Anodized nanoporous WO₃ Schottky contact structures for hydrogen and ethanol sensing

This paper reports the development of nanoporous tungsten trioxide (WO 3 ) Schottky diode-based gas sensors. Nanoporous WO 3 films were prepared by anodic oxidation of tungsten foil in ethylene glycol mixed with ammonium fluoride and a small amount of water. Anodization resulted in highly ordered WO 3 films with a large surface-to-volume ratio. Utilizing these nanoporous structures, Schottky diode-based gas sensors were developed by depositing a platinum (Pt) catalytic contact and tested towards hydrogen gas and ethanol vapour. Analysis of the current-voltage characteristics and dynamic responses of the sensors indicated that these devices exhibited a larger voltage shift in the presence of hydrogen gas compared to ethanol vapour at an optimum operating temperature of 200°C. The gas sensing mechanism was discussed, associating the response to the intercalating H + species that are generated as a result of hydrogen and ethanol molecule breakdowns onto the Pt/WO 3 contact and their spill over into nanoporous WO 3 .