Dual-Gate Carbon-Based FET Trace Gas Sensors: Enhancing Sensitivity through Work Function Modulation

The development of gas sensor chips with high sensitivity is essential for environmental monitoring and disease diagnosis. Traditional strategies for enhancing gas sensor performance, such as heat and light assistance, inevitably influence device integration due to the requirement of auxiliary heating/lighting modules. Herein, a method for adjusting the work function of sensing materials via an electric field is proposed, which allows ppb-level ammonia (NH₃) detection and facilitates on-chip integration of gas sensors by eliminating the requirements of heating or irradiation. Based on this mechanism, a carbon-based field-effect transistor (FET) gas sensor with a dual-gate structure is designed, achieving a detection limit of 40 ppb NH₃ at 25 °C under an optimized control gate (CG) voltage of -8 V. Through density functional theory (DFT) calculations and electronic structure analysis, we reveal that the sensing mechanism originates from CG's work function variations induced by electric fields. Differential charge density calculations further indicate that the adsorption site, distance, and molecular polarization of NH₃ are regulated by the applied electric field, leading to an optimal response at specific gate voltages. This work reveals the mechanism of the electric field on gas sensor performance, providing a novel and universal strategy for developing high-performance gas sensors compatible with on-chip integration.