DIFFUSION ON SIMPLE HETEROGENOUS SURFACES

In this work we use the well-known bivariate trap model with random to pography in order to study the effects of surface heterogeneities on s urface diffusion. Utilizing Monte Carlo simulations we characterize ho w the tracer, jump and chemical diffusion coefficients depend on tempe rature and concentration of deep traps, Theta. In order to calculate t he chemical diffusion coefficient we apply the fluctuation and the Kub o-Green methods. Both methods are in good agreement at large values of Theta only. The discrepancies are discussed and explained. The effect s of heterogeneities are largely pronounced at low total coverage and low temperatures, where most of the adatoms are trapped by the deep tr aps. At high coverages the mobility of adatoms adsorbed on shallow tra ps dominate the diffusion behavior.