Spectroscopic ellipsometry investigations of Cd-Se thin film electrochemically prepared

Abstract

Binary Cadmium selenium (Cd-Se) thin film deposited onto glass substrate coated by indium tin oxide (ITO) using electrodeposition method at room temperature. Structural, morphological and optical properties has been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and variable angle spectroscopic ellipsometry (VESA). XRD pattern shows that the nature film is polycrystalline where both (hexagonal) Se and (hexagonal) CdSe crystalline phases coexist. Based on the (SEM) images, it was found that micro-structures consist of dense layers or agglomerates suggesting an acceptable adhesion between ITO layers and Cd-Se films. VESA measurements on the Cd-Se are presented in the energy range of 1.–5 eV with different incident angles and at room temperature. The experimental data of SE were fit using a linear summation from Gaussian and Tauc-Lorentz oscillator functions. Each function was employed to fit a range of absorption spectrum from ultraviolet, visible and infrared regions. Optical constants such as pseudo refractive index, pseudo extinction coefficient, real and imaginary parts of the pseudo dielectric function were determined. The optical energy band gap (Eg) of prepared film is 2.16 and 1.14 eV for the direct allowed and indirect allowed transitions, respectively.