Effect of film thickness on structural and optical properties of Cd-Zn-Te grown on glass and ITO substrates using electron beam evaporation

Polycrystalline of Cd0.25Zn0.25Te bulk was prepared in terms of mixing stoichiometric amounts of high purity analytical grade powders of CdTe and ZnTe using ball milling. Thin films of Cd0.25Zn0.25Te with different thickness 500, 1000, 1500, 2000 nm were deposited onto glass and ITO substrate using electron beam gun vacuum evaporation. Structural and morphological properties of Cd0.25Zn0.25Te thin films were studied using X-ray diffraction, energy dispersive X-ray spectrometer scanning electron microscopy. Voight method was used for determination both crystallites size and microstrain in terms of main (111) peak. The optical properties of Cd0.25Zn0.25Te thin films were studied using both typical transmission and reflection spectra. The film thickness (d) and refractive index (n) were determined with high precision using envelope method suggested by Swanepoel. The optical study reveals that the optical transition was found to be direct and energy band gap increases with increasing the film thickness. The change in optical results of different thickness of Cd0.25Zn0.25Te thin films deposited on glass and ITO substrates can be explained in terms the change in microstructure parameters.