Role of oxygen in high temperature hydrogen sulfide detection using MISiC sensors

This paper reports on the sensitivity of a MISiC capacitor sensor with a catalytic top contact to gas mixtures, including hydrogen sulfide, at temperatures in excess of 300 degrees C. The gas concentration may be extracted from the change in leakage current through the capacitor and exposure to H2S gives a response similar to that observed in hydrogen. This indicates that the decomposition of the H2S on the catalytic contact is forming atomic hydrogen, which forms a dipole layer at the dielectric/SiO2 interface. Exposure to oxygen and H2S simultaneously gives a larger hydrogen-like response, which is contrary to that observed when hydrogen and oxygen are mixed. We suggest that this response is related to the influence of the choice of dielectric used to fabricate the capacitor structure, offering the opportunity to develop array technology for unique identification of gas species in a mixture.