Surface damage during keV ion irradiation: results of computer simulations

MD simulations have been employed to investigate damage processes near surfaces during keV bombardment of metal targets. For self-ion implantation of Au, Cu, and Pt in the range of 5-20 keV, we have found that the proximity of the surface leads to significantly more damage and atomic mixing in comparison to recoil events occurring in the crystal interior. In some cases, large craters are formed in a micro-explosive event, while in others a convective flow of atoms to the surface creates adatoms and leaves dislocations behind. Both the amount damage created in the surface and its morphology depend sensitively on the details of the energy deposition along individual ion trajectories. The results of these simulations will be summarized and compared to recent scanning tunneling microscopy studies of individual ion impacts in Pt and Ge.