Surface science studies of diamond and MoS2/MoGe films

Abstract

In this thesis, various surface characterization techniques were applied to study two surface phenomena: the organic functionalization of reconstructed diamond surface, and the direct deposition of molybdenum sulfide and germanide materials using a single source precursor.Clean diamond surfaces can be efficiently functionalized by the covalent attachment of multi-functional organic molecules. The diamond (100) surface is thus transformed from a condition of positive electron affinity to negative electron affinity. The chemisorption of aromatics on the diamond (111) surface is influenced largely by the end groups of the benzene ring. Covalent bonding of C60 on the bare C(100) surface will passivate the surface against oxidation and hydrogenation, and produce an interface robust enough to exhibit characteristic C60 redox peaks in solution. While both C60 and C60F36 do not form a reactive interface on the hydrogenated surface, surface transfer-doping by C60F36 is evident with a coverage-dependent band bending.The single source precursor tetrakis-(diethylaminodithiocarbomato)-molybdate (IV) can be evaporated at 300B0C and decompose on substrate surfaces by 400B0C to form crystalline MoS2. Elemental substrates which form eutectic alloys with gold favor the elimination of sulfur from the MoS2 film. Using this approach, unprecedented low-temperature growth of tetragonal MoSi2 or orthorhombic MoGe2 can be obtained on Au-coated silicon or germanium. Hollow carbon nanofibers are produced if the precursor is dosed onto Au-Si substrate at 1000 degree, mediated by the catalytic effect.