Porous WO3 from anodized sputtered tungsten thin films for NO2 detection

In this paper, porous WO3 films were prepared by anodic oxidation of metallic tungsten (W) films deposited on alumina substrates. The structural and morphological properties of the porous WO3 films were investigated using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A large number of cracks appeared on the surface of films after anodization, which makes the films porous. The porous WO3 sensors achieved their maximum response values to NO2 at a low operating temperature of 150 °C. The porous WO3 sensors showed high response values, great stability and fast response-recovery characteristics to different concentration of NO2 gas due to the high specific surface area and special structural and morphological properties.

.Highlights► Porous WO3 gas sensors were prepared by anodization of metallic tungsten films. ► Cracks appeared on the surface after anodization, which makes the films porous. ► The optimal operating temperature for porous WO3 sensors to NO2 was 150 °C. ► The porous WO3 showed high response values to different concentration of NO2 gas. ► The porous WO3 kept its gas sensing properties to NO2 even after two weeks.