OPTICAL AND PHOTOLUMINESCENCE CHARACTERISTICS OF POLYCRYSTALLINE ZINC OXIDE THIN FILMS

Zinc oxide (ZnO) thin films were prepared by thermal oxidation in open atmosphere of vacuum evaporated zinc metallic films. The investigations of film structure, performed by X-ray diffraction technique, showed that ZnO films are polycrystalline and have a wurtzite (hexagonal) structure with film crystallites preferentially oriented with (002) planes parallel to the substrate surface. Some values of structural parameters (lattice constants of wurtzite cell, crystallite size, Zn-O bond length) of the ZnO films were determined. The transsmision and absorption spectra were studied for incident photon energies ranged between 1.50 eV and 4.50 eV. The optical energy bandgap, calculated from the absorption spectra, is ranged from 3.36 eV to 3.45 eV. Photoluminescence (PL) spectra at temperatures 293 K and 78 K have been analysed. The PL is dominated by the emission at 3.338 eV. Temperature dependence of the intensity of the main peaks has been discussed.