Effect of Annealing Temperature on Structural, Optical and Electrical Properties of ZnO Thin Films Prepared by Sol-Gel Method

Abstract

A transparent semiconductor ZnO thin film was prepared on glass substrates using spin coating sol-gel method. The coated ZnO films were annealed in air for 2 hours at different temperatures of 0, 450, 500, 550 and 600 °C. The films were obtained at a concentration of sol-gel solution is 0.5 M. In present paper, the structural, optical and electrical properties of the ZnO thin films were studied as a function of the annealing temperature. The DRX analyses indicated that the coated ZnO films exhibit an hexagonal structure wurtzite and (002) oriented with the maximum value of crystallite size G = 69.32 nm is measured of ZnO film annealed at 600 °C. The crystallinity of the thin films improved at high annealing temperature which was depends too few defects. Spectrophotometer (UV-vis) of a ZnO films deposited at different annealing temperatures shows an average transmittance of about 88 %. The band gap energy decreased after annealing temperature from Eg = 3.359 to 3.117 eV for without annealing and annealed films at 450 °C, respectively, than increased at 600 °C to reaching the maximum value 3.251 eV. The minimum value of the sheet resistance Rsh of the films is 107635 Ω was obtained for ZnO thin film annealed at 600 °C. The best estimated structure, optical and electrical results are achieved in annealed ZnO film at 600 °C.