ions. A great volume of the optimisation process has addressed the issue of an immense background contribution by investigation of its identity and origin. Moreover, the atmosphere encompassing the sampling area was investigated and the effect of different angles and types of a sheath gas directing the sample was tested. The following work of this thesis demonstrates the application assessment of AP MeV SIMS. Here results of analysis of amino acids, explosives and synthetic organic pigments are presented. Finally, a description of a feasibility study on merging of AP MeV SIMS and HIPIXE with a purpose of simultaneous molecular and elemental imaging under ambient conditions is given.
An increased rate of cellular proliferation is a hallmark of cancer cells and may be accompanied by an increase in ribosome biogenesis and dysregulation in rRNA synthesis. In this regard CX-5461 has been developed as a novel RNA polymerase I inhibitor and is currently in Phase I/II clinical trials. The work described herein sets out to explore the use of this agent in combination with radiation therapy in solid cancer cell lines to understand the associated molecular mechanisms using this approach. Previous work has examined the CX-5461 in haematological malignancies and some solid cancers. Reports have shown that, treatment with CX-5461 induces potent anti-proliferative effects alongside induction of apoptosis in haematological malignancies. A panel of solid human tumour cell lines treated with CX-5461 indicated a broad spectrum of sensitivity (MTS Assay) with IC50 values ranging from 35nM to 1μM. The mode of cell death following CX-5461 exposure in the cancer cell lines studied was cell context dependent- either via autophagy (LC3I ® LC3II conversion alongside p62 sequestosome decrease) or via apoptosis (AnnexinV staining and late PARP cleavage). Treatment with CX-5461 also induced marked levels of DNA damage as detected through increased gH2AX foci staining. The presence of senescence marker β-galactosidase in CX-5461 treated cells indicates cell cycle arrest alongside the potent anti-proliferative effects of CX-5461 being highlighted through the clonogenic assays and decreased Ki-67 expression (flow cytometry). Through combination experiments involving CX-5461 and X-ray radiotherapy the current study has identified the highest levels of increased effectiveness in interactions between CX- 5461 and X-rays within the CaSki cervical cancer cell line. Highly significant effects were seen when low dose radiation and low dose CX-5461 were used together (combination index CI - < 0.2 with 6.25nM CX-5461 and 2Gy X-rays) through isobologram analysis. Cell cycle analysis of CaSki and A375 cells treated with single dose CX-5461 resulted in G2M cell cycle arrest and combination treatments with X-rays indicated cell cycle disruption with prolonged S-phase. The work described herein identifies the synergistic role of CX-5461 in combination with X- rays in solid cancers and may also inform the design of clinical trials of this novel agent.
About 50% of all cancer patients receive radiotherapy in the course of their disease. Hadron therapy uses protons or ions and shows a more advantageous depth-dose characteristic compared to photons. The superior dose distribution of particles enables to deliver a high dose to the tumour whilst sparing normal tissue. Although hadron therapy is believed to be superior to advanced photon therapies for certain types of cancers it has yet not been possible to draw definite conclusions from current clinical studies. To support the necessary extensive documentation of tumour, treatment and side effects data a database model for hadron therapy was established. It was implemented in a prototype hadron therapy information sharing platform. The assessment of a new treatment modality is based on the evaluation of treatment outcome and treatment related side effects. For this a generic Markov model for the evaluation of side effects was developed. Data from the database can automatically be used to refine the model and convert it into a tumour or treatment specific prediction model. Treatment models are a very powerful tool to investigate therapy options within silico clinical trials. A novel analytical model is introduced which describes the response of solid tumours to radiation therapy in a simple yet effective way. The introduction of proliferating and quiescent tumour cells enables to simulate important characteristics of tumour behaviour like sigmoid growth, cell quiescence, cell death and response to radiation therapy with different beam qualities. Main basic principles of fractionation like repair, redistribution, repopulation, reoxygenation and radiosensitivity are naturally contained within the model. The model involves the patient, tumour growth and fractionated radiotherapy to predict tumour recurrence. It is successfully applied to clinical data of patients treated with photons, protons and carbon ions for skull base chordoma and investigated for indications for hadron therapy.
A new protocol using time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been developed to identify the deposition order of a fingerprint overlapping an ink line on paper. By taking line scans of fragment ions characteristic of the ink molecules (m/z 358.2 and 372.2) where the fingerprint and ink overlap and by calculating the normalised standard deviation of the intensity variation across the line scan, it is possible to determine whether or not a fingerprint is above ink on a paper substrate. The protocol adopted works for a selection of fingerprints from four donors tested here and for a fingerprint that was aged for six months; for one donor, the very faint fingerprints could not be visualized using either standard procedures (ninhydrin development) or SIMS and therefore the protocol correctly gives an inconclusive result.
The effect of vacuum exposure on latent fingerprint chemistry has been evaluated. Fingerprints were analysed using a quartz crystal microbalance to measure changes in mass, gas chromatography mass spectrometry to measure changes in lipid composition and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine changes in the content of water, fatty acids and their esters after exposure to vacuum. The results are compared with samples aged under ambient conditions. It was found that fingerprints lose around 26% of their mass when exposed to vacuum conditions, equivalent to around 5 weeks ageing under ambient conditions. Further exposure to vacuum causes a significant reduction in the lipid composition of a fingerprint, in particular with the loss of tetradecanoic and pentadecanoic acid, that was not observed in ambient aged samples. There are therefore implications for sequence in which fingerprint development procedures (for example vacuum metal deposition) are carried out, as well as the use of vacuum based methods such as secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption ionisation (MALDI) in the study of fingerprint chemistry. © 2013 .
Glioblastoma is an aggressive brain cancer with a median survival rate of 14.6 months post diagnosis. Treatments for glioblastoma include surgery, radiotherapy, and chemotherapy with the alkylating agent temozolomide (TMZ). In 50% of patients, TMZ treatment is ineffective due to the reparative action of the protein O6- MeG DNA methyltransferase (MGMT). The base excision repair (BER) pathway repairs the most common lesions caused by TMZ. This work reports the characterization of several glioblastoma cell lines in terms of their repair status and sensitivity to traditional therapy of X-ray irradiation and TMZ. We find that the expression of BER proteins differed between cell lines, with alkyladenine-DNA-glycosylase (AAG) showing the greatest variation in expression. Sensitivity to TMZ and X-rays was MGMT dependent. Moreover, our results suggest that cell lines expressing higher AAG levels display increased sensitivity to X-rays and TMZ combination treatment in an MGMT independent fashion. Pharmacological inhibition of BER enzymes AP-endonuclease (APE) and polymerase (PolB) was examined, intending to enhance sensitivity of the glioblastoma cell lines to TMZ and X-ray or proton treatment. Methoxyamine (MX), an inhibitor of AP-endonuclease (APE) activity, leads to a modest increase in TMZ sensitivity. The combination of X-rays, MX and TMZ sensitised MGMT-negative cell lines, this was not seen in proton radiation. PolB inhibition greatly increased TMZ toxicity in conjunction with radiation in glioblastoma cell lines. Proton irradiation systems were analysed and developed within this work, leading to a high-throughput broadbeam irradiation system. These methodologies lead to differences being detected in response to proton irradiation depending on the method used. This might in future, lead to further understanding of low-dose hypersensitivity. In conclusion, the modulation of BER can enhance glioblastoma sensitivity to current treatment modalities, however, this is in an MGMT dependent fashion. These studies could provide insight for current clinical trials.
Melanie Bailey, R Bradshaw, S Francese, T Salter, M De Puit, Catia Costa, M Ismail, I Bosman, K Wolff, Roger Webb (2015)Rapid Detection of Cocaine, Benzoylecgonine and Methylecgonine in Fingerprints using Surface Mass Spectrometry, In: The Analyst140pp. 6254-6259
This book is an introduction to the application of computer simulation and theory in the study of the interaction of energetic particles (1 ev to the MeV range) with solid surfaces. The authors describe methods that are applicable both to hard collisions between nuclear cores of atoms down to soft interactions, where chemical effects or long-range forces dominate. The range of potential applications of the technique is enormous. In surface science, applications include surface atomic structure determination using ion scattering spectroscopy or element analysis using SIMS or other techniques that involve depth profiling. Industrial applications include optical or hard coating deposition, ion implantation in semiconductor device manufacture or nanotechnology. The techniques described will facilitate studying plasma-sidewall interaction in fusion devices. This book will be of interest to graduate students and researchers, both academic and industrial, in surface science, semiconductor engineering, thin-film deposition and particleSHsurface interactions in departments of physics, chemistry and electrical engineering.
The creation of stable, highly conductive ultrashallow junctions in strained Si is a key requirement for future Si based devices. It is shown that in the presence of tensile strain, Sb becomes a strong contender to replace As as the dopant of choice due to advantages in junction depth, junction steepness, and crucially, sheet resistance. While 0.7% strain reduces resistance for both As and Sb, a result of enhanced electron mobility, the reduction is significantly larger for Sb due to an increase in donor activation. Differential Hall and secondary-ion mass spectroscopy measurements suggest this to be a consequence of a strain-induced Sb solubility enhancement following epitaxial regrowth, increasing Sb solubility in Si to levels approaching 10(21) cm(-3). Advantages in junction depth, junction steepness, and dopant activation make Sb an interesting alternative to As for ultrashallow doping in strain-engineered complementary metal-oxide semiconductor devices. (c) 2008 American Vacuum Society.
DJ Kang, NH Peng, R Webb, C Jeynes, G Burnell, JH Yun, SH Moon, B Oh, EJ Tarte, DF Moore, M Kelly, MG Blamire (2002)Irradiation damage technology for manufacturable Josephson junctions, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS188pp. 183-188
The International Roadmap for Semiconductors requires ultrashallow, highly activated, abrupt dopant profiles in the source/drain extension regions, for technology nodes beyond 45 nm. The authors contrast B and BF2 implants in Si and silicon on insulator (SOI) substrates with and without a preamorphizing implant (PAI). The objective of the study is to compare between Si and SOI substrates, PAI and non-PAI condition, and B and BF2 implants. The results show the absence of the "reverse annealing effect" in BF2 implants, which is observed in B implants. The presence of F appears to impede the formation of boron interstitial clusters, which is shown in the case of B implant. The BF2 implants follow a similar trend for SOI and Si with and without PAI. (C) 2008 American Vacuum Society.
RM GEATCHES, KJ REESON, AJ CRIDDLE, RP WEBB, PJ PEARSON, PLF HEMMENT, A NEJIM (1994)NONDESTRUCTIVE CHARACTERIZATION OF SIMOX STRUCTURES, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS84(2)pp. 258-264
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I CHAKAROV, BV KING, RP WEBB, R SMITH (1992)COMPUTER-SIMULATION OF CAICISS OF ALAS(001), In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS67(1-4)pp. 332-334
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Secondary Ion Mass spectrometry (SIMS) has been generally used in the field of material sciences. In recent years, it has also been applied for molecular imaging of biological samples. Nevertheless, molecular ions derived from the large molecules (more than 1 kDa) were detected with very low sensitivity. Plasma desorption mass spectrometry (PDMS) is known as mass spectrometry for large organic molecule. In PDMS, fission fragments bombard samples and the impact induces molecular ionization by electronic excitation. Large organic molecules are detected by using swift heavy ions in SIMS. In this work, 6 MeV Cu4+ we irradiated angiotensin II, a class of peptides. The intact molecular ions generated by swift heavy ion irradiation were analyzed by time‐of‐flight (TOF) measurement. The yields are compared with some other probe ions, bismuth or flurane. Swift heavy ion bombardment ionized large organic molecules more effectively than other probes. Therefore, high energy ion can be applied in high resolution molecular imaging.
A Simon, C Jeynes, RP Webb, R Finnis, Z Tabatabian, PJ Sellin, MBH Breese, DF Fellows, R van den Broek, RM Gwilliam (2004)The new Surrey ion beam analysis facility, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS219pp. 405-409
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The use of polyatomic (cluster) ion beams for SIMS has proven to be an efficient method for the characterization of solids. Computer simulation programs such as Molecular Dynamics (MD) are often run to gain an insight into the ion-solid interactions that take place under these circumstances; however, for simulations to be able to make accurate predictions, a massive amount of computational resources are required to be at hand. These include several months in simulation time and the use of very large targets, not to mention that a single simulation run is a representation of only a single ion trajectory. Thus, MD simulations are invaluable for gaining insight into ion-solid interactions but are less so for being able to provide information when time constraints are put in place. The work here aims to achieve a prediction model that, when completely functional, will be able to deal with the pressures of the clock. This, we believe, is achievable by employing simpler modeling criteria that are dependant upon aspects of an initial energy deposition profile within the target under irradiation. Copyright © 2010 John Wiley & Sons, Ltd.
J THORNTON, KC PAUS, RP WEBB, A ALBUYARON, GR BOOKER, IH WILSON (1989)DEFECTS AFTER PREAMORPHIZATION AND ANNEALING, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS39(1-4)pp. 389-392
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A new geometrical theory of sputtering is extended to investigate the behaviour of interface mixing as a function of the angle of ion incidence. It is found that the amount of mixing peaks with the angle of incidence at different angles depending upon the depth of the interface. When the interface is at the surface the mixing parameter behaves as the sputtering yield and maximises around 70 degree , whilst deeper interfaces, around the damage range, have maximum mixing at normal incidence.
P Mistry, I Gomez-Morilla, GW Grime, RP Webb, R Gwilliam, A Cansell, M Merchant, KJ Kirkby, EJ Teo, MBH Breese, AA Bettiol, DJ Blackwood, F Watt (2005)New developments in the applications of proton beam writing, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS237(1-2)pp. 188-192
The Surrey Ion Beam Centre was awarded the Engineering and Physical Sciences Research Council (EPSRC) grant for “Promoting Cross Disciplinary Research: Engineering and Physical Sciences and Social Sciences” allowing continued research into the characteristics of desorption of secondary ions by the impact of fast primary ions in the ambient pressure at the sub-micron scale. To carry out this research a new beamline has been constructed consisting of a time-of-flight secondary ion mass spectrometer combined with the current 2MV Tandem accelerator. This research has already returned many significant results such as the first simultaneous SIMS, PIXE and RBS measurement preformed on an organic sample in vacuum. However, further optimization and validation of the new beamline is still being worked on. This work focuses on the optimization of the end station geometry to allow for high sensitivity ambient pressure measurements. It is concluded that a common geometry can be adopted for a wide variety of smooth samples to ensure optimum sensitivity provided a hard edge of the sample can be found to place the mass spectrometer capillary near.
Analysis using MeV ion beams is a thin film characterisation technique invented some 50 years ago which has recently had the benefit of a number of important advances. This review will cover damage profiling in crystals including studies of defects in semiconductors, surface studies, and depth profiling with sputtering. But it will concentrate on thin film depth profiling using Rutherford backscattering, particle induced X-ray emission and related techniques in the deliberately synergistic way that has only recently become possible. In this review of these new developments, we will show how this integrated approach, which we might call “total IBA”, has given the technique great analytical power.
C Jeynes, MJ Bailey, NJ Bright, ME Christopher, GW Grime, BN Jones, VV Palitsin, RP Webb (2012)"total IBA" - Where are we?, In: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms271pp. 107-118
The suite of techniques which are available with the small accelerators used for MeV ion beam analysis (IBA) range from broad beams, microbeams or external beams using the various particle and photon spectrometries (including RBS, EBS, ERD, STIM, PIXE, PIGE, NRA and their variants), to tomography and secondary particle spectrometries like MeV-SIMS. These can potentially yield almost everything there is to know about the 3-D elemental composition of types of samples that have always been hard to analyse, given the sensitivity and the spacial resolution of the techniques used. Molecular and chemical information is available in principle with, respectively, MeV-SIMS and high resolution PIXE. However, these techniques separately give only partial information – the secret of “Total IBA” is to find synergies between techniques used simultaneously which efficiently give extra information. We here review how far “Total IBA” can be considered already a reality, and what further needs to be done to realise its full potential.
Ion Beam Analysis (IBA) consists of a set of analytical techniques addressing elemental composition of inorganic material normally conducted using ion beams in the MeV kinetic energy range. Secondary Ion Mass Spectrometry using MeV ions (MeV SIMS) is the only IBA technique which can provide extensive molecular information about organic materials. MeV ions can be extracted into air hence offering the potential to apply MeV SIMS under atmospheric pressure. At the University of Surrey Ion Beam Centre, a fully ambient MeV SIMS setup has been developed and termed “Ambient Pressure MeV SIMS”. This AP MeV SIMS can be optimized for analysis and imaging of organic molecules. MeV SIMS relies upon electronic sputtering of the target material and this is much more efficient in insulating or organic targets, and less efficient in conducting metallic materials. PIXE, on the other hand, is efficient at providing good signals from elemental metallic systems, but does not readily provide molecular information from organics. The combination of the two techniques – preferably simultaneously with the same beam – provides useful complementary information which can readily be combined. Here we present pioneering preliminary work in simultaneous molecular and elemental imaging of a complex sample comprising of two organic species and two metallic species by combining AP MeV SIMS with Heavy Ion Particle Induced X-ray emission (HIPIXE).
© 1989 Springer-Verlag Heidelberg. © 1989 Springer-Verlag Bcrbn Heidelberg. All Rights Reserved.This paper correlates photodisplacement thermal wave characterization of ion implanted silicon wafers with the lattice information provided by Rutherford Backscattering Spectrometry.
Recent publications have explored the possibility of using fingerprints to confirm drug use, but none has yet dealt with environmental contamination from fingertips. Here we explored the possibility of establishing an environmental cutoff for drug testing from a single fingerprint. METHODS:
Fingerprint samples (n=100) were collected from the hands of 50 nondrug users before and after handwashing to establish separate environmental cutoff values and testing protocols for cocaine, benzoylecgonine, heroin, and 6-monoacetylmorphine. The cutoff was challenged by testing the fingerprints of drug-free volunteers after shaking hands with drug users. Fingerprints from patients who testified to taking cocaine (n = 32) and heroin (n = 24) were also collected and analyzed. RESULTS:
A different cutoff value needed to be applied, depending on whether the fingerprints were collected as presented or after handwashing. Applying these cutoffs gave a 0%false-positive rate from the drug-free volunteers. After application of the cutoff, the detection rate (compared to patient testimony) for washed hands of patients was 87.5% for cocaine use and 100% for heroin use. CONCLUSIONS:
Fingerprints show enhanced levels of cocaine, heroin, and their respective metabolites in patients who testified to taking the substances, compared with the population of naı¨ve drug users surveyed, and a cutoff (decision level) can be established. The cutoff is robust enough to account for small increases in analyte observed after secondary transfer.
The inherent difficulties in interpreting thermal desorption spectra are discussed. Possible mechanisms which can change the expected form of the evolution spectra are investigated including the possibility of a distribution of activation energies for release of trapped gas and the spatial distribution of the trapped gas. It is shown that the form of the evolution spectra can be quite misleading and unless care is taken the wrong conclusions can be derived. © 1979.
JA Sharp, AJ Smith, RP Webb, KJ Kirkby, NEB Cowern, D Giubertoni, S Gennaro, M Bersani, MA Foad, PF Fazzini, F Cristiano (2008)Surface proximity and boron concentration effects on end-of-range defect formation during nonmelt laser annealing, In: APPL PHYS LETT92(8)082109
AMER INST PHYSICS
The effects of surface proximity and B concentration on end-of-range defect formation during nonmelt laser annealing in preamorphized silicon have been studied. These effects were analyzed by observing the activation and diffusion of an ultrashallow B implant, using Hall effect and secondary ion mass spectrometry measurements. By adjusting the preamorphizing implant and laser annealing conditions, B deactivation and diffusion were minimized, resulting in a sheet resistance of similar to 600 Omega/sq with a 16 nm junction depth. This is attributed to a combination of enhanced dissolution of end-of-range defects and preferential formation of B-interstitial clusters due to the surface proximity and high B concentration, respectively. (C) 2008 American Institute of Physics.
DJ Kang, G Burnell, SJ Lloyd, RS Speaks, NH Peng, C Jeynes, R Webb, JH Yun, SH Moon, B Oh, EJ Tarte, DF Moore, MG Blamire (2002)Realization and properties of YBa2Cu3O7-delta Josephson junctions by metal masked ion damage technique, In: APPLIED PHYSICS LETTERS80(5)pp. 814-816
AMER INST PHYSICS
N Peng, C Jeynes, MJ Bailey, D Adikaari, V Stolojan, RP Webb (2009)High concentration Mn ion implantation in Si, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS267(8-9)pp. 1623-1625
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Normal incidence argon-copper sputtering mechanisms have been investigated for ion energies just above threshold. Identical mechanisms operate in both the (111) and (001) surface orientations. Adsorption of an ordered oxygen overlay on the surface does not destroy the ejection processes. Although the mechanisms produce similar ejected atom energy distributions, the processes may be experimentally distinguishable through the angular emission spectrum of the ejected copper atoms.
P Mistry, I Gomez-Morilla, RC Smith, D Thomson, GW Grime, RP Webb, R Gwilliam, C Jeynes, A Cansell, M Merchant, KJ Kirkby (2007)Maskless proton beam writing in gallium arsenide, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS260(1)pp. 437-441
Both Rutherford backscatterings of He-4(+) beams and non-Rutherford backscatterings of He-4(+) and H+ beams have been used in this study to investigate the depth profiles of B dopant in Mg target upon B implantation and post annealing. Primitive data analysis suggests an enhanced diffusion of surface C contaminant during the B implantation process, together with enhanced surface oxidation upon implantation and thermal annealing in flowing N-2 atmosphere. Published by Elsevier B.V.
The spatial variation of energy deposited in a solid can lead to local variations in sputtering yield at points on the surface neighbouring the point of ion impact. An approximate theory is developed to describe this local sputtering yield variation in terms of the local morphology. It is then shown how, if this local variation merely moderates the standard sputtering yield-projectile incidence angle function by multiplication, an erosion slowness theory can be simply modified and generalized to allow prediction of the time development of sputtered surface morphology. Both transient and steady-state morphologies are explored. © 1981 Chapman and Hall Ltd.
This chapter describes the methods and applications for the use of multi-atom, ionized species, containing 10s to several thousand atoms, for high-flux ion doping and modification of surfaces with sub-keV energies per atom. “Massive” ion beams are formed using molecular species, liquids and gas clusters. Ion beam systems for such “massive” ions include the use of novel vaporizer methods, adiabatic cooling, electron beam ionization, and other techniques to provide stable, high-fluence beams. Applications include high-dose ion implantation for ultra-shallow junctions, room-temperature deposition of semiconductor and other layers, smoothing and high-rate etching of surfaces.
A molecular dynamics simulation has been used to investigate the sensitivity of atom ejection processes from a single-crystal target to changes in the atom-atom potential function. Four functions, three constructed from the Gibson potentials with Anderman's attractive well, and a fourth specifically developed for this investigation, were investigated in the Cu/Ar+ system over a range of ion energies from 1.0 to 10.0 kev with the KSE-B ion-atom potential. Well depths and widths also were varied. The calculations were done at normal incidence on the fcc (111) crystal orientation. Computed values were compared with experimental data where they exist. Sputtering yields, multimer yield ratios, layer yield ratios, and the ejected atom energy distribution vary systematically with the parameters of the atom-atom potential function. Calculations also were done with the modified Moliere function. Yields and other properties fall exactly into the positions predicted from the Born-Mayer function analysis. Simultaneous analysis of the ejected atom energy distribution and the ion energy dependence of the sputtering yield curve provides information about the parameters of both the wall and well portions of the atom-atom potential function.
DJ Kang, NH Peng, C Jeynes, R Webb, HN Lee, B Oh, SH Moon, G Burnell, NA Stelmashenko, EJ Tarte, DF Moore, MG Blamire (2003)Josephson effects in MgB2 metal masked ion damage junctions, In: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY13(2)pp. 1071-1074
A molecular dynamics multiple interactions simulation computer code has been used to study the near-surface effect of cascade mixing due to ion bombardment. 90% of all moved atoms recoil forward or backward only one layer and 70% of all recoil atoms are displaced to their nearest neighbour positions. A comparison of the computed results and the results predicted from statistical theories indicates that both models would produce similar results if the lower limit in the energy threshold of the statistical theories were decreased sufficiently to include the movement of many more low energy recoils. A further comparison is made between the distributions of recoil-atom displacements at the end of the dynamic regime, and after the damaged crystallite has coalesced. There is a small degree of rearrangement, due to the collapse of collision spikes, but the resultant displacement distributions are similar. © 1983.
In this paper, the technique of microscope-spectrophotometry, used to nondestructively characterize the microstructure of ion beam synthesized iron-disilicide layers, is described. The results obtained agree extremely well, in terms of layer thickness and interfacial roughness, with those from Rutherford backscattering. The results also show that it is possible to interpret the measured spectral reflectance data in terms of: 1) defect annealing; 2) iron redistribution; and 3) phase transformations from the β to the α phase.
PMM Rombouts, I Gomez-Morilla, GW Grime, RP Webb, L Cuenca, R Rodriguez, M Browton, N Wardell, B Underwood, NF Kirkby, KJ Kirkby (2007)A microPIXE investigation of the interaction of cells of Schizosaccharomyces pombe with the culture medium, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS260(1)pp. 231-235
The proton beam writing (PBW) technique was used to fabricate microfluidic structures in SU-8 resist. A network of the buried channels was fabricated as part of a project to develop functional microfluidic device for neuronal studies and self-powered microfluidics. Protons with energies between 2.5 MeV and 0.75 MeV were used to fabricate the buried channels with a minimum feature size of around 1 μm and depths of 40–55 μm. Roughness of channels sidewalls was around 2.5 nm rms. Exposure regime and examples of functional networks fabricated using PBW are described. COMSOL Multiphysics® software was used to model the flow characteristics of fluid in the SU-8 microchannels structured by PBW. The results obtained using PBW are compared with the structures fabricated by UV-lithography.
Molecular dynamics computer simulations have been used to study the development of ion-induced cascades in the surface region of an initially perfect single crystal metal target. A 16 mm movie has been produced to show the temporal progress of individual cascades. The cascades can then be seen to be formed from a few high energy primary knock-on initiated replacement collision sequences which overlap to form the more usual interpretation of a mature collision cascade. However, it is before the collision cascade has matured, and while the replacement sequences are spreading, that the majority of atoms (>80%) are ejected. These qualitative observations are also upheld more quantitatively in a global average, over many cascades, of the ejection time of each atom. This gives rise to the appearance of a statistical ejection front which propagates radially outwards, from the impact point on the crystal surface, with a well defined velocity. © 1984.
Fingerprints have been proposed as a promising new matrix for drug testing. In previous work it has been shown that a fingerprint can be used to distinguish between drug users and non-users. Herein, we look at the possibility of using a fingerprint to distinguish between dermal contact and administration of heroin.
Fingerprint samples were collected from (a) 10 patients attending a drug rehabilitation clinic (b) 50 non-drug users (c) participants who touched 2 mg street heroin, before and after various hand cleaning procedures. Oral fluid was also taken from the patients. All samples were analysed using a liquid chromatography – high resolution mass spectrometry (LC-HRMS) method validated in previous work for heroin and 6-AM. The HRMS data was analysed retrospectively for morphine, codeine, 6-acetylcodeine and noscapine. Heroin and 6-AM were detected in all fingerprint samples produced from contact with heroin, even after handwashing. In contrast, morphine, acetylcodeine and noscapine were successfully removed after handwashing.
In patient samples, the detection of morphine, noscapine and acetylcodeine (alongside heroin and 6-AM) gave a closer agreement to patient testimony on whether they had recently used heroin use than the detection of heroin and 6-AM alone.
This research highlights the importance of washing hands prior to donating a fingerprint sample to distinguish recent contact with heroin from heroin use.
The MIAMI* facility at the University of Huddersfield is one of a number of facilities worldwide that permit the ion irradiation of thin foils in-situ in a transmission electron microscope. MIAMI has been developed with a particular focus on enabling the in-situ implantation of helium and hydrogen into thin electron transparent foils, necessitating ion energies in the range 1 - 10 keV. In addition, however, ions of a variety of species can be provided at energies of up to 100 keV (for singly charged ions), enabling studies to focus on the build up of radiation damage in the absence or presence of implanted gas. This paper reports on a number of ongoing studies being carried out at MIAMI, and also at JANNuS (Orsay, France) and the IVEM / Ion Accelerator Facility (Argonne National Lab, US). This includes recent work on He bubbles in SiC and Cu; the former work concerned with modification to bubble populations by ion and electron beams and the latter project concerned with the formation of bubble super-lattices in metals. A study is also presented consisting of experiments aimed at shedding light on the origins of the dimensional changes known to occur in nuclear graphite under irradiation with either neutrons or ions. Single crystal graphite foils have been irradiated with 60 keV Xe ions in order to create a non-uniform damage profile throughout the foil thickness. This gives rise to varying basal-plane contraction throughout the foil resulting in almost macroscopic (micron scale) deformation of the graphite. These observations are presented and discussed with a view to reconciling them with current understanding of point defect behavior in graphite.*Microscope and Ion Accelerator for Materials Investigations Copyright © Materials Research Society 2014.
A T Kearsley, J L Colaux, D K Ross, P J Wozniakiewicz, L Gerlach, P Anz-Meador, T Griffin, B Reed, J Opiela, V V Palitsin, G W Grime, R P Webb, C Jeynes, J Spratt, T Salge, M J Cole, M C Price, M J Burchell (2017)Hypervelocity impact in low earth orbit: finding subtle impactor signatures on the Hubble Space Telescope, In: Procedia Engineering204pp. 492-499
Return of materials from the Hubble Space Telescope (HST) during shuttle orbiter service missions has allowed inspection of large numbers of hypervelocity impact features from long exposure at about 615 km altitude in low Earth orbit (LEO) [1,2]. Here we describe the application of advanced X-ray microanalysis techniques on scanning electron microscopes (SEM), microprobes and a 2 MV Tandetron, to nearly 400 impacts on the painted metal surface of the Wide Field and Planetary Camera 2 (WFPC2) radiator shield [3,4]. We identified artificial Orbital Debris (OD) and natural Micrometeoroid (MM) origins for small  and even for larger particles , which usually may leave little or no detectable trace on HST solar arrays, as they penetrate through the full cell thickness [2,7].
DJ Kang, NH Peng, R Webb, C Jeynes, JH Yun, SH Moon, B Oh, G Burnell, EJ Tarte, DF Moore, MG Blamire (2002)Realization and properties of MgB2 metal-masked ion damage junctions, In: APPLIED PHYSICS LETTERS81(19)pp. 3600-3602
AMER INST PHYSICS
Computer simulations of ion-bombardment events which recrystallize the target demonstrate pit formation at 1.0 keV. Atoms are ejected from the first two target layers in the pit region. The remainder of the pit is created by replacement-collision sequences. Linear-cascade and spike-regime events are dynamically indistinguishable. © 1983 The American Physical Society.
Surface mass spectrometry methods can be difficult to use effectively with low cost, portable mass spectrometers. This is because commercially available portable (single quadrupole) mass spectrometers lack the mass resolution to confidently differentiate between analyte and background signals. Additionally, current surface analysis methods provide no facility for chromatographic separation and therefore are vulnerable to ion suppression. Here we present a new analytical method where analytes are extracted from a sample using a solvent flushed across the surface under high pressure, separated using a chromatography column and then analysed using a portable mass spectrometer. The use of chromatography reduces ion suppression effects and this, used in combination with in-source fragmentation, increases selectivity, thereby allowing high sensitivity to be achieved with a portable and affordable quadrupole mass spectrometer. We demonstrate the efficacy of the method for the quantitative detection of cocaine and benzoylecgonine in urine and oral fluid. The method gives relative standard deviations below 15% (with one exception), and R2 values above 0.998. The limits of detection for these analytes in oral fluid and urine are <30 ng/ml, which are comparable to the cut-offs currently used in drug testing, making the technique a possible candidate for roadside or clinic-based drug testing..
Computer simulation of ion-bombardment events has been extended to coalesce and recrystallise the target, so that the surface damage created when a single ion strikes a metal surface can now be studied directly. Qualitative and quantitative information on pit formation, other surface damage and recoil mixing can be obtained from the model. Many characteristics of the target's final condition are evident before the excess energy has been removed. Small structured and faceted surface pits are found at 1.0 keV ion energy for both low and high energy-density potential functions. Atoms are only sputtered from the first two layers of the pit region. The rest of the pit is formed by atoms displaced laterally or downward, initiating replacement collision sequences. A movie has been produced which presents the temporal development and creation of surface damage, and demonstrates surface reconstruction processes. © 1983.
A molecular dynamics simulation has been used to study the times at which atoms are ejected during sputtering events. Plots of the atom ejection time versus distance from the impact point indicate that many sputtering events occur along a roughly circular front that propagates outward at hypersonic speed.
NEB Cowern, AJ Smith, N Bennett, BJ Sealy, R Gwilliam, RP Webb, B Colombeau, S Paul, W Lerch, A Pakfar (2008)Vacancy engineering - An ultra-low thermal budget method for high-concentration 'diffusionless' implantation doping, In: Materials Science Forum573-57pp. 295-304
Multiple interaction computer simulations of bombardment cascades have been used to study the surface damage created by an ion. Qualitative information on the temporal evolution of the dynamic cascade is obtained from an animated movie of the process. A comparison is made between the final damage states of high energy-density trajectories. A number of ion-atom potential functions have been investigated over a wide range of ion energies. Only superficial differences are found. © 1984.
Ultra-shallow B and BF 2 implants in silicon pre-amorphised with Ge have been activated using a scanning non-melt laser. The implants were activated either by using 1 or 10 laser scans. Isochronal 60s post-laser annealing between 700-1000°C were then undertaken to study the deactivation and reactivation of the B. Both B and BF2 samples were implanted with a dose of 1×10 15 B cm -2 at an effective energy of 500eV. The presence of F from the BF 2 implants, which is superimposed over the boron profile increases the sheet resistance of the initial fabricated junction (from 600-700 ohms/sq from B implants only to 750-1100 ohms/sq for BF2 implants). Fluorine also changes the deactivation and reactivation behaviour of the boron during the post-anneals by increasing the amount of deactivation of the boron. © 2006 Materials Research Society.
Ambient Pressure MeV SIMS (AP MeV SIMS) is a special application of MeV SIMS technique for molecular detection and imaging under ambient conditions. There are several advantages of using ambient over nonambient techniques such as minimising or completely avoiding sample preparation that can contribute to the reducing of costs and shortening of analysis. Moreover, by performing analysis in ambient conditions negative vacuum influence on samples will be avoided. The emergence of ambient mass spectrometry techniques over the past decade has been enormous with a broad range of applications such as food quality, environmental analysis and life sciences [1,2]. On the other hand, the disadvantage of ambient pressure mass spectrometry techniques is the influence of the ambient background which can suppress the signal from the target. In AP MeV SIMS, molecular species present in ambient surrounding of the sampling site will also be ionised by ion beams hence secondary ions originating from the sample have to be transported in the most efficient manner from the site of interaction of ion beams and target into the mass spectrometer capillary and, finally, into the mass spectrometer . In this work, we present the optimisation of the mass spectrometer capillary temperature, distances of mass spectrometer and sheath gas, in our case helium, with respect to the beam axis and angle of the helium flow capillary with respect to the sample.
JA Sharp, NEB Cowern, RP Webb, KJ Kirkby, D Giubertoni, S Gennaro, M Bersani, MA Foad, F Cristiano, PF Fazzini (2006)Deactivation of ultrashallow boron implants in preamorphized silicon after nonmelt laser annealing with multiple scans, In: APPLIED PHYSICS LETTERS89(19)ARTN 1pp. ?-?
AMER INST PHYSICS
H Zurrug, J Mefo, B Sealy, G Boudreault, C Jeynes, RP Webb, KJ Kirkby, EJH Collart, B Brown, TL Alford, M Nastasi, MC Vella (2003)Characterization and enviromental impact of plasma products within an ion implanter, In: IIT2002: ION IMPLANTATION TECHNOLOGY, PROCEEDINGSpp. 471-474 NP Barradas, PK Marriott, C Jeynes, RP Webb (1998)The RBS data furnace: Simulated annealing, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS136pp. 1157-1162
BACKGROUND: Paper spray mass spectrometry6 is a technique that has recently emerged and has shown excellent analytical sensitivity to a number of drugs in blood. As an alternative to blood, fingerprints have been shown to provide a noninvasive and traceable sampling matrix. Our goal was to validate the use of fingerprint samples to detect cocaine use.
METHODS: Samples were collected on triangular pieces (168 mm2) of washed Whatman Grade I chromatography paper. Following application of internal standard, spray solvent and a voltage were applied to the paper before mass spectrometry detection. A fingerprint visualization step was incorporated into the analysis procedure by addition of silver nitrate solution and exposing the sample to ultraviolet light.
RESULTS: Limits of detection for cocaine, benzoylecgonine, and methylecgonine were 1, 2, and 31 ng/mL respectively, with relative standard deviations of less than 33%. No matrix effects were observed. Analysis of 239 fingerprint samples yielded a 99% true-positive rate and a 2.5% false-positive rate, based on the detection of cocaine, benzoylecgonine, or methylecgonine with use of a single fingerprint.
CONCLUSIONS: The method offers a qualitative and noninvasive screening test for cocaine use. The analysis method developed is rapid (4 min/sample) and requires no sample preparation.
RP Webb, R Smith, HH Al-Barwarni, IH Wilson (1997)Simple cellular models for growth, In: RADIATION EFFECTS AND DEFECTS IN SOLIDS141(1-4)pp. 211-222
TAYLOR & FRANCIS LTD
One of the greatest challenges in silicon photonics has been to induce light emission in silicon, with the ultimate vision is to have fully silicon-based photonics emitters or lasers which can operate by both optical and electrical pumping. Comprehensive photoluminescence (PL) and electroluminescence (EL) studies are conducted on dislocation engineering light emitting diode structures based on silicon implanted (Si:B) with Ce, Eu, and Yb rare-earth (RE) ions. The PL and EL results show very bright luminescence intensity and dramatic red shifting in luminescence peaks which shows a possible novel phenomenon of RE energy transition modification. The modification is attributed to the direct transition from Si conduction band edge to RE manifolds〖 (_^2)F〗_(7/2)^ , 〖(_^2)F〗_(5/2)^ for 〖Ce〗^(3+), 〖(_^7)F〗_j^ (j=0 to 4) for 〖Eu〗^(3+), 〖(_^2)F〗_(5/2)^ and 〖(_^2)F〗_(7/2)^ for 〖Yb〗^(3+). The emissions are shifted from the conventional lowest internal energy transition in 〖Ce〗^(3+) from around blue spectrum at ~350 nm (due to (_^2)D_(3/2)^ excited state to the 〖(_^2)F〗_(7/2)^ , 〖(_^2)F〗_(5/2)^ transitions) to ~1.35 µm in Si:B&Ce. For 〖Eu〗^(3+) the emission is shifted from around the red spectrum at ~600 nm (due to (_^5)D_0^ excited state to the 〖(_^7)F〗_j^ transitions, j=0 to 4) to ~ 1.40 µm in Si:B&Eu and for 〖Yb〗^(3+) is shifted from slightly beyond the visible region at ~980 nm (due to 〖(_^2)F〗_(5/2)^ excited state to the 〖(_^2)F〗_(7/2)^ transition) to ~ 1.43 µm in Si:B&Yb samples. The new shifting of luminescence peak into NIR region is very important for optical communication in making LEDs and lasers.
This thesis describes the use of proton beam writing (PBW) for the fabrica- tion for microfluidic and microelectromechanical system (MEMS) devices. In particular, the fabrication of three-dimensional (3D) micro or nanostruc- tures with high aspect ratios is of growing interest in these fields. PBW is the only technique that has the capability to satisfy these requirements while providing full control of the geometrical parameters, such as the sur- face roughness and side wall angle. This technique is a direct microfabri- cation method that employs a focused, energetic (MeV) proton beam to structure the input pattern in resist materials. In the present work, a network of buried channels is fabricated as part of a project to develop a functional microfluidic device for neuronal studies and self-powered microfluidics (capillary micropump). Proton beam with energies of 0.75 to 2.5 MeV is used to fabricate the channels in 3D with a minimum feature size of approximately 1 μm and depths of 40 to 60 μm. The roughness of the sidewalls of the written channels is approximately 3 nm root mean square roughness (Rrms). Radio frequency (RF) MEMS switches, which consist of an overhanging structure, are also written using PBW, and new MEMS switch designs are proposed. These designs are constructed so as to provide full control of the main cantilever beam parameters, such as the thickness, spring constant, and actuation. The three main stages of the lithography process, i.e., pre-exposure, expo- sure, and post-exposure, are investigated and optimised for application to poly(methyl methacrylate)(PMMA), pure SU-8 polymer, and SU-8/silver- nanoparticle nanocomposites (SU-8/AgNp). During the exposure process, the proton beam energies, doses, and scanning method are also optimised, in order to attain a good-quality structure (i.e., a robust structure with smooth and straight walls). The mechanical and electrical properties of the nanocomposites, which are irradiated with a range of proton beam doses, are measured. Note that the structures written in this work are numerically validated prior to the writing process using COMSOL Multiphysics R software. The fluid flow in the written buried channels is investigated using numerical methods.
Secondary ion mass spectrometry (SIMS) is a well-known surface analysis technique with numerous applications in materials science. In recent years various types of primary ion beams have emerged to improve SIMS for analysing polymers, organic semiconductors and biological materials. keV cluster ions have given an improvement in producing higher secondary ion yields, reduced topography and reduced interface mixing while MeV SIMS has proven to be better in certain cases especially at desorbing higher mass molecules and has the ability to perform measurements at ambient pressure. This has generally driven the study to understand the interaction between keV cluster ions and MeV ions with insulating materials from both a modelling and an experimental perspective. A simple Monte Carlo model describing the desorption of a molecular solid under keV cluster and MeV ion bombardment is described. The model employs a conical ejection pattern, which has been suggested to be applicable for keV cluster and MeV ions impinging on molecular solids. The conical ejection region is combined with a cylindrical fragmentation region to predict the sputtering behaviour of molecular materials. Molecular dynamics simulations are used to back up this model. The model provides information about surface roughness induced by the process as well as the fragmentation build up during a prolonged sputtering process. This model is expanded to multi-layered systems and has produced some insight on the depth resolution of the analysis. Comparison studies between the model and experiments are also presented with polymer films analysed by a 10keV C60+ time-of-flight (TOF) SIMS. These results are found to compare favourably with each other.
This thesis investigates the possibility of using ambient ionisation and surface mass spectrometry for the detection and quantification of drugs of abuse in latent fingerprints. The use of fingerprints for drug testing in lieu of blood, oral fluid or urine reduces the biological hazard associated with these types of samples. The sample collection procedure is non-invasive, can be monitored to prevent cheating (submitting samples from a drug free individual) and the identity of the donor is embedded in the fingerprint ridge detail. In this thesis, three techniques – desorption electrospray ionisation (DESI), liquid extraction surface analysis (LESA) and paper spray mass spectrometry, were evaluated for their ability to provide a rapid drug test from a fingerprint. Paper spray-mass spectrometry was chosen for further development due to the ease of set-up, rapid nature of the analysis and potential to provide quantitative results. The final optimised method included full scan mass spectrometry measurements (quantitative) followed by tandem mass spectrometry (MS/MS) scans (qualitative) for the detection of cocaine, benzoylecgonine (BZE) and ecgonine methyl ester (EME). Limits of detection (LOD) were calculated to be 1 ng/mL, 2 ng/mL and 31 ng/mL for cocaine, BZE and EME, respectively. Using the optimised method of analysis, 159 individual fingerprint samples (collected from individuals seeking treatment for substance abuse) were analysed with a 99% true positive rate through the detection of either cocaine, BZE or EME. The detection of these substances was corroborated by a positive oral fluid result from samples collected from the same individuals. Analysis of fingerprint samples collected from the non-drug users (n=80) indicated <2.5% false positive rate. The significance of detecting the parent drug or metabolite in fingerprint samples was determined through the analysis of samples after contact with seized cocaine from Forensic Science Ireland. Cocaine, BZE and EME were found in fingerprints produced by contact, showing that the presence of a cocaine metabolite in a fingerprint is not enough to show that a suspect has taken a drug. Furthermore, secondary transfer scenarios showed that cocaine could be transferred through handshakes. None of the hand cleaning methods employed in this research were sufficient to remove all traces of cocaine from contact residues. iii Finally, the possibility of visualising the fingerprint ridge detail prior to analysis was tested and the presence of the analytes was qualitatively confirmed in fingerprint samples after application of silver nitrate. This is an important step that allows for sample traceability, whilst still providing high throughput analysis and sensitivity.