Molecular dynamics simulation of sputtering from a cylindrical track: EAM versus pair potentials

Abstract

Molecular dynamics simulations implementing the thermal spike model for sputtering by energetic particle bombardment are performed for a gold target represented with a many-body embedded atom method (EAM) potential. A linear dependence of sputtering yield on the effective energy deposition is observed over a broad range of sufficiently high excitation energies, suggesting that the conclusions of earlier simulations performed with pair potentials have a general character and are not sensitive to the choice of interatomic potential. At the same time, significant differences in cluster ejection are observed between the simulations performed with EAM and pair potentials. Clusters constitute a much larger fraction of the total yield in the EAM simulations, which is related to the environmental dependence of the interatomic interaction in metals that is correctly reproduced by EAM potential. An apparent disagreement between the analytical thermal spike model and its implementation in MD simulations cannot be attributed to the choice of interatomic potential but reflects a difference in the ejection mechanisms. Thermally activated evaporation from the surface is assumed in the analytical thermal spike model, whereas prompt ejection from a relatively deep part of the excited region and fast non-diffusive cooling of the spike region takes place in MD simulations.