Piezoreflectance study of band-edge excitons of ReS2-xSex single crystals

The temperature dependence of the spectral features in the vicinity of the direct band edge of ReS2-xSex single crystals is measured over a temperatur e range of 25-300 K using piezoreflectance (PzR). From a detailed line-shap e fit of the PzR spectra, the temperature dependence of the energies and br oadening parameters of the band-edge excitons are determined accurately. Th e excitonic transition energies at different temperature vary smoothly with the Se composition x, indicating that the natures of the direct band edges of ReS2-xSex are similar. The parameters that describe the temperature var iation of the energies and broadening function of the excitonic transitions are evaluated and discussed. [S0163-1829(98)06739-3].