Molecular dynamics simulations of inelastic energy loss effects in sputtering II

Abstract

Previous molecular dynamics (MD) simulations of inelastic energy loss effects in sputtering, which have employed pair potentials and velocity-dependent losses [1,2], have attributed significant reductions in sputtering yield (up to 40%) to energy losses in atom-atom collisions. Similar simulations in which the average electron density is replaced by the local electron density as calculated from the embedded-atom method (EAM) and Thomas-Fermi local electron densities also yield significant inelastic energy losses in the collision cascade [A. Caro and M. Victoria, Phys. Rev. A 40 (1989) 2287]. Here we report results of EAM MD inelastic energy loss simulations for the Ar +-Cu system for bombarding energies from 1 keV to 5 keV using a model that includes velocity-dependent losses for collisions with valence electrons and instantaneous losses for collisions involving core electrons. With this model we find that losses attributable to collisions with valence electrons and atom-atom collisions involving core electrons produce negligible reductions in sputtering yield. The inclusion of instantaneous losses from ion-atom collisions, however, produces significant reductions in sputtering yield above a bombarding energy threshold of approximately 2 keV. The polar-angle distributions of atoms sputtered from the Cu(100) surface also are changed significantly by this inelastic loss model.