Optical band gap and refractive index of ternary Ge20Se77.5Bi2.5 semiconducting glass

摘要

The optical transmission spectra at normal incidence of amorphous ternary Ge20Se77.5Bi2.5 glass has been measured in the range from 200nm - 800nm. From the transmission spectrum, the refractive index(n) the thickness(t) of the film, absorption coefficient 'a' and extinction coefficient 'k' have been obtained using Swanepoel's method. The optical band gap (E-g) has been calculated from the optical absorption model using Tauc's model. The variation of refractive index and extinction coefficient with photon energy are studied. The homogeneity of the glass composition was verified using XRD. Thin film of the alloy was prepared by a vacuum evaporation keeping substrate at room temperature and at base pressure of similar to 10(-5) Torr.