Evaluation of spray pyrolysed In:ZnO nanostructures for CO gas sensing at low concentration

Abstract

Herein, we report the role of indium (In) on the carbon monoxide sensing of ZnO thin films using a low-cost spray pyrolysis technique. The decrease in crystalline size was observed from XRD studies and hexagonal wurtzite structure was confirmed. Photoluminescence and XPS studies proved the presence of various defects in the films. The gas-sensing properties of films toward carbon monoxide (CO) gas indicate that 15 wt% of In in ZnO thin films (IZO) exhibit high response (1.84) to a low concentration of the gas (1 ppm) at 300 °C compared to undoped ZnO (0.53). The observed high response of 15 wt% IZO can be mainly endorsed to the oxygen vacancy defects as observed from the photoluminescence and XPS analysis. Further, the high response is complemented by high surface area and smaller grain size (~ 13.1 nm) with well-defined grain boundaries as evident from SEM analysis as well as XRD studies.

An 8 MeV Electron Beam Modified In:ZnO Thin Films for CO Gas Sensing towards Low Concentration

“…The (101) plane is the most intense compared to other planes. For the unirradiated 15 wt% IZO film data, refer back to our previous study [24].…”

“…The (101) plane is the most intense compared to other planes. For the unirradiated 15 wt% IZO film data, refer back to our previous study [24]. The structural parameters, namely crystalline size (D), dislocation density (δ), and strain (ε) is given by the following equations [32,33]: The structural parameters, namely crystalline size (D), dislocation density (δ), and strain (ε) is given by the following equations [32,33]:…”

“…Figure 3 represents the SEM images of 5 kGy, 10 kGy, and 15 kGy irradiated IZO thin films. For the SEM image of unirradiated 15 wt% IZO thin film, refer back to [24]. It is observed that there was no substantial change in morphology when irradiated with 5 kGy, indicating the dose rate was insufficient to produce any variations.…”

“…The Zn, O, and In core level spectra of 10 kGy irradiated 15 wt% IZO film is shown in Figure 5. For the XPS spectra of unirradiated 15 wt% IZO film, refer back to [24].…”

“…In a previous study, we explored the role of indium (In) doping to ZnO thin films prepared by means of the low-cost spray pyrolysis technique in tuning CO gas sensing properties [24]. It was found that 15 wt% indium doped ZnO (IZO) films exhibited better sensing characteristics towards lower CO concentrations, particularly 1 ppm (response = 1.84) compared to pristine, 5 wt%, and 10 wt% films [24]. At present, a post-treatment approach is adopted to further tune CO sensing characteristics.…”