Hydrogen at compact sites in hot-wire chemical vapour deposited polycrystalline silicon films

Polycrystalline silicon (poly-silicon) films made by hot-wire chemical vapo ur deposition (HWCVD) in a controlled range of deposition conditions show t he Si-H stretching vibration at 2000 cm(-1) in infrared absorption. This ba nd is in contrast to commonly observed IR spectra in plasma enhanced chemic al vapour deposition (PECVD) poly-silicon films in which the Si-H vibration is at 2100 cm(-1). Raman spectra of the stretching vibration confirmed tha t the 2000 cm(-1) mode is from the crystalline region (top) of the material . The thickness dependence of the single hydrogen effusion maximum (similar to 640 degrees C) reveal a diffusion-limited effusion of hydrogen migratio n similar to the case of the high-temperature hydrogen effusion maximum of amorphous silicon deposited at 25 degrees C. The diffusion profile of impla nted deuterium confirms the diffusive property in a compact material. The d iffusion is through isolated Si-H sites at a trap depth of similar to 1.5 e V determined by the hydrogen chemical potential. These isolated Si-H bonds, being located at compact sites, have the vibrational mode at 2000 cm(-1) i n their infrared spectra. (C) 2000 Elsevier Science B.V. All rights reserve d.