Effect of compositional variations on the optical properties of SbxSe60Â -xS40 thin films

Thin films of SbxSe60 -xS40(x = 10, 20, 30, and 40) were deposited by thermal evaporation from the prepared bulk materials on glass substrates held at room temperature. The film compositions were confirmed by using energy dispersive X-ray spectroscopy. X-ray diffraction studies revealed that all the as-deposited films have amorphous structure. The optical constants (n, k, Eg, Ee, B1/2) of the films were determined from optical transmittance data, in the spectral range 500-1200 nm, using the Swanepoel method. An analysis of the optical absorption spectra revealed an Urbach's tail in the low absorption region, while in the high absorption region an indirect band gap characterizes the films with different compositions. It was found that the optical band gap energy decreases as the Sb content increases. Finally, in terms of the chemical bond approach, degree of disorderness has been applied to interpret the decrease in the optical gap with increasing Sb content in SbxSe60 -xS40 thin films. The changes in X-ray photo electron spectra and Raman shift in the films show compositional dependence.