Transport in Graphene Tunnel Junctions

Abstract

We present a technique to fabricate tunnel junctions between graphene and Al and Cu, with a Si back gate, as well as a simple theory of tunneling between a metal and graphene. We map the differential conductance of our junctions versus probe and back gate voltage, and observe fluctuations in the conductance that are directly related to the graphene density of states. The conventional strong-suppression of the conductance at the graphene Dirac point can not be clearly demonstrated, but a more robust signature of the Dirac point is found: the inflection in the conductance map caused by the electrostatic gating of graphene by the tunnel probe. We present numerical simulations of our conductance maps, confirming the measurement results. In addition, Al causes strong n-doping of graphene, Cu causes a moderate p-doping, and in high resistance junctions, phonon resonances are observed, as in STM studies.

22 pages, 5 figures

References in corpus (12)

• Ultrahigh electron mobility in suspended graphene
• Doping graphene with metal contacts
• Realization of a High Mobility Dual-gated Graphene Field Effect Transistor with Al2O3 Dielectric
• Transport measurements across a tunable potential barrier in graphene
• Scanning Tunneling Spectroscopy of Graphene on Graphite
• Giant Phonon-induced Conductance in Scanning Tunneling Spectroscopy of Gate-tunable Graphene
• Evidence of the role of contacts on the observed electron-hole asymmetry in graphene
• The Coulomb impurity problem in graphene
• Spatially resolved spectroscopy of monolayer graphene on SiO2
• Effects of metallic contacts on electron transport through graphene
• Phonon mediated tunneling into graphene
• Inter-Layer Screening Length to Electric Field in Thin Graphite Film