Study of the Optical and Morphological Properties of Thin Cadmium Oxide Films Prepared Using Spin Coating Technology

The study aims to prepare thin CdO films with a thickness of 232 nm using the spin coating method. This involved depositing the cadmium acetate in 2-methoxyethanol on glass substrates. This thin layer was prepared at a rotation speed of 3500 rpm for 30 seconds, then dried at 250 °C for 10 minutes, and finally heat-treated at 350 °C for one hour. The optical properties of the prepared CdO thin films were studied using UV-Visible spectroscopy in the wavelength range of 190-1100 nm. The results indicated that the absorptivity was a function of wavelength and recorded an absorptivity peak in the range of 375-450 nm (short wavelength region), then gradually decreased with increasing wavelength and began to stabilize in the range of 850-950 nm. The optical constants were calculated, and the results confirmed that the behavior of the optical constants followed a pattern similar to that of the absorption behavior. The energy gap of the thin film was calculated using the Tauc equation to be 2.30 eV, and direct-type electronic transitions were observed. A scanning electron microscope (SEM) was used to study the surface morphology of the thin films. Microscopic images showed that the nanoparticles formed a semi-spherical (cauliflower-like) cluster structure with a porous surface during the preparation process, which had an average size of 38.43 nm, with an average crystallite size of 12.9 nm, and their transparency in the infrared region, making them suitable for multiple applications in materials science and optoelectronic devices such as sensors.