Study of the Optical and Structural Properties of Cadmium Oxide Thin Films Prepared Using Chemical Spray Pyrolysis Technique

Cadmium oxide (CdO) thin films are synthesized by the chemical spray pyrolysis method on glass. The thin-film substrates are prepared at varying temperatures: 400°C, 450°C, 500°C. The samples are examined using a double beam spectrometer UV–Vis; the absorbance and reflectance spectra of the produced films are measured over a range of wavelengths 310–910 nm in order to study the optical properties of these films. As discovered, the absorbance varies with wavelength. Specifically, we observe that the absorbance behaves in the opposite direction of the transmittance, peaking at 350 nm, after which the absorbance spectrum starts to decay exponentially until the absorbance hits its lowest value at the 700 nm wavelength. The results reveal absorbance spectrum achieving its maximum value at 400°C and lowest value at 500°C. As also observed, the value of the spectrum remains consistent within the range of 700–910 nm; the evaluated energy band gap increases from 2.33 eV to 2.41 eV with the increase of substrate temperature. Furthermore, the results for the optical constants such as the refractive index, extinction coefficient, and absorption coefficient decrease with substrate temperature.