A new capacitive-type NO2 gas sensor combining an MIS with a solid electrolyte

A new capacitive-type gas sensor for NO2 detection was fabricated by depositing NaNO2-based solid electrolyte layer together with an Au electrode over insulator-semiconductor structure. The resulting device exhibited expected metal-insulator-semiconductor (MIS) characteristics at 160 °C in air. In NO2 containing air, the voltage at constant capacitance was found to shift in negative direction in a well-controlled manner as the NO2 concentration increased. The voltage necessary to keep the capacitance was found to decrease linearly with an increase in the logarithm of NO2 concentration. The sensing mechanism seems to involve one electron reduction of NO2 at the Au electrode/NaNO2 interface.