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Balgley J, Butler J, Biswas S, Ge Z, Lagasse S, Taniguchi T, Watanabe K, Cothrine M, Mandrus DG, Velasco J, Valentí R, Henriksen EA. Ultrasharp Lateral p-n Junctions in Modulation-Doped Graphene. NANO LETTERS 2022; 22:4124-4130. [PMID: 35533399 DOI: 10.1021/acs.nanolett.2c00785] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We demonstrate ultrasharp (≲10 nm) lateral p-n junctions in graphene using electronic transport, scanning tunneling microscopy, and first-principles calculations. The p-n junction lies at the boundary between differentially doped regions of a graphene sheet, where one side is intrinsic and the other is charge-doped by proximity to a flake of α-RuCl3 across a thin insulating barrier. We extract the p-n junction contribution to the device resistance to place bounds on the junction width. We achieve an ultrasharp junction when the boundary between the intrinsic and doped regions is defined by a cleaved crystalline edge of α-RuCl3 located 2 nm from the graphene. Scanning tunneling spectroscopy in heterostructures of graphene, hexagonal boron nitride, and α-RuCl3 shows potential variations on a sub 10 nm length scale. First-principles calculations reveal that the charge-doping of graphene decays sharply over just nanometers from the edge of the α-RuCl3 flake.
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Affiliation(s)
- Jesse Balgley
- Department of Physics, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Jackson Butler
- Department of Physics, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Sananda Biswas
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Zhehao Ge
- Physics Department, UC Santa Cruz, 1156 High Street, Santa Cruz, California 95064, United States
| | - Samuel Lagasse
- Electronics Science and Technology Division, United States Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Matthew Cothrine
- Material Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G Mandrus
- Material Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jairo Velasco
- Physics Department, UC Santa Cruz, 1156 High Street, Santa Cruz, California 95064, United States
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Erik A Henriksen
- Department of Physics, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
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2
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Rizzo D, Shabani S, Jessen BS, Zhang J, McLeod AS, Rubio-Verdú C, Ruta FL, Cothrine M, Yan J, Mandrus DG, Nagler SE, Rubio A, Hone JC, Dean CR, Pasupathy AN, Basov DN. Nanometer-Scale Lateral p-n Junctions in Graphene/α-RuCl 3 Heterostructures. NANO LETTERS 2022; 22:1946-1953. [PMID: 35226804 PMCID: PMC8915251 DOI: 10.1021/acs.nanolett.1c04579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The ability to create nanometer-scale lateral p-n junctions is essential for the next generation of two-dimensional (2D) devices. Using the charge-transfer heterostructure graphene/α-RuCl3, we realize nanoscale lateral p-n junctions in the vicinity of graphene nanobubbles. Our multipronged experimental approach incorporates scanning tunneling microscopy (STM) and spectroscopy (STS) and scattering-type scanning near-field optical microscopy (s-SNOM) to simultaneously probe the electronic and optical responses of nanobubble p-n junctions. Our STM/STS results reveal that p-n junctions with a band offset of ∼0.6 eV can be achieved with widths of ∼3 nm, giving rise to electric fields of order 108 V/m. Concurrent s-SNOM measurements validate a point-scatterer formalism for modeling the interaction of surface plasmon polaritons (SPPs) with nanobubbles. Ab initio density functional theory (DFT) calculations corroborate our experimental data and reveal the dependence of charge transfer on layer separation. Our study provides experimental and conceptual foundations for generating p-n nanojunctions in 2D materials.
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Affiliation(s)
- Daniel
J. Rizzo
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Sara Shabani
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Bjarke S. Jessen
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Alexander S. McLeod
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Carmen Rubio-Verdú
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L. Ruta
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G. Mandrus
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephen E. Nagler
- Neutron
Scattering Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Angel Rubio
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Center
for Computational Quantum Physics, Flatiron
Institute, New York, New York 10010, United
States
- Nano-Bio
Spectroscopy Group, Universidad del País
Vasco UPV/EHU, San Sebastián 20018, Spain
| | - James C. Hone
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R. Dean
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N. Pasupathy
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - D. N. Basov
- Department
of Physics, Columbia University, New York, New York 10027, United States
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3
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Ge Z, Wong D, Lee J, Joucken F, Quezada-Lopez EA, Kahn S, Tsai HZ, Taniguchi T, Watanabe K, Wang F, Zettl A, Crommie MF, Velasco J. Imaging Quantum Interference in Stadium-Shaped Monolayer and Bilayer Graphene Quantum Dots. NANO LETTERS 2021; 21:8993-8998. [PMID: 34699239 DOI: 10.1021/acs.nanolett.1c02271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Experimental realizations of graphene-based stadium-shaped quantum dots (QDs) have been few and have been incompatible with scanned probe microscopy. Yet, the direct visualization of electronic states within these QDs is crucial for determining the existence of quantum chaos in these systems. We report the fabrication and characterization of electrostatically defined stadium-shaped QDs in heterostructure devices composed of monolayer graphene (MLG) and bilayer graphene (BLG). To realize a stadium-shaped QD, we utilized the tip of a scanning tunneling microscope to charge defects in a supporting hexagonal boron nitride flake. The stadium states visualized are consistent with tight-binding-based simulations but lack clear quantum chaos signatures. The absence of quantum chaos features in MLG-based stadium QDs is attributed to the leaky nature of the confinement potential due to Klein tunneling. In contrast, for BLG-based stadium QDs (which have stronger confinement) quantum chaos is precluded by the smooth confinement potential which reduces interference and mixing between states.
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Affiliation(s)
- Zhehao Ge
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Dillon Wong
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Juwon Lee
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Frederic Joucken
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Eberth A Quezada-Lopez
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Salman Kahn
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Hsin-Zon Tsai
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Feng Wang
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoSciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alex Zettl
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoSciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Michael F Crommie
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoSciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jairo Velasco
- Department of Physics, University of California, Santa Cruz, California 95064, United States
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LaGasse SW, Cress CD. Unveiling Electron Optics in Two-Dimensional Materials by Nonlocal Resistance Mapping. NANO LETTERS 2020; 20:6623-6629. [PMID: 32787176 DOI: 10.1021/acs.nanolett.0c02443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We propose a technique based on nonlocal resistance measurements for mapping transport in electron optics experiments. Utilizing tight-binding transport methods, we show how to use a four-terminal measurement to isolate the ballistic transport from a single lead of interest and reconstruct its contribution to the local density of states. This enables us to propose an experimentally tractable four-terminal device with via contacts for measuring Veselago lensing in a graphene p-n junction. Furthermore, we demonstrate how to extend this method as a scanning probe technique, implementing mapping of complex electron optics experiments including angled junctions, collimation optics, and beam steering. Our results highlight the fundamental importance of electron dephasing in ballistic transport and provide guidelines for isolating electron optics signals of interest. These findings unveil a fresh approach to performing electron optics experiments, with a plethora of two-dimensional material platforms to explore.
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Affiliation(s)
- Samuel W LaGasse
- NRC Postdoc Residing at the Electronics Science and Technology Division, United States Naval Research Laboratory, Washington D.C. D.C. 20375, United States
| | - Cory D Cress
- Electronics Science and Technology Division, United States Naval Research Laboratory, Washington D.C. 20375, United States
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5
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A corner reflector of graphene Dirac fermions as a phonon-scattering sensor. Nat Commun 2019; 10:2428. [PMID: 31160597 PMCID: PMC6547877 DOI: 10.1038/s41467-019-10326-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 04/30/2019] [Indexed: 11/08/2022] Open
Abstract
Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the corner reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Pérot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.
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