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 experimentally. 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 hampered by a shell of ligands. The geometric and electronic structure of (MeX2)n clusters will first be studied in the gas phase. The main questions are: Do small fullerene-like structures exist or do the clusters form planar platelets? Do magic numbers exist? What is the size dependence of the HOMO-LUMO gap for both geometries? Then the mass-selected cluster ions are softlanded on metal surfaces and the cluster-surface and cluster-cluster interactions are studied with XPS, UPS, HREELS and STM. Platelets form metal-semiconductor nanocontacts with an adjustable and well-defined contact area. Charge transfer and Schottky barrier heights can be studied using XPS and UPS. The transport properties of such nanocontacts can possibly be measured using STM. The experimental work is accompanied by corresponding calculations.