Professor Roger Webb
Director of Ion Beam Centre, Professor of Ion Beam Physics
PA: Karen Arthur
Biography
Biography
Roger joined the Department in 1983 as a Research Fellow with the SRC (as it was then - interesting how the EPSRC has gained letters over the years) Surrey Ion Beam Centre. He was employed to look after the computing facilities associated with the research group - a single pdp11, about half of the computer "power" in the department in those days.
Before this he had spent 3 years as a post doc at the Naval Postgraduate School in Monterey California, making Molecular Dynamics Studies and Computer Animations, which is still the main area of his research activities. He did his PhD work in the Electronic & Electrical Engineering Department of the University of Salford, on the Mathematical Modelling of Atomic Collisions in Solids.
He was made a Lecturer in the Department in 1986, promoted to Senior Lecturer in 1993 and then to Reader in 1997, reaching the dizzy heights of Professor of Ion Beam Physics in 2002. He is the current Director of the Surrey Ion Beam Centre.
He has performed research at Penn State College and the Chinese University of Hong Kong
Research interests
Main area of research is the interaction of energetic ion beams with solids.Current research activities include the use of Molecular Dynamics Simulations to predict the behaviour of cluster and molecular impacts on surfaces. As well as the use of more simple Binary Collisions simulations to predict the effects of energetic particle solid interactions, in particular ion implantation profiles in crystalline solids. Cluster and molecular impacts include fullerene impact induced desorption of molecular solids.Other areas of interest are in automation and control of ion beam analysis equipment. This includes software to automate the collection of data from standard analyses using RBS, PIXE, PIGE, NRA and ERD.He must also take some responsibility for the windows interface to the Data Furnace for the automated and rapid analysis of experimental ion scattering data. Developments in the use of MeV ion beams for Secondary Ion Mass Spectrometry (SIMS) is also of current interest.
Teaching
Multi Disciplinary Design Project module coordinator - stage 4 across the faculty MEng project
Instrumentation - 2nd Year Mech Eng Module
Fundamentals of Nanotechnology - MSc module
Fundamentals of Ion Solid Interactions - PG Training Course
Departmental duties
Director of the Surrey Ion Beam Centre
Chair of the Facilities Directorate
Affiliations
Member of the Institute of Physics
On the International Advisory Boards of the following Conference Series:
- Computer Simulation of Radiation Effects in Solids (COSIRES)
- Ion Beam Analysis (IBA)
- Ion Solid Interactions (ISI)
- Radiation Effects in Matter (REM)
Research Funding
Research Funding over past 10 years
- Knowledge Transfer Partnership on manufacturable X-Ray detectors with Gresham Scientific Instruments and RMGwilliam, £123,792 awarded June 2004
- BioMed Network for High Energy Ion Beams, May '04 - £63,109 - with KJKirkby, GWGrime, SReady, AClough, NSpyrou
- Marie Curie Training Network for Application of MeV Ion Beams to Cell Irradiation Jan '05 - £300,000 - with GWGrime, KJKirkby, NJKirkby - part of a £3M EU grant
- MeV Ion Nanobeams: Nanotechnology for the 21st Century, Sept '05 - £256,845 - with GWGrime, KJKirkby, AClough, RGwilliam, CJeynes
- New Developments in ToF-SIMS Surface Mass Spectrometry with ATR_IR Spectroscopy, Sept '05 - £227,208 - with KJKirkby - part of a £1.9M project with University of Manchester
- University of Surrey Ion Beam Centre, March '06 - £2,271,580 - with BSealy, KKirkby, KHomewood, RGwilliam, CJeynes, GGrime
- The Non Scaling Fixed Field Alternating Gradient (NS-FFAG) Accelerator, April '07 - £7,489,380 - with 5 other University groups and KJKirkby
- Enhancing new developments in ToF-SIMS through researcher exchanges, Oct '07 - £109,825 - with JVickerman and NLockyer
- Laser Induced Beams of Radiation and their Applications (LIBRA), Nov '07 - £4,747,342 - with 4 other Universities and KJKirkby
- SPIRIT - Support for Public & Industrial Research Using Ion Beam Technology, March '09 - £1,069,314 (FP7 with 7 other centres, total value ~£5.5M)
- Coherent Optical and Microwave Physics for Atomic Scale Spintronics in Silicon (COMPASSS) , February '10 - £6,106,847 - with BMurdin, RMGwilliam, JAl-Khalili and 3 other University groups
- Ambient Pressure Mass Spectrometry at the Sub Micron Scale (MeV-SIMS), December '11 - £1,278,391 - with NWard and KJKirkby
My publications
Publications
Al-Shehri S, Palitsin V, Webb RP, Grime GW (2015) Fabrication of three-dimensional SU-8 microchannels by proton beam writing for microfluidics applications: Fluid flow characterisation, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 348 pp. 223-228
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 ¼m and depths of 40?55 ¼m. 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.
Webb RP, Harrison DE, Jakas MM (1986) The computer simulation of ion induced atomic collision cascades, Nuclear Inst. and Methods in Physics Research, B 15 (1-6) pp. 1-7
The use of computer simulation to understand the physics of atomic collision phenomenon has escalated in recent years. Even with this proliferation of simulation codes the majority of programs fall into two categories - the event store and the time step models. These models are discussed, and a hybrid formed from the two is described. The best uses of each model is indicated and some examples given. The event store simulations give an accurate method of evaluating range data and the time step models conveniently give information on cascade propogation and nonlinear behaviour. © 1986.
Webb RP, Harrison DE (1982) Near-threshold sputtering mechanisms from a computer simulation of argon- bombarded clean and oxygen-reacted copper single crystals, Journal of Applied Physics 53 (7) pp. 5243-5249
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.
Kirkby K, Grime G, Webb R, Kirkby N, Folkard M, Prise K, Vojnovic B (2007) A scanning focussed vertical ion nanobeam: A new UK facility for cell irradiation and analysis, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 260 (1) pp. 97-100 ELSEVIER SCIENCE BV
Carter G, Armour DG, Donnelly SE, Webb R (1978) Energy spike generation and quenching processes in ion bombardment induced amorphization of solids, Radiation Effects 36 (1-2) pp. 1-13
A detailed analysis of generation and potential recrystallization of amorphous zones resulting from ion irradiation of solid materials is given. The criterion for generation of such spikes is considered to be that sufficient energy is deposited locally to induce melting. Subsequently the heated zone is considered to cool via unperturbed thermal diffusion from an initial temperature distribution of Gaussian form, although the expected ellipsoidal geometry is idealized to spherical symmetry for analytical convenience. Recrystallization is considered to occur via a thermally activated process during spike quenching and criteria for crystallization at both zone boundaries and centers are deduced. These criteria are shown to correspond well to earlier analyses, but other parameters such as substrate temperature and energy deposition density are found to be of considerable importance. Suggestions for more accurate modeling are also examined.
Webb R, Garrison B (2001) Fifth International Conference on Computer Simulation on Radiation Effects in Solids, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 180 pp. VII-VII ELSEVIER SCIENCE BV
Barradas NP, Marriott PK, Jeynes C, Webb RP (1998) The RBS data furnace: Simulated annealing, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 136 pp. 1157-1162 ELSEVIER SCIENCE BV
Kang DJ, Peng NH, Jeynes C, Webb R, Lee HN, Oh B, Moon SH, Burnell G, Stelmashenko NA, Tarte EJ, Moore DF, Blamire MG (2003) Josephson effects in MgB2 metal masked ion damage junctions, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13 (2) pp. 1071-1074 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Bright NJ, Willson TR, Driscoll DJ, Reddy SM, Webb RP, Bleay S, Ward NI, Kirkby KJ, Bailey MJ (2013) Chemical changes exhibited by latent fingerprints after exposure to vacuum conditions, Forensic Science International 230 (1-3) pp. 81-86
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 .
Bussmann U, Hemment PLF, Webb RP, Robinson AK (1992) Dynamic modelling of high dose oxygen profiles in SIMOX substrates, Materials Science and Engineering B 12 (1-2) pp. 73-76
During the past decade SIMOX (separation by implanted oxygen) has emerged as one of the leading SOI (silicon-on-insulator) technologies. The implantation involves such high doses that sputtering, swelling and the diffusion of excess oxygen within the synthesized layer of SiO2 all contribute to a major oxygen redistribution. The computer program IRIS (implantation of reactive ions into silicon) has been developed to enable fast calculations of these oxygen profiles to be made over a wide range of implantation energies, doses and masking oxide layer thickness. In this paper the model is extended into two dimensions and calculations are performed to simulate high dose implantation through thick patterned masking layers. The resulting oxygen distributions near mask edges are discussed. © 1992.
Kah M, Smith AJ, Hamilton JJ, Yeong SH, Columbeau B, Gwilliam R, Webb RP, Kirkby KJ (2008) A Comparative Study of Interaction of End of Range (EOR) Defect Band with Upper Buried Oxide (BOX) Interface for B and BF(2) Implants in SOI and Bulk Silicon with Pre-Amorphizing Implant, ION IMPLANTATION TECHNOLOGY 2008 1066 pp. 51-54 AMER INST PHYSICS
Richard M, Kirkby KJ, Webb RP, Kirkby NF (2006) A mathematical model of cellular behavior under irradiation, RADIATION RESEARCH 166 (4) pp. 680-681 RADIATION RESEARCH SOC
Mody JD, Webb RP (2011) Modeling the interaction of keV clusters with molecular solids, Surface and Interface Analysis 43 (1-2) pp. 92-94
Kang DJ, Speaks R, Peng NH, Webb R, Jeynes C, Booij WE, Tarte EJ, Moore DF, Blamire MG (2001) Nanometer scale masked ion damage barriers in YBa2Cu3O7-delta, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 11 (1) pp. 780-783 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Chakarov I, Webb R (1993) The effect of beam divergence on single crystal implant profiles, Vacuum 44 (3-4) pp. 325-329
A single crystal implantation program (CRYSTAL) is used to investigate the behaviour of channelled implants of the major dopant ions (As, P, B) in silicon as a function of the divergence of the incident beam. Many experimental results are currently being published from commercially available implanters which have uncharacterized beam divergences. It is shown that the effects of beam divergence on implant profiles in initially single crystal targets can be substantial and should not be ignored in providing experimental details. A triple peak structure for implant profiles of high energy boron in well-channelled conditions is found to be caused by contributions from a randomized component, a planar channelled component and an axial channelled component. © 1993.
Barfoot K, Webb R, Donnelly S (1984) Particle energy loss spectroscopy and SEM studies of topography development in thin aluminium films implanted with high doses of helium, Vacuum 34 (10-11) pp. 825-829
Development of topography in thin (55.5 ¼g cm-2) self-supporting aluminium films, caused by high fluence (
Carter G, Webb R, Collins R (1979) Implant ion collection in the presence of radiation enhanced diffusion and preferential sputtering of implant, Radiation Effects Letters 43 (4-5) pp. 125-132
Webb RP, Harrison DE (1983) Computer simulation of pit formation in metals by ion bombardment, Physical Review Letters 50 (19) pp. 1478-1481
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.
Bailey MJ, Bright NJ, Croxton RS, Francese S, Ferguson LS, Hinder S, Jickells S, Jones BJ, Jones BN, Kazarian SG, Ojeda JJ, Webb RP, Wolstenholme R, Bleay S (2012) Chemical Characterization of Latent Fingerprints by Matrix-Assisted Laser Desorption Ionization, Time-of-Flight Secondary Ion Mass Spectrometry, Mega Electron Volt Secondary Mass Spectrometry, Gas Chromatography/Mass Spectrometry, X-ray Photoelectron Spectroscopy, and Attenuated Total Reflection Fourier Transform Infrared Spectroscopic Imaging: An Intercomparison., Anal Chem 84 (20) pp. 8514-8523 American Chemical Society
The first analytical intercomparison of fingerprint residue using equivalent samples of latent fingerprint residue and characterized by a suite of relevant techniques is presented. This work has never been undertaken, presumably due to the perishable nature of fingerprint residue, the lack of fingerprint standards, and the intradonor variability, which impacts sample reproducibility. For the first time, time-of-flight secondary ion mass spectrometry, high-energy secondary ion mass spectrometry, and X-ray photoelectron spectroscopy are used to target endogenous compounds in fingerprints and a method is presented for establishing their relative abundance in fingerprint residue. Comparison of the newer techniques with the more established gas chromatography/mass spectrometry and attenuated total reflection Fourier transform infrared spectroscopic imaging shows good agreement between the methods, with each method detecting repeatable differences between the donors, with the exception of matrix-assisted laser desorption ionization, for which quantitative analysis has not yet been established. We further comment on the sensitivity, selectivity, and practicability of each of the methods for use in future police casework or academic research.
Webb R (1997) The computer simulation of energetic particle solid interactions, PHYSICS OF IONIZED GASES pp. 165-165
SMITH R, WEBB R (1991) LONG-RANGE CHANNELING IN LOW-ENERGY ION-IMPLANTATION INTO SILICON, PHILOSOPHICAL MAGAZINE LETTERS 64 (5) pp. 253-260
Krantzman KD, Webb RP, Garrison BJ (2008) Simulations of C60 bombardment of Si, SiC, diamond and graphite, Applied Surface Science 255 (4) pp. 837-840
SMITH R, WEBB R (1994) ATOMIC-COLLISIONS IN SEMICONDUCTORS, RADIATION EFFECTS AND DEFECTS IN SOLIDS 130 pp. 433-445
Mistry P, Gomez-Morilla I, Smith RC, Thomson D, Grime GW, Webb RP, Gwilliam R, Jeynes C, Cansell A, Merchant M, Kirkby KJ (2007) Maskless proton beam writing in gallium arsenide, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 260 (1) pp. 437-441 ELSEVIER SCIENCE BV
Sharp JA, Cowern NEB, Webb RP, Kirkby KJ, Giubertoni D, Gennaro S, Bersani M, Foad MA, Cristiano F, Fazzini PF (2006) Deactivation of ultrashallow boron implants in preamorphized silicon after nonmelt laser annealing with multiple scans, APPLIED PHYSICS LETTERS 89 (19) ARTN 192105 AMER INST PHYSICS
Langridge MT, Cox DC, Webb RP, Stolojan V (2014) The fabrication of aspherical microlenses using focused ion-beam techniques, Micron 57 (C) pp. 56-66
© 2013 Elsevier Ltd.Aspheric lenses are the most common method for correcting for spherical aberrations but, in microlens production, highly-controlled lens profiles are hard to achieve. We demonstrate a technique for creating bespoke, highly-accurate aspheric or spherical profile silicon microlens moulds, of almost any footprint, using focused ion-beam milling. Along with this, we present a method of removing induced ion-beam damage in silicon, via a hydrofluoric acid etch, helping to recover the surface's optical and chemical properties. In this paper, we demonstrate that our milled and etched moulds have a roughness of 4.0-4.1. nm, meaning they scatter less than 1% of light, down to wavelengths of 51. nm, showing that the moulds are suitable to make lenses that are able to handle light from UV up to infra-red.Using empirical experiments and computer simulations, we show that increasing the ion-dose when milling increases the amount of gallium a hydrofluoric acid etch can remove, by increasing the degree of amorphisation within the surface. For doses above 3000¼C/cm2 this restores previous surface properties, reducing adhesion to the mould, allowing for a cleaner release and enabling higher quality lenses to be made.Our technique is used to make aspheric microlenses of down to 3. ¼m in size, but with a potential to make lenses smaller than 1. ¼m.
CARTER G, FISCHER G, WEBB R, DZIOBA S, KELLY R, AUCIELLO O (1979) SURFACE-NORMAL ENERGY-DISTRIBUTION OF SPUTTERED RECOILS, RADIATION EFFECTS AND DEFECTS IN SOLIDS 45 (1-2) pp. 45-48
Kerford M, Webb RP (1999) Molecular Dynamics simulation of the desorption of molecules by energetic fullerene impacts on graphite and diamond surfaces, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 153 (1-4) pp. 270-274
King BV, Webb RP (1992) Calculation of ion mixing and energy deposition using a modified version of TRIM, Nuclear Inst. and Methods in Physics Research, B 64 (1-4) pp. 724-729
A computer program, based on TRIM, has been developed to calculate the spatial density of nuclear energy deposited by incident ion beams as well as the magnitude of mixing caused by the ion. The program divides the collision cascade into spherical subcascades formed by energetic recoils and uses a modified Vineyard model of thermal spike mixing to calculate mixing magnitudes. Good agreement is found with experimental results of Fenn-Tye and Marwick [Nucl. Instr. and Meth. B18 (1987) 236] for the high energy mixing of Pt markers in Pd at 10 K. Mixing efficiencies for low energy ion bombardment are predicted from the model. © 1992.
Gillin WP, Kimber AC, Dunstan DJ, Webb RP (1994) Diffusion of ion beam created vacancies and their effect on intermixing: A gambler's ruin approach, Journal of Applied Physics 76 (6) pp. 3367-3371
Ion implantation has frequently been shown to modify the shape of quantum wells following thermal annealing by enhancing the interdiffusion. We have shown that, independent of chemical effects on the interdiffusion, there is a contribution from the vacancies created by the implant. The effects of the diffusion of these vacancies can be modeled using a very simple expression that does not rely on any knowledge of the diffusion coefficients for the vacancies in the material. By comparing the problem to the classic problem of the gambler's ruin, we have shown that implantation into a surface should produce even intermixing of layers at different depths below it, ignoring the effects of vacancy trapping and other depth dependent diffusion processes.
CARTER G, ARMOUR D, DONNELLY S, INGRAM D, WEBB R (1980) THE INJECTION OF INERT-GAS IONS INTO SOLIDS - THEIR TRAPPING AND ESCAPE, RADIATION EFFECTS AND DEFECTS IN SOLIDS 53 (3-4) pp. 143-173
Marriott PK, Jenkin M, Jeynes C, Barradas NP, Webb RP, Sealy BJ (1999) Rapid accurate automated analysis of complex ion beam analysis data, APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY, PTS 1 AND 2 475 pp. 592-595 AMER INST PHYSICS
Webb RP (2008) What do we want from computer simulation of SIMS using clusters?, APPLIED SURFACE SCIENCE 255 (4) pp. 1223-1228 ELSEVIER SCIENCE BV
Jones B, Matsuo J, Nakata Y, Yamada H, Watts J, Hinder S, Palitsin V, Webb R (2010) Comparison of MeV monomer ion and keV cluster ToF-SIMS, Surface and Interface Analysis Wiley Interscience
Barradas NP, Jeynes C, Webb RP, Kreissig U, Grotzschel R (1999) Unambiguous automatic evaluation of multiple Ion Beam Analysis data with Simulated Annealing, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 149 (1-2) pp. 233-237 ELSEVIER SCIENCE BV
Webb RP, Ponomarev M (2007) Molecular dynamics simulation of low energy cluster impacts on carbon nanotubes, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 255 (1) pp. 229-232 ELSEVIER SCIENCE BV
Kerford M, Webb RP (1999) An investigation of the thermal profiles induced by energetic carbon molecules on a graphite surface, CARBON 37 (5) pp. 859-864
Bailey MJ, Jeynes C, Sealy BJ, Webb RP, Gwilliam RM (2010) On artefacts in the secondary ion mass spectrometry profiling of high fluence H+ implants in GaAs, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 268 (11-12) pp. 2051-2055 ELSEVIER SCIENCE BV
Harrison DE, Webb RP (1983) The creation of surface damage by ion-beam bombardment, Nuclear Instruments and Methods In Physics Research 218 (1-3) pp. 727-736
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.
Geatches RM, Reeson KJ, Criddle AJ, Finney MS, Harry MA, Webb RP, Pearson PJ (1994) Characterization of ion beam synthesized materials using microscope-spectrophotometry, Materials Research Society Symposium Proceedings 316 pp. 813-818
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 ² to the ± phase.
Kang DJ, Peng NH, Webb R, Jeynes C, Yun JH, Moon SH, Oh B, Burnell G, Tarte EJ, Moore DF, Blamire MG (2002) Realization and properties of MgB2 metal-masked ion damage junctions, APPLIED PHYSICS LETTERS 81 (19) pp. 3600-3602 AMER INST PHYSICS
Smith R, Webb RP (1991) A single crystal carbon self-sputtering simulation, Nuclear Inst. and Methods in Physics Research, B 59-60 (PART 2) pp. 1378-1382
Carbon bombardment of graphite and diamond is investigated by molecular dynamics simulations using a many-body potential to describe the low energy interactions splined to a Molière potential which describes the hard collisions. It is found that no ejection takes place from the perfect graphite {1000} face at bombardment energies of 100 eV and that at normal incidence the yield is below 1% up to 600 eV. At oblique incidence corresponding to the maximum yield angle, the yield can be in excess of ten times that at normal incidence and a much larger proportion of dimer and trimer molecules are ejected. The bulk terminated diamond surfaces are found to be less resistant to erosion than graphite with as much as 23% of material ejected at normal incidence being in the form of dimers. © 1991.
Merchant M J, Jeynes JCJ, Grime GW, Palitsin V, Tullis IDC, Barber P, Vojnovic B, Webb RP, Kirkby KJ (2012) A focused scanning vertical beam for charged particle irradiation of living cells with single counted particles, Radiation Research: an international journal forthcoming Radiation Research Society
The Surrey vertical beam is a new facility for targeted irradiation of cells
in medium with singly counted ions. A duo-plasmatron ion source and a 2
MV Tandem accelerator supply a range of ions from protons to calcium for
this beamline, with energy ranges from 0.5 to 12 MeV. A magnetic quadrupole
triplet lens is used to focus the beam of ions. We present the design of this
beamline, and early results showing the capability to count single ions with
98% certainty on CR-39 track etch. We also show that the beam targeting
accuracy is within 5 microns and selectively target human broblasts with a
H2AX immuno
uorescence to demonstrate which
cell nuclei were irradiated. We discuss future commissioning steps necessary to
achieve sub-micron targeting accuracy with this beamline.
in medium with singly counted ions. A duo-plasmatron ion source and a 2
MV Tandem accelerator supply a range of ions from protons to calcium for
this beamline, with energy ranges from 0.5 to 12 MeV. A magnetic quadrupole
triplet lens is used to focus the beam of ions. We present the design of this
beamline, and early results showing the capability to count single ions with
98% certainty on CR-39 track etch. We also show that the beam targeting
accuracy is within 5 microns and selectively target human broblasts with a
H2AX immuno
uorescence to demonstrate which
cell nuclei were irradiated. We discuss future commissioning steps necessary to
achieve sub-micron targeting accuracy with this beamline.
Donnelly SE, Greaves G, Hinks JA, Pawley CJ, Beaufort MF, Barbot JF, Oliviero E, Webb RP (2014) In-situ TEM studies of ion-irradiation induced bubble development and mechanical deformation in model nuclear materials, Materials Research Society Symposium Proceedings 1645
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.
Boudreault G, Jeynes C, Wendler E, Nejim A, Webb RP, Watjen U (2002) Accurate RBS measurement of ion implant doses in a silicon, SURFACE AND INTERFACE ANALYSIS 33 (6) pp. 478-486 WILEY-BLACKWELL
Merchant MJ, Grime GW, Kirkby KJ, Webb R (2007) A survey of two-stage focusing systems for nanobeam design, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 260 (1) pp. 8-14 ELSEVIER SCIENCE BV
Fischer G, Carter G, Webb R (1978) Recoil implantation from a thick film source, Radiation Effects 38 (1-2) pp. 41-43
Webb RP, Harrison DE (1984) A molecular dynamics computer simulation of the time dependence of surface damage production in ion irradiated metal targets, Vacuum 34 (10-11) pp. 847-851
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.
BARFOOT K, ALCHALABI S, WEBB R, WEISS B (1986) LATTICE DISORDER AND REFRACTIVE-INDEX CHANGES IN LINBO3 FOLLOWING HELIUM IMPLANTATION, RADIATION EFFECTS AND DEFECTS IN SOLIDS 98 (1-4) pp. 249-257
Webb R, Kerford M, Ali E, Dunn M, Knowles L, Lee K, Mistry J, Whitefoot F (2001) Molecular dynamics simulation of the cluster-impact-induced molecular desorption process, SURFACE AND INTERFACE ANALYSIS 31 (4) pp. 297-301 JOHN WILEY & SONS LTD
Webb RP, Harrison DE (1983) Bombardment induced cascade mixing and the importance of post-cascade relaxation, Nuclear Instruments and Methods In Physics Research 218 (1-3) pp. 697-702
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.
SMITH R, WEBB R (1993) ENERGETIC FULLERENE INTERACTIONS WITH A GRAPHITE SURFACE, PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 441 (1913) pp. 495-499
Mynard JE, Jeynes C, Thornton J, Way A, Webb R, Albury D, Hemment PLF, Stephens KG (1985) Improved facilities for ion beam surface analysis at the University of Surrey, Nuclear Inst. and Methods in Physics Research, B 6 (1-2) pp. 264-269
Additional, facilities, which are being installed on the 2 MeV Van de Graaff accelerator at the University of Surrey, are described. These include improvements to the microbeam equipment and optical viewing system using an image intensifier, modifications to a 3-axis goniometer to provide batch processing, a goniometer control system and new software for data collection and analysis. © 1985.
Webb RP (2004) Computer simulation of energetic cluster impacts on solid surfaces, PHYSICS OF IONIZED GASES 740 pp. 117-131 AMER INST PHYSICS
Bright NJ, Webb RP, Kirkby KJ, Willson TR, Driscoll DJ, Reddy SM, Ward NI, Bailey MJ, Bleay S (2013) Chemical changes exhibited by latent fingerprints after exposure to vacuum conditions, Forensic Science International
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.
Webb R, Kerford M, Way A, Wilson I (1999) Comparison of gold and carbon cluster impacts on graphite using molecular dynamics simulation, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 153 (1-4) pp. 284-291
SIMS experiments using cluster ions show promising results in de-sorbing intact large molecules from the surface of various materials. The optimum size, shape and energy of the clusters and the material surface has not been studied in any detail. Presented here are the results of a comparative study of gold and carbon clusters of similar total mass and energy, in particular Au4 and C60 clusters and Au5 and C100 clusters are compared and contrasted. The behaviour of the graphite lattice, used as the target substrate material, during the impacts is studied in detail and differences in depth of penetration, damage and energy propagation are reported.
Webb RP, Harrison DE (1981) Evidence for ion-induced hypersonic shock waves for computer simulations of argon ion bombardment of copper, Applied Physics Letters 39 (4) pp. 311-312
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.
Crean GM, Jeynes C, Somekh MG, Webb RP (1989) Characterization of shallow junction ion implantation profiles: Correlation between a noncontact photodisplacement thermal wave technique and rutherford backscattering analysis, European Solid-State Device Research Conference pp. 929-932
© 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.
Evdokimov IN, Webb R, Armour DG, Karpuzov DS (1979) Simplified models for surface hyperchannelling, Radiation Effects 42 (1-2) pp. 83-92
Kalsi RS, Webb RP (1988) Calculation of scattering angles in trajectory simulation, Nuclear Inst. and Methods in Physics Research, B 33 (1-4) pp. 530-533
A comparison of the "Magic Formula" as used in the TRIM Monte Carlo simulation program and an analytical approximation to the scattering equation revealed errors in the results of the Magic Formula when used in single precision arithmetic. The errors are not severe but are systematic and could result in accumulation errors. It is shown that the analytical approximation returns a more accurate result in a faster time thus increasing the execution speed of the TRIM program. © 1988.
FAIK A, CHANDLER P, TOWNSEND P, WEBB R (1986) REFRACTIVE-INDEX CHANGES FORMED BY N+ IMPLANTS IN SILICA, RADIATION EFFECTS AND DEFECTS IN SOLIDS 98 (1-4) pp. 233-241
Tognetti NP, Webb RP, Christodoulides CE, Armour DG, Carter G (1981) Ion bombardment induced interface mixing in the AgSi system, Nuclear Instruments and Methods 182-183 (PART 1) pp. 107-114
High resolution Rutherford backscattering has been used to investigate the ion-beam-induced intermixing of silver films deposited onto silicon under increasing fluences of 40 keV Ar+ ions. The onset of atomic mixing in the interface occurs when the Ag layer has been sputtered down to about 300 A
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Peng NH, Jeynes C, Gwilliam RM, Kirkby KJ, Webb RP, Shao GS, Astill DA, Liang WY (2005) A potential integrated low temperature approach for superconducting MgB2 thin film growth and electronics device fabrication by ion implantation, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 (2) pp. 3265-3268 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
WILSON I, WEBB R (1986) A GEOMETRICAL TREATMENT OF MOMENTUM DISTRIBUTION IN THE ATOMIC COLLISION CASCADE APPLIED TO SPUTTERING YIELD AND ATOMIC MIXING, RADIATION EFFECTS AND DEFECTS IN SOLIDS 99 (1-4) pp. 281-291
Simon A, Jeynes C, Webb RP, Finnis R, Tabatabian Z, Sellin PJ, Breese MBH, Fellows DF, van den Broek R, Gwilliam RM (2004) The new Surrey ion beam analysis facility, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 219 pp. 405-409 ELSEVIER SCIENCE BV
Al-Shehri S, Palitsin V, Webb RP, Grime GW (2015) Fabrication of three-dimensional SU-8 microchannels by proton beam writing for microfluidics applications: Fluid flow characterisation, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 348 pp. 223-228 ELSEVIER SCIENCE BV
Peng N, Jeynes C, Gwilliam RM, Webb RP (2012) On fabrication of high concentration Mn doped Si by ion implantation: problem and challenge, 18TH INTERNATIONAL VACUUM CONGRESS (IVC-18) 32 pp. 408-411 ELSEVIER SCIENCE BV
Gillin WP, Bradley IV, Homewood KP, Webb RP (1993) The effect of gallium implantation on the intermixing of InGaAs/GaAs strained quantum wells, Solid State Communications 85 (3) pp. 197-198
The intermixing of InGaAs/GaAs strained quantum wells following gallium ion implantation was characterised using photoluminescence. It was found that the implanted atoms had no effect of the diffusion coefficient for intermixing when compared to an unimplanted control sample. However, it was seen that the well was broadened by a diffusion length of approximately 37Å during the first anneal, before a photoluminescence measurement could be made. A simulation of the implantation process shows that cascade mixing is not sufficient to account for this and it is suggested that we are observing the diffusion of interstitials created by the implantation. © 1993.
Peng N, Jeynes C, Bailey MJ, Adikaari D, Stolojan V, Webb RP (2009) High concentration Mn ion implantation in Si, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 267 (8-9) pp. 1623-1625 ELSEVIER SCIENCE BV
Bailey MJ, Bradshaw R, Francese S, Salter TL, Costa C, Ismail M, Webb RP, Bosman I, Wolff K, de Puit M (2015) Rapid detection of cocaine, benzoylecgonine and methylecgonine in fingerprints using surface mass spectrometry, ANALYST 140 (18) pp. 6254-6259 ROYAL SOC CHEMISTRY
Webb R, Carter G, Collins R (1978) The influence of preferential enhanced diffusion on composition changes in sputtered binary solids, Radiation effects 39 (3-4) pp. 129-139
The preferential sputter enrichment or depletion of a species in a binary solid is a well established experimental observation. This composition change is usually found to occur over a depth similar to that of the penetration depth of the sputtering projectile. This paper therefore considers a model for preferential sputtering based upon a preferentially enhanced diffusion of one species over a finite depth in the solid which acts as a continuous atomic supply to the surface. Exact solutions are determined for steady state surface and depth distributions of the composition ratio of the two species for the time dependent behavior of these concentration distributions. The results are compared with models which assume equal diffusion enhancement of both species over both limited and infinite depth and with experimental studies.
Thornton J, Paus KC, Webb RP, Wilson IH, Booker GR (1988) The production of excess interstitials by pre-amorphisation, Journal of Physics D: Applied Physics 21 (2) pp. 334-338
Single-crystal silicon has been amorphised by bombardment with Si+, Ge+ or Sn+ ions. After conventional annealing (900° C, 30 min) some disorder remained. The amount was measured by ion channelling and transmission electron microscopy and compared with the quantity of excess interstitials predicted by the Monte Carlo computer program TRIM. Both the predicted and measured integral disorder fell as the atomic weight of the projectile increased. Because lattice strain also leads to a reduction in ion channelling this had to be taken into account when estimating residual damage from back-scattering analysis. The results indicate that there are six scattering centres per interstitial. © 1988 IOP Publishing Ltd.
Medeuov B, Daukeev D, Webb R (1994) Oxygen atom interaction with radiation defects in Nb irradiated by He ions, Vacuum 45 (5) pp. 579-582
The aim of this work is to check the hypothesis regarding the formation of complexes such as an interstitial impurity helium-vacancy cluster. Nb wires uniformly implanted by 24 MeV ±-particles at 320 K are investigated by means of the internal friction technique. It is shown that oxygen atoms occupying interstitial sites in Nb BCCC-structure are trapped during irradiation and after annealing up to T
Zurrug H, Mefo J, Sealy B, Boudreault G, Jeynes C, Webb RP, Kirkby KJ, Collart EJH (2003) Characterization and enviromental impact of plasma products within an ion implanter, IIT2002: ION IMPLANTATION TECHNOLOGY, PROCEEDINGS pp. 471-474 IEEE
Jeynes C, Barradas NP, Blewett MJ, Webb RP (1998) Improved ion beam analysis facilities at the University of Surrey, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 136 pp. 1229-1234 ELSEVIER SCIENCE BV
HAMMICHE A, WEBB R, WILSON I (1994) A SCANNING-TUNNELING-MICROSCOPY STUDY OF THIN GOLD-FILMS EVAPORATED ON SILICON, VACUUM 45 (5) pp. 569-573
Jones BN, Palitsin V, Webb R (2010) Surface analysis with high energy time-of-flight secondary ion mass spectrometry measured in parallel with PIXE and RBS, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 268 (11-12) pp. 1714-1717 ELSEVIER SCIENCE BV
Langridge MT, Cox DC, Webb RP, Stolojan V (2013) The fabrication of aspherical microlenses using focused ion-beam techniques., Micron 57 pp. 56-66
Aspheric lenses are the most common method for correcting for spherical aberrations but, in microlens production, highly-controlled lens profiles are hard to achieve. We demonstrate a technique for creating bespoke, highly-accurate aspheric or spherical profile silicon microlens moulds, of almost any footprint, using focused ion-beam milling. Along with this, we present a method of removing induced ion-beam damage in silicon, via a hydrofluoric acid etch, helping to recover the surface's optical and chemical properties. In this paper, we demonstrate that our milled and etched moulds have a roughness of 4.0-4.1 nm, meaning they scatter less than 1% of light, down to wavelengths of 51 nm, showing that the moulds are suitable to make lenses that are able to handle light from UV up to infra-red. Using empirical experiments and computer simulations, we show that increasing the ion-dose when milling increases the amount of gallium a hydrofluoric acid etch can remove, by increasing the degree of amorphisation within the surface. For doses above 3000 ¼C/cm(2) this restores previous surface properties, reducing adhesion to the mould, allowing for a cleaner release and enabling higher quality lenses to be made. Our technique is used to make aspheric microlenses of down to 3 ¼m in size, but with a potential to make lenses smaller than 1 ¼m.
Jeynes C, Bailey MJ, Bright NJ, Christopher ME, Grime GW, Jones BN, Palitsin VV, Webb RP (2012) "total IBA" - Where are we?, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 271 pp. 107-118 Elsevier
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.
Kang DJ, Burnell G, Lloyd SJ, Speaks RS, Peng NH, Jeynes C, Webb R, Yun JH, Moon SH, Oh B, Tarte EJ, Moore DF, Blamire MG (2002) Realization and properties of YBa2Cu3O 7-´ Josephson junctions by metal masked ion damage technique, Applied Physics Letters 80 (5) pp. 814-816
We have developed a simple process to fabricate high-TC Josephson junctions by a combination of focused ion beam milling and 100 keV H2+ ion implantation. The resistively shunted junction-like current-voltage characteristics were observed in the temperature range of 48 to 4.2 K. The devices showed clear dc and ac Josephson effects. This technique is very promising in terms of simplicity and flexibility of fabrication and has potential for high-density integration. © 2002 American Institute of Physics.
Peng NH, Jeynes C, Webb R, Chakarov I, Blamire M (2002) Optimisation of masked ion irradiation damage profiles in YBCO thin films by Monte Carlo simulation, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 372 pp. 55-58 ELSEVIER SCIENCE BV
Thornton J, Webb RP, Wilson IH, Paus KC (1988) Predicted dose, energy and implantation temperature effects on the residual disorder following the annealing of pre-amorphised silicon, Semiconductor Science and Technology 3 (4) pp. 281-285
A band of disorder is observed following the annealing of surface amorphous layers produced by ion bombardment. The depth of the band's centre is just below the original amorphous/crystalline interface. The ion bombardment simulation computer program TRIM.CASCADE has been used in conjunction with ion channelling measurements to predict the areal density of atoms available for the formation of this band of disorder. The variation in the amounts of disorder expected due to changing the implantation parameters: ion dose, ion energy and implantation temperature are reported. The predictions are compared with the published transmission electron microscopy results and electrical measurements of other workers. The implications of this work for the technique of pre-amorphisation are also discussed.
Donnelly SE, Bodart F, Barfoot KM, Werz R, Webb RP (1982) Helium ion bombardment of thin aluminium films, Thin Solid Films 94 (4) pp. 289-305
A study is presented of the effect of 5 keV helium ion bombardment on thin (about 2000 Å) aluminium films using proton backscattering, scanning and transmission electron microscopy and ± particle energy loss spectroscopy. Measurements of helium content after irradiation using proton backscattering indicate low below-saturation retention for both room temperature and low temperature implantations (19% and 24% respectively). Electron microscopy examination of the films reveals a severe deformation in the form of coarse and fine-scale wrinkling whose amplitude increases with increasing helium dose. This deformation does not appear to be the result of bubble swelling. An attempt has been made to quantify the wrinkling by measuring the energy loss spectrum of ± particles transmitted through irradiated films and the combination of these measurements with a simple sinusoidal deformation model indicates an increase in film area of up to 20%. © 1982.
Peng NH, Chakarov I, Jeynes C, Webb R, Booij W, Blamire M, Kelly M (2000) 2D Monte Carlo simulation of proton implantation of superconducting YBa2Cu3O7-delta thin films through high aspect ratio Nb masks, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 164 pp. 979-985 ELSEVIER SCIENCE BV
NOBES M, WEBB R, CARTER G, WHITTON J (1980) THE DEVELOPMENT OF SURFACE-MORPHOLOGY DURING SPUTTERING WITH SPATIALLY NONUNIFORM ION-BEAMS, RADIATION EFFECTS LETTERS 50 (3-6) pp. 133-138
Webb RP, Kerford M (2001) The computer simulation of the scattering of fullerenes from a graphite surface: Energy partitioning and vibrational spectra, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 180 pp. 32-36 ELSEVIER SCIENCE BV
Carter G, Webb R, Collins R, Thompson DA (1979) The influence of incident flux dependent radiation enhanced diffusion on composition changes of sputtered binary solids, Radiation Effects 40 (1-2) pp. 119-121
Barfoot KM, Laursen T, Whitton JL, Weiss BL, Webb RP (1989) In situ channelling analysis during thermal annealing of 4He+ implanted LiNbO3, Nuclear Inst. and Methods in Physics Research, B 44 (2) pp. 141-145
LiNbO3 has been implanted with 1.0 MeV 4He+ in order to create a buried layer of crystal lattice damage which acts as the lower boundary of an optical waveguide with the air surface forming the upper boundary. The annealing behaviour of this damage, in the temperature range 20 ° C to 350 ° C, has been studied in vacuo by performing in situ channelling analysis of the disorder during the thermal processing. It is concluded that the minimum annealing temperature required to reduce waveguide attenuation is 150 ± 10 ° C and the optimum is 180 ± 15°C. The results are seen to be in overall agreement with recent optical waveguide measurements. © 1989.
JAFRI ZH, JEYNES C, WEBB RP, WILSON IH (1990) MASS-TRANSPORT OF SILICON DURING ARGON IRRADIATION EMPLOYING A DOUBLE-MARKER SYSTEM, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 48 (1-4) pp. 457-460 ELSEVIER SCIENCE BV
Hammiche A, Webb R, Wilson I (1994) A novel combined scanning tunnelling/scanning force microscope, Vacuum 45 (5) pp. 575-577
A combined scanning tunnelling/scanning force microscope has been constructed based on a novel design. A single piezoelectric transducer, appropriately shaped, and with appropriately patterned electrodes is used, which acts as flexing element, force sensor, scanner, and height positioner, making the instrument simple and compact. The instrument is described and some results are presented, including characterization of performance. © 1994.
HAMMICHE A, WEBB R, WILSON I (1994) SCANNING-TUNNELING-MICROSCOPY OBSERVATION OF THE GROWTH EVOLUTION OF GOLD-FILMS EVAPORATED ON HIGHLY ORIENTED PYROLITIC GRAPHITE, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 12 (3) pp. 1413-1415
Temkin M, Chakarov I, Webb R (2000) Trajectory separation of channeled ions in crystalline materials, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 164 pp. 74-81
Spatial distributions of ions implanted into crystals can be of a very complex shape with `lobes' due to ions penetrating through open channels in several directions. This paper suggests an analytical model which represents such a distribution as a linear combination of `random' distribution and one or more `channeled' distributions. This study is focused on the algorithm of the separation of ion trajectories into several distributions. The first distribution includes those ions which have undergone predominantly random collisions. The other distributions include those ions which have undergone mainly `weak' collisions and traveled mostly along the main channeling directions. Our binary collision approximation (BCA) simulator is used for generating and analyzing ion trajectories. The spatial moments can be extracted from each separated distribution. It is shown that 2D analytical distributions obtained as a linear combination of distributions derived from these moments and aligned along corresponding channeling direction are in a very good agreement with direct BCA calculations.
Perusko D, Webb MJ, Milinovic V, Timotijevic B, Miosavljevic M, Jeynes C, Webb RP (2008) On the ion irradiation stability of Al/Ti versus AlN/TiN multilayers, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 266 (8) pp. 1749-1753 ELSEVIER SCIENCE BV
Smith R, Harrison M, Webb R (1999) Implantation of silicon using the boron cluster BF2, Thin Solid Films 343-344 (1-2) pp. 602-604
Molecular dynamics simulations have been carried out to model the implantation of boron into silicon at low energies using boron difluoride. It is shown that at a molecular impact energy of 460 eV the implantation profiles have an orientation dependence with penetration of the boron furthest when the F atoms are aligned perpendicular to the surface. The simulations also predict maximum damage in the surface layer where a peak in the fluorine atoms also occurs. The boron distribution is flatter with a peak which is deeper at 10-15 Å. © 1999 Elsevier Science S.A. All rights reserved.
Webb RP (1992) Computer Codes and Simulation Background to Ion Implantation Distribution and Sputtering Programs, In: Briggs D, Seah MP (eds.), Practical Surface Analysis: Ion and neutral spectroscopy 2 Appendix 3 pp. 657-704 John Wiley & Son Ltd
Mistry P, Gomez-Morilla I, Grime GW, Webb RP, Gwilliam R, Cansell A, Merchant M, Kirkby KJ, Teo EJ, Breese MBH, Bettiol AA, Blackwood DJ, Watt F (2005) New developments in the applications of proton beam writing, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 237 (1-2) pp. 188-192 ELSEVIER SCIENCE BV
Carter G, Webb R (1979) The accumulation of amorphousness as a function of irradiation fluence in a composite model of disorder production, Radiation Effects Letters 43 (1) pp. 19-24
Stojanovi? M, Osmokrovi? P, Boreli F, Novkovi? D, Webb R (1997) Characteristics of large area silicon surface barrier detectors, Thin Solid Films 296 (1-2) pp. 181-183
This paper presents a detailed description of an upgraded silicon surface barrier (SB) detector and analysis of X and gamma radiation and of the spectra given by it. The most frequently used application of these detectors was in measurements and analyses of alpha spectra. However, analysis of spectra gained here presented a silicon surface barrier detector showing possibilities of their wider application in various nuclear techniques and technologies. This specially referes to the feasibility of their use in the conditions that are different from those in laboratories, such as mines, surroundings of nuclear power plants etc. Recorded spectra from 57Co, show that SB detectors are very acceptable in nuclear laboratories for nuclear spectroscopy at room temperatures. On the contrary, field application in nuclear techniques connected with the protection of the environment and counting systems is much wider, and the detector temperature could reach 60 °C. © 1997 Elsevier Science S.A.
Kang DJ, Peng NH, Webb R, Jeynes C, Burnell G, Yun JH, Moon SH, Oh B, Tarte EJ, Moore DF, Kelly M, Blamire MG (2002) Irradiation damage technology for manufacturable Josephson junctions, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 188 pp. 183-188 ELSEVIER SCIENCE BV
Smith R, Shaw M, Webb RP, Foad MA (1998) Ultrashallow junctions in Si using decaborane? A molecular dynamics simulation study, Journal of Applied Physics 83 (6) pp. 3148-3152
The feasibility of using decaborane B10H14, for the manufacture of shallow junctions in Si is investigated by means of molecular dynamics simulations. Bombardment energies of 1, 2, and 4 keV are investigated and the simulations run for up to 7 ps in order to ascertain the implantation profiles of the B atoms, the whereabouts of the H from the impacted molecule and the damage to the lattice. The simulations show that if a small binding energy of the B atom in the Si lattice is assumed then most of the B from the cluster is implanted. The implantation distributions are flatter with depth than those for single B interactions and the surface layers undergo damage and amorphisation in the proximity of the impact. © 1998 American Institute of Physics.
Webb R (2004) Energetic cluster induced desorption from a graphite surface, APPLIED SURFACE SCIENCE 231 pp. 59-63 ELSEVIER SCIENCE BV
Webb R, Smith R, Chakarov I, Beardmore K (1996) The computer simulation of energetic particle-solid interactions, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 112 (1-4) pp. 99-104 ELSEVIER SCIENCE BV
Over the last decade the use of computer simulation in predicting physical phenomena associated with ion beam processing of materials has increased both in use and reliability. This is partly due to the dramatic increase in computer power and decrease in computer cost, but is also being achieved due to an increased understanding of the physical processes occurring. With the increase in computer power has come not just the ability to perform more complex calculations but also the methods for complex data representation in animated form. By animating the results it is much easier to observe collective effects such as acoustic wave propagation at a surface due to, for example, molecule impact.
Bailey MJ, Ismail M, Bleay S, Bright N, Levin Elad M, Cohen Y, Geller B, Everson D, Costa C, Webb RP, Watts JF, de Puit M (2013) Enhanced imaging of developed fingerprints using mass spectrometry imaging., Analyst 138 (21) pp. 6246-6250
Latent fingermarks are invisible to the naked eye and normally require the application of a chemical developer followed by an optical imaging step in order to visualize the ridge detail. If the finger deposition is poor, or the fingermark is aged, it can sometimes be difficult to produce an image of sufficient quality for identification. In this work, we show for the first time how mass spectrometry imaging (in this case time-of-flight secondary ion mass spectrometry, ToF-SIMS) can be used to enhance the quality of partially recovered fingermarks. We show three examples of how chemical imaging can be used to obtain enhanced images of fingermarks deposited on aluminium foil, glass and the handle of a hand grenade compared with conventional development techniques.
Richard M, Webb RP, Kirkby KJ, Kirkby NF (2009) A computer model of the Bystander effect: Effects of individual behaviours on the population response, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 440-442 PERGAMON-ELSEVIER SCIENCE LTD
Abu-Hassan LH, Townsend PD, Webb RP (1987) Luminescence excited in SiO2 during ion implantation, Nuclear Inst. and Methods in Physics Research, B 19-20 (PART 2) pp. 927-930
Ion beam induced luminescence of silica has been recorded in the energy ranges 5-55 key and 0.2-2.8 MeV during excitation with H+, H2+, N+ and N2+, for samples at 77 K. The data reveal that the light is stimulated by electronic energy deposition 0 but the efficiency is a function of the damage retained in the silica. Damage retention is a function of the overlap of nuclear collision and 07 electronic excitation processes during the slowing down of the ion beam so the net effect of these competing features is to produce a maximum in the ion energy dependence of the light production for nitrogen ions (near 42 key), whereas for protons the dependence is a monotonic function of energy as it is dominated by the electronic excitation. Computer modelling of the luminescence production predicts a maximum in the energy dependence which is in agreement with the observations. © 1987 Elsevier Science Publishers B.V.
WEBB R, CARTER G (1979) DIFFICULTIES IN DEDUCING DISORDERING MECHANISMS FROM EXPERIMENTAL STUDIES OF DISORDER-ION FLUENCE FUNCTIONS IN ION IRRADIATION OF SEMICONDUCTORS, RADIATION EFFECTS AND DEFECTS IN SOLIDS 42 (3-4) pp. 159-168
CARTER G, ARMOUR D, INGRAM D, WEBB R, NEWCOMBE R (1979) DIFFUSION APPROXIMATIONS TO CASCADE MIXING, RADIATION EFFECTS LETTERS 43 (6) pp. 233-236
Donnelly SE, Greaves G, Hinks JA, Pawley CJ, Beaufort MF, Barbot JF, Oliviero E, Webb RP (2014) In-situ TEM studies of ion-irradiation induced bubble development and mechanical deformation in model nuclear materials, Prehospital and Disaster Medicine 1645
© 2014 Materials Research Society.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.
Webb RP (2007) The computer simulation of energetic cluster-solid interactions, RADIATION EFFECTS AND DEFECTS IN SOLIDS 162 (7-8) pp. 567-572 TAYLOR & FRANCIS LTD
Webb RP (2005) Insight into energetic cluster impacts on solid surfaces provided by computer simulation, Advances in Computational Methods in Sciences and Engineering 2005, Vols 4 A & 4 B 4A-4B pp. 1002-1005 VSP BV-C/O BRILL ACAD PUBL
Webb RP (2014) A festschrift for mark T. Robinson, Radiation Effects and Defects in Solids 169 (5) pp. 369-370
Webb RP, Winston SH, Gwilliam RM, Sealy BJ, Boudreault G, Jeynes C, Kirkby KJ (2003) Comparison of boron halide, decaborane and B implants in Si from molecular dynamics simulations, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 202 pp. 143-148 ELSEVIER SCIENCE BV
Peng NH, Jeynes C, Webb RP, Chakarov IR, Blamire MG (2001) Monte Carlo simulations of masked ion beam irradiation damage profiles in YBa2Cu3O7-delta thin films, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 178 pp. 242-246 ELSEVIER SCIENCE BV
Bright NJ, Webb RP, Bleay S, Hinder S, Ward N, Watts JF, Kirkby KJ, Bailey MJ (2012) Determination of the deposition order of overlapping latent fingerprints and inks using Secondary Ion Mass Spectrometry (SIMS), Analytical Chemistry ACS Publications
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.
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.
Webb RP, Kerford M, Kappes M, Brauchle G (1997) A comparison between fullerene and single particle impacts on graphite, Radiation Effects and Defects in Solids 142 (1-4) pp. 23-26
Romolo FS, Christopher ME, Donghi M, Ripani L, Jeynes C, Webb RP, Ward NI, Kirkby KJ, Bailey MJ (2013) Integrated Ion Beam Analysis (IBA) in Gunshot Residue (GSR) characterisation, Forensic Science International 231 (1-3) pp. 219-228
Gunshot Residue (GSR) is residual material from the discharge of a firearm, which frequently provides crucial information in criminal investigations. Changes in ammunition manufacturing are gradually phasing out the heavy metals on which current forensic GSR analysis is based, and the latest Heavy Metal Free (HMF) primers urgently demand new forensic solutions. Proton scanning microbeam Ion Beam Analysis (IBA), in conjunction with the Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDS), can be introduced into forensic analysis to solve both new and old problems, with a procedure entirely commensurate with current forensic practice. Six cartridges producing GSR particles known to be interesting in casework by both experience and the literature were selected for this study. A standard procedure to relocate the same particles previously analysed by SEM-EDS, based on both secondary electron (SE) and X-ray imaging was developed and tested. Elemental Particle Induced X-ray Emission (PIXE) mapping of the emitted X-rays allowed relocation in a scan of 10¼m×10¼m of even a 1¼m GSR particle. The comparison between spectra from the same particle obtained by SEM-EDS and IBA-PIXE showed that the latter is much more sensitive at mid-high energies. Results that are very interesting in a forensic context were obtained with particles from a cartridge containing mercury fulminate in the primer. Particle-induced gamma-ray emission (PIGE) maps of a particles from HMF cartridges allowed identification of Boron and Sodium in particles from hands using the 10B(p,±1³)7Be, 11B(p,p1³)11B and 23Na(p,p1³)23Na reactions, which is extraordinary in a forensic context. The capability for quantitative analysis of elements within individual particles by IBA was also demonstrated, giving the opportunity to begin a new chapter in the research on GSR particles. The integrated procedure that was developed, which makes use of all the IBA signals, has unprecedented characterisation and discrimination power for GSR samples. © 2013 Elsevier Ireland Ltd.
Webb R, Chatzipanagiotou A (2006) The computer simulation of cluster induced desorption of molecules, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 242 (1-2) pp. 413-416 ELSEVIER SCIENCE BV
Medeuov B, Daukeev D, Chakarov I, Webb R (1994) Investigation of oxygen ion implantation in niobium by internal friction technique and computer simulation, Vacuum 45 (5) pp. 583-586
Niobium wires, outgassed at 2270 K in UHV chamber, were uniformly implanted with 16O+ at 1 MeV and 320 K within the dose range 5×1015-3×1017 cm-2. Internal friction measurements were carried out on computer-controlled inverted torsional pendulum at
Jeynes C, Jafri ZH, Webb RP, Kimber AC, Ashwin MJ (1997) Accurate RBS measurements of the indium content of InGaAs thin films, SURFACE AND INTERFACE ANALYSIS 25 (4) pp. 254-260 JOHN WILEY & SONS LTD
Webb RP, Gras-Marti A, Wilson IA, Harrison DE, Louis E, Guinea F (1987) Geometric structure of ion-induced displacement cascades in solids, Physics Letters A 126 (2) pp. 136-140
The geometric structure of collision cascades developed in solids by energetic ion bombardment is investigated from the view-point of fractal geometry using computer simulated trajectories and defect distributions. The fractal dimension of a collision cascade, as extracted from defect distributions, depends on the effective interaction potential governing the sequence of events in a subcascade, as shown in recent analytical predictions. Possible implications and further work along these lines are suggested. © 1987.
Kah M, Smith AJ, Hamilton JJ, Sharp J, Yeong SH, Colombeau B, Gwilliam R, Webb RP, Kirkby KJ (2008) Interaction of the end of range defect band with the upper buried oxide interface for B and BF2 implants in Si and silicon on insulator with and without preamorphizing implant, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 26 (1) pp. 347-350 A V S AMER INST PHYSICS
Wilson IH, Chereckdjian S, Webb RP (1985) On the variation of sputtering yield with angle of ion incidence, Nuclear Inst. and Methods in Physics Research, B 7-8 (PART 2) pp. 735-741
A geometrical theory is presented which divides the collision cascade into energy groups, each with a characteristic anisotropy in the distribution in space of knock-on trajectories. A simplified two group, four (quasi-two-dimensional) component analytical theory is developed. This is used to fit two experimentally determined sputtering yield versus angle of ion incidence relationships; 50 keV argon ion bombardment of gold and 100 keV argon ion bombardment of germanium. The experimental results were obtained using a triple quartz resonator technique. The effect of ion reflection on the measured sputtering yields was estimated by using the Monte Carlo computer simulation TRIM. A good fit to experimental results was obtained and it was demonstrated that models based solely on energy deposition combined with ion reflection are unsatisfactory for high energy (> 10 keV) high mass (> 10 amu) ions. The parameters determined from the fit of theory to experiment are used to determine the characteristic sputtering depths, and the mean ranges of the high and low energy groups for the two sets of experimental data. © 1985.
Webb RP, Wilson I (1989) Problems using the Sigmund formula for the calculation of sputtering yields, Vacuum 39 (11-12) pp. 1163-1165
A modification to the Sigmund formula using calculations of energy deposition instead of correction factors and stopping power is used to compare over 600 experimental results with simulated values. The results indicate that whilst the use of energy deposition yields better general agreement with experimental behaviour, they also show that there is a factor, important in determining the sputtering yield, which appears to relate to the chemical nature of the target. © 1989.
Hammiche A, Webb RP, Wilson IH (1993) A novel bimorph-type actuator for use in scanning probe microscopes, Review of Scientific Instruments 64 (11) pp. 3332-3333
We describe a novel bimorph-type piezoelectric transducer which achieves three-dimensional positioning in a 70 ¼m ×70 ¼m ×10 ¼m volume with applied voltage ranges less than 100 V. This transducer, appropriately shaped and with appropriately patterned electrodes, has been tested by using it as a scanner in a scanning tunneling microscope. Results obtained in this application of the actuator are presented, including characterization of performance.
Garrison BJ, Postawa Z, Ryan KE, Vickerman JC, Webb RP, Winograd N (2009) Internal Energy of Molecules Ejected Due to Energetic C-60 Bombardment, ANALYTICAL CHEMISTRY 81 (6) pp. 2260-2267 AMER CHEMICAL SOC
Geatches RM, Reason KJ, Griddle AJ, Webb RP, Pearson PJ, Hemment PLF, Nejim A (1994) Nondestructive characterization of SIMOX structures, Nuclear Inst. and Methods in Physics Research, B 84 (2) pp. 258-264
In this paper we show how the technique of microscope-spectrophotometry (MSP) may be used to characterize SIMOX structures nondestructively. A range of SIMOX materials prepared using various implantation conditions were investigated. The structural parameters elucidated using MSP included: silicon overlayer and buried oxide thicknesses; approximate densities of silicon islands in the buried oxide layer and silicon dioxide islands in the silicon overlayer as appropriate. These results compared favourably with those obtained using XTEM and indicates that MSP is a reliable technique for the nondestructive, three dimensional characterization of complex multi-layer structures. Furthermore, the technique is capable of examining very small areas (1 ¼m) which should enable device structures and local inhomogeneities to be characterized. © 1994.
Mistry P, Gornez-Morilla I, Grime GW, Webb R, Jeynes C, Gwilliam R, Cansell A, Merchant M, Kirkby KJ (2005) New developments on the Surrey microbeam applications to lithography, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 231 pp. 428-432 ELSEVIER SCIENCE BV
Bradley IV, Gillin WP, Homewood KP, Webb RP (1993) The effects of ion implantation on the interdiffusion coefficients in Inx Ga1-x As/GaAs quantum well structures, Journal of Applied Physics 73 (4) pp. 1686-1692
Photoluminescence coupled with repetitive thermal annealing has been used to determine the diffusion coefficients for intermixing in InxGa 1-xAs/GaAs quantum wells and to study the subsequent effects of ion implantation on the intermixing. It is shown that following ion implantation there is a very fast interdiffusion process, which is independent of the implanted ion and that is thought to be due to the rapid diffusion of interstitials created during the implantation. Following this rapid process, it was found that neither gallium nor krypton ions had any effect on the subsequent interdiffusion coefficient. Following arsenic implantation in addition to the initial damage related process, an enhanced region of interdiffusion was observed with a diffusion coefficient that was an order of magnitude greater than that of an unimplanted control wafer. This enhanced process is thought to be due to the creation of group III vacancies by the arsenic atoms moving onto group V lattice sites. This fast process was present until the structure had broadened by about 75 Å when the diffusion coefficient returned to the unimplanted control value. The activation energy for the interdiffusion was measured over the temperature range 1050-750°C and a value of 3.7±0.1 eV was measured. This was found to be independent of the implanted ion.
Webb RP, Donnelly SE, Armour DG (1977) The effect of vacuum system time constants on thermal desorption spectra, Vacuum 27 (9) pp. 559-563
A numerical analysis of the pressure time equation relating to first order single-step gas release has been performed. This has been done for two configurations of vacuum system, each having a volume into which gas release proceeds linked by a conductance C to a detector volume. The differences between the release function and the observed pressure transient have been characterized by observing the manner in which the maximum release rate Ám, the temperature for maximum release Tm and the leading and trailing 1/e widths We1 and We2 change as a function of the various vacuum system parameters. © 1977.
Sharp JA, Cowern NEB, Webb RP, Giubertoni D, Gennaro S, Bersani M, Foad MA, Kirkby KJ (2006) Deactivation of low energy boron implants into pre-amorphised Si after non-melt laser annealing with multiple scans, Ion Implantation Technology 866 pp. 33-36 AMER INST PHYSICS
Chakarov IR, Webb RP (1994) Crystal-binary collision simulation of atomic collisions and dynamic damage buildup in crystalline silicon, Radiation Effects and Defects in Solids 130-131 (1) pp. 447-452
Winston SH, Gwilliam RM, Sealy BJ, Boudreault G, Jeynes C, Webb RP, Kirkby KJ (2003) Evaluation of the Boron activation and depth distribution using BBr2+ implants, IIT2002: ION IMPLANTATION TECHNOLOGY, PROCEEDINGS pp. 115-118 IEEE
Kang DJ, Burnell G, Lloyd SJ, Speaks RS, Peng NH, Jeynes C, Webb R, Yun JH, Moon SH, Oh B, Tarte EJ, Moore DF, Blamire MG (2002) Realization and properties of YBa2Cu3O7-delta Josephson junctions by metal masked ion damage technique, APPLIED PHYSICS LETTERS 80 (5) pp. 814-816 AMER INST PHYSICS
Carter G, Webb R, Collins R (1978) The accumulation of disorder, subject to saturation and sputter limitation, in ion irradiated solids, Radiation Effects 37 (1-2) pp. 21-32
The depth distribution of disorder and the depth integrated disorder produced by ion irradiation of solids is analyzed theoretically as a function of increasing ion fluence when disorder saturation processes operate at all depths and the solid surface is continuously uniformly eroded by sputtering. The resulting defining equations are evaluated numerically for a Gaussian approximation to the disorder depth function with parameters appropriate to low, equal and high projectile: substrate mass ratio conditions, for several values of sputtering coefficient and effective atom displacement energy. It is shown that the form, if not the magnitude, of the integrated disorder/projectile fluence function is only weakly dependent upon these parameters.
Webb RP, Mody J (2009) The effect of cluster density on the penetration depth of an energetic large gas cluster impinging on a silicon target, RADIATION EFFECTS AND DEFECTS IN SOLIDS 164 (7-8) pp. 477-480 TAYLOR & FRANCIS LTD
Mistry P, Gomez-Morilla I, Grime GW, Webb R, Jeynes C, Gwilliarn R, Cansell A, Merchant M, Kirkby KJ (2006) Proton beam lithography at the University of Surrey's Ion Beam Centre, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 242 (1-2) pp. 387-389 ELSEVIER SCIENCE BV
BEARDMORE K, SMITH R, WEBB R (1994) ENERGETIC FULLERENE INTERACTIONS WITH SI CRYSTAL-SURFACES, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING 2 (3) pp. 313-328
DONNELLY S, INGRAM D, WEBB R, ARMOUR D (1979) DIFFICULTIES IN INTERPRETING THERMAL EVOLUTION SPECTRA, VACUUM 29 (8-9) pp. 303-307
Abdul-Karim N, Blackman CS, Gill PP, Morgan RM, Matjacic L, Webb R, Ng WH (2016) Morphological Variations of Explosive Residue Particles and Implications for Understanding Detonation Mechanisms, ANALYTICAL CHEMISTRY 88 (7) pp. 3899-3908 AMER CHEMICAL SOC
Barradas NP, Jeynes C, Webb RP, Wendler E (2002) Accurate determination of the stopping power of He-4 in Si using Bayesian inference, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 194 (1) PII S0168-583X(02)00494-9 pp. 15-25 ELSEVIER SCIENCE BV
KING BV, JEYNES C, WEBB RP, KILNER JA (1993) ION-BEAM MIXING OF ISOTOPIC SILVER BILAYERS BY 200 KEV GERMANIUM, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 80-1 pp. 163-166 ELSEVIER SCIENCE BV
Webb RP, Jeynes C, Wilson IH (1986) The effect of angle of incidence on interface broadening, Nuclear Inst. and Methods in Physics Research, B 13 (1-3) pp. 449-452
The broadening of a thin (~3 nm) Au marker, sandwiched between two sputtered silicon films deposited on a single crystal silicon substrate, bombarded with 100 keV argon ions has been observed for different angles of incidence using Rutherford backscattering. The results are compared to a theory used to predict the behaviour of the sputtering yield with angle of incidence. It is found that the effect of incomplete collision cascades and anisotropy of the cascade distribution determine the behaviour of the broadening. © 1986.
Webb RP, Kerford M, Kappes M, Brauchte G (1997) A comparison between fullerene and single atom impacts on graphite, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 122 (3) pp. 318-321
Recent experimental measurements of craters/defects caused by energetic C60 impacts on graphite have shown how the penetration depth of the C60 increases as a function of velocity. We show here Molecular Dynamics Simulations of C60, C70, C76, C78 and C84 impacts on graphite which are in very close agreement with the experimental findings. By comparison with single atom impacts on the same surface and study of the early cascade propogation we obtain an evidence of long time co-operative, non-linear, effects of the molecular surface interaction which give rise to greater displacement of target atoms than would be expected by just scaling up results from single atom interactions. There is little difference found between different impact sites for the molecules, unlike the single atom impact behaviour.
Hillenkamp M, Pfister J, Kappes MM, Webb RP (1999) Glancing incidence scattering of hyperthermal He+, Xe+, and C+60 from graphite: Angular and velocity distributions of neutrals, Journal of Chemical Physics 111 (22) pp. 10303-10313
In a comparative study of size and mass effects in the glancing incidence scattering of hyperthermal ions from a soft surface, He+, Xe+, and C+60 were scattered from highly oriented pyrolitic graphite (HOPG) over an energy range between 200 and 5000 eV. Predominantly neutral scattering products were observed for all projectiles. The corresponding angular and velocity distributions were recorded in the scattering plane. He+ gives rise to broad angular distributions conforming to the predictions of a simple binary collision model. With full widths at half maximum of less than 6 deg at typical collision energies, the angular distributions found for Xe+ and C+60 are very narrow. While Xe+ is always scattered near-specularly independent of collision energy, neutrals resulting from C+60 exit subspecularly - increasingly so the higher the collision energy. The experimental data are discussed in terms of dynamical simulations which indicate that Xe+ collides with a rigid ensemble of six carbon atoms while the fullerene scatters from a larger "moving target." © 1999 American Institute of Physics.
Kirkby K, Grime G, Webb R, Kirkby N, Folkard M, Prise K, Vojnovic B (2006) A scanning focused vertical ion nanobeam: A new UK facility for cell irradiation and analysis, RADIATION RESEARCH 166 (4) pp. 654-655 RADIATION RESEARCH SOC
Alzanki T, Gwilliam R, Emerson N, Smith A, Webb R, Sealy BJ (2006) Electrical profiles of 20 nm junctions in Sb implanted silicon, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 242 (1-2) pp. 693-695 ELSEVIER SCIENCE BV
Donnelly S, Ingram D, Webb R, Armour D (1979) On the difficulties in interpreting thermal evolution spectra, Vacuum 29 (8-9) pp. 303-307
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.
JAFRI ZH, JEYNES C, WEBB RP, WILSON IH (1989) OBSERVATION OF SWELLING AND SPUTTERING OF A SILICON TARGET UNDER ARGON ION IRRADIATION USING A DOUBLE MARKER TECHNIQUE, VACUUM 39 (11-12) pp. 1119-1121 PERGAMON-ELSEVIER SCIENCE LTD
Cowern NEB, Smith AJ, Bennett N, Sealy BJ, Gwilliam R, Webb RP, Colombeau B, Paul S, Lerch W, Pakfar A (2008) Vacancy engineering - An ultra-low thermal budget method for high-concentration 'diffusionless' implantation doping, Materials Science Forum 573-574 pp. 295-304
Webb RP, Current MI, Yamada I, Mack M, Gwinn M, Jacobson D (2006) Molecular and Cluster Ion Beams: Doping and Deposition with "Massive" Ions, In: Ziegler JF (eds.), Ion Implantation Science and Technology 10 pp. 10-1-10-28 Ion Implantation Technology Co.
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.
Geatche RM, Reeson KJ, Criddle AJ, Webb RP, Pearson PJ, Weis BL (1994) Microscope spectrophotometric study of GaAs/alx Ga1-x As mbe structures, Journal of Physics D: Applied Physics 27 (7) pp. 1528-1532
A series of GaAs/AlxGa1?xAs MBE structures, in which x ranged from 0.10 to 0.40, was studied using microscope spectrophotometry (MSP). The MSP reflectance measurements were found to be extremely sensitive to compositional variation, with a clear inverse relationship between Al content and reflected intensity, and a sympathetic relationship between composition and dispersion. Theoretical optical models were simulated and fitted to the measured data to give layer dimensions which fitted remarkably well with SIMS data. It is concluded that MSP has great potential for the non-destructive metrology and quality control of simple and complex multilayer structures. © 1994 IOP Publishing Ltd.
Carter G, Nobes MJ, Webb RP (1981) A second-order erosion slowness theory of the development of surface topography by ion-induced sputtering, Journal of Materials Science 16 (8) pp. 2091-2102
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.
Reeson KJ, Spraggs RS, Gwilliam RM, Webb RP, Sealy BJ, De Veirman A (1991) 1990 C R burch prize-joint award. Ion beam synthesis of epitaxial CoSi2 layers, Vacuum 42 (18) pp. 1163-1171
Epitaxial CoSi2 have been layers fabricated by implanting 200 keV cobalt ions, to doses between 1.5×1017 and 7×1017 Co+ cm-2, into (100), (110) and (111) single crystal silicon substrates. The experimental results after implantation are in close agreement with those obtained from computer simulations using single crystal targets. The as implanted structures for the lower doses (1.5×10173×1017 Co+ cm-2) are silicon rich and consist of a mixture of A- and B-type CoSi2 precipitates interwoven by silicon. For the medium doses (4×10175×1017 Co+ cm-2) an epitaxial layer of CoSi2 is formed with any excess cobalt being incorporated in small CoSi inclusions, at the peak of the implanted distribution. For the highest doses (6×10177×1017 Co+ cm-2) preferential sputtering of silicon at the surface of the silicide causes this region to become increasingly rich in cobalt. To accomodate this cobalt excess, grains of CoSi form above the epitaxial CoSi2 layer. As the dose is increased up to 5×1017 Co+ cm-2 the crystallinity of the synthesised layer improves and there is a corresponding decrease in resistivity, after which any further increase in dose causes the crystallinity to deteriorate again and the resistivity to increase. These changes can be correlated with the value of x in CoSix, i.e. when the layer is either rich in cobalt or silicon (2>×>2) the resistivity increases and there is a corresponding deterioration in crystal quality. For all doses, furnace annealing (at 1000°C, 30 min) causes a decrease in resistivity and a corresponding improvement in crystallinity as the ratio of Co:Si approaches the value for the stoichiometric compound (CoSi2). After rapid thermal annealing (RTA) at 1000°C for 5 s. the resistivity and crystal quality of the synthesised layer for the medium dose specimen (5×1017 cm-2) are close to those achieved by conventional furnace annealing. For the higher and lower doses the crystal quality is slightly worse and the resistivity slightly higher than those for analogous samples which have been furnace annealed. © 1991.
Chakarov IR, Webb RP, Smith R, Beardmore K (1995) An investigation of collision propagation in energetic ion initiated cascades in copper, Nuclear Inst. and Methods in Physics Research, B 102 (1-4) pp. 145-150
Using simple Binary Collision simulations of energetic ion initiated collision cascades, particles are considered to undergo a series of binary collisions with their surroundings. In Molecular Dynamics simulation it is difficult to even define what is meant by a collision as the interaction potentials are infinite in nature and consequently all particles are considered to interact with all other particles. By making a suitable definition of a collision for Molecular Dynamics we are able to compare the temporal behaviour of the number of collisions occurring during the propagation of a collision cascade between the two different calculation schemes. An investigation is made of the number of collisions as a function of time occurring in collision cascades. We compare these results to the time ordered version of MARLOWE. By making further definitions about what makes a many body collision, we further investigate the numbers of many body collisions occurring during a number of collision cascades. © 1995.
Webb RP, Wilson IH (1985) EFFECT OF INCOMPLETE COLLISION CASCADES ON THE ANGLE OF ION INCIDENCE BEHAVIOUR OF INTERFACE MIXING., Materials Research Society Symposia Proceedings 45 pp. 147-152
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.
Jeynes C, Puttick KE, Whitmore LC, Gartner K, Gee AE, Millen DK, Webb RP, Peel RMA, Sealy BJ (1996) Laterally resolved crystalline damage in single-point-diamond-turned silicon, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 118 (1-4) pp. 431-436 ELSEVIER SCIENCE BV
Peach K, Cobb J, Yokoi T, Gardner I, Edgecock R, Poole M, Pozimski J, Cywinski B, Jones B, McKenna G, Vojnovic B, Folkard M, Kirkby K, Webb R, Barlow R, Elliott A (2007) PAMELA - A model for an FFAG based hadron therapy machine, Proceedings of the IEEE Particle Accelerator Conference pp. 2880-2882
Approximately one third of the world's 15000 accelerators are used for tumour therapy and other medical applications [1]. The characteristics of FFAGs make them ideally suited to such applications, as the much smaller magnet size and greater compactness offers considerable cost and operational benefits. In the first stage the work on PAMELA will focus on the optimization of the FFAG design to deliver the specific machine parameters demanded by therapy applications. In this phase of the PAMELA project the effort will concentrate on the design of a semi-scaling type FFAGs to deliver a 450 MeV/u carbon ion beam, including detailed lattice and tracking studies. The second stage will use the existing expertise in the BASROC consortium [2] to undertake a design of the magnets and RF system for PAMELA. An outline of the overall concept of PAMELA will be discussed and the actual status of the work will be presented. ©2007 IEEE.
Peng N, Shao G, Jeynes C, Webb RP, Gwilliam RM, Boudreault G, Astill DM, Liang WY (2003) Ion beam synthesis of superconducting MgB2 thin films, APPLIED PHYSICS LETTERS 82 (2) pp. 236-238 AMER INST PHYSICS
Webb R, Kirkby K (2005) Impact-induced desorption of large molecular structures from graphitic substrates, MOLECULAR SIMULATION 31 (2-3) pp. 95-100 TAYLOR & FRANCIS LTD
Rombouts PMM, Gomez-Morilla I, Grime GW, Webb RP, Cuenca L, Rodriguez R, Browton M, Wardell N, Underwood B, Kirkby NF, Kirkby KJ (2007) A microPIXE investigation of the interaction of cells of Schizosaccharomyces pombe with the culture medium, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 260 (1) pp. 231-235 ELSEVIER SCIENCE BV
Chakarov I, King BV, Webb RP, Smith R (1992) Computer simulation of CAICISS of AlAs(001), Nuclear Inst. and Methods in Physics Research, B 67 (1-4) pp. 332-334
Recent coaxial impact-collision ion scattering spectroscopy (CAICISS) experiments studying growth kinetics have indicated that 2 keV He ions can be backscattered through 180° from deep - 56 Å - within the target without losing more than a few hundred eV above the kinematic energy loss for 180° scattering. Using simple average stopping data it is difficult to satisfactorily explain how particles can penetrate this deep and come back retaining so much of their initial energy. We use the MARLOWE binary collision code to show that it is indeed possible for particles to be scattered from this deep in the solid and still have sufficient energy to appear in the surface peak. © 1992.
Richard M, Kirkby KJ, Webb RP, Kirkby NF (2009) Cellular automaton model of cell response to targeted radiation, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 443-446 PERGAMON-ELSEVIER SCIENCE LTD
Wakamatsu Y, Yamada H, Ninomiya S, Jones BN, Seki T, Aoki T, Webb R, Matsuo J (2010) Biomolecular emission by swift heavy ion bombardment, AIP Conference Proceedings: 18th International Conference on Ion Implantation Technology 1321 pp. 233-236
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.
Harrison DE, Webb RP (1982) A molecular dynamics simulation study of the influence of the lattice atom potential function upon atom ejection processes, Journal of Applied Physics 53 (6) pp. 4193-4201
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.
Webb RP (2005) Binary Collision Algorithms, In: Smith R (eds.), Atomic and Ion Collisions in Solids and at Surfaces 7 Cambridge Univ Pr
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.
Jeynes C, Barradas NP, Marriott PK, Boudreault G, Jenkin M, Wendler E, Webb RP (2003) Elemental thin film depth profiles by ion beam analysis using simulated annealing - a new tool, JOURNAL OF PHYSICS D-APPLIED PHYSICS 36 (7) PII S0022-3727(03)34952-6 pp. R97-R126 IOP PUBLISHING LTD
Sharp JA, Cowern NEB, Webb RP, Giubertoni D, Gennaro S, Bersani M, Foad MA, Kirkby KJ (2006) Deactivation of B and BF2 profiles after non-melt laser annealing, Materials Research Society Symposium Proceedings 912 pp. 159-163
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.
Wakamatsu Y, Yamada H, Ninomiya S, Jones BN, Seki T, Aoki T, Webb R, Matsuo J (2011) Highly sensitive molecular detection with swift heavy ions, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 269 (20) pp. 2251-2253
Webb RP, Foad MA, Gwilliam RM, Knights AP, Thomas G (1997) Anomalous diffusion of ultra low energy boron implants in silicon, Materials Research Society Symposium - Proceedings 469 pp. 59-63
Ultra low energy boron implants (0.2 to 3 keV) have been carried out on Si (100) at doses between 1×1014cm-2 and 1×1015cm-2 using xRLEAP. The samples were annealed at temperatures between 900 °C and 1050 °C. The atomic profiles of these samples was measured using SIMS. Monte Carlo and diffusion simulations were performed using the SSupreme code. Comparisons between the simulations and experimental measurements show interesting differences these are discussed.
Peng NH, Jeynes C, Webb R, Chakarov I, Kang DJ, Moore D, Blamire M (2002) Monte Carlo simulations of energetic proton beam irradiation damage defect productions in YBCO thin films with Au masks, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 188 pp. 189-195 ELSEVIER SCIENCE BV
PEEL RMA, MILLEN D, JEYNES C, WEBB RP (1994) TRANSPUTERS IN A DISTRIBUTED DATA-COLLECTION SYSTEM FOR MEV ION MICROBEAM ANALYSIS, PROGRESS IN TRANSPUTER AND OCCAM RESEARCH 38 pp. 87-97 I O S PRESS
Nejim A, Jeynes C, Webb RP, Cowern NEB, Patel CJ (1997) Influence of dynamic annealing on the depth distribution of germanium implanted in (100) silicon at elevated temperatures, DEFECTS AND DIFFUSION IN SILICON PROCESSING 469 pp. 387-393 MATERIALS RESEARCH SOCIETY
Webb R, Kerford M, Way A (1999) Computer simulation of sputtering of gold targets using Sb and Sb2 ions, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 153 (1-4) pp. 309-313
It is well known that energetic impacts of Sb and Sb2 ions on gold substrates give rise to high energy density collision cascades and potentially very high sputtering yields. A large component of the sputtering mechanism is due to the presence of a thermal spike which causes prolonged ejection of material with thermal energies. This phenomenon is investigated using molecular dynamics simulations. The energy dissipation mechanisms and the effects of molecular orientation are investigated. The overall sputtering yields are compared to experimental measurements.
Bailey MJ, Jones BN, Hinder S, Watts J, Bleay S, Webb RP (2010) Depth profiling of fingerprint and ink signals by SIMS and MeV SIMS, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 268 (11-12) pp. 1929-1932 ELSEVIER SCIENCE BV
Barradas NP, Jeynes C, Webb RP (1997) Simulated annealing analysis of Rutherford backscattering data, APPLIED PHYSICS LETTERS 71 (2) pp. 291-293 AMER INST PHYSICS
Hammiche A, Wei Y, Wilson IH, Webb RP (1991) The Surrey STM: Construction, development, and evaluation of a scanning tunneling microscope, Review of Scientific Instruments 62 (12) pp. 3010-3021
A scanning tunneling microscope has been built together with the necessary controlling electronics. Currently this is used at atmospheric pressure but is capable of use under vacuum with minor modifications. Trials of the system, and subsequent adjustments, have taken place using highly oriented pyrolitic graphite and gold evaporated on silicon samples. Good and versatile control of tunneling current was achieved. We report on the design, development, construction, and evaluation of the instrument. Preliminary results illustrating reproducible topographical images are presented and discussed. Gap-versus-bias voltage and gap-versus-tunneling current characteristics are also presented and discussed.
Webb RP, Smith R, Al-Barwarni HH, Wilson IH (1997) Simple cellular models for growth, Radiation Effects and Defects in Solids 141 (1-4) pp. 211-222
This paper examines some simple growth models of surface morphology on the atomistic scale from a single point nucleation source. Cellular Automata and Monte Carlo simulations are described and compared for growth from a point source. They are then applied to demonstrate the growth of spiral morphology from a screw dislocation. The shape of the spiral is shown to be dependant both on the parameters used in the models and the type of algorithm chosen.
Wilson IH, Xu JB, Devine RAB, Webb RP (1996) Energetic ion impacts on quartz surfaces: A study by atomic force microscopy, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 118 (1-4) pp. 473-477
Individual impacts have been observed on quartz surfaces resulting from very low dose (typically 1010 to 1011 ions cm-2) energetic ion bombardment (species: Pb, Ni, O, Si, Ar, In, energy: 30 keV to 0.73 GeV). The work was undertaken in part to test a hypothesis drawn from earlier work that the change in surface topography around the ion track at the surface arises from a change in density brought about by radiation damage. The earlier work led us to predict that, whilst craters are seen from impacts on amorphous SiO2 (a-SiO2) due to an increase in density, we should see asperities on single crystal quartz due to a reduction in density. We also expected that the effect would be much larger in the case of quartz as the density change is much greater. The results reported here certainly support this hypothesis in general. Bombardment regimes have been chosen to enable us to compare directly with earlier measurements on a-SiO2, also to compare predominantly (near surface) electronic stopping with predominantly nuclear stopping regimes. In all cases, the areal density of asperities is less than that expected if every ion impact resulted in an observable effect and there is a great variation in asperity size.
CARTER G, NOBES M, WEBB R (1981) A 2ND-ORDER EROSION SLOWNESS THEORY OF THE DEVELOPMENT OF SURFACE-TOPOGRAPHY BY ION-INDUCED SPUTTERING, JOURNAL OF MATERIALS SCIENCE 16 (8) pp. 2091-2102
Jeynes C, Webb RP, Lohstroh A (2011) Ion Beam Analysis: A Century of Exploiting the Electronic and Nuclear Structure of the Atom for Materials Characterisation, Reviews of Accelerator Science and Technology 4 pp. 41-82 World Scientific
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.
Way AS, Jeynes C, Webb RP (1999) Measurement of lateral stress in argon implanted thin gold films using quartz resonator techniques, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 148 (1-4) pp. 238-241 ELSEVIER SCIENCE BV
Smith R, Webb RP (1992) Computational models in atomic collision studies, Nuclear Inst. and Methods in Physics Research, B 67 (1-4) pp. 373-383
Some recent developments in computational models of atomic collision studies are described and the relative merits of the binary collision and molecular dynamics approaches are discussed. © 1992.
Webb RP, Garrison BJ, Vickerman JC (2011) The effect of the H:C ratio on the sputtering of molecular solids by fullerenes, Surface and Interface Analysis 43 (1-2) pp. 116-119
Sharp JA, Cowern NEB, Webb RP, Giubertoni D, Gennaro S, Bersani M, Foad MA, Kirkby KJ (2006) Deactivation of ultra shallow B and BF2 profiles after non-melt laser annealing, Doping Engineering for Device Fabrication 912 pp. 159-163 MATERIALS RESEARCH SOCIETY
Webb RP (2006) Computer Simulation of Energetic Cluster Surface Interactions, In: Rieth M, Schommers W (eds.), Handbook of Theoretical and Computational Nanotechnology: Nanocomposites, nano-assemblies, and nanosurfaces 7
Peng NH, Kang DJ, Jeynes C, Webb RP, Moore DF, Blamire MG, Chakarov IR (2003) High quality YBa2Cu3O7-delta Josephson junctions and junction arrays fabricated by masked proton beam irradiation damage, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13 (2) pp. 889-892 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Richard M, Kirkby KJ, Webb RP, Kirkby NF (2007) A mathematical model of response of cells to radiation, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 255 (1) pp. 18-22 ELSEVIER SCIENCE BV
Bennett NS, Smith AJ, Gwilliam RM, Webb RP, Sealy BJ, Cowern NEB, O'Reilly L, McNally PJ (2008) Antimony for n-type metal oxide semiconductor ultrashallow junctions in strained Si: A superior dopant to arsenic?, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 26 (1) pp. 391-395 A V S AMER INST PHYSICS
Kerford M, Webb RP (2001) Desorption of molecules by cluster impact. A preliminary molecular dynamics study, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 180 pp. 44-52 ELSEVIER SCIENCE BV
Blamire MG, Kang DJ, Burnell G, Peng NH, Webb R, Jeynes C, Yun JH, Moon SH, Oh B (2002) Masked ion damage and implantation for device fabrication, VACUUM 69 (1-3) pp. 11-15 PERGAMON-ELSEVIER SCIENCE LTD
Thornton J, Paus KC, Webb RP, Albu-Yaron A, Booker GR, Wilson IH (1989) Defects after preamorphisation and annealing, Nuclear Inst. and Methods in Physics Research, B 39 (1-4) pp. 389-392
The control of implanted depth distributions by preamorphising silicon results in the production of defects in sensitive regions of devices fabricated in this fashion. The most stable - and therefore the most troublesome - defects are the dislocation loops that form at the original amorphous/crystalline interface on annealing. Our models suggest that the dislocation loops evolve from atoms injected into the underlying crystalline region during the amorphising implant. The idea was tested by annihilating these excess atoms with excess vacancies produced during the formation of a deep buried amorphous layer as our model predicted. No dislocation loops were then observed in this region. © 1989.
Webb RP, Harrison DE (1984) A computer simulation of high energy density cascades, Nuclear Inst. and Methods in Physics Research, B 2 (1-3) pp. 660-665
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.
Foad MA, Webb R, Smith R, Matsuo J, Al-Bayati A, T-Sheng-Wang, Cullis T (2000) Shallow junction formation by decaborane molecular ion implantation, Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 18 (1) pp. 445-449
P+/N Shallow junctions formation for 0.18 technology by low-energy implantation of boron atoms into Si using decaborane is demonstrated by molecular dynamics simulations. The simulations also show that some H is also implanted, although the amount is less than B. Transient enhanced diffusion appears to be limited .
Webb RP, Wilson IH (2003) Comparison of protons, carbon and fullerene impacts on a carbon cylinder, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 202 pp. 217-223 ELSEVIER SCIENCE BV
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
Christopher ME, Warmenhoeven JW, Romolo FS, Donghi M, Webb RP, Jeynes C, Ward NI, Kirkby KJ, Bailey MJ (2013) A new quantitative method for gunshot residue analysis by ion beam analysis., Analyst 138 (16) pp. 4649-4655
Imaging and analyzing gunshot residue (GSR) particles using the scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDS) is a standard technique that can provide important forensic evidence, but the discrimination power of this technique is limited due to low sensitivity to trace elements and difficulties in obtaining quantitative results from small particles. A new, faster method using a scanning proton microbeam and Particle Induced X-ray Emission (¼-PIXE), together with Elastic Backscattering Spectrometry (EBS) is presented for the non-destructive, quantitative analysis of the elemental composition of single GSR particles. In this study, the GSR particles were all Pb, Ba, Sb. The precision of the method is assessed. The grouping behaviour of different makes of ammunition is determined using multivariate analysis. The protocol correctly groups the cartridges studied here, with a confidence >99%, irrespective of the firearm or population of particles selected.
Sharp JA, Smith AJ, Webb RP, Kirkby KJ, Cowern NEB, Giubertoni D, Gennaro S, Bersani M, Foad MA, Fazzini PF, Cristiano F (2008) Surface proximity and boron concentration effects on end-of-range defect formation during nonmelt laser annealing, APPLIED PHYSICS LETTERS 92 (8) ARTN 082109 AMER INST PHYSICS
WEBB R, CARTER G (1981) THE EFFECTS OF ANNEALING UPON THE ACCUMULATION OF AMORPHOUSNESS IN A COMPOSITE MODEL OF DISORDER PRODUCTION, RADIATION EFFECTS AND DEFECTS IN SOLIDS 59 (1-2) pp. 69-76
Webb RP, Maydell E (1988) Comparisons of fast algorithms for calculation of range profiles in layered structures, Nuclear Inst. and Methods in Physics Research, B 33 (1-4) pp. 117-121
There are at least 3 known fast techniques for calculating the range profiles of ions implanted into layered structures which utalise the implantation profiles of the ions in bulk material of the individual layers. A fourth model - Layer - is introduced. These models are discussed and compared with experimental results, Monte Carlo calculations and each other. All models perform well in most layered materials where the stopping powers differ only slightly between the layers, but some perform better then others when there are large differences in stopping powers between layers. Layer is found to behave very well in most circumstances. © 1988.
Smith R, Beardmore K, Gras-Marti A, Kirchner R, Webb RP (1995) A molecular dynamics study of energetic particle impacts on carbon and silicon, Nuclear Inst. and Methods in Physics Research, B 102 (1-4) pp. 211-217
Molecular dynamics simulations of energetic particle interactions with silicon and graphite crystal surfaces are discussed. The simulations can be used to describe the physical state of the surface after such interactions and the dynamic development of the resulting surface damage can be examined. We demonstrate in the case of atomic impact at energies {greater-than or approximate} a few hundred eV, that craters can form on silicon while bumps are formed on graphite. Impact of C60 molecules is also discussed. On graphite, hexagonal surface waves propagate from the impact point and surface bonds remain unbroken at energies H a few hundred eV. The interactions with silicon surfaces at impact energies of H few eV depend crucially on the form of the potential. At keV energies the C60 molecule disintegrates and a large crater forms near the impact point. © 1995.
Webb RP (2005) Simulation of cluster impact induced desorption and cooling, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 228 pp. 9-15 ELSEVIER SCIENCE BV
Bergsåker H, Lama F, Smith R, Webb R (1993) A comparison of TRIM and molecular dynamics in calculating the backscattering yield of carbon incident on graphite, Vacuum 44 (3-4) pp. 341-344
This report is an attempt to assess the validity of the binary collisions approximation by comparing TRIM and molecular dynamics in calculating the backscattering of carbon ions off a graphite surface. The TRIM calculations were performed for an amorphous target with smooth surface. In the molecular dynamics calculations, a recently available semi-empirical many body potential by Tersoff was used. The calculations were made for a perfect crystal at zero temperature, consisting of 1342 atoms in five layers. The probability of reflection was calculated as a function of energy and angle of incidence of the projectile. Compared with the binary collisions calculations, molecular dynamics predicts a significantly higher backscattering probability. For instance, at normal incidence TRIM shows less than one per cent reflection in the whole energy range up to 1 keV, whereas in molecular dynamics the reflection yield peaks around 20 eV with more than 40% reflection. The case of a head-on collision with a surface at normal incidence is discussed in detail. © 1993.
Webb R, Kirkby K (2004) Impact induced desorption of large molecular structures from graphitic substrates, NSTI NANOTECH 2004, VOL 3, TECHNICAL PROCEEDINGS pp. 84-86 NANO SCIENCE & TECHNOLOGY INST
EVDOKIMOV I, WEBB R, ARMOUR D (1981) ON THE VALIDITY OF THE CONTINUOUS POTENTIAL APPROXIMATION FOR THE DESCRIPTION OF SURFACE HYPER-CHANNELLING EFFECTS, RADIATION EFFECTS LETTERS 58 (1-2) pp. 59-64
Webb RP, Harrison DE, Barfoot KM (1985) Microscopic phase transitions in molecular dynamics simulations of low energy ion irradiations of metals, Nuclear Inst. and Methods in Physics Research, B 7-8 (PART 1) pp. 143-146
The special properties of molecular dynamics multiple interaction simulations make it possible to analyse in detail the spatio-temporal history of every atom within a fixed region of a target during ion irradiation. When the positions of each particle are analysed, with respect to all other atoms, a radial distribution function is readily obtainable. These distributions can give detailed information as to the degree of damage, up to amorphisation, and can determine an effective temperature of a collision cascade. It is found that at least 2% of the trajectories for 5 keV Ar ion normal incidence irradiation of a Cu target give rise to extensive (> 1000 atomic volumes) amorphous regions which can later be recrystallised. Comparison with the energy deposition distribution indicates above average surface deposited energy density in these cases and consequently a higher effective cascade temperature. © 1985.
Peng N, Jeynes C, Gwilliam RM, Kirkby KJ, Webb RP (2007) Depth profile analysis for MgB2 thin films, formed by B implantation in Mg ribbons using energetic ion backscatterings, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 pp. 600-601 ELSEVIER SCIENCE BV
Ponomarev MG, Garrison BJ, Vickerman JC, Webb RP (2011) A molecular dynamics study of a 5 keV C60 fullerene impact on a two-component organic molecular sample, Surface and Interface Analysis 43 (1-2) pp. 107-111
A study has been made to explore impact-induced desorption of C 60 fullerenes embedded in a benzene matrix as a model of matrix assisted secondary ion mass spectrometry. A fullerene concentration of about 0.5% was incorporated in a coarse-grained benzene target and then struck by a 5 keV fullerene projectile. The response of the benzene target was compared with a pure benzene target to observe the effects of the embedded molecules on the matrix. Three different trajectories were investigated. In the first, a single sputtered fullerene was ejected joined to a carbon atom from the projectile. In the second, an undamaged C60 was ejected, and in the third, no intact fullerenes were ejected. In all three cases, 4-6 fullerenes were pushed above the initial surface but were relocated into the crater rim, enriching the surface layer with the heavier and more strongly bound component. It is observed that the sputtered fullerenes are ejected with a number of matrix molecules, and that there is a small decrease in the internal energy of the ejected fullerene that corresponds to the gradual separation of the surrounding matrix molecules from the larger molecule. This evaporative cooling may provide a potential benefit to Matrix Assisted SIMS. Copyright © 2010 John Wiley & Sons, Ltd
Kang DJ, Peng NH, Webb R, Jeynes C, Yun JH, Moon SH, Oh B, Burnell G, Tarte EJ, Moore DF, Blamire MG (2002) Realization and properties of MgB2 metal-masked ion damage junctions, Applied Physics Letters 81 (19) pp. 3600-3602
Ion beam damage combined with nanoscale focused-ion-beam direct milling was used to create manufacturable superconductor-normal-superconductor type (SNS) Josephson junctions in 100-nm-thick MgB2 with TC of 38 K. The junctions show nonhysteretic current-voltage characteristics between 36 and 4.2 K. Experimental evidence for the dc and ac Josephson effects in MgB 2 metal-masked ion damage junctions are presented. This technique is particularly useful for prototyping devices due to its simplicity and flexibility of fabrication and has a great potential for high-density integration. © 2002 American Institute of Physics.
Carter G, Nobes MJ, Arshak KI, Webb RP, Evanson D, Eghawary BDL, Williamson JH (1979) The influence of non-uniform incident flux upon surface erosion processes, Journal of Materials Science 14 (3) pp. 728-736
The surface topographic development by sputter erosion of a solid resulting from spatially non-uniform projectile bombardment is considered theoretically. It is shown that whilst formal prediction of time-dependent surface geometry is possible, analytic solution of the defining equations is generally unachievable, although an approximate treatment may be made for the case of a Gaussian flux distribution profile and an initially plane surface. It is shown that profile perturbations resulting from erosion rate-projectile incidence angle variations can assume importance when erosion crater depths become of similar order to projectile beam width. This behaviour is also revealed by computer simulation of the erosion process and a sand blasting experimental analogue study. © 1979 Chapman and Hall Ltd.
ARMOUR D, CARTER G, WEBB R, INGRAM D, NEWCOMBE R (1980) INTERFACE BROADENING DURING ION PLATING, RADIATION EFFECTS LETTERS 50 (2) pp. 45-50
Webb R, Bailey M, Jeynes C, Grime G (2010) 19th International Conference on Ion Beam Analysis, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 268 (11-12)
Ismail M, Baumert M, Stevenson D, Watts JF, Webb RP, Costa CDS, Robinson F, Bailey MJ (2016) A diagnostic test for cocaine and benzoylecgonine in urine and oral fluid using portable mass spectrometry, Analytical Methods: advancing methods and applications 9 pp. 1839-1847 Royal Society of Chemistry
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
Bright N, Webb RP, Hinder SJ, Kirkby KJ, Ward NI, Watts JF, Bleay S, Bailey M (2012) Determination of the deposition order of overlapping latent fingerprints and inks using Secondary Ion Mass Spectrometry (SIMS)., Anal Chem 84 (9) pp. 4083-4087 American Chemical Society
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.
Costa Catia, Webb Roger, Palitsin Vladimir, Ismail Mahado, de Puit Marcel, Atkinson Samuel, Bailey Melanie (2017) Rapid, secure drug testing using fingerprint development and paper spray mass spectrometry, Clinical Chemistry 63 (11) pp. 1745-1752 American Association for Clinical Chemistry
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.
Ismail M, Stevenson D, Costa C, Webb R, de Puit M, Bailey M (2018) Noninvasive Detection of Cocaine and Heroin Use with Single Fingerprints: Determination of an Environmental Cutoff, Clinical Chemistry 64 (6) pp. 909-917 American Association for Clinical Chemistry
BACKGROUND:
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 na1¨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.
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.
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.
De Jesus Janella, Bunch Josephine, Verbeck Guido, Webb Roger, Costa Katia, Goodwin Richard, Bailey Melanie (2018) Application of Various Normalisation Methods for Microscale Analysis of Tissues Using Direct Analyte Probed Nano-extraction (DAPNe), Analytical Chemistry 90 (20) pp. 12094-12100 American Chemical Society
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.
Costa Catia (2017) Development of a confirmatory test for cocaine and metabolites in latent fingerprints.,
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 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.
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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.
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 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.
Mohammad Sofi Imran (2017) PL and EL investigation of Cerium, Europium and Ytterbium-Doped silicon for active silicon photonic devices.,
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.