ON THE KINETICS OF AG PHOTODISSOLUTION IN AS2S3 CHALCOGENIDE GLASS-FILMS - OSCILLATORY BEHAVIOR OF THE REACTION-RATE

The kinetics of Ag photodissolution into As2S3 glass films have been investigated by monitoring the electrical resistance of the Ag layer during the process. The thickness dependence of the Ag electrical resistivity predicted by the thick-film approximation of Sondheimer's theory has been used (reasonable agreement was found), in order to obtain the curve of Ag thickness against illumination time. The thickness ranges of Ag and As2S3 layers studied were around 1000-1500 angstrom and 3000-5000 angstrom respectively. The main feature found is the appearance of an oscillatory behaviour of the reaction rate, with the illumination from the As2S3 side and wavelengths lower than a threshold value, which increased when the thicknesses of the layers were increased. In contrast, when the samples were irradiated on the Ag side, the sigmoidal kinetic curve very often reported was observed. These data could support the idea that the actinic light absorption occurs in the vicinity of the doped-undoped chalcogenide interface.