AC phase sensing of graphene FETs for chemical vapors with fast recovery and minimal baseline drift

This work utilizes an AC phase sensing approach of chemical vapors to achieve minimal baseline drift and fast recovery on graphene-based field effect transistors (FETs). Phase lag signals between channel resistance and gate voltage are detected with ultrafast recovery speed (∼10 s) on defect-rich FETs made of chemical vapor deposition (CVD) graphene as the channel materials without surface functionalization at room temperature. The responses of the phase change upon exposure to water, methanol and ethanol vapors show at least ten times faster recovery speed than those of the conventional DC resistance measurements with minimal baseline drift, large dynamic range, and good stability. The effects of relative humidity on methanol and ethanol gas response properties are also studied. As such, the AC phase sensing scheme could open up a new class of research in gas sensors for improved sensing speed and baseline stability.