Submonolayer epitaxy with impurities: Kinetic Monte Carlo simulations and rate-equation analysis

The effect of impurities on epitaxial growth in the submonolayer regime is studied using kinetic Monte Carlo simulations of a two-species solid-on-sol id growth model. Both species are mobile, and attractive interactions among adatoms and between adatoms and impurities are incorporated. Impurities ca n be codepositod with the growing material or predeposited prior to growth. The activated exchange of impurities and adatoms is identified as the key kinetic process in the formation of a growth morphology in which the impuri ties decorate the island edges. The dependence of the island density on flu x and coverage is studied in detail. The impurities strongly increase the i sland density without appreciably changing its power-law dependence on flux , apart from a saturation of the flux dependence at high fluxes and low cov erages. A simple analytic theory taking into account only the dependence of the adatom diffusion constant on impurity coverage is shown to provide a s emiquantitative agreement with many features observed in the simulations.