Temperature dependence of the optical gap CuGa5Se8

Abstract

The investigation of the absorption coefficient spectra below the fundamental edge of ordered vacancy compound CuGa5Se8 was studied early for samples prepared by Bridgman method. Compositional measurements were carried out by Energy Dispersive X-ray Microanalysis (EDAX). The optical transmittance spectra in the spectral range 600–900 nm were measured with MDR2 monochromator using halogen lamp as a light source. The transmitted radiation was detected by a Ge photodetector and Unipan amplifier. The temperature interval between 10 and 300K was supplied by close cycle helium Leybold system. Three-parameter thermodynamic model of O’Donnell and Chen, the Einstein model and the Passler model have been employed to describe the temperature variation of the energy gap.