Substrate Temperature Effects on Room Temperature Sensing Properties of Nanostructured ZnO Thin Films

Abstract

Zinc oxide (ZnO) thin films were deposited on glass substrates using chemical spray pyrolysis technique at different substrate temperatures such as 523, 623 and 723 K. X-ray diffraction (XRD) patterns confirmed the formation of polycrystalline films with hexagonal wurtzite crystal structure and revealed the change in preferential orientation of the crystal planes. Scanning electron micrographs showed the formation of uniformly distributed spherical shaped grains at low deposition temperature and pebbles like structure at the higher temperature. Transmittance of 85% was observed for the film deposited at 723 K. The band gap of the films was found to be increased from 3.15 to 3.23 eV with a rise in deposition temperature. The electrical conductivity of the films was found to be improved with an increase in substrate temperature. Surface of ZnO thin films deposited at 523 K, 623 K and 723 K were found to be hydrophobic with the contact angles of 92°, 105° and 128° respectively. The room temperature gas sensing characteristics of all the films were studied and found that the film deposited at 623 K showed a better response towards ammonia vapour.

Effect of Sn-incorporation on the Structural and Optical Properties of ZnO Thin Films Prepared by Sol-Gel Method

“…We hypothesized that raising the doping concentration reduced the size of grain of Sn doping thin film and that tiny grain does not produce any pores. According to the author 25 the observed spherical grain morphology which well match with our SEM photograph. The Crystalline size of the (002) peak at different Sn doping concentrations Undoped, 2% and 4% are 100.47nm, 95.76nm and 84.66nm so when doping concentration increased grain size decreased.…”

Effect of Post-Annealing Treatment on Mechanical Properties of ZnO Thin Films

“…Hence, ZnO thin films can be employed for sensing NH3 [10,11] due to its remarkable properties as higher photoelectric response with higher electron mobility and semi-conducting nature [12].…”