Transport of hydrogen in films of graphite, amorphous silicon, and nickel oxide

Abstract

A new concentration pulse method is used to study the transport of hydrogen in three semiconducting materials deposited in the form of films on nickel substrates. The most probable models for the transport are proposed. In graphite hydrogen diffuses in the form of molecules and its diffusion is accompanied by reversible capture; transport occurs along microscopic voids between scales of graphite. Valence unsaturated bonds at the boundaries of the scales serve as capture centers. Diffusion in amorphous silicon is also accompanied by capture, but takes place in an atomic form along interstices; valence unsaturated Si-bonds serve as capture centers. In nickel oxide, as in graphite, diffusive transport takes place in the form of molecules, but capture of hydrogen on valence unsaturated bonds has not been observed. A comparative analysis is made of the properties manifested by these materials for oxygen in order to establish their correlation with the structure and electronic properties of the semiconductors.