Fabrication and characterization of nanocrystalline cobalt oxide thin films

A simple solution growth route has been employed to synthesize nanocrystalline cobalt oxide thin films on glass substrates. The obtained films were characterized by X-ray diffraction and FTIR spectroscopy. The as-deposited films were identified as a mixture of different phases of Co(OH)2, while the annealed ones as Co3O4. The absorption of the annealed films gradually decreases with an increase of the wavelength in the 310–820 nm region. Upon annealing, the absorption coefficient decreases. The calculated band gap energy from optical absorption data for annealed films is 2.2 eV. The as-deposited thin films are dielectric, while the post-deposition heat-treated ones are characterized by resistivity of several MΩs/cm2 at room temperature.