LABEL-FREE AC SENSING BY A GRAPHENE TRANSISTOR FOR 100-PPB FORMALDEHYDE IN AIR

This work marks the first use of an AC sensing technique on a graphene transistor to realize label-free gas sensing of 100 ppb-level formaldehyde in the air at room temperature. Compared with the state-of-art technology, three distinctive advances have been achieved: (1) extraordinary sensitivity of trace amount of formaldehyde using an AC phase detection method on a single graphene transistor made of the monolayer graphene from the chemical vapor deposition (CVD) process without adding functional materials; (2) high signal stability on devices with or without artificial defects; (3) fast response time of 10 seconds and recovery time of 60 seconds with minimal baseline drifts. As such, the proposed AC sensing method can achieve fast detection of the low concentration formaldehyde in air with reproducible performances on CVD graphene with different defect densities.