Reversible photoinduced change in intermolecular distance in amorphous As2S3 network

A reversible photoinduced change in the intermolecular distance has been observed in a well−annealed As2S3 film using a detailed x−ray diffraction technique. This phenomenon is strongly related to the reversible optical absorption edge shift (i.e., photodarkening) by successive cycles of band−gap illumination and annealing. A quantitative interpretation is given for both phenomena in connection with the pressure−induced optical absorption edge shift.