ATHERMAL LIGHT-INDUCED VITRIFICATION OF AS50SE50 FILMS

The first observation is reported of a novel amorphization process, namely photo-induced vitrification, in a chalcogenide material, As50Se50, which in the crystalline phase is a molecular solid consisting of As4Se4 molecules. The phenomenon is reversible and is athermal, in that local melting is not thought to be involved, but the process does appear to be thermally activated with an activation energy of 0.15 eV. Although the mechanism of photo-induced vitrification is not known, two possibilities are suggested: either photon-induced intramolecular bond-breaking leading to a cross-linked CRN-like network, or intermolecular bond-breaking resulting in an orientationally disordered molecular glass.