Annealing and recrystallization of hydrogenated amorphous silicon

Abstract

Using a combination of positron annihilation and x-ray-diffraction techniques, we have shown that low hydrogen concentration hot wire chemical vapor deposition grown $a\ensuremath{-}\mathrm{S}\mathrm{i}:\mathrm{H}$ forms a continuous random network with no detectable free volume in the form of microvoids, and no evidence of a microcrystalline phase. On annealing up to 400 \ifmmode^\circ\else\textdegree\fi{}C, the amorphous network is seen to relax and the first stages of recrystallization occur. There is also evidence of vacancy clustering to form a low concentration of microvoids. The structural relaxation has a very low activation energy, around 0.1 eV, and is probably caused by a reconfiguration of hydrogen-terminated dangling, bond defects. The formation of microvoids and the recrystallization can both be interpreted by the migration of unterminated dangling-bond defects.