Relaxation of photodarkening in amorphous As–Se films doped with metals

Photodarkening relaxation under light exposure of a-As2Se3 amorphous films doped with 0.5 at.% of metals Sn, Mn, Sm or Dy and a-AsSe films doped up to 10.0 at.% Sn was studied to determine its dependence on the type and concentration of impurities and thermal treatments. Both factors reduce photodarkening with the degree of reduction dependent on the type of impurity. The relaxation process may be described by a stretched exponential with the dispersion parameter 0.4⩽α<0.9 and the time constant increasing with impurity concentration or thermal annealing. The results are discussed in the context of the recently formulated `slip-motion' model of photodarkening in chalcogenide glasses.