MOLECULAR-DYNAMICS STUDY OF ION IMPACT PHENOMENA

We use molecular dynamics to study the phenomena occurring after ion impact. The simulations are two dimensional, the target contains approximately 5000 nickel atoms and the impacting ions have an energy in the range 100-1000keV. The phenomena observed include focused collision sequences, sputtering and a thermal spike. The focused collision sequences transport much of the ion's energy away from the impact site and significantly reduce the size of the thermal spike. In an analogous process to Cerenkov radiation, it is shown that the focused collision sequences travel at supersonic speeds and lose energy via the production of sound waves. When an electron-phonon interaction is included the phenomena are slightly damped, but their essential features are unchanged.