Thermoreflectance study of the electronic structure of Ge(Se1-xSx)2 -: art. no. 125313

The band structure of Ge(Se1-xSx)(2) (0 <= x <= 1) series solids was probed experimentally by thermoreflectance (TR) measurements in the energy range of 2-6.5 eV. The TR measurements were done with the layered samples put in air and operated at room temperature. The TR spectra of the Ge(Se1-xSx)(2) series layers exhibit derivative-like spectral features in the vicinity of band edge as well as higher-lying interband transitions. The energies and broadening parameters of the interband transition features of Ge(Se1-xSx)(2) are analyzed by detailed line-shape fits to the TR spectra. Compositional dependences of the transition energies of the Ge(Se1-xSx)(2) are analyzed. The presence of higher-lying interband transitions as well as the analysis of line-width broadening of the direct band gap indicates that the Ge(Se1-xSx)(2) series should not be amorphous but belong to the polycrystalline solids with medium-range order. Based on the experimental results of TR measurements together with referring to previous band-structure calculations of crystalline and glassy GeX2 (X=S,Se), a probable experimental band structure near the fundamental edge of Ge(Se1-xSx)(2) is proposed.