Is interstitial hydrogen playing a role in the Staebler-Wronski effect ?

Abstract

ABSTRACTWe have studied the density of states (DOS) of many different series of a-Si:H samples prepared in radio-frequency powered deposition systems. Samples were obtained from decomposition of pure silane or of mixtures of silane with argon, helium or hydrogen. The DOS were investigated in the as-deposited, light-soaked and annealed states. For all the samples the light-soaking behaviour is almost the same: 2 min of light-soaking are enough to increase the deep states density and after full saturation both the deep states and the conduction band tail exhibit a large increase. The effect of the annealing process is sample dependent, the DOS being restored for some samples or almost insensitive to the annealing process in some cases. To explain all these results, we propose a mechanism of light-soaking/annealing in which interstitial H2 molecules and voids play a major role.