The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Greg Gillen - One of the best experts on this subject based on the ideXlab platform.
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Techniques for Improving SIMS Depth ResolutIon: C60+ Primary Ions and Backside Depth Profile Analysis
Characterization and Metrology for ULSI Technology, 2005Co-Authors: Eric S. Windsor, Greg Gillen, Albert J. Fahey, David S. Bright, James D. BatteasAbstract:We are evaluating methods to improve depth resolutIon for SIMS analyses of semiconductors. Two methods that show promise are: (1) backside depth profile analysis and (2) the use of cluster Primary Ion beams. Backside analysis improves depth resolutIon by eliminating sample‐induced artifacts caused by sputtering through processing layers on the front side of the wafer. Mechanical backside sample preparatIon however, also introduces artifacts. The most troublesome artifact is inclined (non‐planar) polishing. Using a combinatIon of both secondary Ion image depth profiling and image analysis techniques, the effects of inclined polishing are minimized. A Buckminsterfullerene C60+ Primary Ion source has been interfaced to a magnetic sector SIMS instrument for the purpose of depth profile analysis. ApplicatIon of this source to NIST SRM 2135a (nickel/ chromium multilayer depth profile standard) demonstrated that all layers of this standard were completely resolved. Initial applicatIons of C60+ to silicon have pr...
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dynamic sims utilizing sf5 polyatomic Primary Ion beams for drug delivery applicatIons
Applied Surface Science, 2004Co-Authors: Christine M Mahoney, Sonya Roberson, Greg GillenAbstract:Abstract The behavior of various biodegradable polymer films (e.g. polylactic acid, polyglycolic acid and polycaprolactone) as well as some model drugs (theophylline and 4-acetamidophenol) under dynamic SF 5 + Primary Ion bombardment is explored. A series of polylactic acid films containing varying concentratIons of 4-acetamidophenol are also analyzed under similar conditIons. The resultant molecular depth profiles obtained from these polymer films doped with drug show very little degradatIon in molecular signal as a functIon of SF 5 + Primary Ion dose, and it was found that the molecular Ion signals of both polymer and drug remained constant for Ion doses up to ∼5×10 15 Ions/cm 2 . In additIon, the polymer film/Si interface was well defined which may imply that sputter-induced topography formatIon was not a significant limitatIon. These results suggest that the structure of the biodegradable polymers studied here which all have the common main chain structural unit, RCOOR, allows for a greater ability to depth profile due to ease of bond cleavage. Most importantly, however, these results indicate that in these particular polymer systems, the distributIon of the drug as a functIon of depth can be monitored.
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secondary Ion mass spectrometry using cluster Primary Ion beams
Applied Surface Science, 2003Co-Authors: Greg Gillen, Albert J. FaheyAbstract:Abstract We have a developed a capability for conducting cluster secondary Ion mass spectrometry (SIMS) experiments on commercially available SIMS instrumentatIon. This paper reviews our recent work on cluster Ion source development, elemental depth profiling with cluster Primary Ion beams and the use of cluster Ion beams for organic surface characterizatIon. An area of particular interest is the observatIon that beam-induced damage for some organic materials is substantially reduced under cluster bombardment. This unique feature of cluster SIMS is utilized for molecular depth profiling of selected polymer films and for studying the spatial distributIon of high explosive particles by SIMS imaging. We also describe recent studies that may provide additIonal insight into possible mechanisms for the molecular secondary Ion yield enhancement observed for organic thin films under cluster bombardment.
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Cluster Primary Ion beam secondary Ion mass spectrometry for semiconductor characterizatIon
Characterization and Metrology for ULSI Technology, 2001Co-Authors: Greg Gillen, Sonya Roberson, Albert J. Fahey, Marlon L. Walker, Joe Bennett, Richard T. LareauAbstract:We are evaluating the use of polyatomic and cluster Primary Ion beams for characterizatIon of semiconductor materials by secondary Ion mass spectrometry using both magnetic sector and time-of-flight SIMS instruments. Primary Ion beams of SF5+, C8− and CsC6− have been used to analyze low energy arsenic implants in silicon, boron delta-doped structures, thin gate oxides, metal multilayers, organic surface contaminatIon and photoresist thin films. Compared to monoatomic bombardment under the same conditIons, cluster Ion beams offer improved depth resolutIon for silicon depth profiling and a reductIon in sputter-induced topography for metals. For organic materials, the use of a cluster Ion beam can give large improvements in yield for characteristic secondary Ions and can minimize beam-induced degradatIon in some materials.
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negative cesium sputter Ion source for generating cluster Primary Ion beams for secondary Ion mass spectrometry analysis
Journal of Vacuum Science and Technology, 2001Co-Authors: Greg Gillen, Joe Bennett, Richard T. Lareau, Lance King, Brian Freibaum, Frank ChmaraAbstract:A cesium sputter Ion source has been used to generate novel cluster and monoatomic Primary Ion beams for secondary Ion mass spectrometry (SIMS). The source produces a variety of Primary Ion beam species with sufficient flux to be usable for both organic surface analysis and semiconductor depth profiling. The Primary focus of this work is on the generatIon and use of carbon and carbon-containing cluster Primary Ion beams for SIMS. Stability of the sputter Ion source is a few percent over 20 min, has useful lifetimes of weeks to months, and produces total Primary Ion beam currents for C2− Ions, measured at the sample, of >1 μA at an extractIon voltage of 10 kV. Larger cluster Ions (Cx−x=4–10 and CsCx−x=2–8) are produced with tens of nA of beam current. Due to the divergence of the source, focused beam operatIon gives current densities under optimal conditIons of 0.4–0.5 mA/cm2. Cluster bombardment studies of organic films using carbon clusters Cx−x=1–10 indicate that large enhancements (up to a factor of 80...
John C. Vickerman - One of the best experts on this subject based on the ideXlab platform.
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prospect of increasing secondary Ion yields in tof sims using water cluster Primary Ion beams
Surface and Interface Analysis, 2014Co-Authors: Sadia Sheraz, Nicholas P. Lockyer, John S. Fletcher, Andrew M Barber, Berrueta I Razo, John C. VickermanAbstract:Low IonizatIon yields in time of flight secondary Ion mass spectrometry (ToF-SIMS) particularly from single cells and tissues are proving to be a significant limitatIon in allowing this technique to reach its full potential. A number of approaches including embedding the sample in water or spraying water above sample surface has shown great prospective for increasing the IonizatIon yield by a factor of 10 to 100 through proton mediated' reactIon. Based on this hypothesis, a water cluster Primary Ion source has been developed in collaboratIon with Ionoptika Ltd to generate giant water cluster Ions (H2O)(n)(+) (n=1-10000) using a similar supersonic jet expansIon methodology as for argon cluster beams. The Ion yields of arginine, cholesterol, angiotensin II and a lipid mix have been measured under static and high Ion dose conditIons using (H2O)(5000)(+), (H2O)(3000)(+), Ar-3000(+) and C-60(+) Primary Ion beams at 20keV. An enhancement in yields up to a factor of around 4 is observed under water cluster impact, in comparison with C-60(+) at 1x10(11)Ions/cm(2) Ion dose, whereas this increases by around 10-50 times at high Ion dose conditIons. Copyright (c) 2014 John Wiley & Sons, Ltd.
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comparison of c60 and gcib Primary Ion beams for the analysis of cancer cells and tumour sectIons
Surface and Interface Analysis, 2013Co-Authors: John S. Fletcher, Nicholas P. Lockyer, Andrew M Barber, Sadia Rabbani, John C. VickermanAbstract:We have implemented a gas cluster Ion beam (GCIB) system developed by Ionoptika Ltd (Southampton, UK) with sufficient control to allow us to exploit the unique capabilities of our J105 instrument for imaging and depth profiling. The J105 allows us to use the GCIB as continuous Primary Ion beam, thereby overcoming the issues associated with pulsing these slow moving, mixed species beams. We have performed a direct comparison with C60 Ions on the same samples in the same instrument. The GCIB beams are more difficult to focus than the C60+ Ion beam, making single-cell imaging difficult, although spot sizes of 15?20?�m are readily obtainable for Ar1000 and Ar2000, providing good resolutIon for larger area imaging on tissue sectIon/biopsy samples. In this paper, we present results from the assessment of these new beams as Primary Ions for the analysis of ?real?, complex biological systems. Initial spectra and those following increased Primary Ion bombardment were compared for in vitro cultured cells deposited on silicon and cryo-sectIoned tumour samples originating in vivo. Ar1000+ and Ar2000+ showed increased persistence of the signals from intact molecular Ions of phospholipids and a reductIon in the accumulatIon of chemical background noise compared with C60+ analysis.
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InvestigatIon of molecular weight effects of polystyrene in ToF-SIMS using C60+ and Au+ Primary Ion beams
Applied Surface Science, 2008Co-Authors: Alan M. Piwowar, Nicholas P. Lockyer, John C. VickermanAbstract:Abstract In secondary Ion mass spectrometry, polyatomic Primary Ion sources are known to enhance yields from many surfaces including polymers. In order to understand the fundamental causes for these increases, the enhancement as a functIon of material type and molecular weight needs to be delineated. In this article, we report results from a systematic investigatIon of polymeric films of polystyrene (PS) with varying molecular weights to examine the influence of the Primary Ion beam on the secondary Ion yields in time of flight secondary Ion mass spectrometry (ToF-SIMS). The masses of the polymers investigated ranged from 1000 to 20,000 Da, or from about n = 10 to 200 where n indicates the number of polymeric units in a polymer chain. The polymers had a narrow molecular weight range (PDI + and C 60 + Primary Ion beams. The analysis with the two beams provided a useful comparison between atomic and polyatomic Primary Ion sources. InformatIon gathered from this study provides insight into the role of molecular weight on the observed yield enhancement from polyatomic Ion sources.
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depth profiling brain tissue sectIons with a 40 kev c60 Primary Ion beam
Analytical Chemistry, 2008Co-Authors: Emrys A Jones, Nicholas P. Lockyer, John C. VickermanAbstract:In this paper, the effect of prolonged C60+ Primary Ion bombardment on the chemical informatIon available from a sectIon of rat brain is discussed. Initial attempts demonstrate the rapid loss of molecular signal from the bombarded area with both C60+ and Au+ used as a monatomic comparison. However, the nature of this signal disappearance is shown to be different. Analysis of the C60+ data indicates a correlatIon between signal loss and the appearance of sodium and potassium adducts of phosphate and protein fragments; this is supported by model systems. By using an ammonium formate wash to reduce the salt levels within the tissue this effect is removed, allowing the chemistry of the tissue sectIon to be better probed. Results collected from multiple sectIons suggest that at room temperature under vacuum conditIons there is a migratIon of lipids to the surface of the tissue. Three-dimensIonal (3D) imaging is used to demonstrate that once these lipids are removed other species, such as proteins, are uncovere...
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Mass spectral analysis and imaging of tissue by ToF-SIMS—The role of buckminsterfullerene, C60+, Primary Ions
International Journal of Mass Spectrometry, 2007Co-Authors: Emrys A Jones, Nicholas P. Lockyer, John C. VickermanAbstract:Abstract Recent developments in desorptIon/IonisatIon mass spectrometry techniques have made their applicatIon to biological analysis a realistic and successful propositIon. Developments in Primary Ion source technology, mainly through the advent of polyatomic Ion beams, have meant that the technique of secondary Ion mass spectrometry (SIMS) can now access the depths of informatIon required to allow biological imaging to be a viable optIon. Here the role of the Primary Ion C 60 + is assessed with regard to molecular imaging of lipids and pharmaceuticals within tissue sectIons. High secondary Ion yields and low surface damage accumulatIon are demonstrated on both model and real biological samples, indicating the high secondary Ion efficiency afforded to the analyst by this Primary Ion when compared to other cluster Ion beams used in imaging. The newly developed 40 keV C 60 + Ion source allows the beam to be focused such that high resolutIon imaging is demonstrated on a tissue sample, and the greater yields allow the molecular signal from the drug raclopride to be imaged within tissue sectIon following in vivo dosing. The localisatIon shown for this drug alludes to issues regarding the chemical environment affecting the IonisatIon probability of the molecule; the importance of this effect is demonstrated with model systems and the possibility of using laser post-IonisatIon as a method for reducing this consequence of bio-sample complexity is demonstrated and discussed.
Sonya Roberson - One of the best experts on this subject based on the ideXlab platform.
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dynamic sims utilizing sf5 polyatomic Primary Ion beams for drug delivery applicatIons
Applied Surface Science, 2004Co-Authors: Christine M Mahoney, Sonya Roberson, Greg GillenAbstract:Abstract The behavior of various biodegradable polymer films (e.g. polylactic acid, polyglycolic acid and polycaprolactone) as well as some model drugs (theophylline and 4-acetamidophenol) under dynamic SF 5 + Primary Ion bombardment is explored. A series of polylactic acid films containing varying concentratIons of 4-acetamidophenol are also analyzed under similar conditIons. The resultant molecular depth profiles obtained from these polymer films doped with drug show very little degradatIon in molecular signal as a functIon of SF 5 + Primary Ion dose, and it was found that the molecular Ion signals of both polymer and drug remained constant for Ion doses up to ∼5×10 15 Ions/cm 2 . In additIon, the polymer film/Si interface was well defined which may imply that sputter-induced topography formatIon was not a significant limitatIon. These results suggest that the structure of the biodegradable polymers studied here which all have the common main chain structural unit, RCOOR, allows for a greater ability to depth profile due to ease of bond cleavage. Most importantly, however, these results indicate that in these particular polymer systems, the distributIon of the drug as a functIon of depth can be monitored.
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Cluster Primary Ion beam secondary Ion mass spectrometry for semiconductor characterizatIon
Characterization and Metrology for ULSI Technology, 2001Co-Authors: Greg Gillen, Sonya Roberson, Albert J. Fahey, Marlon L. Walker, Joe Bennett, Richard T. LareauAbstract:We are evaluating the use of polyatomic and cluster Primary Ion beams for characterizatIon of semiconductor materials by secondary Ion mass spectrometry using both magnetic sector and time-of-flight SIMS instruments. Primary Ion beams of SF5+, C8− and CsC6− have been used to analyze low energy arsenic implants in silicon, boron delta-doped structures, thin gate oxides, metal multilayers, organic surface contaminatIon and photoresist thin films. Compared to monoatomic bombardment under the same conditIons, cluster Ion beams offer improved depth resolutIon for silicon depth profiling and a reductIon in sputter-induced topography for metals. For organic materials, the use of a cluster Ion beam can give large improvements in yield for characteristic secondary Ions and can minimize beam-induced degradatIon in some materials.
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preliminary evaluatIon of an sf5 polyatomic Primary Ion beam for analysis of organic thin films by secondary Ion mass spectrometry
Rapid Communications in Mass Spectrometry, 1998Co-Authors: Greg Gillen, Sonya RobersonAbstract:Organic vapor deposited thin films of pure biomolecules, polymer films and biomolecules dispersed in gelatin and biological tissue have been analyzed in a magnetic sector secondary Ion mass spectrometer using an SF5+ Primary Ion beam at keV impact energies. In comparison to Ar+ bombardment under identical conditIons, bombardment with SF5+ gives a 10 to 50 fold enhancement in the secondary Ion yields for characteristic molecular Ions. The SF5+ Primary Ion beam can be focussed to a small spot allowing molecular Ion images to be obtained at micrometer spatial resolutIon with enhanced sensitivity. More importantly, the decay in molecular Ion signal as a functIon of Primary Ion dose commonly observed in SIMS using monoatomic Primary Ions is either eliminated or greatly reduced, allowing molecular depth profiles to be obtained of organic thin films. By continuing to sample intact molecules as sputtering proceeds into the sample, the total number of detected characteristic secondary Ions is increased by as much as a factor of ∼700 for SF5+ bombardment as compared to Ar+ bombardment under identical analytical conditIons. This effect is thought to be a result of the high erosIon rate and the low penetratIon depth inherent in the use of a polyatomic Primary projectile. © 1998 John Wiley & Sons, Ltd. This paper was produced under the auspices of the US Government and it is therefore not subject to copyright in the US.
A Benninghoven - One of the best experts on this subject based on the ideXlab platform.
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ApplicatIon of atomic and molecular Primary Ions for TOF–SIMS analysis of additive containing polymer surfaces
Applied Surface Science, 2001Co-Authors: D Stapel, A BenninghovenAbstract:Abstract The influence of Primary Ion mass and compositIon on secondary Ion emissIon of the additive Irganox 1010 ( m =1176 u) in polyethylene was investigated. O + , Ar + , Xe + , O 2 + , CO 2 + , SF 5 + , C 7 H 7 + , C 10 H 8 + , C 6 F 6 + , and C 10 F 8 + with a total energy of 11 keV were used as Primary Ions under static secondary Ion mass spectrometry (SIMS) conditIons. Positive and negative molecular secondary Ions characterizing the additive were determined and their yields were evaluated. For all characteristic secondary Ions we found a strong yield enhancement with increasing mass for atomic Primary Ions and increasing number of constituents for molecular Primary Ions. This yield enhancement is saturated once the molecular Primary Ion is made of more than six heavy atoms. In additIon this yield increase depends on the mass and structure of the considered secondary Ion. We did not find any evidence for an influence of the chemical compositIon of the applied molecular Primary Ions on the secondary Ion emissIon when static SIMS conditIons were met. The improved imaging capabilities of molecular Primary Ions was demonstrated by comparing focused Ar + and SF 5 + Primary Ion beams when mapping characteristic secondary Ion emissIon from a structured additive containing polypropylene surface.
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Secondary Ion emissIon from polymethacrylate LB-layers under 0.5–11 keV atomic and molecular Primary Ion bombardment
Applied Surface Science, 2000Co-Authors: D Stapel, M Thiemann, A BenninghovenAbstract:Abstract Secondary Ion yields Y (X i q ) increase considerably when changing from atomic to molecular Primary Ions, whereas the parallel increase in the corresponding damage cross sectIons σ (X i q ) is much smaller. This results in a net increase of Ion formatIon efficiencies E (X i q )= Y / σ . For a more detailed understanding of the complex sputtering and Ion formatIon processes, in particular for molecular Primary Ion bombardment, the secondary Ion emissIon of well-defined polymethacrylate LB mono- and multilayers on Ag was investigated. For characteristic secondary Ions X i q emitted from these overlayers Y (X i q ) and σ (X i q ) for 11 keV Ne + , Ar + , Xe + , O 2 + , SF 5 + , C 7 H 7 + , C 10 H 8 + , C 6 F 6 + and C 10 F 8 + bombardment were determined and compared. The influence of Primary Ion energy was investigated in the energy range between 0.5 and 10 keV for Xe + and SF 5 + bombardment. For multilayers we found yield increases up to nearly a factor of 1000, when changing from Ne + to SF 5 + bombardment. We found a more pronounced yield and efficiency enhancement for multi than for monolayer coverages, a saturatIon of Y, σ and E enhancement for Primary Ions made of more than 6 heavy constituents at constant Primary Ion energy, no chemical effect on the secondary Ion yields under static SIMS conditIons (SF 5 + / C 7 H 7 + e.g.), and a pronounced decrease in secondary Ion yields and secondary Ion formatIon efficiencies for SF 5 + Primary Ions with impact energies below 2 keV.
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secondary Ion emissIon from polymethacrylate lb layers under 0 5 11 kev atomic and molecular Primary Ion bombardment
Applied Surface Science, 2000Co-Authors: D Stapel, M Thiemann, A BenninghovenAbstract:Abstract Secondary Ion yields Y (X i q ) increase considerably when changing from atomic to molecular Primary Ions, whereas the parallel increase in the corresponding damage cross sectIons σ (X i q ) is much smaller. This results in a net increase of Ion formatIon efficiencies E (X i q )= Y / σ . For a more detailed understanding of the complex sputtering and Ion formatIon processes, in particular for molecular Primary Ion bombardment, the secondary Ion emissIon of well-defined polymethacrylate LB mono- and multilayers on Ag was investigated. For characteristic secondary Ions X i q emitted from these overlayers Y (X i q ) and σ (X i q ) for 11 keV Ne + , Ar + , Xe + , O 2 + , SF 5 + , C 7 H 7 + , C 10 H 8 + , C 6 F 6 + and C 10 F 8 + bombardment were determined and compared. The influence of Primary Ion energy was investigated in the energy range between 0.5 and 10 keV for Xe + and SF 5 + bombardment. For multilayers we found yield increases up to nearly a factor of 1000, when changing from Ne + to SF 5 + bombardment. We found a more pronounced yield and efficiency enhancement for multi than for monolayer coverages, a saturatIon of Y, σ and E enhancement for Primary Ions made of more than 6 heavy constituents at constant Primary Ion energy, no chemical effect on the secondary Ion yields under static SIMS conditIons (SF 5 + / C 7 H 7 + e.g.), and a pronounced decrease in secondary Ion yields and secondary Ion formatIon efficiencies for SF 5 + Primary Ions with impact energies below 2 keV.
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secondary Ion emissIon from arachidic acid lb layers under ar xe ga and sf5 Primary Ion bombardment
Applied Surface Science, 1999Co-Authors: D Stapel, O Brox, A BenninghovenAbstract:Abstract The influence of Primary Ion energy, mass and compositIon on sputtering and secondary Ion emissIon of arachidic acid Langmuir–Blodgett mono- and multilayers, deposited on gold substrates, has been investigated. Ga+, Ar+, 129 Xe + and SF5+ in the energy range 5–25 keV were used as Primary Ions. Yields Y, damage cross-sectIons σ, and Ion formatIon efficiencies E have been determined for selected secondary Ions, characterizing the molecular overlayer, the overlayer substrate interface and the substrate. We found a strong influence of layer thickness and of Primary Ion energy, mass and compositIon on Y, σ and E. InformatIon depth increases with increasing Ion energy and decreasing mass of Primary Ions, being higher for SF5+ than for Xe+. Y, σ and E increase with increasing Primary Ion mass. They are considerably higher for a molecular (SF5+) than for atomic Ions of comparable mass ( 129 Xe + ). The experimental results supply informatIon on the extensIon of impact cascades, generated in different substrate materials by different Primary Ion species and different energies. They demonstrate that in analytical SIMS applicatIon informatIon depths can be minimized and yields and Ion formatIon efficiencies can be maximized by the use of molecular Primary Ions.
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Secondary Ion emissIon from arachidic acid LB-layers under Ar+, Xe+, Ga+ and SF5+ Primary Ion bombardment
Applied Surface Science, 1999Co-Authors: D Stapel, O Brox, A BenninghovenAbstract:Abstract The influence of Primary Ion energy, mass and compositIon on sputtering and secondary Ion emissIon of arachidic acid Langmuir–Blodgett mono- and multilayers, deposited on gold substrates, has been investigated. Ga+, Ar+, 129 Xe + and SF5+ in the energy range 5–25 keV were used as Primary Ions. Yields Y, damage cross-sectIons σ, and Ion formatIon efficiencies E have been determined for selected secondary Ions, characterizing the molecular overlayer, the overlayer substrate interface and the substrate. We found a strong influence of layer thickness and of Primary Ion energy, mass and compositIon on Y, σ and E. InformatIon depth increases with increasing Ion energy and decreasing mass of Primary Ions, being higher for SF5+ than for Xe+. Y, σ and E increase with increasing Primary Ion mass. They are considerably higher for a molecular (SF5+) than for atomic Ions of comparable mass ( 129 Xe + ). The experimental results supply informatIon on the extensIon of impact cascades, generated in different substrate materials by different Primary Ion species and different energies. They demonstrate that in analytical SIMS applicatIon informatIon depths can be minimized and yields and Ion formatIon efficiencies can be maximized by the use of molecular Primary Ions.
Nicholas P. Lockyer - One of the best experts on this subject based on the ideXlab platform.
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prospect of increasing secondary Ion yields in tof sims using water cluster Primary Ion beams
Surface and Interface Analysis, 2014Co-Authors: Sadia Sheraz, Nicholas P. Lockyer, John S. Fletcher, Andrew M Barber, Berrueta I Razo, John C. VickermanAbstract:Low IonizatIon yields in time of flight secondary Ion mass spectrometry (ToF-SIMS) particularly from single cells and tissues are proving to be a significant limitatIon in allowing this technique to reach its full potential. A number of approaches including embedding the sample in water or spraying water above sample surface has shown great prospective for increasing the IonizatIon yield by a factor of 10 to 100 through proton mediated' reactIon. Based on this hypothesis, a water cluster Primary Ion source has been developed in collaboratIon with Ionoptika Ltd to generate giant water cluster Ions (H2O)(n)(+) (n=1-10000) using a similar supersonic jet expansIon methodology as for argon cluster beams. The Ion yields of arginine, cholesterol, angiotensin II and a lipid mix have been measured under static and high Ion dose conditIons using (H2O)(5000)(+), (H2O)(3000)(+), Ar-3000(+) and C-60(+) Primary Ion beams at 20keV. An enhancement in yields up to a factor of around 4 is observed under water cluster impact, in comparison with C-60(+) at 1x10(11)Ions/cm(2) Ion dose, whereas this increases by around 10-50 times at high Ion dose conditIons. Copyright (c) 2014 John Wiley & Sons, Ltd.
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comparison of c60 and gcib Primary Ion beams for the analysis of cancer cells and tumour sectIons
Surface and Interface Analysis, 2013Co-Authors: John S. Fletcher, Nicholas P. Lockyer, Andrew M Barber, Sadia Rabbani, John C. VickermanAbstract:We have implemented a gas cluster Ion beam (GCIB) system developed by Ionoptika Ltd (Southampton, UK) with sufficient control to allow us to exploit the unique capabilities of our J105 instrument for imaging and depth profiling. The J105 allows us to use the GCIB as continuous Primary Ion beam, thereby overcoming the issues associated with pulsing these slow moving, mixed species beams. We have performed a direct comparison with C60 Ions on the same samples in the same instrument. The GCIB beams are more difficult to focus than the C60+ Ion beam, making single-cell imaging difficult, although spot sizes of 15?20?�m are readily obtainable for Ar1000 and Ar2000, providing good resolutIon for larger area imaging on tissue sectIon/biopsy samples. In this paper, we present results from the assessment of these new beams as Primary Ions for the analysis of ?real?, complex biological systems. Initial spectra and those following increased Primary Ion bombardment were compared for in vitro cultured cells deposited on silicon and cryo-sectIoned tumour samples originating in vivo. Ar1000+ and Ar2000+ showed increased persistence of the signals from intact molecular Ions of phospholipids and a reductIon in the accumulatIon of chemical background noise compared with C60+ analysis.
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InvestigatIon of molecular weight effects of polystyrene in ToF-SIMS using C60+ and Au+ Primary Ion beams
Applied Surface Science, 2008Co-Authors: Alan M. Piwowar, Nicholas P. Lockyer, John C. VickermanAbstract:Abstract In secondary Ion mass spectrometry, polyatomic Primary Ion sources are known to enhance yields from many surfaces including polymers. In order to understand the fundamental causes for these increases, the enhancement as a functIon of material type and molecular weight needs to be delineated. In this article, we report results from a systematic investigatIon of polymeric films of polystyrene (PS) with varying molecular weights to examine the influence of the Primary Ion beam on the secondary Ion yields in time of flight secondary Ion mass spectrometry (ToF-SIMS). The masses of the polymers investigated ranged from 1000 to 20,000 Da, or from about n = 10 to 200 where n indicates the number of polymeric units in a polymer chain. The polymers had a narrow molecular weight range (PDI + and C 60 + Primary Ion beams. The analysis with the two beams provided a useful comparison between atomic and polyatomic Primary Ion sources. InformatIon gathered from this study provides insight into the role of molecular weight on the observed yield enhancement from polyatomic Ion sources.
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depth profiling brain tissue sectIons with a 40 kev c60 Primary Ion beam
Analytical Chemistry, 2008Co-Authors: Emrys A Jones, Nicholas P. Lockyer, John C. VickermanAbstract:In this paper, the effect of prolonged C60+ Primary Ion bombardment on the chemical informatIon available from a sectIon of rat brain is discussed. Initial attempts demonstrate the rapid loss of molecular signal from the bombarded area with both C60+ and Au+ used as a monatomic comparison. However, the nature of this signal disappearance is shown to be different. Analysis of the C60+ data indicates a correlatIon between signal loss and the appearance of sodium and potassium adducts of phosphate and protein fragments; this is supported by model systems. By using an ammonium formate wash to reduce the salt levels within the tissue this effect is removed, allowing the chemistry of the tissue sectIon to be better probed. Results collected from multiple sectIons suggest that at room temperature under vacuum conditIons there is a migratIon of lipids to the surface of the tissue. Three-dimensIonal (3D) imaging is used to demonstrate that once these lipids are removed other species, such as proteins, are uncovere...
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Mass spectral analysis and imaging of tissue by ToF-SIMS—The role of buckminsterfullerene, C60+, Primary Ions
International Journal of Mass Spectrometry, 2007Co-Authors: Emrys A Jones, Nicholas P. Lockyer, John C. VickermanAbstract:Abstract Recent developments in desorptIon/IonisatIon mass spectrometry techniques have made their applicatIon to biological analysis a realistic and successful propositIon. Developments in Primary Ion source technology, mainly through the advent of polyatomic Ion beams, have meant that the technique of secondary Ion mass spectrometry (SIMS) can now access the depths of informatIon required to allow biological imaging to be a viable optIon. Here the role of the Primary Ion C 60 + is assessed with regard to molecular imaging of lipids and pharmaceuticals within tissue sectIons. High secondary Ion yields and low surface damage accumulatIon are demonstrated on both model and real biological samples, indicating the high secondary Ion efficiency afforded to the analyst by this Primary Ion when compared to other cluster Ion beams used in imaging. The newly developed 40 keV C 60 + Ion source allows the beam to be focused such that high resolutIon imaging is demonstrated on a tissue sample, and the greater yields allow the molecular signal from the drug raclopride to be imaged within tissue sectIon following in vivo dosing. The localisatIon shown for this drug alludes to issues regarding the chemical environment affecting the IonisatIon probability of the molecule; the importance of this effect is demonstrated with model systems and the possibility of using laser post-IonisatIon as a method for reducing this consequence of bio-sample complexity is demonstrated and discussed.
