Hydrogen related effects in semiconductor layers

In low temperature processed amorphous silicon and its alloys like silicon nitride and carbide the presence and the behavior of hydrogen is of utmost importance for the applicability of these materials. Besides to beneficially passivate Si-dangling bond defects, hydrogen increases the reactivity of these materials and is a cause for instability. In this review we discuss examples of the study of the migration of single and molecular hydrogen inside the material as distinct steps in the process of effusion of H from the plasma deposited films. Also examples of the reverse process i.e. the uptake of hydrogen during a post deposition hydrogen treatment or during the deposition itself are presented. In these studies fruitfully use is made of (bi)layer structures in which hydrogenated and deuterated materials are spatially separated. We apply ~MeV ion beam techniques to measure concentration depth profiles of H and D. The high energy ion beams are also used to provoke molecule formation in the material, enabling in a novel manner the study of the permeability of thin films for H₂ and D₂ at relatively low temperature