Comparison of reversible photodarkening in As_2S_3 and As_2Se_3 amorphous thin films

摘要

Photoinduced darkening of well annealed amorphous As_2S_3 and As_2Se_3 films induced by exposure to near-band gap monochromatic light with various intensities was studied. Under well comparable conditions of exposure the magnitude of photodarkening of As_2S_3 exceeds the one of As_2Se_3. In both cases, the kinetics of photoinduced darkening follows single exponential and the formal rate constant of photodarkening of As_2S_3 was found almost one order magnitude higher compared to As_2Se_3. Exposure by medium and high intensities enhances the red shift of the gap. This enhancement is, however, unstable and can be erased either by a dark relaxation or by illumination using the same near-band gap monochromatic light with low intensity. Observed differences in photodarkening of As_2S_3 and As_2Se_3 thin films are briefly discussed.