Co: ZnO nanocomposite thin films were deposited on glass substrates by Spray pyrolysis at relatively low temperature of 350⁰C. X-ray diffraction, atomic force microscopy and UV–VIS optical spectrophotometry were used to characterize the structural and optical properties of the as-prepared nanocomposite thin films. X-ray diffraction patterns of the films showed that the films exhibited mixed structure of ZnO with hexagonal wurtzite structure and Co₃O₄ with cubic Spinal structure, and both crystalline structures have preferred orientation along (002) and (111) respectively. Topography of the films obtained by atomic force microscope revealed that the nanocomposite thin films have higher grain size and roughness in comparison with ZnO and Co₃O₄ thin films. The optical absorption spectra showed that the nanocomposite Co: ZnO films have lower transmittance than ZnO films and higher than Co₃O₄ films. Investigation of the optical absorption coefficient indicated that the adding of Co ratio leads to narrowing the band gap of the thin films from 3.2 to 2 eV.
