Photo-amorphization and photo-oxidation of As50Se50 thin films deposited onto silicon substrates

The photo-vitrification of As,,Se,, thin films deposited onto silicon wafer substrates is reported. This process, which was found to be athermal, has been studied using X-ray diffraction measurements,far infrared spectroscopy, EDAX-measurements, and scanning electron microscopy. When the crystallized films were illuminated in order to be amorphized, photo-oxidation of the thin-film samples was also detected. As a consequence, arsenic trioxide microcrystals were formed in the whole matrix of the films. Such behaviour has not been observed with As,,Se,, films deposited on glass substrates, which clearly demonstrates that the photo-vitrification phenomenon depends strongly on the type of substrate the As,,Se,, thin film is deposited on. The radiation source is another factor that clearly influences the light-amorphization of a previously crystallized As,,Se,, thin film. (C) 1998 Elsevier Science B.V. All rights reserved.