Analysis of a 'perfect' sputter experiment

A recent experiment by Wittmaack demonstrated that simultaneous sputter profiling by ion scattering and secondary ion mass spectrometry of a two-component target yields information on the depth of origin of sputtered 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 preferential behaviour affects the difference between the two signals noticeably. The quantitative analysis hinges on material parameters characterizing the low-energy behaviour of collision cascades. We have determined such parameters from a computer simulation code under conditions pertaining to Wittmaack's experiment. The sensitivity to details of the simulational model has been studied extensively. While the resulting sputter depth is only slightly greater than the one emerging from the original analysis, the apparent scatter in the measured values is asserted to be a systematic feature resulting from preferential sputtering. (C) 1998 John Whey & Sons, Ltd.