Effect of Annealing Temperature on the Structural Properties and Performance of ZnO/SnO<sub>2</sub> Nanostructure of AZO-Based Humidity Sensor

Abstract

Advanced research in metal oxide-based nanotechnology has led to its broad applications, which include humidity sensors as well as electronic devices. Meanwhile, zinc oxide (ZnO)/tin oxide (SnO2) composite nanostructure has established a presence in many electronic devices, and their performance can be further enhanced by electrospraying at high annealing temperatures. This paper explores how annealing temperature influences the structural properties and performance of ZnO/SnO2 nanostructures in AZO-based humidity sensors. The ZnO/SnO2 nanostructures were fabricated on AZO glass utilising electrospraying and then subjected to annealing at various temperatures: 100°C, 200°C, 300°C, 400°C as well as 500°C. The structural characteristics of the synthesized films were analysed utilising Field-Emission Scanning Electron Microscopy (FESEM) as well as X-ray Diffraction (XRD). Additionally, the humidity sensing performance of the films was evaluated based on their response time, sensitivity as well as recovery time. Following the results, a higher annealing temperature resulted in smaller crystallites and smaller diameters within the 71.6–91.9 nm range. Besides, the XRD patterns demonstrate a shift in the (002) peaks towards a higher angle value with incremental annealing temperature. In terms of the humidity sensing performance, the sensitivity level increased with increasing annealing temperature, while the recovery period and response time were reduced. In summary, the annealing temperature significantly influenced the performance of the ZnO/SnO2 composite nanostructures, which recorded the best sensitivity of 173.10, 234 seconds response time, and 80 seconds recovery time after annealing at 500°C.