Photo-induced structural changes in obliquely deposited arsenic-based amorphous chalcogenides: a model for photostructural changes

The effect of bandgap illumination and annealing below the glass transition temperature on the thickness and the optical bandgap of As-based (As2Se3 a nd As2S3), obliquely deposited chalcogenide thin films has been studied. It is observed that illumination increases the thickness and decreases the ba ndgap. By annealing the samples, before and/or after illumination, the tren ds of changes in thickness and bandgap are reversed. These changes have bee n explained on the basis of ordering of the structure by annealing, and of repulsion and slip motion by illumination, the latter processes being due t o the negative charging of layers by electron accumulation in conduction-ba nd tails.