Raman and Photoluminescence Spectra of Crystalline and Glassy GeS2xSe2 – 2x Solid Solutions

Abstract

We have studied the effects of compositional and structural disorder on the Raman and photoluminescence (PL) spectra of crystalline and glassy GeS2xSe2 – 2x solid solutions. The influence of structural disorder (variations in bond lengths and bond angles at the vertices of [GeX4] (X = S, Se) tetrahedra) is shown to be comparable to that of local inhomogeneities in the solid solutions. The PL spectra of the crystalline phases are, on the whole, similar to those of the glasses: they show one, broad emission band, which shifts to lower photon energies in going from the crystals to glasses over the entire solid-solution series. The luminescence excitation spectra of the crystals differ markedly from those of the glassy solid solutions. In contrast to crystalline GeS2 and GeSe2, the solid solutions exhibit PL fatigue. Our results indicate that radiative processes in the crystalline and glassy GeS2xSe2 – 2x solid solutions are determined by native point defects and depend little on the degree of long-range ordering, whereas nonradiative processes are rather sensitive to topological disorder in the structure of the solid solutions.