DEPOSITION AND DIFFUSION OF SIZE-SELECTED (AG-400(+)) CLUSTERS ON A STEPPED GRAPHITE SURFACE

We have investigated the deposition (at 500 eV) and subsequent diffusi on of Ag-400 clusters on a stepped graphite surface by a combination o f scanning electron microscopy experiments and computer simulations (m olecular dynamics and Monte Carlo methods). We find that the shape of the clusters is only partially deformed by the impact with the surface , moreover the clusters do not create surface defects upon landing, an d so are able to diffuse freely over the surface. Many clusters are fo und to become trapped at surface steps, where their mobility is reduce d by the higher binding energy. Exploring the 1-D diffusion of cluster s along the steps reveals the low mobility for larger islands, as well as the importance of defects on the step (for example kinks), which t rap the mobile clusters.