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.

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氩簇离子溅射产率：硅的分子动力学模拟和估算总溅射产率的方程

近年来，氩气簇离子束源已广泛用于 X 射线光电子能谱 (XPS) 和二次离子质谱 (SIMS) 仪器，但文献中关于溅射产量的参考数据很少。为了校准 XPS 或 SIMS 深度剖面的深度标度，需要总溅射产量参考数据。我们之前发表了一个半经验“阈值”方程，用于根据簇的每原子能量和材料的有效单原子溅射阈值来估计簇总溅射产量。这已被证明与对大约一千个原子簇的范围或有机和无机材料的溅射产率测量非常吻合。在这里，我们使用分子动力学 (MD) 方法来探索更广泛的能量和簇大小，这比通过实验达到高精度要容易做到。我们使用高性能计算机 (HPC) 系统上的“大规模原子/分子大规模并行模拟器” (LAMMPS) 并行 MD 代码。我们对硅（100）表面作为原型无机基板的单独碰撞进行了 1150 次模拟，簇大小在 30 到 3000 个氩原子之间，每个原子的能量在 5 到 40 eV 范围内。这对应于 SIMS 和 XPS 中实验集群深度剖析的最重要机制。我们的 MD 结果显示依赖于簇大小以及每个原子的能量。使用 Paruch 等人先前建议的指数，我们修改了先前发布的阈值模型方程以考虑到这一点。修改后的阈值方程非常适合我们所有的 MD 结果，建立在其成功拟合实验溅射产量测量的基础上。