High-quality graphene p-n junctions via resist-free fabrication and solution-based noncovalent functionalization.

An essential issue in graphene nanoelectronics is to engineer the carrier type and density and still preserve the unique band structure of graphene. We report the realization of high-quality graphene p-n junctions by noncovalent chemical functionalization. A generic scheme for the graphene p-n junction fabrication is established by combining the resist-free approach and spatially selective chemical modification process. The effectiveness of the chemical functionalization is systematically confirmed by surface topography and potential measurements, spatially resolved Raman spectroscopic imaging, and transport/magnetotransport measurements. The transport characteristics of graphene p-n junctions are presented with observations of high carrier mobilities, Fermi energy difference, and distinct quantum Hall plateaus. The chemical functionalization of graphene p-n junctions demonstrated in this study is believed to be a feasible scheme for modulating the doping level in graphene for future graphene-based nanoelectronics.