Structural and Optical Properties of Nanostructured Zinc Oxide Thin Films by Spray Pyrolysis and Ethanol Sensing

Abstract

Polycrystalline Zinc Oxide thin films were deposited on a glass substrate by Spray Pyrolysis technique using zinc acetate dehydrate precursor at 220˚C substrate temperature. The concentration of the solution was 0.05 M, the deposited films are annealed at 300˚C temperature in air atmosphere. The X-ray diffraction pattern shows that the films are in the hexagonal Wurtzite phase with preferential orientation (002) along the c-axis. It confirms polycrystalline nature and grain size is 14.666 nm. Scanning Electron Microscope images reveals that the surface of the films are flat and smooth, spherical and wheat in shape and grain size is about 30- 50 nm. Optical spectrum shows that the films are having high transmittance and low absorption in the visible region. Ultra violet-visible spectra shown that the optical energy gaps for ZnO films were estimated in the range 3.25 and 3.31 eV. It confirms zinc oxide thin films are semiconductors with wide band gap energy. The applications of zinc oxide thin films are sensing towards various concentrations of ethanol at an operating temperature of 100 °C. It shows that the resistance increases with increasing the concentration of Ethanol gas.