THE EFFECTS OF MOBILITY COALESCENCE ON THE EVOLUTION OF SURFACE ATOMIC CLUSTERS

A numerical study of the effects of cluster mobility on the clustering kinetics during deposition of atoms on a substrate surface is presented. The pertinent rate equations are solved by a two-group approach of using discrete equations for small clusters and moment equations for large ones. The study is restricted to systems where the critical nucleus is a monomer (e.g. Ag/NaCl at low temperatures). It is shown that if small clusters are fairly mobile their population will quickly be depleted, resulting in an overall reduction of the total cluster density. Cluster mobility coalescence reduces the concentration and increases the growth of surface atomic clusters. The effects of cluster mobility coalescence are analyzed in terms of two mobility models: (1) where only small clusters, here up to dimers, are mobile, and (2) where all clusters are mobile with a diffusion coefficient given by size power law. Results of the analysis are presented for the total density of surface atomic clusters and their size distributions.