Synthesis and Characterization of Cadmium-Oxide Thin Films Prepared by Sol–Gel Spin Coating Method

In this work, cadmium-oxide films are prepared using the spin-coating technique. The study is focused on clarifying the effect of changing the thickness of the film on the optical properties of cadmium-oxide films deposited on 1.5×2 cm² glass substrates at a temperature of 400°C. The behaviour of the visible and ultraviolet absorption spectra of cadmium-oxide films are also studied as functions of wavelength. These results show that the intensity of absorption increases with increasing membrane thickness; this indicates an increase in the concentration of the membrane material. Some optical constants are also studied, such as the index of refraction and the real and imaginary dielectric constants, in addition to the extinction coefficient and electrical conductivity. As found, their values change with increasing film thickness. Through the absorption spectrum, the optical energy gap is calculated, and it is found that there is a slight change with increasing film thickness, as its value decreases from 2.22 eV to 2.20 eV, when the film thickness increases from 143 nm to 368 nm.