We report scanning tunneling microscopy and spectroscopy (STM and STS) studies of graphene formed from a nitrogen-seeded SiC(0001¯) surface. STM indicates that much of the graphene consists of wide flat plateaus with hexagonal features bounded by pleats and regions with disordered character. Nitrogen impurities are not observed in the epitaxial graphene layers. STS measurements on this surface show peaks corresponding to Landau levels associated with pseudo-magnetic fields as high as 1000 T. The energy distribution of Landau levels is consistent with an electronic model employing a finite bandgap.
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We are grateful to T. Low for insightful discussions, and P. Zahl, and J. Wang for assistance in the data acquisition and analysis. We acknowledge funding from NSF-DMR 1206793 , 1206655 , 1606256 . Use of the Center for Nanoscale Materials at Argonne was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences , under Contract No. DE-AC02-06CH11357 . This research was also carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences , under Contract No. DE- SC0012704 . Another portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility at Oak Ridge National Laboratory.