Dissertation Nr. 12333

Abstract

Films of aluminium, iron and copper with thicknesses of 2000 Å and films of nickel with thicknesses of 400 Å were deposited by thermal evaporation onto crystalline silicon(100)-plates covered with 60 Å of chromium as an adhesion promoter. Films of titanium and chromium with thicknesses of 2000 Å were deposited directly onto silicon(100)-plates. Films of gold were prepared with different carriers, adhesion promoters and thicknesses. Silicon(100)-templated and mica-templated gold surfaces as well as gold surfaces on heated substrates were also used. All these films of metals were investigated with x-ray photoelectron spectroscopy (XPS), scanning tunnelling microscopy (STM), atomic force microscopy (AFM), surface profilometry, infrared spectroscopy at grazing incidence reflection (GIR), ellipsometry or contact angle measurements. Silicon(100)-plates and steel plates were also characterised. All surfaces, with the exeption of gold, show natural oxide layers, which can contain several different oxides. The roughness of the different inorganic surfaces varies from < 3 Å to 130 Å over horizontal distances of 1.5 µm and 1 mm, and the microscopic structure differs in the different substrates. On a macroscopic scale the gold surfaces on heated substrates appeared inhomogeneous by eye. Small amounts of organic impurities are present on all surfaces. The surfaces were modified with low and high molecular weight compounds by adsorption from solution. Long-chain iodoalkanes form mixed monolayers of AuI and AuC species on gold surfaces upon cleavage of the C I bonds after adsorption from solution. a,w-Diiodoalkanes react with both chain ends. The mixed monolayers are stable at room temperature in pure solvent or in the open atmosphere for at least two days. Corresponding reactions with bromoalkanes do not occur under the same reaction conditions. Adsorbed compounds which initially contained Si-H, Sn-H or Ge-H bonds form strong adhering layers on different inorganic surfaces in the presence of cis dichlorobis(styrene)platinum(II). The driving force for the formation of these layers is the activation of the Si-H, Sn-H or Ge-H bonds with a platinum compound and the transfer to the surface. Hydride-terminated polydimethylsiloxanes build up polymeric surface layers for example on gold, aluminium, titanium, chromium, iron and copper. Polyhydromethylsiloxanes form polymeric surface layers for example on gold, aluminium, iron, nickel, copper and silicon(100). These layers still contain intact Si-H groups, which can be used for further reactions on the surfaces. Methylhydrosiloxane-phenylmethylsiloxane-copolymers build up polymeric surface layers on gold and copper for example, which no longer show Si-H groups. 1,2 Dimethylsilazane-1 methylsilazane-copolymers form partly hydrolysed polymeric surface layers on gold, aluminium, iron, copper and silicon(100) for example. These layers have still intact Si H groups. Low-molecular-weight silanes build up oligomeric or polymeric siloxane layers on gold, which no longer show Si-H groups. Tributylstannane and tributylgermane form low-molecular-weight surface layers on gold and copper for example, which no longer contain Sn-H or Ge-H groups