Thickness effect of the photodarkening in amorphous chalcogenide films

The dependence of the photodarkening phenomenon in amorphous As,Se, films on thickness was investigated by photoacoustic spectroscopy. The photodarkening disappeared when the thickness of the film was less than 50 nm. In the thinner films the initial optical absorption edge before irradiation with bandgap light shifted toward the final optical absorption edge after photodarkening. One explanation for this anomalous behavior on the thickness dependence of the photodarkening may be that in the thinner films the strain induced by the lattice mismatch between the film and the substrate is important. (C) 2002 Elsevier Science B.V. All rights reserved.