Highly c-axis Oriented ZnO Thin Films by Sol-gel Method

Abstract This study reports the effect of annealing temperature on the structural, morphological, and optical properties of ZnO (Zinc Oxide) thin films deposited on a glass substrate by the sol-gel spin coating method. Those properties of ZnO were examined with UV-Vis, Fourier transform infrared (FTIR) and Raman spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray diffraction (XRD), before and after annealing. XRD results revealed that all the samples had a highly c-axis oriented wurtzite structure. A 1 (LO) mode in Raman spectra also confirmed the highly oriented ZnO films. Optical measurement indicated that transmittance of the films was above %85, and the optical band gap slightly decreased with the increasing annealing temperature from 350 to 550 °C. Morphological analysis displayed that increasing annealing temperature improved surface morphology and enlarged the grain size from 2-3 nm for as-deposited samples to 150 nm for annealed at 550 °C.