Detecting ions in air using a nanofield-effect transistor (nanoFET)

Abstract

In this study, we first demonstrate the quantitative detection of negative ions in air using a nano field-effect transistor (nanoFET). We propose an airborne anion-detecting sensor using a nanoFET suitable for a very small, low-cost device for detecting ions in air. We fabricated such a nanoFET device and evaluated its anion detection characteristics in air. The conductance change of the FET channel induced by the adsorption of airborne negative ions on the floating gate of the nanoFET device was measured in real time. The detection sensitivity of the nanoFET was evaluated by comparison with the measurement results of a conventional airborne ion counter. We then implemented a small, low-cost device for detecting air anions using a nanoFET sensor, circuits to drive the back-gate voltage and read out conductance changes, and a digital microprocessor.