Scanning tunneling microscopy results on the Brownian motion of two-dimensional vacancy islands on Ag(110) had been presented. While the detachment of adatoms from the island and their diffusion on the terrace was permitted between 180 and 220K, the peripheral 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 simulations. Here, the results were elaborated and, in particular, a detailed derivation was presented of the equation that related the diffusivity of an anisotropic island to its size. Further details and results on the kinetic Monte Carlo simulations were presented. The results shed light on the issue of attempt frequencies for surface diffusion. In this specific case of an anisotropic surface, pre-factor ratios were obtained for the exchange and hopping mechanisms.

Motion of Vacancy Islands on an Anisotropic Surface: Theory and Kinetic Monte Carlo Simulations. K.Morgenstern, E.Lægsgaard, F.Besenbacher: Physical Review B - Condensed Matter and Materials Physics, 2002, 66[11], 115408