Electron work function decrease in SIMS analysis induced by neutral cesium deposition

Philipp, Patrick; Wirtz, Tom; Migeon, H.-N.; Scherrer, H.

doi:10.1016/j.ijms.2007.03.019

Cited by 25 publications

(15 citation statements)

References 39 publications

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“…In particular, the model predicts an exponential dependence on the sample work function. A change of this work function with varying cesium concentration could be measured by recording energy spectra, both for cesium ion bombardment and metallic cesium deposition coupled by simultaneous ion bombardment using different species . At the same time, the model predicts an exponential dependence on the normal component of the velocity that could not be observed in this experimental data and which suggests that local effects are important and need to be explored in order to understand ion formation.…”

Section: Introductionmentioning

confidence: 82%

Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

Philipp¹,

Barry²,

Wirtz³

2014

Surface & Interface Analysis

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In the present paper, we focus on the diffusion behaviour of cesium atoms implanted into silicon. This aspect has not been investigated directly up to now but is of utmost importance to understand the ionisation mechanisms in more detail. Density functional theory calculations combined with ab initio molecular dynamics simulations have been used to study the different aspects of cesium diffusion to the sample surface as a function of cesium concentration and sample temperature. In general, the solubility of cesium atoms in a silicon matrix is small, and the diffusion of the cesium atoms towards the surface is almost immediate, depending on how and where the cesium atom is incorporated in the silicon lattice. Depending on the defects introduced into the Si substrate, the diffusion could be largely reduced or cannot be observed during the few picosecond time range that can be explored by ab initio molecular dynamics simulations.

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Section: Introductionmentioning

confidence: 82%

Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

Philipp¹,

Barry²,

Wirtz³

2014

Surface & Interface Analysis

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“…Flooding of neutral caesium on the sample surface increases significantly the useful yield of secondary ions [26]–[28]. The use of caesium flooding therefore increases the capacity of SIMS to detect single enriched molecules even if these molecules are small.…”

Section: Discussionmentioning

confidence: 99%

50nm-Scale Localization of Single Unmodified, Isotopically Enriched, Proteins in Cells

et al. 2013

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Imaging single proteins within cells is challenging if the possibility of artefacts due to tagging or to recognition by antibodies is to be avoided. It is generally believed that the biological properties of proteins remain unaltered when 14N isotopes are replaced with 15N. 15N-enriched proteins can be localised by dynamic Secondary Ion Mass Spectrometry (D-SIMS). We describe here a novel imaging analysis algorithm to detect a few 15N-enriched proteins - and even a single protein - within a cell using D-SIMS. The algorithm distinguishes statistically between a low local increase in 15N isotopic fraction due to an enriched protein and a stochastic increase due to the background. To determine the number of enriched proteins responsible for the increase in the isotopic fraction, we use sequential D-SIMS images in which we compare the measured isotopic fractions to those expected if 1, 2 or more enriched proteins are present. The number of enriched proteins is the one that gives the best fit between the measured and the expected values. We used our method to localise 15N-enriched thymine DNA glycosylase (TDG) and retinoid X receptor α (RXRα) proteins delivered to COS-7 cells. We show that both a single TDG and a single RXRα can be detected. After 4 h incubation, both proteins were found mainly in the nucleus; RXRα as a monomer or dimer and TDG only as a monomer. After 7 h, RXRα was found in the nucleus as a monomer, dimer or tetramer, whilst TDG was no longer in the nucleus and instead formed clusters in the cytoplasm. After 24 h, RXRα formed clusters in the cytoplasm, and TDG was no longer detectable. In conclusion, single unmodified proteins in cells can be counted and localised with 50 nm resolution by combining D-SIMS with our method of analysis.

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“…Additionally, MD simulations are able to provide information which is complementary to the experimental results obtained in our group on the enhancement of secondary ion emission under Cs + 0168-583X/$ -see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2010.12.059 bombardment combined with simultaneous Cs 0 deposition [23][24][25][26] or the fragmentation of organic molecules [27,28]. For the MD simulations, we will use the force field developed by Kieffer et al which has already been applied successfully, for example, to the study of phase transitions in cristobalite [1,[29][30][31] and B 2 O 3 [2,32].…”

Section: Introductionmentioning

confidence: 99%

Low-energy oxygen bombardment of silicon by MD simulations making use of a reactive force field

Philipp¹,

Briquet²,

Wirtz³

et al. 2011

Nuclear Instruments and Methods in Physics Research Section B:

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Electron work function decrease in SIMS analysis induced by neutral cesium deposition

Cited by 25 publications

References 39 publications

Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

50nm-Scale Localization of Single Unmodified, Isotopically Enriched, Proteins in Cells

Low-energy oxygen bombardment of silicon by MD simulations making use of a reactive force field

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