Effect of preparation conditions on the microstructural characteristics and optical properties of oxidized zinc films

Thin films of zinc (Zn) were deposited onto glass substrates (maintained at room temperature) by thermal evaporation under vacuum. The metallic zinc films were submitted to thermal oxidation in air at 670 K and 770 K, respectively, for 5–90 min, in order to obtain zinc oxide (ZnO) thin films. X-ray diffraction patterns revealed that the ZnO thin films were polycrystalline and had a wurtzite (hexagonal) structure. The morphology of the prepared ZnO thin films was investigated using atomic force microscopy and scanning electron microscopy techniques. Transmission spectra were recorded in the spectral domain from 300 nm to 1400 nm. The optical energy bandgap calculated from the absorption spectra (supposing allowed direct transitions) was in the range 3.05–3.30 eV.