Deterministic fabrication of graphene hexagonal boron nitride moiré superlattices

• 成果类型: Article
• 署名作者: Kamat, Rupini, V; Sharpe, Aaron L.; Pendharkar, Mihir; Hu, Jenny; Tran, Steven J.; Zaborski Jr, Gregory; Hocking, Marisa; Finney, Joe; Watanabe, Kenji; Taniguchi, Takashi; Kastner, Marc A.; Mannix, Andrew J.; Heinz, Tony; Goldhaber-Gordon, David
• 署名单位: Stanford University; Stanford University; United States Department of Energy (DOE); SLAC National Accelerator Laboratory; Stanford University; National Institute for Materials Science; Massachusetts Institute of Technology (MIT)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12779
• DOI: 10.1073/pnas.2410993121
• 发表日期: 2024-10-01
• 关键词: dirac fermions; insulator; STATES; ferromagnetism

摘要

The electronic properties of moir & eacute; 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 degrees 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 degrees, not 30 degrees, relative twist angle. We confirm this alignment by torsional force microscopy of the graphene/hBN moir & eacute; 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 moir & eacute; heterostructures.