Motion of vacancy islands on an anisotropic surface:: Theory and kinetic Monte Carlo simulations -: art. no. 115408

Recently, scanning tunneling microscopy results on the Brownian motion of two-dimensional vacancy islands on Ag(110) were presented. While the detachment of adatoms from the island and their diffusion on the terrace was permitted in the temperature range between 180 K and 220 K, the periphery diffusion of single adatoms was prohibited. The Brownian motion of the islands was found to follow a simple scaling law with terrace diffusion being the rate-limiting process. The scaling of the experimental results was confirmed by kinetic Monte Carlo (kMC) simulations. Here, we elaborate on the results and especially present a detailed derivation of the equation that relates the diffusivity of an anisotropic island to its size. Further details and results on the kMC simulations will be presented as well. Our results shed light on the recently discussed issue of attempt frequencies for surface diffusion. In this specific case of an anisotropic surface, we obtain prefactor ratios for exchange and hopping mechanisms.