Influence of annealing temperature on physical properties of Sn-doped CdO thin films by nebulized spray pyrolysis technique

Tin (Sn) doped cadmium oxide (CdO) thin films deposited onto the glass substrates by nebulized spray pyrolysis technique (NSP) were annealed for 20 min at different temperatures of 473-548 K in steps of 25 K. X-ray diffraction study showed that all these thin films were polycrystalline with major reflection along (1 1 1) plane and the crystallite size had increased at elevated annealing temperatures. From SEM images, it was found that annealing causes notable changes in the surface morphology. The oxidation states of Cd2+, O2- and Sn4+ were confirmed by X-ray photoelectron spectroscopy analysis. These films were found to have direct band gap energy lying in the range of 2.55-2.42 eV and the average transmittance varies from 73 to 87% with various annealing temperatures. The CdO thin films annealed at 523 K exhibited the lowest resistivity (1.03 x 10(-4) Omega cm).