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Gobato YG, de Brito CS, Chaves A, Prosnikov MA, Woźniak T, Guo S, Barcelos ID, Milošević MV, Withers F, Christianen PCM. Distinctive g-Factor of Moiré-Confined Excitons in van der Waals Heterostructures. Nano Lett 2022; 22:8641-8646. [PMID: 36279205 DOI: 10.1021/acs.nanolett.2c03008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We investigated the valley Zeeman splitting of excitonic peaks in the microphotoluminescence (μPL) spectra of high-quality hBN/WS2/MoSe2/hBN heterostructures under perpendicular magnetic fields up to 20 T. We identify two neutral exciton peaks in the μPL spectra; the lower-energy peak exhibits a reduced g-factor relative to that of the higher energy peak and much lower than the recently reported values for interlayer excitons in other van der Waals (vdW) heterostructures. We provide evidence that such a discernible g-factor stems from the spatial confinement of the exciton in the potential landscape created by the moiré pattern due to lattice mismatch or interlayer twist in heterobilayers. This renders magneto-μPL an important tool to reach a deeper understanding of the effect of moiré patterns on excitonic confinement in vdW heterostructures.
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Affiliation(s)
- Y Galvão Gobato
- Physics Department, Federal University of São Carlos, São Carlos, São Paulo13565-905, Brazil
| | - C Serati de Brito
- Physics Department, Federal University of São Carlos, São Carlos, São Paulo13565-905, Brazil
| | - A Chaves
- Departamento de Física, Universidade Federal do Ceará, Fortaleza, Ceará60455-760, Brazil
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, 2020Antwerp, Belgium
| | - M A Prosnikov
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, 6525 EDNijmegen, The Netherlands
| | - T Woźniak
- Department of Semiconductor Materials Engineering, Wrocław University of Science and Technology, 50-370Wrocław, Poland
| | - Shi Guo
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, U.K
| | - Ingrid D Barcelos
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, São Paulo13083-970, Brazil
| | - M V Milošević
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, 2020Antwerp, Belgium
- Instituto de Física, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso78060-900, Brazil
| | - F Withers
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, U.K
| | - P C M Christianen
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, 6525 EDNijmegen, The Netherlands
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2
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Covre FS, Faria PE, Gordo VO, de Brito CS, Zhumagulov YV, Teodoro MD, Couto ODD, Misoguti L, Pratavieira S, Andrade MB, Christianen PCM, Fabian J, Withers F, Galvão Gobato Y. Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe 2. Nanoscale 2022; 14:5758-5768. [PMID: 35348558 DOI: 10.1039/d2nr00315e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Strain plays an important role for the optical properties of monolayer transition metal dichalcogenides (TMDCs). Here, we investigate strain effects in a monolayer MoSe2 sample with a large bubble region using μ-Raman, second harmonic generation (SHG), μ-photoluminescence and magneto μ-photoluminescence at low temperature. Remarkably, our results reveal the presence of a non-uniform strain field and the observation of emission peaks at lower energies which are the signatures of exciton and trion quasiparticles red-shifted by strain effects in the bubble region, in agreement with our theoretical predictions. Furthermore, we have observed that the emission in the strained region decreases the trion binding energy and enhances the valley g-factors as compared to non-strained regions. Considering uniform biaxial strain effects within the unit cell of the TMDC monolayer (ML), our first principles calculations predict the observed enhancement of the exciton valley Zeeman effect. In addition, our results suggest that the exciton-trion fine structure plays an important role for the optical properties of strained TMDC ML. In summary, our study provides fundamental insights on the behaviour of excitons and trions in strained monolayer MoSe2 which are particularly relevant to properly characterize and understand the fine structure of excitonic complexes in strained TMDC systems/devices.
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Affiliation(s)
- F S Covre
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - P E Faria
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - V O Gordo
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - C Serati de Brito
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - Y V Zhumagulov
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M D Teodoro
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - O D D Couto
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - L Misoguti
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - S Pratavieira
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - M B Andrade
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - P C M Christianen
- High Field Magnet Laboratory (HFML - EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands
| | - J Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - F Withers
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - Y Galvão Gobato
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
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3
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Lyons TP, Gillard D, Molina-Sánchez A, Misra A, Withers F, Keatley PS, Kozikov A, Taniguchi T, Watanabe K, Novoselov KS, Fernández-Rossier J, Tartakovskii AI. Interplay between spin proximity effect and charge-dependent exciton dynamics in MoSe 2/CrBr 3 van der Waals heterostructures. Nat Commun 2020; 11:6021. [PMID: 33244001 PMCID: PMC7691354 DOI: 10.1038/s41467-020-19816-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 10/30/2020] [Indexed: 11/18/2022] Open
Abstract
Semiconducting ferromagnet-nonmagnet interfaces in van der Waals heterostructures present a unique opportunity to investigate magnetic proximity interactions dependent upon a multitude of phenomena including valley and layer pseudospins, moiré periodicity, or exceptionally strong Coulomb binding. Here, we report a charge-state dependency of the magnetic proximity effects between MoSe2 and CrBr3 in photoluminescence, whereby the valley polarization of the MoSe2 trion state conforms closely to the local CrBr3 magnetization, while the neutral exciton state remains insensitive to the ferromagnet. We attribute this to spin-dependent interlayer charge transfer occurring on timescales between the exciton and trion radiative lifetimes. Going further, we uncover by both the magneto-optical Kerr effect and photoluminescence a domain-like spatial topography of contrasting valley polarization, which we infer to be labyrinthine or otherwise highly intricate, with features smaller than 400 nm corresponding to our optical resolution. Our findings offer a unique insight into the interplay between short-lived valley excitons and spin-dependent interlayer tunneling, while also highlighting MoSe2 as a promising candidate to optically interface with exotic spin textures in van der Waals structures.
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Affiliation(s)
- T P Lyons
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK.
| | - D Gillard
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - A Molina-Sánchez
- QuantaLab, International Iberian Nanotechnology Laboratory, Braga, 4715-330, Portugal
| | - A Misra
- School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- Department of Physics, Indian Institute of Technology Madras (IIT Madras), Chennai, India
| | - F Withers
- Department of Physics and Astronomy, University of Exeter, Exeter, EX4 4QL, UK
| | - P S Keatley
- Department of Physics and Astronomy, University of Exeter, Exeter, EX4 4QL, UK
| | - A Kozikov
- School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - K S Novoselov
- School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
- Centre for Advanced 2D Materials, National University of Singapore, Singapore, 117546, Singapore
- Chongqing 2D Materials Institute, Liangjiang New Area, Chongqing, 400714, China
| | - J Fernández-Rossier
- QuantaLab, International Iberian Nanotechnology Laboratory, Braga, 4715-330, Portugal
| | - A I Tartakovskii
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK.
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Emmanuele RPA, Sich M, Kyriienko O, Shahnazaryan V, Withers F, Catanzaro A, Walker PM, Benimetskiy FA, Skolnick MS, Tartakovskii AI, Shelykh IA, Krizhanovskii DN. Highly nonlinear trion-polaritons in a monolayer semiconductor. Nat Commun 2020; 11:3589. [PMID: 32680995 PMCID: PMC7368028 DOI: 10.1038/s41467-020-17340-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 06/24/2020] [Indexed: 11/08/2022] Open
Abstract
Highly nonlinear optical materials with strong effective photon-photon interactions are required for ultrafast and quantum optical signal processing circuitry. Here we report strong Kerr-like nonlinearities by employing efficient optical transitions of charged excitons (trions) observed in semiconducting transition metal dichalcogenides (TMDCs). By hybridising trions in monolayer MoSe2 at low electron densities with a microcavity mode, we realise trion-polaritons exhibiting significant energy shifts at small photon fluxes due to phase space filling. We find the ratio of trion- to neutral exciton-polariton interaction strength is in the range from 10 to 100 in TMDC materials and that trion-polariton nonlinearity is comparable to that in other polariton systems. The results are in good agreement with a theory accounting for the composite nature of excitons and trions and deviation of their statistics from that of ideal bosons and fermions. Our findings open a way to scalable quantum optics applications with TMDCs.
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Affiliation(s)
- R P A Emmanuele
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - M Sich
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - O Kyriienko
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia.
| | - V Shahnazaryan
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland
| | - F Withers
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
| | - A Catanzaro
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - P M Walker
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - F A Benimetskiy
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia
| | - M S Skolnick
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia
| | - A I Tartakovskii
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - I A Shelykh
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia
- Science Institute, University of Iceland, Dunhagi-3, IS-107, Reykjavik, Iceland
| | - D N Krizhanovskii
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK.
- Department of Physics and Engineering, ITMO University, St. Petersburg, 197101, Russia.
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5
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Peimyoo N, Barnes MD, Mehew JD, De Sanctis A, Amit I, Escolar J, Anastasiou K, Rooney AP, Haigh SJ, Russo S, Craciun MF, Withers F. Laser-writable high-k dielectric for van der Waals nanoelectronics. Sci Adv 2019; 5:eaau0906. [PMID: 30746444 PMCID: PMC6357741 DOI: 10.1126/sciadv.aau0906] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 12/07/2018] [Indexed: 05/14/2023]
Abstract
Similar to silicon-based semiconductor devices, van der Waals heterostructures require integration with high-k oxides. Here, we demonstrate a method to embed and pattern a multifunctional few-nanometer-thick high-k oxide within various van der Waals devices without degrading the properties of the neighboring two-dimensional materials. This transformation allows for the creation of several fundamental nanoelectronic and optoelectronic devices, including flexible Schottky barrier field-effect transistors, dual-gated graphene transistors, and vertical light-emitting/detecting tunneling transistors. Furthermore, upon dielectric breakdown, electrically conductive filaments are formed. This filamentation process can be used to electrically contact encapsulated conductive materials. Careful control of the filamentation process also allows for reversible switching memories. This nondestructive embedding of a high-k oxide within complex van der Waals heterostructures could play an important role in future flexible multifunctional van der Waals devices.
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Affiliation(s)
- N. Peimyoo
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - M. D. Barnes
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - J. D. Mehew
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - A. De Sanctis
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - I. Amit
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - J. Escolar
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - K. Anastasiou
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - A. P. Rooney
- School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - S. J. Haigh
- School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - S. Russo
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - M. F. Craciun
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - F. Withers
- Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
- Corresponding author.
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6
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Dufferwiel S, Lyons TP, Solnyshkov DD, Trichet AAP, Catanzaro A, Withers F, Malpuech G, Smith JM, Novoselov KS, Skolnick MS, Krizhanovskii DN, Tartakovskii AI. Valley coherent exciton-polaritons in a monolayer semiconductor. Nat Commun 2018; 9:4797. [PMID: 30442886 PMCID: PMC6237922 DOI: 10.1038/s41467-018-07249-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 10/19/2018] [Indexed: 11/11/2022] Open
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) provide a unique possibility to generate and read-out excitonic valley coherence using linearly polarized light, opening the way to valley information transfer between distant systems. However, these excitons have short lifetimes (ps) and efficiently lose their valley coherence via the electron-hole exchange interaction. Here, we show that control of these processes can be gained by embedding a monolayer of WSe2 in an optical microcavity, forming part-light-part-matter exciton-polaritons. We demonstrate optical initialization of valley coherent polariton populations, exhibiting luminescence with a linear polarization degree up to 3 times higher than displayed by bare excitons. We utilize an external magnetic field alongside selective exciton-cavity-mode detuning to control the polariton valley pseudospin vector rotation, which reaches 45° at B = 8 T. This work provides unique insight into the decoherence mechanisms in TMDs and demonstrates the potential for engineering the valley pseudospin dynamics in monolayer semiconductors embedded in photonic structures. The short exciton life time in atomically thin transition metal dichalcogenides poses limitations to efficient control of the valley pseudospin and coherence. Here, the authors manipulate the exciton coherence in a WSe2 monolayer embedded in an optical microcavity in the strong light-matter coupling regime.
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Affiliation(s)
- S Dufferwiel
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK.
| | - T P Lyons
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK.
| | - D D Solnyshkov
- Institut Pascal, PHOTON-N2, Université Clermont Auvergne, CNRS, SIGMA Clermont, F-63000, Clermont-Ferrand, France
| | - A A P Trichet
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - A Catanzaro
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
| | - F Withers
- Centre for Graphene Science, CEMPS, University of Exeter, Exeter, EX4 4QF, UK
| | - G Malpuech
- Institut Pascal, PHOTON-N2, Université Clermont Auvergne, CNRS, SIGMA Clermont, F-63000, Clermont-Ferrand, France
| | - J M Smith
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - K S Novoselov
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - M S Skolnick
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
| | - D N Krizhanovskii
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
| | - A I Tartakovskii
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK.
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7
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Woods CR, Withers F, Zhu MJ, Cao Y, Yu G, Kozikov A, Ben Shalom M, Morozov SV, van Wijk MM, Fasolino A, Katsnelson MI, Watanabe K, Taniguchi T, Geim AK, Mishchenko A, Novoselov KS. Macroscopic self-reorientation of interacting two-dimensional crystals. Nat Commun 2016; 7:10800. [PMID: 26960435 PMCID: PMC4792927 DOI: 10.1038/ncomms10800] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 01/20/2016] [Indexed: 11/16/2022] Open
Abstract
Microelectromechanical systems, which can be moved or rotated with nanometre precision, already find applications in such fields as radio-frequency electronics, micro-attenuators, sensors and many others. Especially interesting are those which allow fine control over the motion on the atomic scale because of self-alignment mechanisms and forces acting on the atomic level. Such machines can produce well-controlled movements as a reaction to small changes of the external parameters. Here we demonstrate that, for the system of graphene on hexagonal boron nitride, the interplay between the van der Waals and elastic energies results in graphene mechanically self-rotating towards the hexagonal boron nitride crystallographic directions. Such rotation is macroscopic (for graphene flakes of tens of micrometres the tangential movement can be on hundreds of nanometres) and can be used for reproducible manufacturing of aligned van der Waals heterostructures.
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Affiliation(s)
- C. R. Woods
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - F. Withers
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - M. J. Zhu
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Y. Cao
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - G. Yu
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - A. Kozikov
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - M. Ben Shalom
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - S. V. Morozov
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
- Institute of Microelectronics Technology and High Purity Materials RAS, Chernogolovka 142432, Russia
- National University of Science and Technology ‘MISiS', Moscow 119049, Russia
| | - M. M. van Wijk
- Institute for Molecules and Materials,Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - A. Fasolino
- Institute for Molecules and Materials,Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - M. I. Katsnelson
- Institute for Molecules and Materials,Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - K. Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T. Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - A. K. Geim
- Centre for Mesoscience and Nanotechnology, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - A. Mishchenko
- National Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - K. S. Novoselov
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
- National Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, UK
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8
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Withers F, Del Pozo-Zamudio O, Schwarz S, Dufferwiel S, Walker PM, Godde T, Rooney AP, Gholinia A, Woods CR, Blake P, Haigh SJ, Watanabe K, Taniguchi T, Aleiner IL, Geim AK, Fal'ko VI, Tartakovskii AI, Novoselov KS. WSe₂ Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature. Nano Lett 2015; 15:8223-8228. [PMID: 26555037 DOI: 10.1021/acs.nanolett.5b03740] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Monolayers of molybdenum and tungsten dichalcogenides are direct bandgap semiconductors, which makes them promising for optoelectronic applications. In particular, van der Waals heterostructures consisting of monolayers of MoS2 sandwiched between atomically thin hexagonal boron nitride (hBN) and graphene electrodes allows one to obtain light emitting quantum wells (LEQWs) with low-temperature external quantum efficiency (EQE) of 1%. However, the EQE of MoS2- and MoSe2-based LEQWs shows behavior common for many other materials: it decreases fast from cryogenic conditions to room temperature, undermining their practical applications. Here we compare MoSe2 and WSe2 LEQWs. We show that the EQE of WSe2 devices grows with temperature, with room temperature EQE reaching 5%, which is 250× more than the previous best performance of MoS2 and MoSe2 quantum wells in ambient conditions. We attribute such different temperature dependences to the inverted sign of spin-orbit splitting of conduction band states in tungsten and molybdenum dichalcogenides, which makes the lowest-energy exciton in WSe2 dark.
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Affiliation(s)
- F Withers
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
- National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - O Del Pozo-Zamudio
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - S Schwarz
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - S Dufferwiel
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - P M Walker
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - T Godde
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - A P Rooney
- School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - A Gholinia
- School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - C R Woods
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - P Blake
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
- National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - S J Haigh
- School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - K Watanabe
- National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - I L Aleiner
- National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
- Physics Department, Columbia University , New York, New York 10027, United States
| | - A K Geim
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - V I Fal'ko
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
- National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
| | - A I Tartakovskii
- School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K
| | - K S Novoselov
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
- National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K
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9
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Withers F, Del Pozo-Zamudio O, Mishchenko A, Rooney AP, Gholinia A, Watanabe K, Taniguchi T, Haigh SJ, Geim AK, Tartakovskii AI, Novoselov KS. Light-emitting diodes by band-structure engineering in van der Waals heterostructures. Nat Mater 2015; 14:301-6. [PMID: 25643033 DOI: 10.1038/nmat4205] [Citation(s) in RCA: 600] [Impact Index Per Article: 66.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/23/2014] [Indexed: 05/20/2023]
Abstract
The advent of graphene and related 2D materials has recently led to a new technology: heterostructures based on these atomically thin crystals. The paradigm proved itself extremely versatile and led to rapid demonstration of tunnelling diodes with negative differential resistance, tunnelling transistors, photovoltaic devices and so on. Here, we take the complexity and functionality of such van der Waals heterostructures to the next level by introducing quantum wells (QWs) engineered with one atomic plane precision. We describe light-emitting diodes (LEDs) made by stacking metallic graphene, insulating hexagonal boron nitride and various semiconducting monolayers into complex but carefully designed sequences. Our first devices already exhibit an extrinsic quantum efficiency of nearly 10% and the emission can be tuned over a wide range of frequencies by appropriately choosing and combining 2D semiconductors (monolayers of transition metal dichalcogenides). By preparing the heterostructures on elastic and transparent substrates, we show that they can also provide the basis for flexible and semi-transparent electronics. The range of functionalities for the demonstrated heterostructures is expected to grow further on increasing the number of available 2D crystals and improving their electronic quality.
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Affiliation(s)
- F Withers
- School of Physics and Astronomy, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - O Del Pozo-Zamudio
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
| | - A Mishchenko
- School of Physics and Astronomy, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - A P Rooney
- School of Materials, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - A Gholinia
- School of Materials, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki Tsukuba 305-0044, Japan
| | - S J Haigh
- School of Materials, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - A K Geim
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester, Oxford Road Manchester M13 9PL, UK
| | - A I Tartakovskii
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
| | - K S Novoselov
- School of Physics and Astronomy, University of Manchester, Oxford Road Manchester M13 9PL, UK
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10
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Schwarz S, Dufferwiel S, Walker PM, Withers F, Trichet AA, Sich M, Li F, Chekhovich EA, Borisenko DN, Kolesnikov NN, Novoselov KS, Skolnick MS, Smith JM, Krizhanovskii DN, Tartakovskii AI. Two-dimensional metal-chalcogenide films in tunable optical microcavities. Nano Lett 2014; 14:7003-7008. [PMID: 25375802 PMCID: PMC4335560 DOI: 10.1021/nl503312x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 11/05/2014] [Indexed: 05/31/2023]
Abstract
Integration of quasi-two-dimensional (2D) films of metal-chalcogenides in optical microcavities permits new photonic applications of these materials. Here we present tunable microcavities with monolayer MoS2 or few monolayer GaSe films. We observe significant modification of spectral and temporal properties of photoluminescence (PL): PL is emitted in spectrally narrow and wavelength-tunable cavity modes with quality factors up to 7400; a 10-fold PL lifetime shortening is achieved, a consequence of Purcell enhancement of the spontaneous emission rate.
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Affiliation(s)
- S. Schwarz
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - S. Dufferwiel
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - P. M. Walker
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - F. Withers
- School
of Physics and Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - A. A.
P. Trichet
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United
Kingdom
| | - M. Sich
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - F. Li
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - E. A. Chekhovich
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - D. N. Borisenko
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka 142432, Russia
| | - N. N. Kolesnikov
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka 142432, Russia
| | - K. S. Novoselov
- School
of Physics and Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - M. S. Skolnick
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - J. M. Smith
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United
Kingdom
| | - D. N. Krizhanovskii
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - A. I. Tartakovskii
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
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11
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Mishchenko A, Tu JS, Cao Y, Gorbachev RV, Wallbank JR, Greenaway MT, Morozov VE, Morozov SV, Zhu MJ, Wong SL, Withers F, Woods CR, Kim YJ, Watanabe K, Taniguchi T, Vdovin EE, Makarovsky O, Fromhold TM, Fal'ko VI, Geim AK, Eaves L, Novoselov KS. Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures. Nat Nanotechnol 2014; 9:808-813. [PMID: 25194946 DOI: 10.1038/nnano.2014.187] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 08/05/2014] [Indexed: 05/28/2023]
Abstract
Recent developments in the technology of van der Waals heterostructures made from two-dimensional atomic crystals have already led to the observation of new physical phenomena, such as the metal-insulator transition and Coulomb drag, and to the realization of functional devices, such as tunnel diodes, tunnel transistors and photovoltaic sensors. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology.
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Affiliation(s)
- A Mishchenko
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - J S Tu
- Centre for Mesoscience &Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - Y Cao
- Centre for Mesoscience &Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - R V Gorbachev
- Centre for Mesoscience &Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - J R Wallbank
- Physics Department, Lancaster University, Lancaster University LA1 4YB, UK
| | - M T Greenaway
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - V E Morozov
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - S V Morozov
- Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - M J Zhu
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - S L Wong
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - F Withers
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - C R Woods
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Y-J Kim
- 1] Centre for Mesoscience &Nanotechnology, University of Manchester, Manchester M13 9PL, UK [2] Department of Chemistry, Seoul National University, Seoul 151-747, Korea
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - E E Vdovin
- 1] School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK [2] Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - O Makarovsky
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - T M Fromhold
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - V I Fal'ko
- Physics Department, Lancaster University, Lancaster University LA1 4YB, UK
| | - A K Geim
- 1] School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK [2] Centre for Mesoscience &Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - L Eaves
- 1] School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK [2] School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - K S Novoselov
- School of Physics &Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
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12
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Gorbachev RV, Song JCW, Yu GL, Kretinin AV, Withers F, Cao Y, Mishchenko A, Grigorieva IV, Novoselov KS, Levitov LS, Geim AK. Detecting topological currents in graphene superlattices. Science 2014; 346:448-51. [PMID: 25342798 DOI: 10.1126/science.1254966] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Topological materials may exhibit Hall-like currents flowing transversely to the applied electric field even in the absence of a magnetic field. In graphene superlattices, which have broken inversion symmetry, topological currents originating from graphene's two valleys are predicted to flow in opposite directions and combine to produce long-range charge neutral flow. We observed this effect as a nonlocal voltage at zero magnetic field in a narrow energy range near Dirac points at distances as large as several micrometers away from the nominal current path. Locally, topological currents are comparable in strength with the applied current, indicating large valley-Hall angles. The long-range character of topological currents and their transistor-like control by means of gate voltage can be exploited for information processing based on valley degrees of freedom.
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Affiliation(s)
- R V Gorbachev
- Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK. School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - J C W Song
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - G L Yu
- Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - A V Kretinin
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - F Withers
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Y Cao
- Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - A Mishchenko
- Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK
| | - I V Grigorieva
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - K S Novoselov
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - L S Levitov
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - A K Geim
- Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK. School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
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13
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Withers F, Yang H, Britnell L, Rooney AP, Lewis E, Felten A, Woods CR, Sanchez Romaguera V, Georgiou T, Eckmann A, Kim YJ, Yeates SG, Haigh SJ, Geim AK, Novoselov KS, Casiraghi C. Heterostructures produced from nanosheet-based inks. Nano Lett 2014; 14:3987-3992. [PMID: 24871927 DOI: 10.1021/nl501355j] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The new paradigm of heterostructures based on two-dimensional (2D) atomic crystals has already led to the observation of exciting physical phenomena and creation of novel devices. The possibility of combining layers of different 2D materials in one stack allows unprecedented control over the electronic and optical properties of the resulting material. Still, the current method of mechanical transfer of individual 2D crystals, though allowing exceptional control over the quality of such structures and interfaces, is not scalable. Here we show that such heterostructures can be assembled from chemically exfoliated 2D crystals, allowing for low-cost and scalable methods to be used in device fabrication.
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Affiliation(s)
- F Withers
- School of Physics and Astronomy, ‡School of Chemistry, §School of Materials, and #Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Oxford Road, Manchester, M13 9PL, United Kingdom
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14
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Kravets VG, Jalil R, Kim YJ, Ansell D, Aznakayeva DE, Thackray B, Britnell L, Belle BD, Withers F, Radko IP, Han Z, Bozhevolnyi SI, Novoselov KS, Geim AK, Grigorenko AN. Graphene-protected copper and silver plasmonics. Sci Rep 2014; 4:5517. [PMID: 24980150 PMCID: PMC4076691 DOI: 10.1038/srep05517] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/13/2014] [Indexed: 12/23/2022] Open
Abstract
Plasmonics has established itself as a branch of physics which promises to revolutionize data processing, improve photovoltaics, and increase sensitivity of bio-detection. A widespread use of plasmonic devices is notably hindered by high losses and the absence of stable and inexpensive metal films suitable for plasmonic applications. To this end, there has been a continuous search for alternative plasmonic materials that are also compatible with complementary metal oxide semiconductor technology. Here we show that copper and silver protected by graphene are viable candidates. Copper films covered with one to a few graphene layers show excellent plasmonic characteristics. They can be used to fabricate plasmonic devices and survive for at least a year, even in wet and corroding conditions. As a proof of concept, we use the graphene-protected copper to demonstrate dielectric loaded plasmonic waveguides and test sensitivity of surface plasmon resonances. Our results are likely to initiate wide use of graphene-protected plasmonics.
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Affiliation(s)
- V G Kravets
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - R Jalil
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Y-J Kim
- 1] School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK [2] Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 151-747, Korea
| | - D Ansell
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - D E Aznakayeva
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - B Thackray
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - L Britnell
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - B D Belle
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - F Withers
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - I P Radko
- Institute of Technology and Innovation (ITI), University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark
| | - Z Han
- Institute of Technology and Innovation (ITI), University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark
| | - S I Bozhevolnyi
- Institute of Technology and Innovation (ITI), University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark
| | - K S Novoselov
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - A N Grigorenko
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
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15
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Kretinin AV, Cao Y, Tu JS, Yu GL, Jalil R, Novoselov KS, Haigh SJ, Gholinia A, Mishchenko A, Lozada M, Georgiou T, Woods CR, Withers F, Blake P, Eda G, Wirsig A, Hucho C, Watanabe K, Taniguchi T, Geim AK, Gorbachev RV. Electronic properties of graphene encapsulated with different two-dimensional atomic crystals. Nano Lett 2014; 14:3270-6. [PMID: 24844319 DOI: 10.1021/nl5006542] [Citation(s) in RCA: 198] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are found to exhibit consistently high carrier mobilities of about 60 000 cm(2) V(-1) s(-1). In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide, and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of ∼1000 cm(2) V(-1) s(-1). We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN, and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates.
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Affiliation(s)
- A V Kretinin
- Centre for Mesoscience and Nanotechnology, ‡School of Physics and Astronomy, and §School of Materials, University of Manchester , Manchester M13 9PL, United Kingdom
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