Changes in variable-energy positron annihilation spectroscopic measurements of undoped hydrogenated amorphous films, following light-soaking, were studied. The changes, which were seen mainly in the high-momentum band of annihilation radiation, were not reversed by thermal annealing. It was suggested, on the basis of models for the Staebler-Wronski effect, that exposure to light induced the H which was trapped in vacancy-like defects to become mobile in the network. The observations placed constraints on models of H motion which fitted macroscopic Staebler-Wronski effect kinetics, and were expected to help to achieve a definitive description of metastability in amorphous hydrogenated Si.

Photoinduced DeHation of Defects in Undoped a-Si:H using Positron Annihilation Spectroscopy X.Zou, Y.C.Chan, D.P.Webb, Y.W.Lam, Y.F.Hu, C.D.Beling, S.Fung, H.M.Weng: Physical Review Letters, 2000, 84[4], 769-72