Annealing Effects on Structure, Surface Morphology, and Optical Properties of Cu-Doped CdOₓ Thin Films Grown by Spray Pyrolysis

This work reports the influence of Cu dopant and annealing temperature on CdOx thin films deposited on glass substrates by spray-pyrolysis method. The Cu doping concentrations were 0, 0.46, and 1.51 at% with respect to the CdOx undoped material. Then, the fabricated films were subjected to annealing process at temperature of 450°C. X-ray diffraction (XRD) examination confirms that the as-deposited films show a cubic crystallographic structure with high purity of CdO in the annealed films. It was found that the (111) peak is the most predominant diffraction orientation in the surveyed samples. At the microscopic scale, AFM machine was operated to quantify the three important parameters of the mean roughness (Ra), rms value (Rq), and z scale. These parameters hold highest values for the sample with 0.46 at% of Cu. Finally, reflectance, absorbance, transmittance and other optical parameters dielectric measurements were comprehensively analyzed. Our evaluation of optical band gaps for the studied samples reveals that the synthesized films have direct band gap character with the fact that the rise in the Cu contents in the as-deposited films lead to lessen the band gap values. In contrast, annealing process results in raising the band gap.