Ultrathin MoOx/Graphene Hybrid Field Effect Transistor Sensors Prepared Simply by a Shadow Mask Approach for Selective ppb‐Level NH3 Sensing with Simultaneous Superior Response and Fast Recovery

Both simultaneous achievement of high response, low limit of detection, and full recovery at room temperature (RT) for weak reducing gases like NH3 and facile and batchable fabrication approach are quite challenging for sensors. Herein, ultrathin MoOx layers are hybridized with mono layer graphene with different coverage percentages, into MoOx/GFET (graphene field effect transistor) devices for selective NH3 sensing fabricated by a facile, cost effective, and contamination‐free shadow mask approach instead of conventional lithography processes. A response of −18.10% for 12 ppm NH3 with full recovery of 356 s, superior repeatability, low detection limit of 310 ppb, and strong selectivity is simultaneously achieved for MoOx/GFET sensors at RT. The superior sensing and recovery performance of MoOx/GFET sensors is predominantly attributed to the effective tuning of Schottky barrier height and the Coulomb interaction between charged polar donor molecules and positively polarized surface enhanced by the positive bias voltage. The energy band diagrams well explain the sensing mechanism for reducing/oxidizing gases. The idea proposed in this study offers a feasible solution for highly selective sensing of different gases by oxides/graphene hybrid FET based gas sensors with superior RT performances fabricated by a facile, contamination‐free, batchable, and generalized approach. Ultrathin MoOx/graphene field effect transistor sensors with 100% molybdenum coverage (D100) favor the room temperature NH3 sensing performance. The higher positive bias voltage (+75 V) effectively modulates the Schottky barrier height for simultaneous achievement of high sensitivity, low detection limit, fast recovery, superior repeatability, strong selectivity, and long term stability for 12 ppm NH3.