Diffusion and evaporation kinetics of large islands and vacancies on surfaces

Abstract

The diffusion and evaporation kinetics of two-dimensional islands and vacancy islands on surfaces are studied over a wide range of island sizes. These kinetic processes are central in surface phenomena such as thin film coarsening, island aggregation, and coalescence on surfaces. Several studies have utilized scaling theories to infer the atomic level mechanisms responsible for the kinetics of island diffusion and evaporation. Using a dynamic Monte Carlo model, we study a model system where two-dimensional islands diffuse via an evaporation-condensation mechanism on a face-centered-cubic (100) surface. We examine the diffusion (evaporation) kinetics for isolated islands as a function of the island’s size in the range of 100 to 100 000 atoms. The diffusion coefficient and the island evaporation rate exhibit a power law scaling of the island size. We find crossover behavior in the scaling exponents between the regime of intermediate sized islands (between 100 and 1000 atoms) and large islands (greater than 1000 atoms). At high coverages, we also examine these quantities for vacancy islands. We find that intermediate island sizes exhibit unusual scaling behavior.