On the kinetics of Ag photodissolution in As₂S₃ chalcogenide glass films: Oscillatory behaviour of the reaction rate

Abstract

The kinetics of Ag photodissolution into As₂S₃ glass films have been inves-tigated 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 Iayers studied were around 1000–1500 Å and 3000–5000 Å 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 Iayers 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 yicinity of the doped-undoped chalcogenide interface.