Platelets and inorganic fullerenes on metal surfaces

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The properties of clusters of layered semiconductors like (MoS2)n deposited on metal surfaces are studied theoretically. The possible advantages of these materials compared to Si or GaAs are the lack of dangling bonds, surface states and surface reconstruction. The clusters may be stochiometrically saturated and chemically inert allowing use at ambient conditions. Electric transport will not be influenced by a shell of ligands. The geometric and electronic structure of "free" (MeX2)n clusters will first be studied. The main questions are: Do small fullerene-like structures exist or form the clusters planar platelets? Do magic numbers exist? What is the size dependence of the HOMO-LUMO gap for both geometries? Then the "soft landing" of mass-selected cluster ions on metal surfaces will be simulated and the cluster-surface and cluster-cluster interactions are studied. Platelets form metal-semiconductor nanocontacts with an adjustable and well-defined contact area. Charge transfer and barrier heights will be studied. The transport properties of such nano-contacts can be investigated using Greens function techniques. The theoretical investigations will be accompanied by corresponding experiments.