An optical study ofa-Ge20Se80−xInxthin films in sub-band gap region

The present paper reports a study of optical parameters, refractive index ( n ) and extinction coefficient ( k ), by analysing the transmission spectrum of thin films prepared from samples of Ge 20 Se 80− x In x ( x = 0, 5, 10, 15, 20) in the range 400–1500 nm. The dispersion parameters are calculated by using the Wemple–DiDomenico model. The optical band gap of the thin films is obtained by Tauc plots. The variation in the optical parameters for different thin films is explained on the basis of the presence of defect states and the change in the average bond energy of the system. The dielectric constants (ε r and ε i ) and optical conductivity (σ) of the thin films are also reported.