Structural and optical properties of polycrystalline NiO thin films prepared by using the oxidation of the metallic Ni

Abstract

Here, we report on the structural and the optical properties of polycrystalline NiO thin films prepared by using the thermal oxidation of metallic Ni. After the deposition of the Ni films, they were placed in a thermal oxidation furnace at different temperatures (400, 500, 600, 700, and 1000 °C), resulting in mean crystallite sizes between 6 nm and 40 nm. From the optical absorption spectra, we determined the energy gaps of these films. Interestingly, the energy gaps were in the range of 3.13 ∼ 3.29 eV, which were smaller than those of the bulk.