Deterministic fabrication of graphene hexagonal boron nitride moiré superlattices

Authors:
Open Access
Publisher website
Google Scholar
Abstract
The electronic properties of moiré heterostructures depend sensitively on the relative orientation between layers of the stack. For example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample with one of the graphene layers rotationally aligned to a hexagonal Boron Nitride (hBN) cladding layer provided experimental observation of orbital ferromagnetism. To create samples with aligned graphene/hBN, researchers often align edges of exfoliated flakes that appear straight in optical micrographs. However, graphene or hBN can cleave along either zig-zag or armchair lattice directions, introducing a 30 ° ambiguity in the relative orientation of two flakes. By characterizing the crystal lattice orientation of exfoliated flakes prior to stacking using Raman and second-harmonic generation for graphene and hBN, respectively, we unambiguously align monolayer graphene to hBN at a near- 0 ° , not 30 ° , relative twist angle. We confirm this alignment by torsional force microscopy of the graphene/hBN moiré on an open-face stack, and then by cryogenic transport measurements, after full encapsulation with a second, nonaligned hBN layer. This work demonstrates a key step toward systematically exploring the effects of the relative twist angle between dissimilar materials within moiré heterostructures.
Funding Information
  • DOE | Office of Science (DE-AC02-76SF00515)
  • DOE | Office of Science (DE-AC02-76SF00515)
  • JSPS KAKENHI (21H05233)
  • JSPS KAKENHI (23H02052)
  • National Science Foundation (ECCS-2026822)
  • Gordon and Betty Moore Foundation (GBMF9460)

This publication has 51 references indexed in Scilit: