Effect of sulfur substitutions on optical, electrical and structural properties of Ge(S xSe 1− x) 2 system

Abstract

Glasses in the system Ge–Se–S were prepared with different Se/S ratios in order to investigate the compositional dependence of selected physical properties. We report the results of a systematic study examining the UV–vis transmission, dc electrical conductivity and X-ray diffraction of the system Ge(S x Se 1 −x ) 2 with x=0, 0.1, 0.4 and 1.0 where replacement of S by Se was made. The changes in the optical energy gap, E g , (from 1.95 to 2.43 eV) and band tail width, E e , (from 103 to 243 meV) behave contrarily to the change in refractive index, n, (from 2.3 to 2) with the progressive replacement of S by Se. This behavior was discussed and interpreted with the changes in cohesive energy. The analysis of defects in the prepared films was carried out by the examination of activation energies obtained from dc electrical conductivity. The analysis of the X-ray diffraction pattern revealed a remarkable reduction in the intensity of the first and second diffraction peaks with the progressive replacement of S content, which confirms a change in the intermediate range order structure: reorganization of the structural properties.