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Binder J, Dabrowska AK, Tokarczyk M, Rousseau A, Valvin P, Bozek R, Nogajewski K, Kowalski G, Pacuski W, Gil B, Cassabois G, Stepniewski R, Wysmolek A. Homoepitaxy of Boron Nitride on Exfoliated Hexagonal Boron Nitride Flakes. NANO LETTERS 2024; 24:6990-6996. [PMID: 38818969 PMCID: PMC11177313 DOI: 10.1021/acs.nanolett.4c01310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/23/2024] [Accepted: 05/23/2024] [Indexed: 06/01/2024]
Abstract
Although large efforts have been made to improve the growth of hexagonal boron nitride (hBN) by heteroepitaxy, the non-native substrates remain a fundamental factor that limits the quality. This problem can be solved by homoepitaxy, which is the growth of hBN on hBN substrates. In this report, we demonstrate the homoepitaxial growth of triangular BN grains on exfoliated hBN flakes by Metal-Organic Vapor Phase Epitaxy and show by atomic force microscopy and photoluminescence that the stacking of these triangular islands can deviate from the AA' stacking of hBN. We show that the stacking order is enforced by the crystallographic direction of the edge of the exfoliated hBN flakes, with armchair edges allowing for centrosymmetric stacking, whereas zigzag edges lead to the growth of noncentrosymmetric BN polytypes. Our results indicate pathways to grow homoepitaxial BN with tunable layer stacking, which is required to induce piezoelectricity or ferroelectricity.
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Affiliation(s)
- Johannes Binder
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | | | - Mateusz Tokarczyk
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Adrien Rousseau
- Laboratoire
Charles Coulomb, UMR 5221, CNRS-Université
de Montpellier, 34095 Montpellier, France
| | - Pierre Valvin
- Laboratoire
Charles Coulomb, UMR 5221, CNRS-Université
de Montpellier, 34095 Montpellier, France
| | - Rafal Bozek
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Karol Nogajewski
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Grzegorz Kowalski
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Wojciech Pacuski
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Bernard Gil
- Laboratoire
Charles Coulomb, UMR 5221, CNRS-Université
de Montpellier, 34095 Montpellier, France
| | - Guillaume Cassabois
- Laboratoire
Charles Coulomb, UMR 5221, CNRS-Université
de Montpellier, 34095 Montpellier, France
- Institut
Universitaire de France, 75231 Paris, France
| | - Roman Stepniewski
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Andrzej Wysmolek
- Faculty
of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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2
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Jat MK, Mishra S, Mann HK, Bajaj R, Watanabe K, Taniguchi T, Krishnamurthy HR, Jain M, Bid A. Controlling Umklapp Scattering in a Bilayer Graphene Moiré Superlattice. NANO LETTERS 2024; 24:2203-2209. [PMID: 38345527 DOI: 10.1021/acs.nanolett.3c04223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
We present experimental findings on electron-electron scattering in two-dimensional moiré heterostructures with a tunable Fermi wave vector, reciprocal lattice vector, and band gap. We achieve this in high-mobility aligned heterostructures of bilayer graphene (BLG) and hBN. Around the half-full point, the primary contribution to the resistance of these devices arises from Umklapp electron-electron (Uee) scattering, making the resistance of graphene/hBN moiré devices significantly larger than that of non-aligned devices (where Uee is forbidden). We find that the strength of Uee scattering follows a universal scaling with Fermi energy and is nonmonotonically dependent on the superlattice period. The Uee scattering can be tuned with the electric field and is affected by layer polarization of BLG. It has a strong particle-hole asymmetry; the resistance when the chemical potential is in the conduction band is significantly lower than when it is in the valence band, making the electron-doped regime more practical for potential applications.
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Affiliation(s)
- Mohit Kumar Jat
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Shubhankar Mishra
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | | | - Robin Bajaj
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - 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
| | - H R Krishnamurthy
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Manish Jain
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Aveek Bid
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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3
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Carrasco JA, Congost-Escoin P, Assebban M, Abellán G. Antimonene: a tuneable post-graphene material for advanced applications in optoelectronics, catalysis, energy and biomedicine. Chem Soc Rev 2023; 52:1288-1330. [PMID: 36744431 PMCID: PMC9987414 DOI: 10.1039/d2cs00570k] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Indexed: 02/07/2023]
Abstract
The post-graphene era is undoubtedly marked by two-dimensional (2D) materials such as quasi-van der Waals antimonene. This emerging material has a fascinating structure, exhibits a pronounced chemical reactivity (in contrast to graphene), possesses outstanding electronic properties and has been postulated for a plethora of applications. However, chemistry and physics of antimonene remain in their infancy, but fortunately recent discoveries have shed light on its unmatched allotropy and rich chemical reactivity offering a myriad of unprecedented possibilities in terms of fundamental studies and applications. Indeed, antimonene can be considered as one of the most appealing post-graphene 2D materials reported to date, since its structure, properties and applications can be chemically engineered from the ground up (both using top-down and bottom-up approaches), offering an unprecedented level of control in the realm of 2D materials. In this review, we provide an in-depth analysis of the recent advances in the synthesis, characterization and applications of antimonene. First, we start with a general introduction to antimonene, and then we focus on its general chemistry, physical properties, characterization and synthetic strategies. We then perform a comprehensive study on the allotropy, the phase transition mechanisms, the oxidation behaviour and chemical functionalization. From a technological point of view, we further discuss the applications recently reported for antimonene in the fields of optoelectronics, catalysis, energy storage, cancer therapy and sensing. Finally, important aspects such as new scalable methodologies or the promising perspectives in biomedicine are discussed, pinpointing antimonene as a cutting-edge material of broad interest for researchers working in chemistry, physics, materials science and biomedicine.
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Affiliation(s)
- Jose A Carrasco
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán Martínez, 2, 46980 Paterna, Spain.
| | - Pau Congost-Escoin
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán Martínez, 2, 46980 Paterna, Spain.
| | - Mhamed Assebban
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán Martínez, 2, 46980 Paterna, Spain.
| | - Gonzalo Abellán
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán Martínez, 2, 46980 Paterna, Spain.
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4
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Liirò-Peluso L, Wrigley J, Amabilino DB, Beton PH. Submolecular Resolution Imaging of P3HT:PCBM Nanostructured Films by Atomic Force Microscopy: Implications for Organic Solar Cells. ACS APPLIED NANO MATERIALS 2022; 5:13794-13804. [PMID: 36338328 PMCID: PMC9623582 DOI: 10.1021/acsanm.2c01399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The efficiency of organic bulk-heterojunction (BHJ) solar cells depends greatly on both the bulk and surface structure of the nanostructured bicontinuous interpenetrating network of materials, known as the active layer. The morphology of the top layer of a coated film is often resolved at the scale of a few nanometers, but fine details of the domains and the order within them are more difficult to identify. Here, we report a high-resolution atomic force microscopy (AFM) investigation of various stoichiometries of the well-studied poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) active layer mixture. Images of the surface were obtained using AC-mode AFM exciting higher-order resonance frequencies of a standard silicon probe, a promising technique for acquiring real-space images of organic-based thin films with nanoscale and even submolecular resolution. We provide firm evidence of the nanoscale organization of the P3HT polymer and of the P3HT:PCBM stoichiometric mixtures at the surface-air interface of the BHJ architecture. Our study shows the characteristic periodicity of the regioregular P3HT identified in the nanoscale domain areas with submolecular resolution. Such areas are then distorted in place when adding different quantities of PCBM forming stoichiometric mixtures. When the samples were exposed to ambient light, the morphologies were very different, and submolecular resolution was not achieved. This approach is shown to provide a precise view of the active layer's nanostructure and will be useful for studies of other materials as a function of various parameters, with particular attention to the role of the acceptor in tuning morphology for understanding optimum performance in organic photovoltaic devices.
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Affiliation(s)
- Letizia Liirò-Peluso
- The
GSK Carbon Neutral Laboratories for Sustainable Chemistry, School
of Chemistry, University of Nottingham, Triumph Road, Nottingham NG7 2TU, U.K.
- School
of Physics and Astronomy, University of
Nottingham, University
Park, Nottingham NG7 2RD, U.K.
| | - James Wrigley
- School
of Physics and Astronomy, University of
Nottingham, University
Park, Nottingham NG7 2RD, U.K.
| | - David B. Amabilino
- The
GSK Carbon Neutral Laboratories for Sustainable Chemistry, School
of Chemistry, University of Nottingham, Triumph Road, Nottingham NG7 2TU, U.K.
- Institut
de Ciència de Materials de Barcelona, Consejo Superior de Investigaciones
Científicas, Carrer dels Til.lers, Campus Universitari de Bellaterra, 08193 Cerdanyola del Vallès, Spain
| | - Peter H. Beton
- School
of Physics and Astronomy, University of
Nottingham, University
Park, Nottingham NG7 2RD, U.K.
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5
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Kim S, Moon D, Jeon BR, Yeon J, Li X, Kim S. Accurate Atomic-Scale Imaging of Two-Dimensional Lattices Using Atomic Force Microscopy in Ambient Conditions. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:1542. [PMID: 35564252 PMCID: PMC9104726 DOI: 10.3390/nano12091542] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 04/28/2022] [Accepted: 04/29/2022] [Indexed: 02/04/2023]
Abstract
To facilitate the rapid development of van der Waals materials and heterostructures, scanning probe methods capable of nondestructively visualizing atomic lattices and moiré superlattices are highly desirable. Lateral force microscopy (LFM), which measures nanoscale friction based on the commonly available atomic force microscopy (AFM), can be used for imaging a wide range of two-dimensional (2D) materials, but imaging atomic lattices using this technique is difficult. Here, we examined a number of the common challenges encountered in LFM experiments and presented a universal protocol for obtaining reliable atomic-scale images of 2D materials under ambient environment. By studying a series of LFM images of graphene and transition metal dichalcogenides (TMDs), we have found that the accuracy and the contrast of atomic-scale images critically depended on several scanning parameters including the scan size and the scan rate. We applied this protocol to investigate the atomic structure of the ripped and self-folded edges of graphene and have found that these edges were mostly in the armchair direction. This finding is consistent with the results of several simulations results. Our study will guide the extensive effort on assembly and characterization of new 2D materials and heterostructures.
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Affiliation(s)
- Sunghyun Kim
- Department of Applied Physics, Hanyang University, Ansan 15588, Korea; (S.K.); (B.R.J.); (J.Y.)
| | - Donghyeon Moon
- Department of Photonics and Nanoelectronics, Hanyang University, Ansan 15588, Korea;
| | - Bo Ram Jeon
- Department of Applied Physics, Hanyang University, Ansan 15588, Korea; (S.K.); (B.R.J.); (J.Y.)
| | - Jegyeong Yeon
- Department of Applied Physics, Hanyang University, Ansan 15588, Korea; (S.K.); (B.R.J.); (J.Y.)
| | - Xiaoqin Li
- Center for Complex Quantum Systems, Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA;
- Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA
| | - Suenne Kim
- Department of Photonics and Nanoelectronics, Hanyang University, Ansan 15588, Korea;
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6
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Kim JM, Haque MF, Hsieh EY, Nahid SM, Zarin I, Jeong KY, So JP, Park HG, Nam S. Strain Engineering of Low-Dimensional Materials for Emerging Quantum Phenomena and Functionalities. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021:e2107362. [PMID: 34866241 DOI: 10.1002/adma.202107362] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 11/11/2021] [Indexed: 06/13/2023]
Abstract
Recent discoveries of exotic physical phenomena, such as unconventional superconductivity in magic-angle twisted bilayer graphene, dissipationless Dirac fermions in topological insulators, and quantum spin liquids, have triggered tremendous interest in quantum materials. The macroscopic revelation of quantum mechanical effects in quantum materials is associated with strong electron-electron correlations in the lattice, particularly where materials have reduced dimensionality. Owing to the strong correlations and confined geometry, altering atomic spacing and crystal symmetry via strain has emerged as an effective and versatile pathway for perturbing the subtle equilibrium of quantum states. This review highlights recent advances in strain-tunable quantum phenomena and functionalities, with particular focus on low-dimensional quantum materials. Experimental strategies for strain engineering are first discussed in terms of heterogeneity and elastic reconfigurability of strain distribution. The nontrivial quantum properties of several strain-quantum coupled platforms, including 2D van der Waals materials and heterostructures, topological insulators, superconducting oxides, and metal halide perovskites, are next outlined, with current challenges and future opportunities in quantum straintronics followed. Overall, strain engineering of quantum phenomena and functionalities is a rich field for fundamental research of many-body interactions and holds substantial promise for next-generation electronics capable of ultrafast, dissipationless, and secure information processing and communications.
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Affiliation(s)
- Jin Myung Kim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Md Farhadul Haque
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Ezekiel Y Hsieh
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Shahriar Muhammad Nahid
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Ishrat Zarin
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Kwang-Yong Jeong
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
- Department of Physics, Jeju National University, Jeju, 63243, Republic of Korea
| | - Jae-Pil So
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
| | - Hong-Gyu Park
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul, 02841, Republic of Korea
| | - SungWoo Nam
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Mechanical and Aerospace Engineering, University of California Irvine, Irvine, CA, 92697, USA
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7
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Rosenberger MR, Chuang HJ, Phillips M, Oleshko VP, McCreary KM, Sivaram SV, Hellberg CS, Jonker BT. Twist Angle-Dependent Atomic Reconstruction and Moiré Patterns in Transition Metal Dichalcogenide Heterostructures. ACS NANO 2020; 14:4550-4558. [PMID: 32167748 DOI: 10.1021/acsnano.0c00088] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Van der Waals layered materials, such as transition metal dichalcogenides (TMDs), are an exciting class of materials with weak interlayer bonding, which enables one to create so-called van der Waals heterostructures (vdWH). One promising attribute of vdWH is the ability to rotate the layers at arbitrary azimuthal angles relative to one another. Recent work has shown that control of the twist angle between layers can have a dramatic effect on TMD vdWH properties, but the twist angle has been treated solely through the use of rigid-lattice moiré patterns. No atomic reconstruction, that is, any rearrangement of atoms within the individual layers, has been reported experimentally to date. Here, we demonstrate that vdWH of MoSe2/WSe2 and MoS2/WS2 at twist angles ≤1° undergo significant atomic level reconstruction leading to discrete commensurate domains divided by narrow domain walls, rather than a smoothly varying rigid-lattice moiré pattern as has been assumed in prior experimental work. Using conductive atomic force microscopy (CAFM), we show that TMD vdWH at small twist angles exhibit large domains of constant conductivity. The domains in samples with R-type stacking are triangular, whereas the domains in samples with H-type stacking are hexagonal. Transmission electron microscopy provides additional evidence of atomic reconstruction in MoSe2/WSe2 structures and demonstrates the transition between a rigid-lattice moiré pattern for large angles and atomic reconstruction for small angles. We use density functional theory to calculate the band structures of the commensurate reconstructed domains and find that the modulation of the relative electronic band edges is consistent with the CAFM results and photoluminescence spectra. The presence of atomic reconstruction in TMD heterostructures and the observed impact on nanometer-scale electronic properties provide fundamental insight into the behavior of this important class of heterostructures.
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Affiliation(s)
| | - Hsun-Jen Chuang
- U.S. Naval Research Laboratory, Washington, DC 20375, United States
| | | | - Vladimir P Oleshko
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | | | - Saujan V Sivaram
- U.S. Naval Research Laboratory, Washington, DC 20375, United States
| | | | - Berend T Jonker
- U.S. Naval Research Laboratory, Washington, DC 20375, United States
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8
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Heilmann M, Prikhodko AS, Hanke M, Sabelfeld A, Borgardt NI, Lopes JMJ. Influence of Proximity to Supporting Substrate on van der Waals Epitaxy of Atomically Thin Graphene/Hexagonal Boron Nitride Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2020; 12:8897-8907. [PMID: 31971775 DOI: 10.1021/acsami.9b21490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Combining graphene and the insulating hexagonal boron nitride (h-BN) into two-dimensional heterostructures is promising for novel, atomically thin electronic nanodevices. A heteroepitaxial growth, in which these materials are grown on top of each other, will be crucial for their scalable device integration. However, during this so-called van der Waals epitaxy, not only the atomically thin substrate itself must be considered but also the influences from the supporting substrate below it. Here, we report not only a substantial difference between the formation of h-BN on single- (SLG) and on bi-layer epitaxial graphene (BLG) on SiC, but also vice versa, that the van der Waals epitaxy of h-BN at growth temperatures well below 1000 °C affects the varying number of graphene layers differently. Our results clearly demonstrate that the additional graphene layer in BLG enhances the distance to the corrugated, carbon-rich interface of the supporting SiC substrate and thereby diminishes its influence on the van der Waals epitaxy, leading to a homogeneous formation of a smooth, atomically thin heterostructure, which will be required for a scalable device integration of 2D heterostructures.
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Affiliation(s)
- Martin Heilmann
- Leibniz-Institut im Forschungsverbund Berlin e.V. , Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Alexander S Prikhodko
- National Research University of Electronic Technology (MIET) , Zelenograd 124498 , Moscow , Russia
| | - Michael Hanke
- Leibniz-Institut im Forschungsverbund Berlin e.V. , Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Alexander Sabelfeld
- Leibniz-Institut im Forschungsverbund Berlin e.V. , Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Nikolai I Borgardt
- National Research University of Electronic Technology (MIET) , Zelenograd 124498 , Moscow , Russia
| | - J Marcelo J Lopes
- Leibniz-Institut im Forschungsverbund Berlin e.V. , Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
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9
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Korolkov VV, Summerfield A, Murphy A, Amabilino DB, Watanabe K, Taniguchi T, Beton PH. Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy. Nat Commun 2019; 10:1537. [PMID: 30948725 PMCID: PMC6449331 DOI: 10.1038/s41467-019-09571-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 03/19/2019] [Indexed: 11/09/2022] Open
Abstract
Real-space images of polymers with sub-molecular resolution could provide valuable insights into the relationship between morphology and functionality of polymer optoelectronic devices, but their acquisition is problematic due to perceived limitations in atomic force microscopy (AFM). We show that individual thiophene units and the lattice of semicrystalline spin-coated films of polythiophenes (PTs) may be resolved using AFM under ambient conditions through the low-amplitude (≤ 1 nm) excitation of higher eigenmodes of a cantilever. PT strands are adsorbed on hexagonal boron nitride near-parallel to the surface in islands with lateral dimensions ~10 nm. On the surface of a spin-coated PT thin film, in which the thiophene groups are perpendicular to the interface, we resolve terminal CH3-groups in a square arrangement with a lattice constant 0.55 nm from which we can identify abrupt boundaries and also regions with more slowly varying disorder, which allow comparison with proposed models of PT domains.
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Affiliation(s)
- Vladimir V Korolkov
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Alex Summerfield
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Alanna Murphy
- School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - David B Amabilino
- School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Peter H Beton
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.
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10
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Summerfield A, Kozikov A, Cheng TS, Davies A, Cho YJ, Khlobystov AN, Mellor CJ, Foxon CT, Watanabe K, Taniguchi T, Eaves L, Novoselov KS, Novikov SV, Beton PH. Moiré-Modulated Conductance of Hexagonal Boron Nitride Tunnel Barriers. NANO LETTERS 2018; 18:4241-4246. [PMID: 29913062 PMCID: PMC6095635 DOI: 10.1021/acs.nanolett.8b01223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 06/13/2018] [Indexed: 05/27/2023]
Abstract
Monolayer hexagonal boron nitride (hBN) tunnel barriers investigated using conductive atomic force microscopy reveal moiré patterns in the spatial maps of their tunnel conductance consistent with the formation of a moiré superlattice between the hBN and an underlying highly ordered pyrolytic graphite (HOPG) substrate. This variation is attributed to a periodc modulation of the local density of states and occurs for both exfoliated hBN barriers and epitaxially grown layers. The epitaxial barriers also exhibit enhanced conductance at localized subnanometer regions which are attributed to exposure of the substrate to a nitrogen plasma source during the high temperature growth process. Our results show clearly a spatial periodicity of tunnel current due to the formation of a moiré superlattice and we argue that this can provide a mechanism for elastic scattering of charge carriers for similar interfaces embedded in graphene/hBN resonant tunnel diodes.
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Affiliation(s)
- Alex Summerfield
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Aleksey Kozikov
- School of Physics and
Astronomy and National Graphene Institute, University
of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Tin S. Cheng
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Andrew Davies
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
- School of Chemistry and Nottingham Nanoscale and Microscale Research Centre, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Yong-Jin Cho
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Andrei N. Khlobystov
- School of Chemistry and Nottingham Nanoscale and Microscale Research Centre, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Christopher J. Mellor
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - C. Thomas Foxon
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibraki 305-0044, Japan
| | - Laurence Eaves
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Kostya S. Novoselov
- School of Physics and
Astronomy and National Graphene Institute, University
of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sergei V. Novikov
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Peter H. Beton
- School of Physics
and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
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11
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Tian H, Khanaki A, Das P, Zheng R, Cui Z, He Y, Shi W, Xu Z, Lake R, Liu J. Role of Carbon Interstitials in Transition Metal Substrates on Controllable Synthesis of High-Quality Large-Area Two-Dimensional Hexagonal Boron Nitride Layers. NANO LETTERS 2018; 18:3352-3361. [PMID: 29727192 DOI: 10.1021/acs.nanolett.7b05179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Reliable and controllable synthesis of two-dimensional (2D) hexagonal boron nitride (h-BN) layers is highly desirable for their applications as 2D dielectric and wide bandgap semiconductors. In this work, we demonstrate that the dissolution of carbon into cobalt (Co) and nickel (Ni) substrates can facilitate the growth of h-BN and attain large-area 2D homogeneity. The morphology of the h-BN film can be controlled from 2D layer-plus-3D islands to homogeneous 2D few-layers by tuning the carbon interstitial concentration in the Co substrate through a carburization process prior to the h-BN growth step. Comprehensive characterizations were performed to evaluate structural, electrical, optical, and dielectric properties of these samples. Single-crystal h-BN flakes with an edge length of ∼600 μm were demonstrated on carburized Ni. An average breakdown electric field of 9 MV/cm was achieved for an as-grown continuous 3-layer h-BN on carburized Co. Density functional theory calculations reveal that the interstitial carbon atoms can increase the adsorption energy of B and N atoms on the Co(111) surface and decrease the diffusion activation energy and, in turn, promote the nucleation and growth of 2D h-BN.
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Affiliation(s)
- Hao Tian
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Alireza Khanaki
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Protik Das
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Renjing Zheng
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Zhenjun Cui
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Yanwei He
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Wenhao Shi
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Zhongguang Xu
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Roger Lake
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
| | - Jianlin Liu
- Department of Electrical and Computer Engineering , University of California , Riverside , California 92521 , United States
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12
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Huder L, Artaud A, Le Quang T, de Laissardière GT, Jansen AGM, Lapertot G, Chapelier C, Renard VT. Electronic Spectrum of Twisted Graphene Layers under Heterostrain. PHYSICAL REVIEW LETTERS 2018; 120:156405. [PMID: 29756887 DOI: 10.1103/physrevlett.120.156405] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 02/12/2018] [Indexed: 05/13/2023]
Abstract
We demonstrate that stacking layered materials allows a strain engineering where each layer is strained independently, which we call heterostrain. We combine detailed structural and spectroscopic measurements with tight-binding calculations to show that small uniaxial heterostrain suppresses Dirac cones and leads to the emergence of flat bands in twisted graphene layers (TGLs). Moreover, we demonstrate that heterostrain reconstructs, much more severely, the energy spectrum of TGLs than homostrain for which both layers are strained identically, a result which should apply to virtually all van der Waals structures opening exciting possibilities for straintronics with 2D materials.
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Affiliation(s)
- Loïc Huder
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
| | - Alexandre Artaud
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
- Université Grenoble Alpes, CNRS, Institut NEEL, F-38000 Grenoble, France
| | - Toai Le Quang
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
| | - Guy Trambly de Laissardière
- Laboratoire de Physique Théorique et Modélisation, Université de Cergy-Pontoise-CNRS, F-95302 Cergy-Pontoise, France
| | | | - Gérard Lapertot
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
| | - Claude Chapelier
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
| | - Vincent T Renard
- Université Grenoble Alpes, CEA, INAC, PHELIQS, F-38000 Grenoble, France
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13
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Khanaki A, Tian H, Xu Z, Zheng R, He Y, Cui Z, Yang J, Liu J. Effect of high carbon incorporation in Co substrates on the epitaxy of hexagonal boron nitride/graphene heterostructures. NANOTECHNOLOGY 2018; 29:035602. [PMID: 29165320 DOI: 10.1088/1361-6528/aa9c58] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We carried out a systematic study of hexagonal boron nitride/graphene (h-BN/G) heterostructure growth by introducing high incorporation of a carbon (C) source on a heated cobalt (Co) foil substrate followed by boron and nitrogen sources in a molecular beam epitaxy system. With the increase of C incorporation in Co, three distinct regions of h-BN/G heterostructures were observed from region (1) where the C saturation was not attained at the growth temperature (900 °C) and G was grown only by precipitation during the cooling process to form a 'G network' underneath the h-BN film; to region (2) where the Co substrate was just saturated by C atoms at the growth temperature and a part of G growth occurs isothermally to form G islands and another part by precipitation, resulting in a non-uniform h-BN/G film; and to region (3) where a continuous layered G structure was formed at the growth temperature and precipitated C atoms added additional G layers to the system, leading to a uniform h-BN/G film. It is also found that in all three h-BN/G heterostructure growth regions, a 3 h h-BN growth at 900 °C led to h-BN film with a thickness of 1-2 nm, regardless of the underneath G layers' thickness or morphology. Growth time and growth temperature effects have been also studied.
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14
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Davies A, Albar JD, Summerfield A, Thomas JC, Cheng TS, Korolkov VV, Stapleton E, Wrigley J, Goodey NL, Mellor CJ, Khlobystov AN, Watanabe K, Taniguchi T, Foxon CT, Eaves L, Novikov SV, Beton PH. Lattice-Matched Epitaxial Graphene Grown on Boron Nitride. NANO LETTERS 2018; 18:498-504. [PMID: 29211487 DOI: 10.1021/acs.nanolett.7b04453] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band gap but requires the formation of highly strained material and has not hitherto been realized. We demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600-1710 °C and coexists with a topologically modified moiré pattern with regions of strained graphene which have giant moiré periods up to ∼80 nm. Raman spectra reveal narrow red-shifted peaks due to isotropic strain, while the giant moiré patterns result in complex splitting of Raman peaks due to strain variations across the moiré unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel-Kontorova-type domain walls and also the topological defects where they terminate. We relate these results to theoretical models of band gap formation in graphene/boron nitride heterostructures.
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Affiliation(s)
- Andrew Davies
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
- School of Chemistry, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Juan D Albar
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Alex Summerfield
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - James C Thomas
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Tin S Cheng
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Vladimir V Korolkov
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Emily Stapleton
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - James Wrigley
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Nathan L Goodey
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Christopher J Mellor
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Andrei N Khlobystov
- School of Chemistry, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - C Thomas Foxon
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Laurence Eaves
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Sergei V Novikov
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Peter H Beton
- School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, United Kingdom
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15
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Naumis GG, Barraza-Lopez S, Oliva-Leyva M, Terrones H. Electronic and optical properties of strained graphene and other strained 2D materials: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:096501. [PMID: 28540862 DOI: 10.1088/1361-6633/aa74ef] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review presents the state of the art in strain and ripple-induced effects on the electronic and optical properties of graphene. It starts by providing the crystallographic description of mechanical deformations, as well as the diffraction pattern for different kinds of representative deformation fields. Then, the focus turns to the unique elastic properties of graphene, and to how strain is produced. Thereafter, various theoretical approaches used to study the electronic properties of strained graphene are examined, discussing the advantages of each. These approaches provide a platform to describe exotic properties, such as a fractal spectrum related with quasicrystals, a mixed Dirac-Schrödinger behavior, emergent gravity, topological insulator states, in molecular graphene and other 2D discrete lattices. The physical consequences of strain on the optical properties are reviewed next, with a focus on the Raman spectrum. At the same time, recent advances to tune the optical conductivity of graphene by strain engineering are given, which open new paths in device applications. Finally, a brief review of strain effects in multilayered graphene and other promising 2D materials like silicene and materials based on other group-IV elements, phosphorene, dichalcogenide- and monochalcogenide-monolayers is presented, with a brief discussion of interplays among strain, thermal effects, and illumination in the latter material family.
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Affiliation(s)
- Gerardo G Naumis
- Depto. de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20-364, Mexico City 01000, Mexico
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16
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Albar JD, Summerfield A, Cheng TS, Davies A, Smith EF, Khlobystov AN, Mellor CJ, Taniguchi T, Watanabe K, Foxon CT, Eaves L, Beton PH, Novikov SV. An atomic carbon source for high temperature molecular beam epitaxy of graphene. Sci Rep 2017; 7:6598. [PMID: 28747805 PMCID: PMC5529545 DOI: 10.1038/s41598-017-07021-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/20/2017] [Indexed: 12/04/2022] Open
Abstract
We report the use of a novel atomic carbon source for the molecular beam epitaxy (MBE) of graphene layers on hBN flakes and on sapphire wafers at substrate growth temperatures of ~1400 °C. The source produces a flux of predominantly atomic carbon, which diffuses through the walls of a Joule-heated tantalum tube filled with graphite powder. We demonstrate deposition of carbon on sapphire with carbon deposition rates up to 12 nm/h. Atomic force microscopy measurements reveal the formation of hexagonal moiré patterns when graphene monolayers are grown on hBN flakes. The Raman spectra of the graphene layers grown on hBN and sapphire with the sublimation carbon source and the atomic carbon source are similar, whilst the nature of the carbon aggregates is different - graphitic with the sublimation carbon source and amorphous with the atomic carbon source. At MBE growth temperatures we observe etching of the sapphire wafer surface by the flux from the atomic carbon source, which we have not observed in the MBE growth of graphene with the sublimation carbon source.
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Affiliation(s)
- J D Albar
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - A Summerfield
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - T S Cheng
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - A Davies
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.,Nanoscale and microscale research centre (NMRC) and School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - E F Smith
- Nanoscale and microscale research centre (NMRC) and School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - A N Khlobystov
- Nanoscale and microscale research centre (NMRC) and School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - C J Mellor
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - T Taniguchi
- The National Institute for Materials Science, Advanced Materials Laboratory, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - K Watanabe
- The National Institute for Materials Science, Advanced Materials Laboratory, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - C T Foxon
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - L Eaves
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - P H Beton
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - S V Novikov
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.
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17
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Preparing local strain patterns in graphene by atomic force microscope based indentation. Sci Rep 2017; 7:3035. [PMID: 28596579 PMCID: PMC5465061 DOI: 10.1038/s41598-017-03332-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 04/26/2017] [Indexed: 11/22/2022] Open
Abstract
Patterning graphene into various mesoscopic devices such as nanoribbons, quantum dots, etc. by lithographic techniques has enabled the guiding and manipulation of graphene’s Dirac-type charge carriers. Graphene, with well-defined strain patterns, holds promise of similarly rich physics while avoiding the problems created by the hard to control edge configuration of lithographically prepared devices. To engineer the properties of graphene via mechanical deformation, versatile new techniques are needed to pattern strain profiles in a controlled manner. Here we present a process by which strain can be created in substrate supported graphene layers. Our atomic force microscope-based technique opens up new possibilities in tailoring the properties of graphene using mechanical strain.
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18
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Jiang Y, Mao J, Duan J, Lai X, Watanabe K, Taniguchi T, Andrei EY. Visualizing Strain-Induced Pseudomagnetic Fields in Graphene through an hBN Magnifying Glass. NANO LETTERS 2017; 17:2839-2843. [PMID: 28409936 DOI: 10.1021/acs.nanolett.6b05228] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Graphene's remarkable properties are inherent to its two-dimensional honeycomb lattice structure. Its low dimensionality, which makes it possible to rearrange the atoms by applying an external force, offers the intriguing prospect of mechanically controlling the electronic properties. In the presence of strain, graphene develops a pseudomagnetic field (PMF) that reconstructs the band structure into pseudo Landau levels (PLLs). However, a feasible route to realizing, characterizing and controlling PMFs is still lacking. Here we report on a method to generate and characterize PMFs in a graphene membrane supported on nanopillars. A direct measure of the local strain is achieved by using the magnifying effect of the moiré pattern formed against a hexagonal boron nitride substrate under scanning tunneling microscopy. We quantify the strain-induced PMF through the PLLs spectra observed in scanning tunneling spectroscopy. This work provides a pathway to strain induced engineering and electro-mechanical graphene-based devices.
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Affiliation(s)
- Yuhang Jiang
- Department of Physics and Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Jinhai Mao
- Department of Physics and Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Junxi Duan
- Department of Physics and Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States
| | - Xinyuan Lai
- Department of Physics and Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States
| | - 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
| | - Eva Y Andrei
- Department of Physics and Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States
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19
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Wofford JM, Nakhaie S, Krause T, Liu X, Ramsteiner M, Hanke M, Riechert H, J Lopes JM. A hybrid MBE-based growth method for large-area synthesis of stacked hexagonal boron nitride/graphene heterostructures. Sci Rep 2017; 7:43644. [PMID: 28240323 PMCID: PMC5327397 DOI: 10.1038/srep43644] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 01/25/2017] [Indexed: 01/13/2023] Open
Abstract
Van der Waals heterostructures combining hexagonal boron nitride (h-BN) and graphene offer many potential advantages, but remain difficult to produce as continuous films over large areas. In particular, the growth of h-BN on graphene has proven to be challenging due to the inertness of the graphene surface. Here we exploit a scalable molecular beam epitaxy based method to allow both the h-BN and graphene to form in a stacked heterostructure in the favorable growth environment provided by a Ni(111) substrate. This involves first saturating a Ni film on MgO(111) with C, growing h-BN on the exposed metal surface, and precipitating the C back to the h-BN/Ni interface to form graphene. The resulting laterally continuous heterostructure is composed of a top layer of few-layer thick h-BN on an intermediate few-layer thick graphene, lying on top of Ni/MgO(111). Examinations by synchrotron-based grazing incidence diffraction, X-ray photoemission spectroscopy, and UV-Raman spectroscopy reveal that while the h-BN is relaxed, the lattice constant of graphene is significantly reduced, likely due to nitrogen doping. These results illustrate a different pathway for the production of h-BN/graphene heterostructures, and open a new perspective for the large-area preparation of heterosystems combining graphene and other 2D or 3D materials.
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Affiliation(s)
- Joseph M Wofford
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Siamak Nakhaie
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Thilo Krause
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Xianjie Liu
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden
| | - Manfred Ramsteiner
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Michael Hanke
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Henning Riechert
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - J Marcelo J Lopes
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
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20
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Hexagonal Boron Nitride Tunnel Barriers Grown on Graphite by High Temperature Molecular Beam Epitaxy. Sci Rep 2016; 6:34474. [PMID: 27681943 PMCID: PMC5041098 DOI: 10.1038/srep34474] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 09/14/2016] [Indexed: 12/12/2022] Open
Abstract
We demonstrate direct epitaxial growth of high-quality hexagonal boron nitride (hBN) layers on graphite using high-temperature plasma-assisted molecular beam epitaxy. Atomic force microscopy reveals mono- and few-layer island growth, while conducting atomic force microscopy shows that the grown hBN has a resistance which increases exponentially with the number of layers, and has electrical properties comparable to exfoliated hBN. X-ray photoelectron spectroscopy, Raman microscopy and spectroscopic ellipsometry measurements on hBN confirm the formation of sp2-bonded hBN and a band gap of 5.9 ± 0.1 eV with no chemical intermixing with graphite. We also observe hexagonal moiré patterns with a period of 15 nm, consistent with the alignment of the hBN lattice and the graphite substrate.
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21
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Wang J, Long M, Zhao WS, Hu Y, Wang G, Chan KS. A valley and spin filter based on gapped graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:285302. [PMID: 27230498 DOI: 10.1088/0953-8984/28/28/285302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We study highly valley- and spin-polarized current in single-layer gapped graphene without spin-orbit coupling. The structure considered is a three-barrier structure with one spin-splitting barrier and two electrical potential barriers with vector potentials. The electrons in the two valleys transmit differently because of the valley-dependent reflection between two adjacent barriers, while the spin-up and spin-down electrons transmit differently because of the spin splitting. The structure is different from other structures in which spin-orbit coupling plays an important role in the observation of valley- and spin-polarized current. We can control the spin and valley polarization by changing the width of the barrier or the strength of the spin splitting. The structure proposed in this paper can be used to make valley and spin devices.
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Affiliation(s)
- Jing Wang
- Key Laboratory of RF Circuits and Systems of Ministry of Education of China, Hangzhou Dianzi University, Hangzhou 310018, People's Republic of China
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