MC COMPUTER-SIMULATIONS OF THE PREFERENTIAL SPUTTERING OF SI-GE ALLOYS

The ability of MC codes to predict the preferential sputtering of comp ound targets is investigated. The DYNA and TRIDYN codes are run for 3 keV Ar+ bombardment of a SiGe binary target. The preferential sputteri ng of Si and Ge, the depth dependence of the sputter cross-section and the relocation operators are calculated. Difficulties arise in trying to reproduce the experimentally reported absence of preferentiality i n the sputtered flux. The models used for the surface barriers, as wel l as the barrier heights, influences strongly the predicted quantities . A spherical surface barrier predicts much closer to stoichiometric f luxes than a planar barrier. Different codes give different collisiona l diffusivities for the target species in the bulk. The need for furth er experiments is stressed if some guidance in the choice of input par ameters in the codes is desired.