Synergism of spray-pyrolyzed aliovalent Ga (iii) ions and ZnO nanostructures for selective sensing of hazardous CO gas towards low ppm levels

Ga-doped ZnO (GZO) nanostructures deposited via low-cost spray pyrolysis process are employed in this study to identify low quantities of carbon monoxide gas. XRD studies reveal the single-phase wurtzite structure of ZnO thin films, thereby confirming the structural stability post-Ga doping. Raman examination discloses the vibrational characteristics and provides some early insights into the existence of defects in the films. The nanograins having well-defined grain boundaries noticed from the inspection of SEM images participate in the gas sensing performance as the site for the active adsorption of CO molecules. The defects, mainly oxygen vacancies responsible for the enhancement in the CO sensing characteristics were confirmed from room temperature photoluminescence (RTPL) spectra and XPS analysis. The CO sensing measurements reveal that 15 wt% GZO exhibited the highest sensing performance of 0.08 towards 1 ppm and 0.41 towards 5 ppm.