Highly sensitive bilayer structured graphene sensor

This paper presents a nanosensor with an “inter-sheet” configuration formed by making electrical contacts on different atomic sheets of a bilayer structured graphene to expose the inter-sheet effects. An oxygen plasma etching (OPE) technique is developed to tailor the shape and number of layers of a graphene flake. Both “intra-sheet” and “inter-sheet” structured graphene sensors on either separated graphenes or a same graphene were fabricated and tested as ethanol molecule sensors. Our sensors exhibit a higher sensitivity than conventional “intra-sheet” structured graphene sensors. The gas sensitivity was demonstrated by the 42.48% and 185.25% relative resistance changes achieved from “inter-sheet” sensors upon exposure to the 0.5% ethanol in nitrogen environment. This is a remarkable enhancement on sensitivity compared with that of “intra-layer” sensors, which had only 7.51% and 22.79% relative resistance changes under the same conditions. This improvement can be attributed to the strong exponential relationship between inter-sheet tunneling current and layer separation.