A study was made of the first stages of growth of thin films produced by low-energy cluster beam deposition on graphite. The experiments were analyzed within the framework of new models including three physical ingredients, which were the deposition, diffusion and aggregation of the clusters. The comparison between computer simulations of the model and the experimental structures revealed that only the incident clusters diffuse on the graphite, the clusters stick irreversibly upon contact, and permitted quantification of the diffusion of clusters on graphite. Two kinds of metallic cluster films were studied: thin films produced by deposition of antimony clusters (containing 2300 and 250 atoms) and others by deposition of gold clusters (containing about 250 atoms). In both cases, it was found that the clusters, in spite of their large size, diffuse very rapidly on the surface. The different microscopic diffusion mechanisms proposed in the literature were investigated, but none was compatible with the experimental results. Finally, a collective mechanism was suggested in which the cluster rotated on the surface as a rigid entity.

Diffusion and Aggregation of Large Antimony and Gold Clusters Deposited on Graphite. Bardotti, L., Jensen, P., Hoareau, A., Treilleux, M., Cabaud, B., Perez, A., Aires, F.C.S.: Surface Science, 1996, 367[3], 276-92