ANALYSIS OF A PERFECT SPUTTER EXPERIMENT

A recent experiment by Wittmaack demonstrated that simultaneous sputte r profiling by ion scattering and secondary ion mass spectrometry of a two-component target yields information on the depth of origin of spu ttered atoms. We have studied the relation between the two signals and the depth of origin theoretically. The main features emerge from just considering stoichiometric mixing and sputtering, but even weakly pre ferential behaviour affects the difference between the two signals not iceably. The quantitative analysis hinges on material parameters chara cterizing the low-energy behaviour of collision cascades. We have dete rmined such parameters from a computer simulation code under condition s pertaining to Wittmaack's experiment. The sensitivity to details of the simulational model has been studied extensively. While the resulti ng sputter depth is only slightly greater than the one emerging from t he original analysis, the apparent scatter in the measured values is a sserted to be a systematic feature resulting from preferential sputter ing. (C) 1998 John Whey & Sons, Ltd.