Percolative growth of photodarkening in amorphous As2S3 films

The time evolution of changes in the optical absorption coefficient with illumination has been studied for a-As2S3 films at 50, 100, 200, and 300 K in order to characterize the dynamics of photodarkening. The magnitude of the changes is larger at the lower temperatures. A model of photon-assisted site switching is proposed for the Variation of photodarkening with time, in which the fractional growth in the concentration of photodarkened sites is expressed by a stretched exponential function.