Effect of Temperature on Morphological, Structural and Optical Properties of Cadmium Selenide (CdSe) Thin Films Deposited by Chemical Bath Deposition Method

Abstract

In this work CdSe thin films were successfully deposited on glass substrates by using tartaric acid as complexing agents, sodium selenosulphite as source of Se^2- and cadmium acetate as sources of Cd²⁺ in basic medium. The thin films of the binary compound CdSe were also deposited at various temperature ranges and the effects of these deposition temperatures on the properties of the thin films were investigated. The as-deposited CdSe thin films were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and optical absorption spectroscopy. The XRD studies showed that all the CdSe samples had cubic crystal structure with space group F-43m. This is the XRD pattern of CdSe thin films at different deposition temperature. The diffracted peaks are indexed as the (111), (220) and (311) planes which are coincided with 26.001, 42.985 and 49.848 angle 2θ. XRD results showed that as the deposition temperature increased three peaks were appeared. This may be attributed with the enhancement of the crystal size with temperature. It is also noticed that the preferred orientation of the crystal was along the (111) plane for the two samples. The crystalline size of the CdSe thin films increases as the bath temperature increase. Conversely the interplanar distance between the lattice points were decreased.  The SEM and EDX investigations revealed that, the CdSe thin films deposited at 60 ⁰C and 80 ⁰C were free from cracks and the deposited films were composed of the desired elements. The band gaps of the films were 1.78 eV, 1.75 eV and 1.70 eV for the deposition temperatures 60 ⁰C, 70 ⁰C and 80 ⁰C respectively.

Keywords: Cadmium Selenide (CdSe), thin film