Study of the Effect of Irradiation on Some Optical Properties of Cadmium Oxide Films Prepared by the Thermal Chemical Spraying Method

In this study, thin films of cadmium oxide (CdO) were synthesized using the chemical thermal decomposition method. The films were deposited onto a glass substrate measuring 2.5 cm x 2.5 cm x 1 mm at a temperature of 400°C and a pressure of 2 bars. A total of 20 spray applications were performed, with each spray lasting approximately 10 seconds, and a 180-second interval between sprays. A dedicated chemical decomposition system was established to facilitate the preparation of thin film materials for this research.  Subsequently, the prepared films were subjected to ultraviolet (UV) light irradiation for a total of five hours, with each irradiation session lasting one hour. Absorbance and transmittance spectra were recorded after each hour of irradiation across a wavelength range of 350-950 nm using a UV-VIS Double Beam Spectrophotometer. The results indicated that absorbance varied with wavelength, showing a decrease in the absorbance spectrum as irradiation time increased, reaching its minimum at the end of the fifth hour. Conversely, transmittance exhibited a direct increase with longer irradiation durations. Additionally, it was observed that the energy gap decreases with increasing irradiation time, ranging from 2.511 eV to 2.458 eV over the 0 to 5-hour period, with measurements taken at one-hour intervals.  The analysis of certain optical constants revealed a decline in the absorption coefficient, extinction coefficient and refractive index as irradiation time increased.