Structural changes in amorphous hydrogenated material, in going from the annealed state to the light-soaked state, were studied by means of X-ray photo-emission spectroscopy. The latter spectra revealed a reversible shift of about 0.1eV, in the 2p peak, to a lower binding energy; with no corresponding shift in the 2s peak in going from the annealed to the light-soaked state. Density functional calculations of a Si6H14 prototype molecule were also performed. These results suggested that the Si core energy levels could be shifted by comparable amounts when small structural rearrangements were caused to the structure. The change in the 2p peak was considered to be too large to be caused by a rearrangement of the amorphous lattice which was restricted to the immediate surroundings of the defects that were responsible for the Staebler-Wronski effect (with a density of less than 1017/cm3). It was instead proposed that the formation of dangling bonds during exposure to light was also accompanied by long-range structural rearrangements of the amorphous network. It was concluded that other published results indicated the occurrence of long-range structural rearrangements during the Staebler-Wronski effect.

D.P.Masson, A.Ouhlal, A.Yelon: Journal of Non-Crystalline Solids, 1995, 190[1-2], 151-6