Pinning of size-selected Ag clusters on graphite surfaces

We have explored the deposition of size-selected Ag-N(+) clusters (N=50-200 ) onto the graphite surface (at room temperature) over the impact energy ra nge of 250-2500 eV, via a combination of scanning tunneling microscopy expe riments and molecular dynamics simulations. We show that the clusters are p inned to the surface when the impact energy exceeds a critical value, which is proportional to the cluster size, N, via the formation of a point defec t at the impact site. This prevents lateral diffusion of the clusters even at room temperature. (C) 2000 American Institute of Physics. [S0021-9606(00 )71742-9].