Some optical properties of evaporated zinc telluride films

The absorption and transmission of ZnTe thin films are measured at wavelengths of 0.32-2.3 mu m. The optical constants (n, K) are measured in this range, although the short wavelength refractive index n measurement is limited by the band gap. A theoretical calculation of n near the band gap is made from experimental parameters. An explanation is given for the abnormal decrease of refractive index near the band gap. The effects of film thickness and doping with impurities like In, PbCl₂, BaF₂ have also been investigated. Effective crystallite size and strain have been determined by the method of variance analysis of the X-ray diffraction line profile on the same films. Lattice constants have also been calculated using the Nelson-Riley plots. It has been observed that there is an increase in optical band gap with decrease in crystallite size, increase in strain and decrease in lattice constant value.