Molecular dynamics investigations of surface damage produced by kiloelectronvolt self-bombardment of solids

Molecular dynamics computer simulations were employed to study damage produ ction mechanisms at solid surfaces during bombardment with kilo-electronvol t ions. Three separate mechanisms are identified: ballistic damage, viscous How and microexplosions. Ballistic damage is created by the direct knock-o n of atoms onto the surface as described within the binary collision approx imation. Viscous flow refers to local melting and the forced flow of liquid onto the surface, and microexplosions occur when the high pressures in cas cades lead to rupturing of the nearby surface. The relative importance of e ach mechanism depends on several parameters: atomic mass, melting temperatu re. atomic density, structure and atomic bonding of the target, and the mas s and energy of the projectile. The simulations were performed for Pt, Au, Cu, Ni and Ge self-atom bombardment. Cascades in the interior of the target s were also examined to provide a comparison for the surface events. In add ition several events of 4.5 keV Ne and Xe bombardment of Pt(lll) were simul ated for comparison with experimental studies of these same bombardments us ing scanning tunnelling microscopy.