Detection of dilute nitrogen dioxide and thickness effect of tungsten oxide thin film sensors

WO3 thin film sensors have been fabricated by suspension dropping on SiO2/Si substrate equipped with Au microelectrodes, and subjected to the detection of dilute NO2 less than ppm level. The WO3 thin film with the thickness of ca. 0.6μm showed the extremely high sensitivity to dilute NO2 at 200°C (for example, S=9.4 to 0.2ppm NO2). The Au electrodes were visible for the thin film of 0.6μm, inducing the easy access of NO2 molecules to a part between electrodes. Moreover, the high sensitivity suggests the possibility of environmental monitoring using WO3 thin film sensors.