Variations of surface resistivitles of some amorphous chalcogenide thin films along with heat treatment temperatures are described in present paper. The surface resistivity of most of the thin films will exhibit a sudden decrease(by approximately 4 orders of magnitude)at acertain temperature

X-ray diffraction analysis and Transmission Electron Microrcopicl study show that amorphous-to-crystal phase transition occurs at the temperature where the surface resistivity exhibits sudden decrease. This temperature is calleas phase transition temperature and depends upon the composition and preparation method of the thin film. The reflectivity of the film will also change largely as a result of the phase transition

implying that these materials can be used as optical memory media.