Field-effect NO2 sensors with group 1B metal gates

Flat-band voltage shifts of MOS capacitors with continuous Cu, Ag and Au gates, in response to controlled NO2 bearing atmospheres, are inversely related to changes in the work function, measured by ultraviolet photoelectron spectroscopy. Device sensitivity is conditioned by the rate of analyte arrival to the gate–dielectric interface, which decreases by reactive behavior of Cu and Ag gates, evidenced by concentration independence of the response and discharge times. Maximum response is obtained for Au gates, in which NO2 adsorption is molecular and non-dissociative, despite minimal work function change.