Landau level splitting in nitrogen-seeded epitaxial graphene

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.