Christopher Jeynes | University of Surrey (original) (raw)

Papers by Christopher Jeynes

Journal of Materials Science & Technology, 2010

Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxys... more Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxysulphide thin films which were deposited on sodalime glass substrates using metal organic chemical vapour deposition (MOCVD) technique at a temperature of 420 • C. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy (SEM) micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 µm. X-ray diffraction (XRD) showed that the deposited films were crystalline in nature.

Vacuum, 2002

Several groups have recently demonstrated junction formation by masked ion damage in which ions f... more Several groups have recently demonstrated junction formation by masked ion damage in which ions from a broad beam ion source locally damage regions of superconductor to form the junction barriers. However, the difficulties of preparing successful mask structures have meant the progress to date has been relatively slow. Using masks of high electron density metals such as Au and protons as the irradiating species, we have shown in a series of studies that irradiation of YBa2Cu3O7−δ (YBCO) with ions of energy in the range of 30–350keV can be used to create highly localised damage regions in the films. This technique has been successfully employed to create high quality Josephson junctions in YBCO. The fabricated devices show 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.

Essderc 89 19th European Solid State Device Research Conference, Sep 1, 1989

ABSTRACT

Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufa... more Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufacturable SNS type Josephson junctions in 100 nm thick MgB$_{2}$ with T$_{C}$ of 38 K. The junctions show non-hysteretic 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

SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002

... J. Mefo, K. J Kirkby, BJ Sealy, G. Boudreault, C. Jeynes School of Electronics and Physical S... more ... J. Mefo, K. J Kirkby, BJ Sealy, G. Boudreault, C. Jeynes School of Electronics and Physical Sciences University of Surrey, Guildford, Surrey, GU2 7XH. ... The flakes were approximately 100 microns thick and appeared silvery on one side but had a dark matt finish on the other. ...

The new external microbeam at the University of Surrey is capable of mapping areas of 3mm x3 mm. ... more The new external microbeam at the University of Surrey is capable of mapping areas of 3mm x3 mm. In this study it has been used to map the metal composition of 2 inks in a German 1920's bank note. The major constituents of the red ink are mercury and barium, while those in the green ink, which was applied first,

SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002

The way in which the plasma in the ion source interacts with the constituent elements of the sour... more The way in which the plasma in the ion source interacts with the constituent elements of the source chamber can provide important insights into the plasma chemistry and may facilitate improvements in ion source design and operation. It is also an important parameter in determining the environmental impact of the implantation process. It is worth noting that less than 0.4% of the material placed into the ion source is actually implanted as a dopant into the target wafers; the rest remains as a solid residue or gaseous emission. As many of the materials used for dopant implantation are either highly toxic, pyrophoric, greenhouse gases or powerful ozone depleters, or combinations of the above it is imperative, that the extent, location and chemical composition of these residues are quantified and understood. This will enable their impact on the environment, economy and society, the three pillars of sustainable development [1] to be assessed. In this study small pieces of silicon were placed at predetermined points within the source chamber of a commercial ion implantation system. Antimony was then run using SbF 3 as the feed gas. At the end of the run the silicon samples were retrieved and analysed using Rutherford Backscattering (RBS) and ion channelling. It was found that the location of the samples influenced the elemental composition of the plasma products deposited in the source chamber. A similar experiment was also conducted for BF 2 + implants using a BF 3 feed gas, again the elemental composition varied with the position of the silicon samples allowing the distribution of different elements, within the plasma products, to be mapped around the source chamber.

The University of Surrey Ion Beam Centre has recently installed a beam-line for the analysis of o... more The University of Surrey Ion Beam Centre has recently installed a beam-line for the analysis of objects in air. This complements the existing ion beam analysis capability which is established round a new 2MV Tandetron accelerator and includes a millibeam RBS/channelling chamber and a microbeam facility using a magnetic quadrupole triplet. The new external beam uses a magnetic quadrupole doublet

2006 International Workshop on Junction Technology, 2006

The paper summarises recent findings concerning the fabrication of ultra-shallow junctions in sil... more The paper summarises recent findings concerning the fabrication of ultra-shallow junctions in silicon for future generations of CMOS devices. In particular we concentrate on vacancy engineering to achieve carrier concentrations of 5-6 x 1020 cm-3 for boron in silicon without diffusion ...

ABSRACT Investigations into the lithography applications using MeV protons and alpha particles ar... more ABSRACT Investigations into the lithography applications using MeV protons and alpha particles are being performed at the Ion Beam Centre of the University of Surrey, UK. This is a new application of the microbeam in this laboratory, resulting in new sample preparation and after-irradiation treatment facilities being installed.

Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 1999

Amorphous GaN was synthesised by Ga implantation into N-rich PECVD a-SiN x :H ®lms after annealin... more Amorphous GaN was synthesised by Ga implantation into N-rich PECVD a-SiN x :H ®lms after annealing between 200°C and 500°C. Similar implantation into Si-rich ®lms did not form GaN. X-ray Photoelectron Spectroscopy (XPS) demonstrated the presence of GaN bonds in the former, but not the latter, case. Rutherford backscattering (RBS) and Elastic Recoil Detection Analysis (ERDA) demonstrated that implanted Ga substituted for Si in the N-rich ®lms but not in the Si-rich ones. The RBS/ERDA analysis used self-consistent ®tting of multiple spectra using the combinatorial optimisation Simulated Annealing algorithm, followed by a determination of the con®dence limits on the depth pro®les obtained using Bayesian Inference. Ó 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 0 7 0 2 -2

Journal of Materials Science, 2001

The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer cat... more The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer catalysts (PTCs) has been investigated. Rutherford backscattering spectrometry (RBS) has been used to determine the depth of modification achieved and to provide compositional depth profiles of modified PVdF samples. The complex chemical nature of the modified substrate, and the overlap of the elemental scattering edges within the depths involved (up to 1.4 µm), create RBS spectra which are difficult to interpret. The DataFurnace software has been applied to the data, leading to excellent results. Defluorination and oxygenation of PVdF occurs on treatment with NaOH and PTC. Through the use of samples prepared with the aim of establishing the kinetics of the modification, a mechanism concerning elimination of fluorine followed by oxygenation, is shown to occur. The RBS analysis indicates that the kinetics of the defluorination reaction follows the Case 1 (Fickian) diffusion law, and that the depth of treatment is of the order of 1.4 µm.

Thin Solid Films, 2004

The bonding structure and hydrogen content of amorphous hydrogenated silicon nitride (a-SiN x :H)... more The bonding structure and hydrogen content of amorphous hydrogenated silicon nitride (a-SiN x :H) thin films have been investigated by infrared spectroscopy and ion beam techniques. Electron cyclotron resonance plasma enhanced chemical vapor deposition was used to produce these films under different values of gas flow ratio, deposition temperature, and microwave power.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 2006

A time series of 5 · 10 15 As/cm 2 100 keV implantations into 100 mm silicon wafers has been anal... more A time series of 5 · 10 15 As/cm 2 100 keV implantations into 100 mm silicon wafers has been analysed by RBS, using the amorphous Si yield to determine the charge solid-angle product for each spectrum. Wafers are also annealed and the resistivity characterised by the four point probe. The implants are demonstrated by four point probe to be uniform at 0.7%. Very high precision down to 0.5% in the determination of implanted average fluence is obtained by analysing the sum of RBS spectra obtained over the whole wafer, with total collected charges of up to about 1 mC. An accurate pileup correction does not contribute significantly to this uncertainty which is dominated by the electronic gain. A full uncertainty budget is presented. The absolute accuracy is still dominated by the uncertainty of the silicon stopping force (2%). The implanted fluence is demonstrated to be consistently within about 3% of nominal. (C. Jeynes).

Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 2007

... Kai.Arstila@iki.fi, NDF: DataFurnace, Nuno Barradas, Windows, UNIX, Commercial through Univer... more ... Kai.Arstila@iki.fi, NDF: DataFurnace, Nuno Barradas, Windows, UNIX, Commercial through University of Surrey. Evaluation copies available by request, Restricted to author – not available. ... 1 h, S1, RBS, 4 He +, 1.5, 16, Bohr a, 1, 10, –, Rutherford, None, No, 150, 60, 30, IBM, Ideal ...

The combinatorial optimization simulated annealing algorithm is applied to the analysis of Ruther... more The combinatorial optimization simulated annealing algorithm is applied to the analysis of Rutherford backscattering data. The analysis is fully automatic, i.e., it does not require time-consuming human intervention. The algorithm is tested on a complex iron-cobalt silicide spectrum, and all the relevant features are successfully determined. The total analysis time using a PC 486 processor running at 100 MHz is comparable to the data collection time, which opens the way for on-line automatic analysis. © 1997 American Institute of Physics.

X-Ray Spectrometry, 2009

A feasibility study was carried out into the use of particle-induced x-ray emission (PIXE) on the... more A feasibility study was carried out into the use of particle-induced x-ray emission (PIXE) on the ion microprobe for the characterisation of gunshot residues (GSR). We compare these results with the conventional technique, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). Samples of gunshot residue from four different sources were collected. Individual particles of GSR were analysed by SEM-EDS using a 30-keV electron beam focussed to ∼10 nm, and PIXE using a 2.5-MeV proton beam focussed to ∼4 µm. PIXE revealed trace or minor elements undetectable by SEM-EDS, thereby strengthening the discrimination between different types of GSR.

Thin Solid Films, 2008

To evaluate potential solutions for reducing the damage to ultra low-k dielectrics during photore... more To evaluate potential solutions for reducing the damage to ultra low-k dielectrics during photoresist stripping in advanced interconnect technology, we have investigated the mechanisms of interactions between remote H 2 , D 2 and N 2 discharges and porous organo-silicate materials. Extended sub-surface modifications take place in high carbon-content organo-silicates, whereas silica-rich dielectrics show negligible chemical damages during the same treatments. The nature of plasma/dielectric interactions depends primarily on the organic fraction of the ULK material. Methyl groups in silica-rich organosilicates withstand the interaction with the plasma species. Conversely, large organic compounds in carbon-rich dielectrics experience cleavage reactions leading to volatile hydrocarbon formation and compositional changes. For conditions where stripping-induced damage is introduced, the effects scale with the substrate temperature in the range 200°C-300°C. The permeation of the ULK material by remote plasma species depends on its porosity.

The Analyst, 2013

The cell-to-cell variation of gold nanoparticle (GNP) uptake is important for therapeutic applica... more The cell-to-cell variation of gold nanoparticle (GNP) uptake is important for therapeutic applications. We directly counted the GNPs in hundreds of individual cells, and showed that the large variation from cell-to-cell could be directly modelled by assuming log-normal distributions of both cell mass and GNP rate of uptake. This was true for GNPs non-specifically bound to fetal bovine serum or conjugated to a cell penetrating peptide. Within a population of cells, GNP content varied naturally by a factor greater than 10 between individual cells.

The Analyst, 2013

Imaging and analyzing gunshot residue (GSR) particles using the scanning electron microscope equi... more 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 (m-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.

Journal of Materials Science & Technology, 2010

Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxys... more Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxysulphide thin films which were deposited on sodalime glass substrates using metal organic chemical vapour deposition (MOCVD) technique at a temperature of 420 • C. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy (SEM) micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 µm. X-ray diffraction (XRD) showed that the deposited films were crystalline in nature.

Vacuum, 2002

Several groups have recently demonstrated junction formation by masked ion damage in which ions f... more Several groups have recently demonstrated junction formation by masked ion damage in which ions from a broad beam ion source locally damage regions of superconductor to form the junction barriers. However, the difficulties of preparing successful mask structures have meant the progress to date has been relatively slow. Using masks of high electron density metals such as Au and protons as the irradiating species, we have shown in a series of studies that irradiation of YBa2Cu3O7−δ (YBCO) with ions of energy in the range of 30–350keV can be used to create highly localised damage regions in the films. This technique has been successfully employed to create high quality Josephson junctions in YBCO. The fabricated devices show 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.

Essderc 89 19th European Solid State Device Research Conference, Sep 1, 1989

ABSTRACT

Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufa... more Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufacturable SNS type Josephson junctions in 100 nm thick MgB$_{2}$ with T$_{C}$ of 38 K. The junctions show non-hysteretic 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

SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002

... J. Mefo, K. J Kirkby, BJ Sealy, G. Boudreault, C. Jeynes School of Electronics and Physical S... more ... J. Mefo, K. J Kirkby, BJ Sealy, G. Boudreault, C. Jeynes School of Electronics and Physical Sciences University of Surrey, Guildford, Surrey, GU2 7XH. ... The flakes were approximately 100 microns thick and appeared silvery on one side but had a dark matt finish on the other. ...

The new external microbeam at the University of Surrey is capable of mapping areas of 3mm x3 mm. ... more The new external microbeam at the University of Surrey is capable of mapping areas of 3mm x3 mm. In this study it has been used to map the metal composition of 2 inks in a German 1920's bank note. The major constituents of the red ink are mercury and barium, while those in the green ink, which was applied first,

SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002

The way in which the plasma in the ion source interacts with the constituent elements of the sour... more The way in which the plasma in the ion source interacts with the constituent elements of the source chamber can provide important insights into the plasma chemistry and may facilitate improvements in ion source design and operation. It is also an important parameter in determining the environmental impact of the implantation process. It is worth noting that less than 0.4% of the material placed into the ion source is actually implanted as a dopant into the target wafers; the rest remains as a solid residue or gaseous emission. As many of the materials used for dopant implantation are either highly toxic, pyrophoric, greenhouse gases or powerful ozone depleters, or combinations of the above it is imperative, that the extent, location and chemical composition of these residues are quantified and understood. This will enable their impact on the environment, economy and society, the three pillars of sustainable development [1] to be assessed. In this study small pieces of silicon were placed at predetermined points within the source chamber of a commercial ion implantation system. Antimony was then run using SbF 3 as the feed gas. At the end of the run the silicon samples were retrieved and analysed using Rutherford Backscattering (RBS) and ion channelling. It was found that the location of the samples influenced the elemental composition of the plasma products deposited in the source chamber. A similar experiment was also conducted for BF 2 + implants using a BF 3 feed gas, again the elemental composition varied with the position of the silicon samples allowing the distribution of different elements, within the plasma products, to be mapped around the source chamber.

The University of Surrey Ion Beam Centre has recently installed a beam-line for the analysis of o... more The University of Surrey Ion Beam Centre has recently installed a beam-line for the analysis of objects in air. This complements the existing ion beam analysis capability which is established round a new 2MV Tandetron accelerator and includes a millibeam RBS/channelling chamber and a microbeam facility using a magnetic quadrupole triplet. The new external beam uses a magnetic quadrupole doublet

2006 International Workshop on Junction Technology, 2006

The paper summarises recent findings concerning the fabrication of ultra-shallow junctions in sil... more The paper summarises recent findings concerning the fabrication of ultra-shallow junctions in silicon for future generations of CMOS devices. In particular we concentrate on vacancy engineering to achieve carrier concentrations of 5-6 x 1020 cm-3 for boron in silicon without diffusion ...

ABSRACT Investigations into the lithography applications using MeV protons and alpha particles ar... more ABSRACT Investigations into the lithography applications using MeV protons and alpha particles are being performed at the Ion Beam Centre of the University of Surrey, UK. This is a new application of the microbeam in this laboratory, resulting in new sample preparation and after-irradiation treatment facilities being installed.

Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 1999

Amorphous GaN was synthesised by Ga implantation into N-rich PECVD a-SiN x :H ®lms after annealin... more Amorphous GaN was synthesised by Ga implantation into N-rich PECVD a-SiN x :H ®lms after annealing between 200°C and 500°C. Similar implantation into Si-rich ®lms did not form GaN. X-ray Photoelectron Spectroscopy (XPS) demonstrated the presence of GaN bonds in the former, but not the latter, case. Rutherford backscattering (RBS) and Elastic Recoil Detection Analysis (ERDA) demonstrated that implanted Ga substituted for Si in the N-rich ®lms but not in the Si-rich ones. The RBS/ERDA analysis used self-consistent ®tting of multiple spectra using the combinatorial optimisation Simulated Annealing algorithm, followed by a determination of the con®dence limits on the depth pro®les obtained using Bayesian Inference. Ó 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 0 7 0 2 -2

Journal of Materials Science, 2001

The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer cat... more The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer catalysts (PTCs) has been investigated. Rutherford backscattering spectrometry (RBS) has been used to determine the depth of modification achieved and to provide compositional depth profiles of modified PVdF samples. The complex chemical nature of the modified substrate, and the overlap of the elemental scattering edges within the depths involved (up to 1.4 µm), create RBS spectra which are difficult to interpret. The DataFurnace software has been applied to the data, leading to excellent results. Defluorination and oxygenation of PVdF occurs on treatment with NaOH and PTC. Through the use of samples prepared with the aim of establishing the kinetics of the modification, a mechanism concerning elimination of fluorine followed by oxygenation, is shown to occur. The RBS analysis indicates that the kinetics of the defluorination reaction follows the Case 1 (Fickian) diffusion law, and that the depth of treatment is of the order of 1.4 µm.

Thin Solid Films, 2004

The bonding structure and hydrogen content of amorphous hydrogenated silicon nitride (a-SiN x :H)... more The bonding structure and hydrogen content of amorphous hydrogenated silicon nitride (a-SiN x :H) thin films have been investigated by infrared spectroscopy and ion beam techniques. Electron cyclotron resonance plasma enhanced chemical vapor deposition was used to produce these films under different values of gas flow ratio, deposition temperature, and microwave power.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 2006

A time series of 5 · 10 15 As/cm 2 100 keV implantations into 100 mm silicon wafers has been anal... more A time series of 5 · 10 15 As/cm 2 100 keV implantations into 100 mm silicon wafers has been analysed by RBS, using the amorphous Si yield to determine the charge solid-angle product for each spectrum. Wafers are also annealed and the resistivity characterised by the four point probe. The implants are demonstrated by four point probe to be uniform at 0.7%. Very high precision down to 0.5% in the determination of implanted average fluence is obtained by analysing the sum of RBS spectra obtained over the whole wafer, with total collected charges of up to about 1 mC. An accurate pileup correction does not contribute significantly to this uncertainty which is dominated by the electronic gain. A full uncertainty budget is presented. The absolute accuracy is still dominated by the uncertainty of the silicon stopping force (2%). The implanted fluence is demonstrated to be consistently within about 3% of nominal. (C. Jeynes).

Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 2007

... Kai.Arstila@iki.fi, NDF: DataFurnace, Nuno Barradas, Windows, UNIX, Commercial through Univer... more ... Kai.Arstila@iki.fi, NDF: DataFurnace, Nuno Barradas, Windows, UNIX, Commercial through University of Surrey. Evaluation copies available by request, Restricted to author – not available. ... 1 h, S1, RBS, 4 He +, 1.5, 16, Bohr a, 1, 10, –, Rutherford, None, No, 150, 60, 30, IBM, Ideal ...

The combinatorial optimization simulated annealing algorithm is applied to the analysis of Ruther... more The combinatorial optimization simulated annealing algorithm is applied to the analysis of Rutherford backscattering data. The analysis is fully automatic, i.e., it does not require time-consuming human intervention. The algorithm is tested on a complex iron-cobalt silicide spectrum, and all the relevant features are successfully determined. The total analysis time using a PC 486 processor running at 100 MHz is comparable to the data collection time, which opens the way for on-line automatic analysis. © 1997 American Institute of Physics.

X-Ray Spectrometry, 2009

A feasibility study was carried out into the use of particle-induced x-ray emission (PIXE) on the... more A feasibility study was carried out into the use of particle-induced x-ray emission (PIXE) on the ion microprobe for the characterisation of gunshot residues (GSR). We compare these results with the conventional technique, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). Samples of gunshot residue from four different sources were collected. Individual particles of GSR were analysed by SEM-EDS using a 30-keV electron beam focussed to ∼10 nm, and PIXE using a 2.5-MeV proton beam focussed to ∼4 µm. PIXE revealed trace or minor elements undetectable by SEM-EDS, thereby strengthening the discrimination between different types of GSR.

Thin Solid Films, 2008

To evaluate potential solutions for reducing the damage to ultra low-k dielectrics during photore... more To evaluate potential solutions for reducing the damage to ultra low-k dielectrics during photoresist stripping in advanced interconnect technology, we have investigated the mechanisms of interactions between remote H 2 , D 2 and N 2 discharges and porous organo-silicate materials. Extended sub-surface modifications take place in high carbon-content organo-silicates, whereas silica-rich dielectrics show negligible chemical damages during the same treatments. The nature of plasma/dielectric interactions depends primarily on the organic fraction of the ULK material. Methyl groups in silica-rich organosilicates withstand the interaction with the plasma species. Conversely, large organic compounds in carbon-rich dielectrics experience cleavage reactions leading to volatile hydrocarbon formation and compositional changes. For conditions where stripping-induced damage is introduced, the effects scale with the substrate temperature in the range 200°C-300°C. The permeation of the ULK material by remote plasma species depends on its porosity.

The Analyst, 2013

The cell-to-cell variation of gold nanoparticle (GNP) uptake is important for therapeutic applica... more The cell-to-cell variation of gold nanoparticle (GNP) uptake is important for therapeutic applications. We directly counted the GNPs in hundreds of individual cells, and showed that the large variation from cell-to-cell could be directly modelled by assuming log-normal distributions of both cell mass and GNP rate of uptake. This was true for GNPs non-specifically bound to fetal bovine serum or conjugated to a cell penetrating peptide. Within a population of cells, GNP content varied naturally by a factor greater than 10 between individual cells.

The Analyst, 2013

Imaging and analyzing gunshot residue (GSR) particles using the scanning electron microscope equi... more 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 (m-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.