Electrostatic gas sensor with a porous silicon diaphragm

An electrostatic gas sensor with a porous silicon diaphragm was fabricated, and its sensing characteristics towards isopropyl alcohol (IPA) as a model gas were examined. The DC-biased diaphragm in the sensor vibrated under an alternating electric field in a frequency range of 0.5–40 kHz. For the annealed porous silicon diaphragm, four strong resonance peaks were observed in the frequency response. Furthermore, the frequency response properties, which changed with exposure to IPA gas, were used as response signals of the electrostatic gas sensor. As a function of IPA gas concentration, the vibration amplitude increased non-linearly, but the resonance frequency was shifted linearly. Furthermore, the operating voltage dependencies on the vibration amplitude of the diaphragm were investigated, and directions for future study to enhance sensor performance were also discussed.