2, KAIST Institute for Nanocentury, Daejeon, , Korea (the Republic of)
3, Drexel University, Philadelphia, Pennsylvania, United States
2D materials have exciting prospects for chemical sensing devices due to their exceptional electrical, mechanical, and surface properties. Large surface-to-volume ratio of the 2D materials leads to dense number of adsorption sites, and the customized sensing channel with appropriate band gap can be easily realized by tuning the number of the layers in the 2D materials. Also, these materials have various active sties for selective molecular adsorption including vacancy, edge, basal planes, and defects. In addition, 2D materials can be operated in room temperature, which is impossible in metal oxide based semiconductors. Various 2D materials, which include graphene, transition metal dichalcogenides (TMDs), boron/carbon nitride and MXene, have been suggested as potential chemical sensing materials. Each material has its own advantages onto target molecules depending on their band gap opening status, molecular adsorption energy, and physical properties. For examples, graphene and reduced graphene oxide (rGO) possess low signal-to-noise level and stable response to target analytes, which arise from high electrical conductivity of semi-metallic channel characteristics. Also, graphene has high charge carrier mobility at room temperature and strong mechanical stability, which is critical to practical chemical sensing applications. On the other hand, TMDs such as MoS2 or WS2 are layer dependent semiconducting materials, which can be fabricated into highly sensitive and user-defined sensing circuits with mono to few layers. Further surface functionalization and defect engineering such as exposure of edge sites of TMDs, ligand conjugation, chemical doping, and molecular physisorption can improve chemical sensing performance and lead to easy modulation of response onto target. Recently, it is demonstrated that black phosphorus (BP), a new emerging class of 2D materials can show both high sensitivity and selectivity onto paramagnetic molecules. In this talk, we present precise comparison study of sensing performance of each 2D materials including rGO, MoS2, and BP. In addition, based on discovered basic characteristics of each materials, we show how we can efficiently enhance their sensitivity and selectivity: via alignment control and chemical doping status. These studies are expected to elucidate the key morphological, materials, and chemical factors that govern the sensing performance of 2D materials. The chemical sensing ability of MXene is also discussed.