Studies on some structural and optical properties of ZnxCd1−xTe thin films

Five ZnxCd1−xTe solid solutions with x=0.1, 0.3, 0.5, 0.7 and 0.9 at.% were synthesized by fusing stoichiometric amounts of Zn, Cd and Te constituents in silica tubes. Each composition was used in the preparation of a group of thin films with different thicknesses. Structural investigation of prepared films indicates that they have polycrystalline structure of four predominant diffraction peaks corresponding to (1 1 1), (2 2 0), (3 1 1) and (3 3 1) reflecting planes. The refractive index, n, and the extinction coefficient, k, of ZnxCd1−xTe thin films of different compositions were determined in the spectral range, 500–2000 nm. It was found that at a certain wavelength these constants depend on the film’s structure, i.e. they are decreased with increasing the atomic percentage x. Also, plots of (αhν)2 versus hν yield straight lines corresponding to direct allowed transitions. However, the band gap showed a non-linear variation with the value of x. The refractive index data were analyzed by using the Wemple–DiDomenico single oscillator fit. The effective masses of the carriers and the band gap bowing parameters of ZnxCd1−xTe thin films were estimated.