Improvement of the sensing characterizations of ZnO nanostructure by using thermal annealing prepared through R. F. magnetron sputtering technique

Abstract

Abstract Zinc oxide (ZnO) nanostructure s were deposited by RF magnetron sputtering onto silicon wafer substrates. This study analyses the effects of varying annealing temperatures (RT, 350, 550, and 850 C) on physical properties of ZnO nanostructure. The crystalline structure, topography, electrical, optical and gas sensing properties of ZnO nanostructure were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Visible Spectrometry and gas sensing system, respectively. X-ray diffraction (XRD) was used to characterise the structural and to determine the crystallite size of the ZnO nanostructure. XRD showed that the annealed ZnO nanostructure were polycrystalline in nature of hexagonal wurtzite structure. The crystallite size of the nanostructure was found to increase with thermal annealing from 38.76 nm to 68.21 nm for temperatures RT, 350 °C, 550 °C, and 850 °C respectively. AFM analyses showed a rise in roughness and grain size with increasing temperature. The variations in the optical properties before and after the temperatures were measured in the wavelength range of (200–1000) nm by using a spectrophotometer. Optical band gap was found to be increased from 3.13 to 3.42 eV with annealing. Electrical conductivity increased with the annealing. Also, in this study, CO2 gas sensing properties of ZnO nanostructure s were investigated at different temperatures. It was found that the sensor response, response time and recovery time of ZnO nanostructure improved with increased annealing temperature.