Pseudo-magnetic fields in rippled nitrogenated graphene

We demonstrate a new form of semiconducting graphene which is fabricated via controlled silicon sublimation on carbon face SiC(000$\bar{1}$), previously seeded with a submonolayer of nitrogen. Nitrogenated graphene (NG) films between 2 - 8 layers have been examined [F. Wang et al. Nano Lett. 13, 4827 (2013)]. Scanning tunneling microscopy (STM) shows that NG films have ripples and folds over the entire surface. The ripples are of variable size but typically about 2 nm wide and 2-4 nm high. They meander from 5-20 nm in length. STM images show graphene flowing continuously over all folds. Scanning tunneling spectroscopy (STS) at 50 K shows peaks corresponding to Landau levels, implying a pseudo magnetic field of about 100 T. Little variation in peak position is noted in spectra taken across a fold. Levy et al. observed similar STS spectra taken near graphene nano bubbles [N. Levy et al. Science 329, 544 (2010)]. Near the Dirac point in NG STS spectra, the peaks are weak and broad corresponding to a bandgap of less than 1.5 eV. For a similar film, angle resolved photoemission measures an offset of 0.7 eV, which is a measurement of the portion of the gap below the fermi level. We thank N. Guisinger and T. Low for their support and valuable discussions.