Electrical and optical properties of Sn10Sb20−xBixSe70 (0 x 8) glassy films

Chalcogenide glasses are interesting materials due to their infrared transmitting properties and photo-induced effects exhibited by them. Thin films of the glasses Sn₁₀Sb_20−xBi_xSe₇₀ (0 x 8) prepared by melt quenching technique were evaporated in a vacuum better than 10⁻⁵ mbar. Optical transmission spectra of all the deposited films were obtained in a range 400–2500 nm. The optical band gap and the absorption coefficient were calculated from the transmission data and refractive index was calculated using the swanepoel method. The optical band gap initially increases with increase in Bi content (for x = 2) and then decreases sharply for higher Bi concentrations. The refractive index as well as absorption coefficient decrease with increase in wavelength. The dark activation energy initially increases with increase in Bi content and then decreases with further addition.