Effect of Thickness on the Structural and Optical Properties of Cadmium Oxide Thin Films Deposited by Thermal Vacuum Evaporation Technique

In this work, a vacuum thermal evaporation technique was used to produce cadmium oxide thin films with thicknesses of 100, 200, and 300 nm. The X-ray diffraction analysis showed the formation of the cadmium oxide phase, characterized by diffraction peaks indicating a high degree of crystallinity. The average crystallite size ranged from 12.01 nm to 10.9 nm, and this size variation was observed as the thickness of the deposited films increased. Field emission scanning electron microscopy verified the existence of a uniform distribution of nanoparticles with various lengths ranging from 13.93 to 18.33 nm. Additionally, an increase in film thickness transformed the surface morphology into a nanofiber-like structure. Optical investigation reveals that the transmittance is influenced by the thickness of the cadmium oxide. The transmittance reaches its lowest point when the thickness is 300 nm, accompanied by a distinct absorption edge. The optical energy gap data supported the development of a blue shift. Additionally, the increase in film thickness led to a corresponding rise in the optical energy gap, from 3.2 eV to 3.5 eV. The authors propose that the current findings can significantly enhance the utilization of optoelectronics and gas sensors owing to their unique characteristics.