Matthias Rebhan

CVD of silicon and silicides on iron

Abstract Silicon and iron silicides are promising candidates as adhesion promoters on iron. The formation of silicon and iron silicides films on polycrystalline iron is studied in a CVD process with monosilane. The process is performed between 475°C and 800°C with a silane partial pressure of 0.2 to 10 mbar to a total pressure of the silane–hydrogen mixture of 100 to 990 mbar. A model of the reaction mechanism is presented which includes the transport of the gases, the adsorption on the surface, the chemical decomposition of the silane and the interdiffusion between Si and Fe.

Electrochemical properties of iron covered by CVD-silicon and silicon-organic molecules

The adhesion of polymeric coatings on iron and steel is interesting especially for industrial applications. Lacquers are important because of their optical properties but also because they protect the metallic surface e.g. from corrosion. The new concept of using adhesion promoters between the polymeric coating and the metallic surface was introduced recently. But the adhesion of polymeric coatings is a difficult task on iron since the surface must be oxide free. This problem can be avoided by covering the iron surface with a thin film of silicon, silicides and SiO 2 . Silane molecules chemisorb on top of it and act as adhesion promoters. The silicon reacts with the iron in a CVD process and the silane via a self-assembly process. We describe the electrochemical properties and the stability of the iron covered by silicon and by silicon-organic molecules. Impedance and current-voltage measurements are used for this. The influence of oxygen and nitrogen solved in the electrolyte is described. Also the time dependence of the stability of the surface layer was measured.