Composition dependence of photoinduced and thermally induced bleachings of amorphous Ge-S and Ge-S-Ag films

Abstract

Photoinduced and thermally induced bleachings of as‐deposited GexS100-x and (Ge0.3S0.7)100-yAgy films were systematically studied in the ranges of 21?x?42 and 0?y?67 using optical transmission measurement. The bleachings for the Ge‐S system show a maximum at around the stoichiometric composition GeS2, whereas that for the Ge‐S‐Ag system become smaller with an increase of the Ag content and vanish above 40 at.%. The composition dependence for the Ge‐S system can reasonably be explained by an increase in the Ge‐S bond density and subsequent decrease of short‐ and medium‐range disordering. The bleaching rates, which are relatively small for Ge‐rich films, are considered to be associated with the flexibility of the local network structure. The photo‐oxidation phenomenon, which is observed for the films illuminated in air, also shows a maximum at around GeS2. The composition dependence for the bleaching of Ag‐containing Ge30S70 films can be understood in a similar way to the Ge‐S system. The vanishing at y?40 is associated with a thermodynamically stable phase at that composition for the Ge‐S‐Ag system