Optical constants of vacuum evaporated Cd0.2Zn0.8Te thin films

The optical constants of Cd0.2Zn0.8Te thin films deposited at different substrate temperatures are calculated in the wavelength range 400–2500 nm. Some parameters which affect these optical properties of thin films, such as the film thickness, substrate temperature are also investigated. Effective crystallite size and strain are determined by the method of variance analysis of the X-ray diffraction line profiles for the films. It is observed that there is decrease in optical band gap with increase in crystallite size and decrease in strain. Band-to-band transitions which give rise to the optical absorption in the visible region of the spectrum may be interpreted in terms of direct allowed transition with the band gap in the range of 2.05–1.92 eV.