Compositional dependence of the photoinduced surface deposition of metallic silver in Ag-As-S glasses

Photoinduced surface deposition (PSD) of metallic Ag for the AgxAs60-xS40 system has been quantitatively studied using bulk glasses with x = 35, 37.5, 40, 42.5, and 45 to determine the compositional dependence of the PSD phenomenon in the Ag-As-S system. The glasses were found to be homogeneous in the range 40 less than or equal to x less than or equal to 45 but phase-separated at 35 less than or equal to x less than or equal to 37.5 based upon compositional trends of physical properties such as Vickers hardness. The minimum Ag content for the appearance of the PSD phenomenon was evaluated as 38 at% in the Ag-As-S system by taking phase separation into consideration. The PSD properties of the homogeneous glasses suggested that the photosensitivity (amount of the photodeposited Ag) and the mean radius of the Ag particles increase with an increase in the Ag content but the number of the Ag particles decreases markedly. The origin of this compositional dependence can be accounted for by the combined effects of diffusivity and insolubility of Ag+ ions in the Ag-rich glasses. This idea can also explain the temperature dependence of the PSD properties.