The effect of light-soaking, using a simulated daylight spectrum (colour temperature 5800K) on the crystallinity, defect structure, and total H concentration of a-Si:H grown by HW-CVD was investigated. Positron beam based electron momentum spectroscopy was applied to the monitoring of the evolution of the open-volume defect structure after each illumination stage. The results indicated an initial increase in free volume at dangling-bond complexes on illumination, with no indication of a change in defect concentration or generation of larger micro-voids. Upon further illumination, there was a reduction in the low electron momentum fraction, which was not accompanied by a similar change in the free-volume. This could be interpreted in terms of a reconfiguration of the H in the dangling-bond complex, followed by its release into a mobile state.

Light-Induced Changes in the Defect Structure of a-Si:H. D.T.Britton, Z.Sigcau, C.M.Comrie, D.F.Kanguwe, E.Minani, D.Knoesen, M.Härting: Thin Solid Films, 2003, 430[1-2], 149-52