Fabrication of ultrasensitive hexagonal disc structured ZnO thin film sensor to trace nitric oxide

Abstract

ZnO thin films were deposited on glass substrate using simple and cost-effective spin coating technique. Further, the deposited sample was annealed in air at various temperatures, such as 400°C, 500°C, 600°C and 700°C. As-prepared and annealed ZnO thin films were characterized for structural, morphological, optical and gas sensing properties. All the films have shown polycrystalline nature with hexagonal wurtzite phase of ZnO. The grain size and the crystalline nature of the film improved with increase in annealing temperature. FESEM results showed a transformation into two-dimensional flower-like structures, enhancing the sensing property of the film with the more improved surface area for gas adsorption as compared to the as-prepared ZnO thin film. Optical band gaps were determined using Tauc’s plot. The gas sensing study toward Nitric oxide is carried out at a low concentration level of 2.75 ppm. At an operating temperature of 150°C, the ZnO film annealed at 400°C has shown a good sensitivity of 1.4 with response and recovery time of 52 sec and 19 seconds respectively.

Keywords

• annealing temperature
• operating temperature
• nitric oxide sensor
• response- recovery time
• thin film zno