Imaging bulk and edge transport near the dirac point in graphene moiré superlattices
File(s)acs.nanolett.8b00228.pdf (5.87 MB)
Published version
Author(s)
Type
Journal Article
Abstract
Van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride exhibit a moiré superlattice that is expected to break sublattice symmetry. Despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behavior, their precise nature is unclear. We present a scanning gate microscopy study of moiré superlattice devices with comparable activation energy but with different charge disorder levels. In the device with higher charge impurity (∼1010 cm–2) and lower resistivity (∼10 kΩ) at the Dirac point we observe current flow along the graphene edges. Combined with simulations, our measurements suggest that enhanced edge doping is responsible for this effect. In addition, a device with low charge impurity (∼109 cm–2) and higher resistivity (∼100 kΩ) shows subgap states in the bulk, consistent with the absence of shunting by edge currents.
Date Issued
2018-04-11
Online Publication Date
2020-07-08T10:26:16Z
Date Acceptance
2018-03-01
ISSN
1530-6984
Publisher
American Chemical Society (ACS)
Start Page
2530
End Page
2537
Journal / Book Title
Nano Letters
Volume
18
Issue
4
Copyright Statement
© 2018 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY)
License, which permits unrestricted use, distribution and reproduction in any medium,
provided the author and source are cited.
License, which permits unrestricted use, distribution and reproduction in any medium,
provided the author and source are cited.
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://pubs.acs.org/doi/10.1021/acs.nanolett.8b00228
Grant Number
EP/L020963/2
Subjects
Nanoscience & Nanotechnology
Publication Status
Published
Date Publish Online
2018-03-12