Chemical and medium-range orders inAs2S3glass

Structures and optical-absorption edges of ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ glasses prepared by quenching at various temperatures have been studied. Raman scattering spectra show that the medium-range order decreases in the specimens rapidly quenched from temperatures higher than the glass-transition temperature, and that in the samples quenched from the vapor phase the homopolar-bond density is substantially increased. The medium-range order is recovered with annealing at the glass-transition temperature, and in contrast, for lessening the homopolar bonds and improving the chemical order, annealing at temperatures higher than the melting temperature is required. Increases in the structural disorders accompany red shifts of the optical-absorption edge and decreases in the slope of the Urbach tail.