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.
Highlights
Air pollution has been increased in a large amount in recent years due to rapid industrialization and urbanization
The linear optical measurements were obtained using UV–visible spectrometer given in S1 of Supporting Information and surface morphological variations were studied from atomic force microscope (AFM) using Bruker Icon in tapping mode and scanning electron microscopy (SEM)
The observed peak intensity varies with the concentration of doping owing to the reduction in crystalline size which causes a decrease in the peak intensity in the preferred orientation
Summary
Air pollution has been increased in a large amount in recent years due to rapid industrialization and urbanization. Among the different kinds of gas sensors, metal oxide semiconductor (MOS)-based gas sensors have gained extensive attention because of its high selectivity, sensitivity, ability to sense a wide variety of gases, and low fabrication cost [12,13,14,15]. They possess high surface area, high electron mobility, and excellent catalytic properties [16]. We successfully synthesized In-doped ZnO-sensing layer that could detect a low concentration of 1 ppm of CO gas
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