CROSSOVER FROM ANISOTROPIC-TO-ISOTROPIC DIFFUSION-MEDIATED ISLAND GROWTH ON SURFACES

We consider processes involving irreversible nucleation and growth of two-dimensional islands during submonolayer deposition, mediated by anisotropic diffusion. If h(parallel-to) and h(perpendicular-to) are bop rates in orthogonal directions, we set epsilon = h(perpendicular-to)/h(parallel-to) much less than 1 and examine the decrease of the island density with increasing h(parallel-to). We find a crossover from scaling characteristic of anistropic diffusion to that characteristic of isotropic diffusion at h(parallel-to) approximately r2tepsilon-2, where r is the deposition rate and t is time. For Si-on-Si(001) deposition with r = 1/600 MLs-1, this crossover should occur around 450 K.