A strategy for improving the sensitivity of a sensor for detecting CO and NH3 gases is presented herein. The gas sensor was fabricated from ZnO metal oxide semiconductor nanostructures grown via a vapor⁻liquid⁻solid process and decorated with α-Fe2O3 nanoparticles via a sol⁻gel process. The response was enhanced by the formation of an α-Fe2O3/ZnO n⁻n heterojunction and the growth of thinner wires. ZnO nanowires were grown on indium⁻tin⁻oxide glass electrodes using Sn as a catalyst for growth instead of Au. The structure and elemental composition were investigated using field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The gas sensing results indicate that the response value to 100 ppm CO was 18.8 at the optimum operating temperature of 300 °C.
Keywords: ZnO; gas sensors; nanowires; n–n heterojunction; sol–gel; vapor–liquid–solid.