It was noted that the Ag content of these glasses could be spatially modified by illumination with visible light. Optical and thermal studies demonstrated that the modification of the Ag content was caused by Ag+ ion migration from the dark to the illuminated regions of a sample. The migration could be reversed by changing the illuminated region. The magnitude of the Ag-content modification was greatest (about 7at%) for the composition: Ag25As25S50. The migration was explained in terms of the diffusion of photo-excited holes, and the composition dependence could be understood on the basis of the Owens thermodynamic model.

N.Yoshida, K.Tanaka: Journal of Applied Physics, 1995, 78[3], 1745-50