Physical characterization of CuO thin films obtained by thermal oxidation of vacuum evaporated Cu

In this work, CuO thin films were obtained from the oxidation, at 300 degrees C, of vacuum evaporated Cu thin films. The XRD patterns revealed the polycrystalline structure of the monoclinic CuO with a preferential orientation along the (111) planes. The direct formation of CuO was confirmed by the Raman spectroscopy. The variation of the crystallographic parameters as a function of the heating time was interpreted by a collective action of intrinsic and thermal stresses. The grain growth of the CuO films was found to be controlled by the surface diffusion of pores. SEM image show the formation of homogenous structure and the O/Cu atomic ratio varied between 0.8 and 1.15 reflecting the nonstoichiometry of CuO films. The UV-visible spectroscopy and the electrical measurements revealed that the band gap energy and the electrical resistivity variations were influenced by the crystallite size and the nonstoichiometry of the CuO films. The band gap energy varied between 1.73 and 2 eV while the electrical resistivity varied between 2.7 and 6.5 k Omega cm.