Multiparametric porous silicon gas sensors with improved quality and sensitivity

We have fabricated a multiparametric gas sensor based on porous silicon. The sensing parameters are the electrical conductivity of a single porous Si layer and the resonance wavelength of a porous silicon microcavity, both fabricated on the same substrate. The electrical conductivity allows detection of 50 ppb of nitrogen dioxide in dry air. Although relative humidity also affects the electrical conductivity, the contributions due to nitrogen dioxide and to humidity can be distinguished by simultaneously monitoring the cavity resonance wavelength and the current. We also demonstrate a three-contact configuration which further increases the sensitivity of the electrical response of the sensor.