Cluster diffusion by evaporation-condensation

Cluster diffusion on surfaces by two-dimensional evaporation-condensation is studied taking into account both temporal and spatial correlations between evaporations and condensations. It is shown that the effect of these correlations increases with time and with the diffusivity of the evaporated adatoms. The time dependence of cluster diffusion is nonlinear and the diffusion constant scales with cluster radius as $R^{-1\mathrm{}}$ for very short times, and as $R^{-2\mathrm{}}$ for the (longer) times experimentally relevant. The effect of the perimeter energy is also shown to be nonnegligible, further changing the size dependence of cluster diffusivity.