Photoenhanced dissolution and lateral diffusion of Ag in amorphous AsS layers

Abstract

The photoenhanced dissolution and lateral diffusion (PLD) of Ag in AsS layers was measured. It was found that the lateral diffusion depends on temperature, composition of the layers, intensity of illumination and also on electrical conductivity of the substrate. The diffusion edge has a step-like form. It is suggested that the sharp drop of Ag content in the vicinity of diffusion edge is a consequence of the existence of two glass-forming regions in AgAsS system. The incorporation of Ag into amorphous As 2S 3 is accompanied by an increase of AsAs bond densities in AsS matrix. The parabolic law of diffusion edge movement ( x ∼ t 1 2 ) on non-conductive substrate is controlled by bipolar diffusion of Ag + ions and electrons in doped layers. The increased rates of Ag + PLD in amorphous chalcogenides deposited on conductive substrates evidently result from a decrease of diffusion field (Nernst potential) created by more mobile Ag + ions and slower electrons and holes. It is suggested that the linear dependence of diffusion edge movement ( x ∼ t) on a conductive substrate is caused by processes on the doped/undoped interface part of the layer.