Diffusion and aggregation of size-selected silver clusters on a graphite surface

We have investigated the early stages of film growth via deposition of size-selected silver clusters on graphite, as a function of incident cluster size. For all sizes from 50 to 250 atoms per cluster, the deposited clusters are mobile and coalesce into three-dimensional particles with a ''universal'' diameter of approximate to 14 nm, possibly a consequence of lattice strain between the silver and graphite. The 14 nm particles are found mainly in small aggregates, indicating that they themselves are to some degree mobile. We have also found evidence that the particle mobility is influenced by the cluster impact angle. (C) 1996 American Institute of Physics.