MOLECULAR-DYNAMICS SIMULATIONS OF INNER-SHELL ELECTRONIC-ENERGY LOSSES IN CLUSTER-SURFACE COLLISIONS

Previous molecular dynamics simulations have predicted that in energet ic cluster-surface collisions atoms can be core-excited leading to Aug er transitions outside the target [5]. However, in these previous simu lations the inelastic energy losses accompanying core-excitations were not taken into account. In our simulations a simple critical distance of approach to detect inner-shell excitations is used. Energy is remo ved from atoms in a single time step by moving the atoms apart from ea ch other, taking away potential energy. Molecular dynamics simulations are carried out for 63-atom Al clusters and composite Al38Au25 cluste rs incident on Au(100) targets and Au(111) targets. Each event is simu lated with and without inelastic losses. Incident cluster energies ran ged from 30 to 100 keV. Our results indicate a threshold for significa nt inelastic loss effects at approximately 70 keV/cluster, i.e., about 1 keV/atom. Above the threshold energy region, sputtered atom and eje cted-cluster atom energy distributions were affected substantially.