DEVELOPING HIGH-PERFORMANCE LOW-TEMPERATURE CO2 GAS SENSORS BASED ON NANOSTRUCTURED CO3O4 THIN FILMS: A SOL–GEL APPROACH AND THE ROLE OF ANNEALING

Abstract

In this study, we synthesized Co3O4 thin films using a sol–gel spin coating method and investigated the effect of heat treatment on their carbon dioxide (CO2) gas sensing properties. To optimize their crystallinity and enhance their CO2 sensitivity, the thin films were annealed at temperatures ranging from 400∘C to 550∘C. We characterized the morphological, structural, electrical, and optical properties of the Co3O4 thin films to gain insights into their behavior in the low operating temperature range (OTR). Our X-ray diffraction (XRD) analysis revealed that all the thin films exhibited a cubic structure, with improved crystallinity observed at higher annealing temperatures. We observed a decrease in band edges in the optical transmittance spectra of the thin films as the annealing temperature increased, indicating a redshift in the absorption edge. Notably, the highest electrical conductivity was observed for the sample annealed at 550∘C, suggesting enhanced crystallinity and improved CO2 gas sensitivity. These findings provide valuable insights into the optimization of Co3O4 thin films for CO2 gas sensing applications.