Signatures of Phonon and Defect-Assisted Tunneling in Planar Metal–Hexagonal Boron Nitride–Graphene Junctions
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2016-11-28 |
| Journal | Nano Letters |
| Authors | U. Chandni, Kenji Watanabe, Takashi Taniguchi, J. P. Eisenstein |
| Institutions | California Institute of Technology, National Institute for Materials Science |
| Citations | 60 |
Abstract
Section titled “Abstract”Electron tunneling spectroscopy measurements on van der Waals heterostructures consisting of metal and graphene (or graphite) electrodes separated by atomically thin hexagonal boron nitride tunnel barriers are reported. The tunneling conductance, dI/dV, at low voltages is relatively weak, with a strong enhancement reproducibly observed to occur at around |V| ≈ 50 mV. While the weak tunneling at low energies is attributed to the absence of substantial overlap, in momentum space, of the metal and graphene Fermi surfaces, the enhancement at higher energies signals the onset of inelastic processes in which phonons in the heterostructure provide the momentum necessary to link the Fermi surfaces. Pronounced peaks in the second derivative of the tunnel current, d<sup>2</sup>I/dV<sup>2</sup>, are observed at voltages where known phonon modes in the tunnel junction have a high density of states. In addition, features in the tunneling conductance attributed to single electron charging of nanometer-scale defects in the boron nitride are also observed in these devices. The small electronic density of states of graphene allows the charging spectra of these defect states to be electrostatically tuned, leading to “Coulomb diamonds” in the tunneling conductance.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 1985 - Principles of Electron Tunneling Spectroscopy
- 2008 - Introduction to Scanning Tunneling Microscopy