Interaction of slow (100 eV/atom) copper clusters with thin gold films: reflection, transmission, and sputtering at normal and oblique incidence

Abstract

The interaction of a Cu13 cluster with a thin Au crystal has been studied by molecular dynamics simulation as a function of the angle of incidence. Initial orientations of the cluster and the target were randomized. Trajectories are shown for two representative events. The average number, energy spectrum, and angular distribution of reflected and transmitted cluster atoms are computed as well as the corresponding quantities for target atoms sputtered from the upstream or downstream surface. Surprisingly strong clearing-the-way effects account for a significant decrease of reflection coefficients and correspondingly enhanced transmission in comparison with atomic bombardment. Also sputter yields are affected significantly. Collisions between cluster atoms account for a broadening of the energy spectrum of transmitted and reflected cluster particles, in particular so for oblique incidence. Multihit processes account for a pronounced high-energy tail in the spectrum of sputtered atoms. Due to computational limitations, the simulations are incomplete from the point of view of sputtering. Nevertheless, evidence is presented that suggests that the sputter yield per cluster atom may be smaller than the one for atomic bombardment in certain situations.