Micromachined gas sensors based on tungsten oxide nanoneedles directly integrated via aerosol assisted CVD

Micromachined gas sensors based on tungsten oxide nanostructures (NSs) in the form of polycrystalline films, non-aligned and quasi-aligned nanoneedles (NNs) films are fabricated by integrating various microsystems technology steps with aerosol assisted chemical vapour deposition (AACVD). Measurement of the performance of these structures to various analytes, including NO2, H2, EtOH, H2S, CO, C6H6, demonstrate enhanced sensing properties for gas sensors based on films comprised of NNs as opposed to polycrystalline, with non-aligned NNs films showing the greatest sensor responses. A marked contribution of the NNs diameter to the sensor response is noticed, particularly for sensors composed of NNs with diameters between 25 and 50 nm. In addition, fabrication variables such as the NNs arrangement and the electrode geometry suggest their contribution to the sensor response is connected with the effects of the gaseous analytes at the surface, i.e. whether these analytes act as reducing or oxidizing agents.