Peculiarities of the Absorption Edge and Photoconductivity Spectra of (GeS2)x(Bi2S3)1-x Glasses

Abstract

The results of spectral investigations of the absorption edge α and photoconductivity (PC) of (GeS2)x(Bi2S3)1-x ternary glasses (0.4 ≤ х ≤ 1) within the temperature intervals of 77-400 K have been reported. For the GeS2 binary glass the absorption edge is described by the Urbach rule. For ternary glasses, the long-wave tail of dependence α = f(hν) shows two exponential regions changing with the temperature and having different slopes. For all the compositions of ternary (GeS2)x(Bi2S3)1-x glassy alloys, the PC spectra within the wavelengths region of 0.4-1 μm exhibit “hysteresis” when the scanning direction is changed from UV to IR. The observed spectral dependences of absorption and PC have been qualitatively explained by the complex band model of the binary GeS2 due to the formation of several types of structural units when the composition is moved toward the ternary glass system based on the atoms of different valency.