Comparison of the structural and optical properties of ZnO thin films deposited by three different methods for optoelectronic applications

ZnO thin films were deposited using three processes e.g.; thermal oxidation of metallic zinc (Zn), sol-gel and RF sputtering. The structural, optical and electrical properties of ZnO films were investigated and compared systematically using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Raman spectroscopy, photoluminescence (PL) and UV measurements. Stoichiometric and surface morphological difference was observed in the films deposited by three different techniques. Thermally oxidized ZnO films and sol-gel derived ZnO film had naturally grown textured surface, while the surface of the sputtered ZnO film was relatively smooth. The electrical transport properties of the Pd/ZnO Schottky contact were studied by using microprobe arrangement. The values of ideality factor and barrier height were found to be significantly good for Schottky contact of thermally oxidized ZnO thin film. The study demonstrates that Pd/ZnO Schottky type contact fabricated by a simple and inexpensive growth technique can be used as a substitute of conventional Schottky diodes for electronic and optoelectronic applications.