Temperature dependence growth of CdO thin film prepared by spray pyrolysis

CdO thin films prepared by spray pyrolysis technique show temperature dependence growth when the spray time is constant. In contrast, the growth is film thickness dependent when the substrate temperature is constant. The films are polycrystalline in the covered spray time and substrate temperature ranges. The crystallite size and microstrain are calculated and analyzed. The Atomic Force Microscopy (AFM) micrographs prove that the grains are uniformly distributed within the scanning areas (5μm×5μm) and (50μm×50μm). The roughness shows a considerable decrease with substrate temperature. All samples show an abrupt change in transmission which indicates a direct transition and good crystallinity. The transmission of films is increased up to 80% with increasing substrate temperature in wavelength ranged from 450nm to 1000nm. Also, a broad absorption band is observed in the range 1500–2000nm. This band could be attributed to the increase in free carrier concentration which confirmed by a reasonable decrease in the film sheet resistance. The band gap Eg is determined and found to be in the range 2.45–2.55eV. The sheet resistance is reduced with increasing deposition temperature due to the increase in free carrier concentration and found to be 66Ω/□ at 450°C.