Carbon doped tungsten oxide nanorods NO₂ sensor prepared by glancing angle RF sputtering

Metal oxide semiconductor nanostructures offer potential advantages in sensing applications due to their large surface to volume ratio, lower electron recombination rate, and high stability. However, most methods produce nanostructures with random sizes, distribution and orientations, which are not reliable for practical applications because of poor reproducibility. In this work, homogeneous carbon-doped WO₃ nanorods are developed based on the glancing angle deposition (GLAD) technique using radio-frequency magnetron sputtering and investigated for NO₂ gas sensing application. The carbon doping is achieved by using acetylene gas as a carbon source. Characterization based on scanning electron microscopy, Auger electron spectroscopy and X-ray diffraction confirm the formation of uniform carbon-doped crystalline WO₃ nanorods. The gas-sensing results reveal that carbon-doped WO₃ nanorods sensor exhibits not only high response and selectivity to NO₂ (0.5-5 ppm) but also at low operating temperature (150 °C) compared with the undoped ones. The observed gas-sensing enhancement may be attributed to the increase of specific surface area and the decrease of activation energy by carbon doping.