Novel working mode of FET gas sensor: Electric double layer capacitance modulation of ionogel dielectric sensing layer

FET-type sensors have attracted considerable attention in trace-level hazardous analytes detection based on signal amplification effect. However, most of these sensors with either sensing gate or sensing channel are susceptible to humidity and signal crosstalk, significantly weakening the sensing performance. Herein, enlightened by the regulation of channel carriers attracted by ions from electric double layer (EDL), a side-gate FET (S-FET) gas sensor with ionogel dielectric sensing layer is rationally designed for proving the feasibility of novel capacitance sensing mode. The side-gate structure adequately exposes the dielectric sensing layer to the target gas and protects the channel region from being directly contacted to the ambient environment, guaranteeing the electrical and sensing stability of the sensor. Meanwhile, the gas volumetric adsorption nature of ionogel directly regulates the migration of ion carriers, macroscopically manifests the changes of EDL capacitance and ultimately influences the channel current of FET. The proposed FET sensor achieves excellent room-temperature gas sensing performances toward 0.02 ∼ 10 ppm of H 2 S, demonstrating an exceptional capability in food spoilage monitoring/halitosis prediagnosis. This work proposes a novel working mode of FET-type gas sensor for extending the categories of FET sensors, and offers relevant design concept in capacitance modulation for amplifying trace-level analytes-induced signal.