Gate-tunable Graphene Flakes Probed by Scanning Tunneling Spectroscopy at Atomic Scale

ORAL

Abstract

The nanometer scale electronic properties of mechanically cleaved graphene flake devices having tunable back-gates are resolved using scanning tunneling microscopy and spectroscopy. We observe an energy gap feature in the graphene tunneling spectrum that is unexpectedly pinned to the Fermi level ($E_{F}$ ) for different gate-induced electron densities. The Dirac point, on the other hand, is shifted by the back-gate by an amount prescribed by the graphene linear band structure. This energy gap is found to arise from a suppression of elastic electronic tunneling to graphene states near $E_{F}$ and a significant enhancement of tunneling (seen as a more than factor of 10 increase in the conductance) at higher energies due to a phonon-mediated inelastic channel. This work reveals important new tunneling processes in gate-tunable graphitic layers.

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Authors

  • Yuanbo Zhang

    Dept. of Physics at U.C. Berkeley, Dept. of Physics, UC Berkeley

  • Victor Brar

    Dept. of Physics at U.C. Berkeley / Lawrence Berkeley National Lab, Dept. of Physics, UC Berkeley/Lawrence Berkeley Laboratory

  • Feng Wang

    Dept. of Physics, UC Berkeley, UC Berkeley

  • Caglar Girit

    Dept. of Physics at U.C. Berkeley, Dept. of Physics, UC Berkeley/Lawrence Berkeley Laboratory, UC Berkeley, LBNL

  • Yossi Yayon

    Dept. of Physics, UC Berkeley

  • Melissa Panlasigui

    Dept. of Physics, UC Berkeley

  • Alex Zettl

    University of California, Berkeley, University of California at Berkeley, Dept. of Physics at U.C. Berkeley / Lawrence Berkeley National Lab, Dept. of Physics, UC Berkeley/Lawrence Berkeley Laboratory, UC Berkeley, LBNL

  • Michael F. Crommie

    University of California at Berkeley, Dept. of Physics at U.C. Berkeley / Lawrence Berkeley National Lab, Dept. of Physics, UC Berkeley/Lawrence Berkeley Laboratory