Study of structural and optical properties of Cd1-xZnxSe thin films

Cd1-xZnxSe (x=0, 0.5 and 1) thin films have been deposited onto glass substrates using thermal evaporation technique. The lattice constants, grain size, microstrain and dislocation density were studied by using X-ray diffraction. In addition the optical constants were calculated in the wavelength range 400–2500nm. Transmittance and reflectance were used to calculate the absorption coefficient α and the optical band gap Eg. The linear relation of (αhυ)2 as a function of photon energy hυ for the thin films illustrated that the films exhibit a direct band gap, which increases with increasing Zn content. This increasing of optical band gap was interpreted in accordance to the increasing in the cohesive energy. Optical constants, such as refractive index n, optical conductivity σopt, complex dielectric constant, relaxation time τ and dissipation factor tanδ were determined. The optical dispersion parameters E0, Ed were determined according to Wemple and Di Domenico method. ► ZnSe thin film has cubic zinc blende structure while CdSe and Cd0.5Zn0.5Se thin films have hexagonal structure. ► Grain size of Cd1-xZnxSe decreases with increasing x (x=0, 0.5 and 1). ► Optical band gap increases with increasing x.