NO2-sensing properties of porous WO3 gas sensor based on anodized sputtered tungsten thin film

In this paper, a novel porous WO3 sensor was prepared by anodic oxidation of DC magnetron sputtered metallic tungsten (W) film deposited on alumina substrate. The structural and morphological properties of these films are investigated using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Coral-like porous crystalline WO3 film with a grain size of about 9.3 nm was obtained after annealing of the anodized W film. The porous WO3 sensor achieved its maximum response value to NO2 at a low operating temperature of 150 °C. In comparison to sputtered WO3 sensor, the porous WO3 sensor showed markedly higher responses, much better response–recovery characteristics and lower optimal operating temperature to different concentration of NO2 gas due to its high specific surface area and small grain size.