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Argon cluster-ion sputter yield: Molecular dynamics simulations on silicon and equation for estimating total sputter yield

Lookup NU author(s): Professor Peter Cumpson

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Abstract

© 2021 John Wiley & Sons, Ltd.Argon Gas Cluster-Ion Beam sources have become widely-used on X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) instruments in recent years, but there is little reference data on sputter yields in the literature as yet. Total sputter yield reference data is needed in order to calibrate the depth scale, of XPS or SIMS depth profiles. We previously published a semi-empirical ‘Threshold’ equation for estimating cluster total sputter yield from the energy-per-atom of the cluster and the effective monatomic sputter threshold of the material. This has been shown to agree extremely well with sputter yield measurements on a range or organic and inorganic materials for clusters of around a thousand atoms. Here we use the molecular dynamics (MD) approach to explore a wider range of energy and cluster size than is easy to do experimentally to high precision. We performed MD simulations using the ‘Large-scale Atomic/Molecular Massively Parallel Simulator’ (LAMMPS) parallel MD code on high-performance computer (HPC) systems. We performed 1150 simulations of individual collisions with a silicon (100) surface as an archetypal inorganic substrate, for cluster sizes between 30 and 3000 argon atoms and energies in the range 5 to 40 eV per atom. This corresponds to the most important regime for experimental cluster depth-profiling in SIMS and XPS. Our MD results show a dependence on cluster size as well as energy-per-atom. Using the exponent previously suggested by Paruch et al., we modified the Threshold model equation published previously to take this into account. The modified Threshold equation fits all our MD results extremely well, building on its success in fitting experimental sputter yield measurements. This work is submitted to the volume dedicated to Dr. Martin P Seah, MBE, who was a great influence on the early career of one of the authors (PJC) and who himself made many valuable contributions to the literature on sputtering as it relates to surface and interface analysis.


Publication metadata

Author(s): Cumpson PJ, Jaskiewicz M, Kim WK

Publication type: Article

Publication status: Published

Journal: Surface and Interface Analysis

Year: 2022

Volume: 54

Issue: 4

Pages: 341-348

Print publication date: 11/03/2022

Online publication date: 27/07/2021

Acceptance date: 15/07/2021

ISSN (print): 0142-2421

ISSN (electronic): 1096-9918

Publisher: John Wiley and Sons Ltd

URL: https://doi.org/10.1002/sia.6996

DOI: 10.1002/sia.6996


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Funding

Funder referenceFunder name
EP/K022679/1EPSRC
EP/K022679/1EPSRC
EP/K022679/1EPSRC

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