Optical and electrical properties of amorphous Cu-rich Cu-Ge-S films: Photoinduced and thermally induced phenomena

Photoinduced and thermally induced phenomena in Cu-rich Cu-Ge-S amorphous alloys were examined. (Ge0.3S0.7)(100-x)Cu-x (0 less than or equal to x less than or equal to 65) films were prepared by co-evaporation of Ge30S70 glass and metallic Cu. Amorphous, homogeneous films were obtained up to Cu contents of 62 at %. Photoinduced and thermal bleaching of the optical absorption were observed in the composition range 0 less than or equal to x<40. Both types of bleaching decrease with increasing Cu content and become negligible at around 40 at.%. The photoinduced surface deposition (PSD) of metal phenomenon was not observed even for the Cu-rich film of x=62. Optical and electrical properties of the films were also examined as a function of Cu content and compared with the data for amorphous (Ge0.3S0.7)(100-x)Ag-x (0 less than or equal to x less than or equal to 67) films. A difference between the Cu and Ag systems is noticeable at metal contents above 25 at.%. It was found that the Cu-rich films did not exhibit ionic conduction of Cu. The absence of the PSD phenomenon in the Cu-rich films can be accounted for by this lack of ionic conduction of Cu.