1
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Shibuta M, Nakajima A. Imaging of ultrafast photoexcited electron dynamics in pentacene nanocrystals on a graphite substrate. NANOSCALE 2024; 16:12397-12405. [PMID: 38832543 DOI: 10.1039/d4nr00720d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Understanding molecular film growth on substrates and the ultrafast electron dynamics at their interface is crucial for advancing next-generation organic electronics. We have focused on studying the ultrafast photoexcited electron dynamics in nanoscale organic crystals of an aromatic molecule, pentacene, on a two-dimensional material of graphite substrate. Through the use of time-resolved two-photon photoelectron emission microscopy (2P-PEEM), we have visualized the ultrafast lateral evolution of photoexcited electrons. By resonantly tuning the incident photon to excite pentacene molecules, polarization-dependent 2P-PEEM has revealed that pentacene nanocrystals (sub- to several μm) on the substrate exhibit a preferential orientation, in which a molecular π-orbital contacts the substrate in a "lying flat" orientation, facilitating electron transfer to the substrate. The time-resolved 2P-PEEM captures the motion of excited electrons in a femto- to pico-second timescale, clearly imaging the ultrafast charge transfer and lateral expansion two-dimensionally on the graphite substrate. Moreover, we found that the lying-flat molecular orientation of pentacene nanocrystals is transformable into a "standing-up" one through gentle heating up to 50 °C. These experimental insights using time-resolved 2P-PEEM will be highly valuable in enhancing the photofunctionalities of organic electronic devices by controlled molecular deposition.
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Affiliation(s)
- Masahiro Shibuta
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
| | - Atsushi Nakajima
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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2
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Hoke JC, Li Y, May-Mann J, Watanabe K, Taniguchi T, Bradlyn B, Hughes TL, Feldman BE. Uncovering the spin ordering in magic-angle graphene via edge state equilibration. Nat Commun 2024; 15:4321. [PMID: 38773076 PMCID: PMC11109299 DOI: 10.1038/s41467-024-48385-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 04/30/2024] [Indexed: 05/23/2024] Open
Abstract
The flat bands in magic-angle twisted bilayer graphene (MATBG) provide an especially rich arena to investigate interaction-driven ground states. While progress has been made in identifying the correlated insulators and their excitations at commensurate moiré filling factors, the spin-valley polarizations of the topological states that emerge at high magnetic field remain unknown. Here we introduce a technique based on twist-decoupled van der Waals layers that enables measurement of their electronic band structure and-by studying the backscattering between counter-propagating edge states-the determination of the relative spin polarization of their edge modes. We find that the symmetry-broken quantum Hall states that extend from the charge neutrality point in MATBG are spin unpolarized at even integer filling factors. The measurements also indicate that the correlated Chern insulator emerging from half filling of the flat valence band is spin unpolarized and suggest that its conduction band counterpart may be spin polarized.
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Affiliation(s)
- Jesse C Hoke
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Yifan Li
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Julian May-Mann
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Barry Bradlyn
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Taylor L Hughes
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Benjamin E Feldman
- Department of Physics, Stanford University, Stanford, CA, 94305, USA.
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA.
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
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3
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Sadeqian A, Ahmadi MT, Bodaghzadeh M, Abazari AM. Calculating and analyzing time delay in zigzag graphene nanoscrolls based complementary metal-oxide-semiconductors. Sci Rep 2024; 14:9009. [PMID: 38637607 DOI: 10.1038/s41598-024-58593-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 04/01/2024] [Indexed: 04/20/2024] Open
Abstract
Graphene Nano Scrolls (GNSs) and Zigzag graphene nanoscrolls (ZGNSs) are semi-one-dimensional materials with exceptional electrical and optical properties, making them attractive to be used in nanoelectronics and complementary metal-oxide-semiconductor (CMOS) technology. With in CMOS device technology, time delay is a crucial issue in the design and implementation of CMOS based ZGNSs. Current paper focus is on ZGNSs application in the channel area of metal-oxide-semiconductor field-effect transistors (MOSFETs) in CMOS technology. We studied analytically, the importance of different parameters on time delay reduction, resulting in faster switching and higher frequency in integrated circuits (ICs). The results of this research demonstrates that, the ZGNS-based CMOS proves considerable variations in the current due to the geometrical parameters, such as chirality number, channel length, and nanoscroll length which can be engineered to produce faster ICs.
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Affiliation(s)
- Ali Sadeqian
- Nanotechnology Research Center, Nanoelectronics Group, Physics Department, Urmia University, Urmia, 57147, Iran
| | - Mohammad Taghi Ahmadi
- Nanotechnology Research Center, Nanoelectronics Group, Physics Department, Urmia University, Urmia, 57147, Iran.
| | - Morteza Bodaghzadeh
- Nanotechnology Research Center, Nanoelectronics Group, Physics Department, Urmia University, Urmia, 57147, Iran
| | - Amir Musa Abazari
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
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4
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Zhang Z, Xie J, Zhao W, Qi R, Sanborn C, Wang S, Kahn S, Watanabe K, Taniguchi T, Zettl A, Crommie M, Wang F. Engineering correlated insulators in bilayer graphene with a remote Coulomb superlattice. NATURE MATERIALS 2024; 23:189-195. [PMID: 38177380 DOI: 10.1038/s41563-023-01754-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 11/06/2023] [Indexed: 01/06/2024]
Abstract
Electron superlattices allow the engineering of correlated and topological quantum phenomena. The recent emergence of moiré superlattices in two-dimensional heterostructures has led to exciting discoveries related to quantum phenomena. However, the requirement for the moiré pattern poses stringent limitations, and its potential cannot be switched on and off. Here, we demonstrate remote engineering and on/off switching of correlated states in bilayer graphene. Employing a remote Coulomb superlattice realized by localized electrons in twisted bilayer WS2, we impose a Coulomb superlattice in the bilayer graphene with period and strength determined by the twisted bilayer WS2. When the remote superlattice is turned off, the two-dimensional electron gas in the bilayer graphene is described by a Fermi liquid. When it is turned on, correlated insulating states at both integer and fractional filling factors emerge. This approach enables in situ control of correlated quantum phenomena in two-dimensional materials hosting a two-dimensional electron gas.
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Affiliation(s)
- Zuocheng Zhang
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Jingxu Xie
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
- Graduate Group in Applied Science and Technology, University of California at Berkeley, Berkeley, CA, USA
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Wenyu Zhao
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Ruishi Qi
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Collin Sanborn
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Shaoxin Wang
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Salman Kahn
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Alex Zettl
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Kavli Energy NanoSciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Michael Crommie
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Kavli Energy NanoSciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Feng Wang
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA.
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Kavli Energy NanoSciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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5
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Huang S, Griffin E, Cai J, Xin B, Tong J, Fu Y, Kravets V, Peeters FM, Lozada-Hidalgo M. Gate-controlled suppression of light-driven proton transport through graphene electrodes. Nat Commun 2023; 14:6932. [PMID: 37907470 PMCID: PMC10618495 DOI: 10.1038/s41467-023-42617-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 10/17/2023] [Indexed: 11/02/2023] Open
Abstract
Recent experiments demonstrated that proton transport through graphene electrodes can be accelerated by over an order of magnitude with low intensity illumination. Here we show that this photo-effect can be suppressed for a tuneable fraction of the infra-red spectrum by applying a voltage bias. Using photocurrent measurements and Raman spectroscopy, we show that such fraction can be selected by tuning the Fermi energy of electrons in graphene with a bias, a phenomenon controlled by Pauli blocking of photo-excited electrons. These findings demonstrate a dependence between graphene's electronic and proton transport properties and provide fundamental insights into molecularly thin electrode-electrolyte interfaces and their interaction with light.
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Affiliation(s)
- S Huang
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - E Griffin
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK.
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK.
| | - J Cai
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- College of Advanced Interdisciplinary Studies, National University of Defence Technology, Changsha, Hunan, 410073, China
| | - B Xin
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - J Tong
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Y Fu
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - V Kravets
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
| | - F M Peeters
- Departamento de Fisica, Universidade Federal do Ceara, 60455-900, Fortaleza, Ceara, Brazil
- Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020, Antwerp, Belgium
| | - M Lozada-Hidalgo
- Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK.
- National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK.
- Research and Innovation Center for graphene and 2D materials (RIC2D), Khalifa University, PO Box 127788, Abu Dhabi, United Arab Emirates.
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6
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Han X, Liu Q, Wang Y, Niu R, Qu Z, Wang Z, Li Z, Han C, Watanabe K, Taniguchi T, Song Z, Mao J, Han ZV, Gan Z, Lu J. Chemical Potential Characterization of Symmetry-Breaking Phases in a Rhombohedral Trilayer Graphene. NANO LETTERS 2023; 23:6875-6882. [PMID: 37466217 DOI: 10.1021/acs.nanolett.3c01262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Rhombohedral trilayer graphene has recently emerged as a natural flat-band platform for studying interaction-driven symmetry-breaking phases. The displacement field (D) can further flatten the band to enhance the density of states, thereby controlling the electronic correlation that tips the energy balance between spin and valley degrees of freedom. To characterize the energy competition, chemical potential measurement─a direct thermodynamic probe of Fermi surfaces─is highly demanding to be conducted under a constant D. In this work, we characterize D-dependent isospin flavor polarization, where electronic states with isospin degeneracies of one and two can be identified. We also developed a method to measure the chemical potential at a fixed D, allowing for the extraction of energy variation during phase transitions. Furthermore, symmetry breaking could also be invoked in Landau levels, manifesting as quantum Hall ferromagnetism. Our work opens more opportunities for the thermodynamic characterization of displacement-field tuned van der Waals heterostructures.
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Affiliation(s)
- Xiangyan Han
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Qianling Liu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Yijie Wang
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Ruirui Niu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuangzhuang Qu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhiyu Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuoxian Li
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Chunrui Han
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Zhida Song
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Jinhai Mao
- School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zheng Vitto Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Optoelectronics, Shanxi University, Taiyuan 030006, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Zizhao Gan
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Jianming Lu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
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7
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Wu PJ, Tsai WC, Yang CS. Electrically tunable graphene-based multi-band terahertz metamaterial filters. OPTICS EXPRESS 2023; 31:469-478. [PMID: 36606981 DOI: 10.1364/oe.477525] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
In this study, we have designed an electrically tunable multi-band terahertz (THz) metamaterial filter based on graphene and multiple-square-loop structures. The structure contains multiple metal square loops, and these loops with different sizes correspond to different THz frequencies, achieving our expected efficacy of a multiband wave filter. Furthermore, by sweeping external voltages, we could change graphene's Fermi levels, and thus the high-sensitivity THz filter's capability from single-band to multi-band filtering can be modulated. We expect that this study of a hybrid THz wave filter would be promising for the development of selecting channels in THz and 6 G communications.
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8
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Gadelha AC, Nguyen VH, Neto EGS, Santana F, Raschke MB, Lamparski M, Meunier V, Charlier JC, Jorio A. Electron-Phonon Coupling in a Magic-Angle Twisted-Bilayer Graphene Device from Gate-Dependent Raman Spectroscopy and Atomistic Modeling. NANO LETTERS 2022; 22:6069-6074. [PMID: 35878122 DOI: 10.1021/acs.nanolett.2c00905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The importance of phonons in the strong correlation phenomena observed in twisted-bilayer graphene (TBG) at the so-called magic-angle is under debate. Here we apply gate-dependent micro-Raman spectroscopy to monitor the G band line width in TBG devices of twist angles θ = 0° (Bernal), ∼1.1° (magic-angle), and ∼7° (large-angle). The results show a broad and p-/n-asymmetric doping behavior at the magic angle, in clear contrast to the behavior observed in twist angles above and below this point. Atomistic modeling reproduces the experimental observations in close connection with the joint density of electronic states in the electron-phonon scattering process, revealing how the unique electronic structure of magic-angle TBGs influences the electron-phonon coupling and, consequently, the G band line width. Overall, the value of the G band line width in magic-angle TBG is larger when compared to that of the other samples, in qualitative agreement with our calculations.
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Affiliation(s)
- Andreij C Gadelha
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Viet-Hung Nguyen
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Eliel G S Neto
- Physics Institute, Universidade Federal da Bahia, Salvador, Bahia 40170-115 Brazil
| | - Fabiano Santana
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| | - Markus B Raschke
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Michael Lamparski
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Jean-Christophe Charlier
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Ado Jorio
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
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9
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Or P, Devidas TR, Taniguchi T, Watanabe K, Sabo-Napadesky I, May-Tal Beck S, Ron G, Steinberg H. Positron charge sensing using a double-gated graphene field effect transistor. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:015002. [PMID: 35104988 DOI: 10.1063/5.0069481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 12/10/2021] [Indexed: 06/14/2023]
Abstract
We utilize a high-mobility double-gated graphene field-effect transistor to measure the accumulated charge created by positron annihilation in its back-gate. The device consists of an exfoliated graphene flake stacked between two hexagonal boron nitride flakes placed on a 1 cm2 substrate of 500 μm thick conducting p-doped Si capped by 285 nm-thick SiO2. The device is placed in close proximity to a 780 kBq 22Na positron source emitting a constant flux of positrons. During the measurement, positrons annihilate within the back-gate, kept floating using a low-capacitance relay. The accumulated positive charge capacitively couples to the graphene device and builds a positive voltage, detectable through a shift in the top-gate dependent graphene resistance characteristic. The shift in the position of the top-gate Dirac peak is then used for extracting the exact voltage buildup and quantitative evaluation of the accumulated charge. Reaching a positron current sensitivity of ∼1.2 fA/Hz, detected over 20 min, our results demonstrate the utility of two-dimensional layered materials as probes for charging dynamics of positrons in solids.
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Affiliation(s)
- Paz Or
- The Racah Institute of Physics, The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel
| | - T R Devidas
- The Racah Institute of Physics, The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel
| | - 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
| | | | | | - Guy Ron
- The Racah Institute of Physics, The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel
| | - Hadar Steinberg
- The Racah Institute of Physics, The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel
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10
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Zheng S, Joo Y, Zhao M, Kang K, Watanabe K, Taniguchi T, Myoung N, Moon P, Son YW, Yang H. Robust Quantum Oscillation of Dirac Fermions in a Single-Defect Resonant Transistor. ACS NANO 2021; 15:20013-20019. [PMID: 34843211 DOI: 10.1021/acsnano.1c07613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The massless nature of Dirac Fermions produces large energy gaps between Landau levels (LLs), which is promising for topological devices. While the energy gap between the zeroth and first LLs reaches 36 meV in a magnetic field of 1 T in graphene, exploiting the quantum Hall effect at room temperature requires large magnetic fields (∼30 T) to overcome the energy level broadening induced by charge inhomogeneities in the device. Here, we report a way to use the robust quantum oscillations of Dirac Fermions in a single-defect resonant transistor, which is based on local tunneling through a thin (∼1.4 nm) hexagonal boron nitride (h-BN) between lattice-orientation-aligned graphene layers. A single point defect in the h-BN, selected by the orientation-tuned graphene layers, probes local LLs in its proximity, minimizing the energy broadening of the LLs by charge inhomogeneity at a moderate magnetic field and ambient conditions. Thus, the resonant tunneling between lattice-orientation-aligned graphene layers highlights the potential to spectroscopically locate the atomic defects in the h-BN, which contributes to the study on electrically tunable single photon source via defect states in h-BN.
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Affiliation(s)
- Shoujun Zheng
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Yanggeun Joo
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Mali Zhao
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
| | - Kyungrok Kang
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 303-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 303-0044, Japan
| | - Nojoon Myoung
- Department of Physics Education, Chosun University, Gwangju 61452, Korea
| | - Pilkyung Moon
- New York University Shanghai and NYU-ECNU Institute of Physics at NYU Shanghai, Shanghai 200122, China
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Korea
| | - Young-Woo Son
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Korea
| | - Heejun Yang
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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11
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Flavour Hund's coupling, Chern gaps and charge diffusivity in moiré graphene. Nature 2021; 592:43-48. [PMID: 33790447 DOI: 10.1038/s41586-021-03366-w] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 02/16/2021] [Indexed: 11/08/2022]
Abstract
Interaction-driven spontaneous symmetry breaking lies at the heart of many quantum phases of matter. In moiré systems, broken spin/valley 'flavour' symmetry in flat bands underlies the parent state from which correlated and topological ground states ultimately emerge1-10. However, the microscopic mechanism of such flavour symmetry breaking and its connection to the low-temperature phases are not yet understood. Here we investigate the broken-symmetry many-body ground state of magic-angle twisted bilayer graphene (MATBG) and its nontrivial topology using simultaneous thermodynamic and transport measurements. We directly observe flavour symmetry breaking as pinning of the chemical potential at all integer fillings of the moiré superlattice, demonstrating the importance of flavour Hund's coupling in the many-body ground state. The topological nature of the underlying flat bands is manifested upon breaking time-reversal symmetry, where we measure energy gaps corresponding to Chern insulator states with Chern numbers 3, 2, 1 at filling factors 1, 2, 3, respectively, consistent with flavour symmetry breaking in the Hofstadter butterfly spectrum of MATBG. Moreover, concurrent measurements of resistivity and chemical potential provide the temperature-dependent charge diffusivity of MATBG in the strange-metal regime11-a quantity previously explored only in ultracold atoms12. Our results bring us one step closer to a unified framework for understanding interactions in the topological bands of MATBG, with and without a magnetic field.
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12
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Deng B, Wang B, Li N, Li R, Wang Y, Tang J, Fu Q, Tian Z, Gao P, Xue J, Peng H. Interlayer Decoupling in 30° Twisted Bilayer Graphene Quasicrystal. ACS NANO 2020; 14:1656-1664. [PMID: 31961130 DOI: 10.1021/acsnano.9b07091] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Stacking order has a strong influence on the coupling between the two layers of twisted bilayer graphene (BLG), which in turn determines its physical properties. Here, we report the investigation of the interlayer coupling of the epitaxially grown single-crystal 30°-twisted BLG on Cu(111) at the atomic scale. The stacking order and morphology of BLG is controlled by a rationally designed two-step growth process, that is, the thermodynamically controlled nucleation and kinetically controlled growth. The crystal structure of the 30°-twisted bilayer graphene (30°-tBLG) is determined to have quasicrystal-like symmetry. The electronic properties and interlayer coupling of the 30°-tBLG are investigated using scanning tunneling microscopy and spectroscopy. The energy-dependent local density of states with in situ electrostatic doping shows that the electronic states in two graphene layers are decoupled near the Dirac point. A linear dispersion originated from the constituent graphene monolayers is discovered with doubled degeneracy. This study contributes to controlled growth of twist-angle-defined BLG and provides insights on the electronic properties and interlayer coupling in this intriguing system.
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Affiliation(s)
- Bing Deng
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Binbin Wang
- School of Physical Science and Technology , ShanghaiTech University , Shanghai 201210 , China
| | - Ning Li
- International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
| | - Rongtan Li
- State Key Laboratory of Catalysis, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM) , Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023 , China
| | - Yani Wang
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Jilin Tang
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
- Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Qiang Fu
- State Key Laboratory of Catalysis, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM) , Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023 , China
| | - Zhen Tian
- School of Physical Science and Technology , ShanghaiTech University , Shanghai 201210 , China
| | - Peng Gao
- International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
| | - Jiamin Xue
- School of Physical Science and Technology , ShanghaiTech University , Shanghai 201210 , China
| | - Hailin Peng
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
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13
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Zhu L, Li L, Tao R, Fan X, Wan X, Zeng C. Frictional Drag Effect between Massless and Massive Fermions in Single-Layer/Bilayer Graphene Heterostructures. NANO LETTERS 2020; 20:1396-1402. [PMID: 31975602 DOI: 10.1021/acs.nanolett.9b05002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The emergence of two-dimensional layered materials offers an excellent opportunity for the fabrication of double-layer electron systems that are in close proximity but electronically isolated. In this work, heterostructures consisting of one single-layer graphene (SLG) and one bilayer graphene (BLG) separated by an ultrathin hBN layer are successfully fabricated, enabling the experimental investigation of the interlayer frictional drag effect between massless and massive fermions. With varying carrier densities, a giant positive peak of drag response emerges at the double neutrality point, around which nonmonotonic temperature dependent behaviors of drag resistance are further observed. These observations can be attributed to the anticorrelations in the distributions of e-h puddles between layers. More importantly, as the system shifts toward the strong coupling regime, the carrier density dependence of drag resistance Rdrag shows a crossover from 1/n3 to 1/n2 for the density matched cases, which is a unique characteristic predicted for massless-massive fermion systems. Consequently, a generalized carrier dependent expression (1/(|nS| + |nB|)2) is obtained for the strong coupling regime, where nS and nB are the carrier densities of SLG and BLG, respectively. Our study provides insight into the electronic frictional effects between massless and massive fermions and thus will promote the investigations of interlayer interactions in hybrid structures hosting different types of carriers.
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Affiliation(s)
- Lijun Zhu
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Lin Li
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Ran Tao
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Xiaodong Fan
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Xinyi Wan
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
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14
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Cheng A, Taniguchi T, Watanabe K, Kim P, Pillet JD. Guiding Dirac Fermions in Graphene with a Carbon Nanotube. PHYSICAL REVIEW LETTERS 2019; 123:216804. [PMID: 31809158 DOI: 10.1103/physrevlett.123.216804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Indexed: 06/10/2023]
Abstract
Relativistic massless charged particles in a two-dimensional conductor can be guided by a one-dimensional electrostatic potential, in an analogous manner to light guided by an optical fiber. We use a carbon nanotube to generate such a guiding potential in graphene and create a single mode electronic waveguide. The nanotube and graphene are separated by a few nanometers and can be controlled and measured independently. As we charge the nanotube, we observe the formation of a single guided mode in graphene that we detect using the same nanotube as a probe. This single electronic guided mode in graphene is sufficiently isolated from other electronic states of linear Dirac spectrum continuum, allowing the transmission of information with minimal distortion.
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Affiliation(s)
- Austin Cheng
- Department of Applied Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | | | - Kenji Watanabe
- National Institute for Material Science, Tsukuba 305-0044, Japan
| | - Philip Kim
- Department of Applied Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jean-Damien Pillet
- LSI, CEA/DRF/IRAMIS, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France
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15
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Bekdüz B, Kampermann L, Mertin W, Punckt C, Aksay IA, Bacher G. Influence of atmospheric species on the electrical properties of functionalized graphene sheets. RSC Adv 2018; 8:42073-42079. [PMID: 35558770 PMCID: PMC9092110 DOI: 10.1039/c8ra08227h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 12/10/2018] [Indexed: 11/21/2022] Open
Abstract
We report on the time-dependent influence of atmospheric species on the electrical properties of functionalized graphene sheets (FGSs). When exposed to laboratory air, FGSs exhibit a significant, irreversible decrease in electrical conductance with time, strongly depending on the oxygen content of the FGSs. To separate the roles of charge carrier density and mobility in this aging process, we performed electron transport measurements using a back-gate field-effect transistor architecture. Investigating the position of the Dirac point under different atmospheres, we found that adsorbed atmospheric species result in pronounced p-doping, which - on a short time scale - can be reversed under nitrogen atmosphere. However, on a time scale of several days, the resistance increases irreversibly, while the Dirac point voltage remains constant. From these experiments, we conclude that the aging of FGSs is related to the chemisorption of atmospheric species leading to enhanced carrier scattering due to an increasing amount of sp3- regions and thus to a reduced charge carrier mobility.
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Affiliation(s)
- Bilge Bekdüz
- Werkstoffe der Elektrotechnik, CENIDE, Universität Duisburg-Essen47057 DuisburgGermany
| | - Laura Kampermann
- Werkstoffe der Elektrotechnik, CENIDE, Universität Duisburg-Essen47057 DuisburgGermany
| | - Wolfgang Mertin
- Werkstoffe der Elektrotechnik, CENIDE, Universität Duisburg-Essen47057 DuisburgGermany
| | - Christian Punckt
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonNew Jersey 08544USA
| | - Ilhan A. Aksay
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonNew Jersey 08544USA
| | - Gerd Bacher
- Werkstoffe der Elektrotechnik, CENIDE, Universität Duisburg-Essen47057 DuisburgGermany
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16
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Kruskopf M, Elmquist RE. Epitaxial graphene for quantum resistance metrology. METROLOGIA 2018; 55:10.1088/1681-7575/aacd23. [PMID: 30996479 PMCID: PMC6463316 DOI: 10.1088/1681-7575/aacd23] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Graphene-based quantised Hall resistance standards promise high precision for the unit ohm under less exclusive measurement conditions, enabling the use of compact measurement systems. To meet the requirements of metrological applications, national metrology institutes developed large-area monolayer graphene growth methods for uniform material properties and optimized device fabrication techniques. Precision measurements of the quantized Hall resistance showing the advantage of graphene over GaAs-based resistance standards demonstrate the remarkable achievements realized by the research community. This work provides an overview over the state-of-the-art technologies in this field.
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Affiliation(s)
- Mattias Kruskopf
- National Institute of Standards and Technology, Fundamental Electrical Measurements, 100 Bureau Drive, Gaithersburg, MD, United States of America
- University of Maryland, Joint Quantum Institute, College Park, MD, United States of America
| | - Randolph E Elmquist
- National Institute of Standards and Technology, Fundamental Electrical Measurements, 100 Bureau Drive, Gaithersburg, MD, United States of America
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17
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Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene. Sci Rep 2016; 6:38068. [PMID: 27905496 PMCID: PMC5131475 DOI: 10.1038/srep38068] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 11/04/2016] [Indexed: 01/29/2023] Open
Abstract
Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states and their transitions due to the interplay of the relative strength of valley, spin and layer polarizations in twisted bilayer graphene. The energy gaps of the broken-symmetry QH states show an electron-hole asymmetric behaviour, and their dependence on the induced displacement field are opposite between even and odd filling factor states. These results strongly suggest that the QH states with broken valley and spin symmetries for individual layer become hybridized via interlayer tunnelling, and the hierarchy of the QH states is sensitive to both magnetic field and displacement field due to charge imbalance between layers.
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18
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Abstract
Insufficient flexibility of existing approaches to controlling the thermal transport in atomic monolayers limits their capability for use in many applications. Here, we examine the means of electrode doping to control the thermal flux Q due to phonons propagating along the atomic monolayer. We found that the frequency of the electron-restricted phonon scattering strongly depends on the concentration nC. of the electric charge carriers, established by the electric potentials applied to local gates. As a result of the electrode doping, nC is increased, causing a sharp rise in both the electrical conductivity and Seebeck coefficient, while the thermal conductivity tumbles. Therefore, the effect of the thermal transistor improves the figure of merit of nanoelectronic circuits.
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Affiliation(s)
- S E Shafranjuk
- Physics and Astronomy Department, Northwestern University, Evanston, IL 60208, USA.
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19
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Cheng B, Wu Y, Wang P, Pan C, Taniguchi T, Watanabe K, Bockrath M. Gate-Tunable Landau Level Filling and Spectroscopy in Coupled Massive and Massless Electron Systems. PHYSICAL REVIEW LETTERS 2016; 117:026601. [PMID: 27447518 DOI: 10.1103/physrevlett.117.026601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Indexed: 06/06/2023]
Abstract
We report transport studies on coupled massive and massless electron systems, realized using twisted monolayer-graphene-natural bilayer-graphene stacks. We incorporate the layers in a dual-gated transistor geometry enabling independently tuning their charge density and the perpendicular electric field. In a perpendicular magnetic field, we observe a distinct pattern of gate-tunable Landau level crossings. Screening and interlayer electron-electron interactions yield a nonlinear monolayer gate capacitance. Data analysis enables determination of the monolayer's Fermi velocity and the bilayer's effective mass. The mass obtained is larger than that expected for isolated bilayers, suggesting that the interlayer interactions renormalize the band structure.
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Affiliation(s)
- Bin Cheng
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Yong Wu
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Peng Wang
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Cheng Pan
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - T Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - K Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - M Bockrath
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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20
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Zhang D, Dietsche W, von Klitzing K. Anomalous Interlayer Transport of Quantum Hall Bilayers in the Strongly Josephson-Coupled Regime. PHYSICAL REVIEW LETTERS 2016; 116:186801. [PMID: 27203339 DOI: 10.1103/physrevlett.116.186801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Indexed: 06/05/2023]
Abstract
We investigate Josephson coupling in a closely spaced quantum Hall bilayer. Reduction of the interlayer barrier from the widely used values of 10-12 nm to the present one of 8 nm leads to qualitatively different interlayer transport properties. The breakdown of interlayer coherence can be spatially confined in regions that are smaller than the device size. Such a spatial inhomogeneity depends crucially on the Josephson-coupling strength and can be removed by adding an in-plane magnetic field of about 0.5 T. At higher in-plane fields, the interlayer tunneling I-V curve develops unexpected overshoot features. These results challenge current theoretical understanding and suggest that our bilayer system has entered a previously unexplored regime.
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Affiliation(s)
- Ding Zhang
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Werner Dietsche
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Klaus von Klitzing
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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21
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Kim W, Li C, Chaves FA, Jiménez D, Rodriguez RD, Susoma J, Fenner MA, Lipsanen H, Riikonen J. Tunable Graphene-GaSe Dual Heterojunction Device. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1845-52. [PMID: 26727653 DOI: 10.1002/adma.201504514] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 11/12/2015] [Indexed: 05/14/2023]
Abstract
A field-effect device based on dual graphene-GaSe heterojunctions is demonstrated. Monolayer graphene is used as electrodes on a GaSe channel to form two opposing Schottky diodes controllable by local top gates. The device exhibits strong rectification with tunable threshold voltage. Detailed theoretical modeling is used to explain the device operation and to distinguish the differences compared to a single diode.
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Affiliation(s)
- Wonjae Kim
- Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150, Espoo, Finland
| | - Changfeng Li
- Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150, Espoo, Finland
| | - Ferney A Chaves
- Departament d'Enginyeria Electrònica, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus UAB, E-08193, Bellaterra, Spain
| | - David Jiménez
- Departament d'Enginyeria Electrònica, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus UAB, E-08193, Bellaterra, Spain
| | - Raul D Rodriguez
- Technische Universität Chemnitz, Institut für Physik, Reichenhainer Str. 70, 09126, Chemnitz, Germany
| | - Jannatul Susoma
- Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150, Espoo, Finland
| | | | - Harri Lipsanen
- Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150, Espoo, Finland
| | - Juha Riikonen
- Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150, Espoo, Finland
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22
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Park JH, Movva HCP, Chagarov E, Sardashti K, Chou H, Kwak I, Hu KT, Fullerton-Shirey SK, Choudhury P, Banerjee SK, Kummel AC. In Situ Observation of Initial Stage in Dielectric Growth and Deposition of Ultrahigh Nucleation Density Dielectric on Two-Dimensional Surfaces. NANO LETTERS 2015; 15:6626-6633. [PMID: 26393281 DOI: 10.1021/acs.nanolett.5b02429] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Several proposed beyond-CMOS devices based on two-dimensional (2D) heterostructures require the deposition of thin dielectrics between 2D layers. However, the direct deposition of dielectrics on 2D materials is challenging due to their inert surface chemistry. To deposit high-quality, thin dielectrics on 2D materials, a flat lying titanyl phthalocyanine (TiOPc) monolayer, deposited via the molecular beam epitaxy, was employed to create a seed layer for atomic layer deposition (ALD) on 2D materials, and the initial stage of growth was probed using in situ STM. ALD pulses of trimethyl aluminum (TMA) and H2O resulted in the uniform deposition of AlOx on the TiOPc/HOPG. The uniformity of the dielectric is consistent with DFT calculations showing multiple reaction sites are available on the TiOPc molecule for reaction with TMA. Capacitors prepared with 50 cycles of AlOx on TiOPc/graphene display a capacitance greater than 1000 nF/cm(2), and dual-gated devices have current densities of 10(-7)A/cm(2) with 40 cycles.
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Affiliation(s)
| | - Hema C P Movva
- Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78712, United States
| | | | | | - Harry Chou
- Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78712, United States
| | | | | | - Susan K Fullerton-Shirey
- Department of Electrical Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Pabitra Choudhury
- Department of Chemical Engineering, New Mexico Tech , Socorro, New Mexico 87801, United States
| | - Sanjay K Banerjee
- Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78712, United States
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23
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Fallahazad B, Lee K, Kang S, Xue J, Larentis S, Corbet C, Kim K, Movva HCP, Taniguchi T, Watanabe K, Register LF, Banerjee SK, Tutuc E. Gate-tunable resonant tunneling in double bilayer graphene heterostructures. NANO LETTERS 2015; 15:428-433. [PMID: 25436861 DOI: 10.1021/nl503756y] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate gate-tunable resonant tunneling and negative differential resistance in the interlayer current-voltage characteristics of rotationally aligned double bilayer graphene heterostructures separated by hexagonal boron nitride (hBN) dielectric. An analysis of the heterostructure band alignment using individual layer densities, along with experimentally determined layer chemical potentials indicates that the resonance occurs when the energy bands of the two bilayer graphene are aligned. We discuss the tunneling resistance dependence on the interlayer hBN thickness, as well as the resonance width dependence on mobility and rotational alignment.
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Affiliation(s)
- Babak Fallahazad
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
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24
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Fatemi V, Hunt B, Steinberg H, Eltinge SL, Mahmood F, Butch NP, Watanabe K, Taniguchi T, Gedik N, Ashoori RC, Jarillo-Herrero P. Electrostatic coupling between two surfaces of a topological insulator nanodevice. PHYSICAL REVIEW LETTERS 2014; 113:206801. [PMID: 25432050 DOI: 10.1103/physrevlett.113.206801] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Indexed: 06/04/2023]
Abstract
We report on electronic transport measurements of dual-gated nanodevices of the low-carrier density topological insulator (TI) Bi_{1.5}Sb_{0.5}Te_{1.7}Se_{1.3}. In all devices, the upper and lower surface states are independently tunable to the Dirac point by the top and bottom gate electrodes. In thin devices, electric fields are found to penetrate through the bulk, indicating finite capacitive coupling between the surface states. A charging model allows us to use the penetrating electric field as a measurement of the intersurface capacitance C_{TI} and the surface state energy-density relationship μ(n), which is found to be consistent with independent angle-resolved photoemission spectroscopy measurements. At high magnetic fields, increased field penetration through the surface states is observed, strongly suggestive of the opening of a surface state band gap due to broken time-reversal symmetry.
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Affiliation(s)
- Valla Fatemi
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Benjamin Hunt
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Hadar Steinberg
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
| | - Stephen L Eltinge
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Fahad Mahmood
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Nicholas P Butch
- Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 6100 Gaithersburg, Maryland 20899, USA and Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA and Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Nuh Gedik
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Raymond C Ashoori
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Pablo Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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25
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Zhang D, Huang X, Dietsche W, von Klitzing K, Smet JH. Signatures for Wigner crystal formation in the chemical potential of a two-dimensional electron system. PHYSICAL REVIEW LETTERS 2014; 113:076804. [PMID: 25170727 DOI: 10.1103/physrevlett.113.076804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 06/03/2023]
Abstract
We investigate the evolution of the chemical potential of a two-dimensional electron system (2DES) as a function of density at a fixed magnetic field. By using a bilayer system, changes in the chemical potential of one 2DES are determined from the density variation induced in the second, nearby 2DES. At high magnetic fields around a filling factor of ν=1 or ν=2, the chemical potential jump associated with the condensation in a quantum Hall state exhibits two anomalies symmetrically located around these integer filling factors. They are attributed to the formation of a 2D Wigner crystal of quasiparticles.
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Affiliation(s)
- Ding Zhang
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Xuting Huang
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Werner Dietsche
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Klaus von Klitzing
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Jurgen H Smet
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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26
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Lee K, Fallahazad B, Xue J, Dillen DC, Kim K, Taniguchi T, Watanabe K, Tutuc E. Chemical potential and quantum Hall ferromagnetism in bilayer graphene. Science 2014; 345:58-61. [DOI: 10.1126/science.1251003] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Kayoung Lee
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
| | - Babak Fallahazad
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
| | - Jiamin Xue
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
| | - David C. Dillen
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
| | - Kyounghwan Kim
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki Tsukuba Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki Tsukuba Ibaraki 305-0044, Japan
| | - Emanuel Tutuc
- Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758, USA
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27
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Gutiérrez-Jáuregui R, Torres M. Nonlinear magnetotransport theory and Hall induced resistance oscillations in graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:235501. [PMID: 24827913 DOI: 10.1088/0953-8984/26/23/235501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The quantum oscillations of nonlinear magnetoresistance in graphene that occur in response to a dc current bias are investigated. We present a theoretical model for the nonlinear magnetotransport of graphene carriers. The model is based on the exact solution of the effective Dirac equation in crossed electric and magnetic fields, while the effects of randomly distributed impurities are perturbatively added. To compute the nonlinear current effects, we develop a covariant formulation of the migration center theory. The current is calculated for short- and large-range scatterers. The analysis of the differential resistivity in the large magnetic field region, shows that the extrema of the Shubnikov de Hass oscillations invert when the dc currents exceed a threshold value. These results are in good agreement with experimental observations. In the small magnetic field regime, corresponding to large filling factors, the existence of Hall induced resistance oscillations are predicted for ultra clean graphene samples. These oscillations originate from Landau-Zener tunneling between Landau levels, that are tilted by the strong electric Hall field.
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Affiliation(s)
- R Gutiérrez-Jáuregui
- Departamento de Física Teórica, Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México Distrito Federal 01000, México, USA
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28
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Larentis S, Tolsma JR, Fallahazad B, Dillen DC, Kim K, MacDonald AH, Tutuc E. Band offset and negative compressibility in graphene-MoS2 heterostructures. NANO LETTERS 2014; 14:2039-2045. [PMID: 24611616 DOI: 10.1021/nl500212s] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We use electron transport to characterize monolayer graphene-multilayer MoS2 heterostructures. Our samples show ambipolar characteristics and conductivity saturation on the electron branch that signals the onset of MoS2 conduction band population. Surprisingly, the carrier density in graphene decreases with gate bias once MoS2 is populated, demonstrating negative compressibility in MoS2. We are able to interpret our measurements quantitatively by accounting for disorder and using the random phase approximation (RPA) for the exchange and correlation energies of both Dirac and parabolic-band two-dimensional electron gases. This interpretation allows us to extract the energetic offset between the conduction band edge of MoS2 and the Dirac point of graphene.
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Affiliation(s)
- Stefano Larentis
- Microelectronics Research Center, Department of Electrical and Computer Engineering and ‡Department of Physics, The University of Texas at Austin , Austin, Texas 78758, United States
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29
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Abstract
The p-n junction diode and field-effect transistor are the two most ubiquitous building blocks of modern electronics and optoelectronics. In recent years, the emergence of reduced dimensionality materials has suggested that these components can be scaled down to atomic thicknesses. Although high-performance field-effect devices have been achieved from monolayered materials and their heterostructures, a p-n heterojunction diode derived from ultrathin materials is notably absent and constrains the fabrication of complex electronic and optoelectronic circuits. Here we demonstrate a gate-tunable p-n heterojunction diode using semiconducting single-walled carbon nanotubes (SWCNTs) and single-layer molybdenum disulfide as p-type and n-type semiconductors, respectively. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias to achieve a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 10(4). This heterojunction diode also responds strongly to optical irradiation with an external quantum efficiency of 25% and fast photoresponse <15 μs. Because SWCNTs have a diverse range of electrical properties as a function of chirality and an increasing number of atomically thin 2D nanomaterials are being isolated, the gate-tunable p-n heterojunction concept presented here should be widely generalizable to realize diverse ultrathin, high-performance electronics and optoelectronics.
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30
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Popov AM, Lebedeva IV, Knizhnik AA, Lozovik YE, Potapkin BV, Poklonski NA, Siahlo AI, Vyrko SA. AA stacking, tribological and electronic properties of double-layer graphene with krypton spacer. J Chem Phys 2013; 139:154705. [DOI: 10.1063/1.4824298] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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