Electron Beam Evaporation of Tungsten Oxide Films for Gas Sensors

Pure and iron incorporated nanostructured Tungsten Oxide (WO
₃
) thin films were investigated for gas sensing applications using noise spectroscopy. The WO
₃
sensor was able to detect lower concentrations (1-10 ppm) of NH
₃
, CO, CH
₄
, and Acetaldehyde gases at operating temperatures between 100°C to 250°C. The iron-doped Tungsten Oxide sensor ( WO
₃
:Fe) showed some response to Acetaldehyde gas at relatively higher operating temperature (250°C) and gas concentration of 10 ppm. The sensitivity of the WO
₃
sensor towards NH
₃
, CH
₄
and Acetaldehyde at lower operating temperatures (50°C-100°C) was significant when the sensor was photo-activated using blue light-emitting diode (Blue-LED). From the results, photo-activated WO
₃
thin film that operates at room temperature appeared to be a promising gas sensor. The overall results indicated that the WO
₃
sensor exhibited reproducibility for the detection of various gasses and the WO
₃
:Fe indicated some response towards Acetaldehyde gas.