Effect of annealing temperature on electrical and optical properties of ZnO thin films prepared by sol gel method

Abstract

In this work, ZnO thin films were deposited on glass substrates using spin coating method. Different annealing temperature from 400 to 550°C significantly distresses the nature of electrical and optical properties of ZnO thin films have been investigated. The effect of annealing temperature on optical and electrical properties of nanostuctured ZnO thin films deposited by spin coating method has been studied. The optical properties were characterized by ultraviolet visible (UV-VIS-NIR) spectrophotometer. The electrical properties were analyzed using I-V measurement (CEP 2000). Gold (Au) was used as a metal contact using electron beam thermal evaporator (ULVAC). The optical transmittance spectrums showed the average transmittance of ZnO thin film with different annealing temperature higher than 90% in visible wavelength region. The optical band properties of the nanostructured ZnO thin films were analyzed by UV Vis and Tauc method was accepted to estimate the optical gap and absorption coefficient. The resistivity of the film decreased as the annealing temperature increased from 400 to 550oC. The highest conductivity values of ZnO thin film was obtained at 500°C with value 0.000197 Scm-1. Moreover, the higher porosity was found at 400oC with value 57.5%. The higher porosity of ZnO thin film can be expected the high sensitivity for gas sensor due to the material has a comparatively large surface area.