NO2 gas sensing characteristics of Pt–Wo3–Si3N4–SiO2–Si–Al capacitor

A new gas-sensitive capacitor utilizing Pt–WO3–Si3N4–SiO2–Si–Al MIS structure has been explored. The incorporation of Pt as the catalytic gate and WO3 as the gas adsorptive oxide with the silicon MIS capacitor enhances the detection of NO2 at a relatively low temperature. Device performance in terms of sensitivity is presented. A new detection model based on a change in concentration of ions at Pt–WO3 interface is proposed for the sensing mechanism. Detection mechanism for NO2 is attributed to the chemisorption at extrinsic surface states on the adsorptive oxide surface in a form of negatively charged nitrogen dioxide ions. The model is confirmed by the reaction kinetic analysis at the interface.