EXCITON OR HYDROGEN DIFFUSION IN SIO2

The appearance of positive interfacial charge at the Si-SiO2 interface in metal (Al) -SiO2-silicon structures illuminated by vacuum ultraviolet (≳ 9 eV) light (Al-negative) or subjected to electron-avalanche injection (Al-positive) has been found to depend on water exposure of the SiO2 layer. This finding raises the possibility that these effects can be explained by the diffusion of water-related species (especially H), rather than by the diffusion of excitons, as has been previously proposed. Although we cannot unambiguously decide whether the source of the vacuum ultraviolet effect is diffusion of excitons or water-related species, it appears more likely that the water enhances the detection efficiency of the diffusing species as they reach the Si-SiO2 interface.