Influence of Annealing on Physical Properties of CdO Thin Films Prepared by SILAR Method

Cadmium oxide (CdO) thin films were prepared by successive ionic layer adsorption and reaction (SILAR) method and annealed at 250-450℃ for 2 h. The prepared films were characterized by X-ray diffraction (XRD), optical spectroscopy, scanning electron microscopy (SEM) and Hall effect measurement. The XRD analysis reveals that the films were polycrystalline with cubic structure. Both crystallinity and the grain size were found to increase with increasing annealing temperature. SEM analysis shows the porous nature of the surface with spherical nanoclusters. Energy dispersive spectroscopic analysis (EDS) confirmed the presence of Cd and O elements without any additional impurities. The films exhibited maximum transmittance (82%-86%) in infra-red (IR) region. Transmittance was found to decrease with increasing annealing temperature and the estimated band gap energy (Eg) was in the range of 2.24-2.44 eV. Hall effect measurement shows an increase in carrier concentration and a decrease in resistivity with increasing annealing temperature. The carrier concentration (N) and resistivity (ρ) of about 1.26×1022 cm-3 and 8.71×10-3Ω cm are achieved for the film annealed at 450℃for 2 h.