title: Direct Probing of the Electronic Structures of Single-Layer and Bilayer Graphene with a Hexagonal Boron Nitride Tunneling Barrier.
abstract: The chemical and mechanical stability of hexagonal boron nitride (h-BN) thin films and their compatibility with other free-standing two-dimensional (2D) crystals to form van der Waals heterostructures make the h-BN-2D tunnel junction an intriguing experimental platform not only for the engineering of specific device functionalities but also for the promotion of quantum measurement capabilities. Here, we exploit the h-BN-graphene tunnel junction to directly probe the electronic structures of single-layer and bilayer graphene in the presence and the absence of external magnetic fields with unprecedented high signal-to-noise ratios. At a zero magnetic field, we identify the tunneling spectra related to the charge neutrality point and the opening of the electric-field-induced bilayer energy gap. In the quantum Hall regime, the quantization of 2D electron gas into Landau levels (LL) is seen as early as 0.2 T, and as many as 30 well-separated LL tunneling conductance oscillations are observed for both electron- and hole-doped regions. Our device simulations successfully reproduce the experimental observations. Additionally, we extract the relative permittivity of three-to-five layer h-BN and find that the screening capability of thin h-BN films is as much as 60% weaker than bulk h-BN.
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.
authors.forename: Suyong
authors.identifier: 0000-0003-3885-9999
authors.initials: S
authors.lastname: Jung
authors.affiliation: Center for Theoretical Physics of Complex Systems, Institute for Basic Science , Daejeon 34051, Korea.
authors.forename: Nojoon
authors.initials: N
authors.lastname: Myoung
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.
authors.forename: Jaesung
authors.initials: J
authors.lastname: Park
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.|Department of Physics, Chungnam National University , Daejeon 34134 Korea.
authors.forename: Tae Young
authors.initials: TY
authors.lastname: Jeong
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.
authors.forename: Hakseong
authors.initials: H
authors.lastname: Kim
authors.affiliation: National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.identifier: 0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.
authors.forename: Dong Han
authors.initials: DH
authors.lastname: Ha
authors.affiliation: Korea Research Institute of Standards and Science , Daejeon 34113, Korea.
authors.forename: Chanyong
authors.initials: C
authors.lastname: Hwang
authors.affiliation: Center for Theoretical Physics of Complex Systems, Institute for Basic Science , Daejeon 34051, Korea.
authors.forename: Hee Chul
authors.initials: HC
authors.lastname: Park
keywords: Electron tunneling spectroscopy; Landau level tunneling spectroscopy; electric-field-induced bilayer graphene energy gap; hexagonal boron nitride; relative permittivity of thin oxide films; van der Waals heterostructures