PHOTOINDUCED REVERSIBLE CHANGES IN LOCAL BONDING CONFIGURATION OF AMORPHOUS GE-S THIN-FILMS

Reversible changes of the Raman spectra by the cycle of band-gap laser irradiation and annealing (storing in the dark) have been observed fo r amorphous Ge20S80 thin films for the first time, The observed change s in the region of stretch vibrations of the chalcogenide atoms is dir ect evidence for the occurrence of gross structural changes in local b onding configuration caused by optical irradiation, It has been shown that under the laser irradiation the bonding tendency of the chalcogen ide atoms is to form rings rather than chains, i,e. the cia-conformati on is preferred over the trans-conformation. (C) 1998 Elsevier Science B.V.