LIGHT-INDUCED-CHANGES IN THE DOS OF CHALCOGENIDE GLASSES STUDIED BY XEROGRAPHIC TECHNIQUES

The extraordinary sensitivity of xerographic potentials to light- and thermally induced fluctuations in trapped space charge, the very feature which contributes to problematic instabilities, has in recent years itself been exploited to provide a means of energetically mapping the traps and thermal emission centers involved in these processes. Three major features have emerged from these studies. (1) Cyclic instabilities are not merely the result of transient fluctuations in the occupancy of a static population of specific deep states. Rather they are associated with systematic and reversible changes in the DOS itself. (2) The near midgap states involved in light and thermally induced metastabilities are energetically coincident. (3) There is strong evidence from doping studies that the states which control light and thermally induced memory effects are in fact valence alternation pair-like native defects.