Synthesis and Characterization of ZnO Thin Films and Study of Thermal Annealing Effects on Their Performance in Gas Sensing

Abstract

ZnO thin films (0.1 M) were deposited on glass substrates using the chemical spray method and annealed at 450°C and 600°C to study the effect of thermal treatment. Field-emission scanning electron microscopy (FE-SEM) revealed grain growth from 12 nm to 24 nm with increasing temperature, indicating enhanced atomic mobility and surface uniformity. X-ray diffraction (XRD) confirmed improved crystallinity and reduced defects, while optical analysis showed a band gap widening up to 4.6 eV. Gas sensing for NO₂ improved with annealing, showing higher sensitivity and shorter response and recovery times, whereas non-annealed films exhibited inherently fast response. The enhancements are attributed to larger grains, better crystallinity, and more active adsorption sites