1
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Ni Y, Deng G, Li J, Hua H, Liu N. The Strain-Tuned Spin Seebeck Effect, Spin Polarization, and Giant Magnetoresistance of a Graphene Nanobubble in Zigzag Graphene Nanoribbons. ACS OMEGA 2021; 6:15308-15315. [PMID: 34151110 PMCID: PMC8210443 DOI: 10.1021/acsomega.1c01640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/25/2021] [Indexed: 06/13/2023]
Abstract
By using first-principle calculations combined with the non-equilibrium Green's function approach, we studied the spin caloritronic properties of zigzag graphene nanoribbons with a nanobubble at the edge (NB-ZGNRs). The thermal spin-polarized currents can be induced by a temperature difference, and the spin Seebeck effect is found in the nanoribbon. The spin polarization, magnetoresistance, and Seebeck coefficients are discussed, which are strongly affected and can be tuned by the geometrical strain. Moreover, some novel spin caloritronic devices are designed, such as a device that generates bidirectional perfect spin currents and thermally induced giant magnetoresistances. Our results open up the possibility of tuning the spin caloritronic properties of the NB-ZGNR-based devices by changing the elastic strain on the graphene nanobubble.
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Affiliation(s)
- Yun Ni
- Hubei
Engineering Technology Research Center of Energy Photoelectric Device
and System, Hubei University of Technology, Wuhan 430068, China
- College
of Science, Hubei University of Technology, Wuhan 430068, China
| | - Gang Deng
- Hubei
Engineering Technology Research Center of Energy Photoelectric Device
and System, Hubei University of Technology, Wuhan 430068, China
- College
of Science, Hubei University of Technology, Wuhan 430068, China
| | - Jia Li
- Hubei
Engineering Technology Research Center of Energy Photoelectric Device
and System, Hubei University of Technology, Wuhan 430068, China
- College
of Science, Hubei University of Technology, Wuhan 430068, China
| | - Hu Hua
- Hubei
Engineering Technology Research Center of Energy Photoelectric Device
and System, Hubei University of Technology, Wuhan 430068, China
- College
of Science, Hubei University of Technology, Wuhan 430068, China
| | - Na Liu
- College
of Physics and Electronic Science, Hubei
Normal University, Huangshi 435002, China
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2
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Ni Y, Li J, Tao W, Ding H, Li RX. The spin-dependent transport properties of defected zigzag graphene nanoribbons with graphene nanobubbles. Phys Chem Chem Phys 2021; 23:2753-2761. [PMID: 33471019 DOI: 10.1039/d0cp05640e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Zigzag-edged graphene nanoribbons (ZGNRs) have important applications in spintronics and spin caloritronics. While in the preparation of a ZGNR, defects like the graphene nanobubbles often appear, which may affect the physical properties of the ZGNR. In this paper, we studied the transport properties of a defected ZGNR with a graphene nanobubble by performing first-principles quantum transport calculations. The results show that when the nanobubble is intact and locates at the centre, the spin polarization and magnetoresistance tend to drop off in the low bias voltage cases, compared to the ideal ZGNR. While when the nanobubble is split and locates at the edge, all the transport properties are significantly affected and altered, such as the spin polarization, the giant magnetoresistance effect and the spin Seebeck effect. Meanwhile, some new results are obtained from the device, including the negative differential resistance effect and the pure thermal-induced spin-current.
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Affiliation(s)
- Yun Ni
- Hubei Engineering Technology Research Center of Energy Photoelectric Device and System, Hubei University of Technology, Wuhan, 430068, China.
| | - Jia Li
- Hubei Engineering Technology Research Center of Energy Photoelectric Device and System, Hubei University of Technology, Wuhan, 430068, China.
| | - Wei Tao
- Department of Basic Science, Wenhua College, Wuhan, 430074, China
| | - Hao Ding
- Department of Basic Science, Wenhua College, Wuhan, 430074, China
| | - Rui-Xue Li
- College of Science, Henan University of Engineering, Zhengzhou, 451191, China
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3
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Ben Gouider Trabelsi A, V. Kusmartsev F, Kusmartseva A, H. Alkallas F, AlFaify S, Shkir M. Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2234. [PMID: 33187068 PMCID: PMC7696917 DOI: 10.3390/nano10112234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 11/17/2022]
Abstract
Graphene distinctive electronic and optical properties have sparked intense interest throughout the scientific community bringing innovation and progress to many sectors of academia and industry. Graphene manufacturing has rapidly evolved since its discovery in 2004. The diverse growth methods of graphene have many comparative advantages in terms of size, shape, quality and cost. Specifically, epitaxial graphene is thermally grown on a silicon carbide (SiC) substrate. This type of graphene is unique due to its coexistence with the SiC underneath which makes the process of transferring graphene layers for devices manufacturing simple and robust. Raman analysis is a sensitive technique extensively used to explore nanocarbon material properties. Indeed, this method has been widely used in graphene studies in fundamental research and application fields. We review the principal Raman scattering processes in SiC substrate and demonstrate epitaxial graphene growth. We have identified the Raman bands signature of graphene for different layers number. The method could be readily adopted to characterize structural and exceptional electrical properties for various epitaxial graphene systems. Particularly, the variation of the charge carrier concentration in epitaxial graphene of different shapes and layers number have been precisely imaged. By comparing the intensity ratio of 2D line and G line-"I2D/IG"-the density of charge across the graphene layers could be monitored. The obtained results were compared to previous electrical measurements. The substrate longitudinal optical phonon coupling "LOOPC" modes have also been examined for several epitaxial graphene layers. The LOOPC of the SiC substrate shows a precise map of the density of charge in epitaxial graphene systems for different graphene layers number. Correlations between the density of charge and particular graphene layer shape such as bubbles have been determined. All experimental probes show a high degree of consistency and efficiency. Our combined studies have revealed novel capacitor effect in diverse epitaxial graphene system. The SiC substrate self-compensates the graphene layer charge without any external doping. We have observed a new density of charge at the graphene-substrate interface. The located capacitor effects at epitaxial graphene-substrate interfaces give rise to an unexpected mini gap in graphene band structure.
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Affiliation(s)
- A. Ben Gouider Trabelsi
- Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, Riyadh PO Box 84428, Saudi Arabia;
| | - F. V. Kusmartsev
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK; (F.V.K.); (A.K.)
- Micro/Nano Fabrication Laboratory, Microsystem & Terahertz Research Centre of CAEP, Chengdu, China
| | - A. Kusmartseva
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK; (F.V.K.); (A.K.)
| | - F. H. Alkallas
- Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, Riyadh PO Box 84428, Saudi Arabia;
| | - S. AlFaify
- Department of Physics, Faculty of Sciences, King Khalid University, Abha PO Box 61421, Saudi Arabia; (S.A.); (M.S.)
| | - Mohd Shkir
- Department of Physics, Faculty of Sciences, King Khalid University, Abha PO Box 61421, Saudi Arabia; (S.A.); (M.S.)
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4
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Villegas KHA, Kusmartsev FV, Luo Y, Savenko IG. Optical Transistor for Amplification of Radiation in a Broadband Terahertz Domain. PHYSICAL REVIEW LETTERS 2020; 124:087701. [PMID: 32167339 DOI: 10.1103/physrevlett.124.087701] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 10/13/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
We propose a new type of optical transistor for a broadband amplification of terahertz radiation. It is made of a graphene-superconductor hybrid, where electrons and Cooper pairs couple by Coulomb forces. The transistor operates via the propagation of surface plasmons in both layers, and the origin of amplification is the quantum capacitance of graphene. It leads to terahertz waves amplification, the negative power absorption, and as a result, the system yields positive gain, and the hybrid acts like an optical transistor, operating with the terahertz light. It can, in principle, amplify even a whole spectrum of chaotic signals (or noise), which is required for numerous biological applications.
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Affiliation(s)
- K H A Villegas
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science (IBS), Daejeon 34126, Korea
| | - F V Kusmartsev
- Micro/Nano Fabrication Laboratory (MNFL), Microsystem and Terahertz Research Center, Chengdu, China
- Physics Department, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - Y Luo
- Micro/Nano Fabrication Laboratory (MNFL), Microsystem and Terahertz Research Center, Chengdu, China
| | - I G Savenko
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science (IBS), Daejeon 34126, Korea
- A. V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
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5
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Vasić B, Matković A, Gajić R. Phase imaging and nanoscale energy dissipation of supported graphene using amplitude modulation atomic force microscopy. NANOTECHNOLOGY 2017; 28:465708. [PMID: 29059053 DOI: 10.1088/1361-6528/aa8e3b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigate the phase imaging of supported graphene using amplitude modulation atomic force microscopy (AFM), the so-called tapping mode. The phase contrast between graphene and the neighboring substrate grows in hard tapping conditions and the contrast is enhanced compared to the topographic one. Therefore, phase measurements could enable the high-contrast imaging of graphene and related two-dimensional materials and heterostructures, which is not achievable with conventional AFM based topographic measurements. Obtained phase maps are then transformed into energy dissipation maps, which are important for graphene applications in various nano-mechanical systems. From a fundamental point of view, energy dissipation gives further insight into mechanical properties. Reliable measurements, obtained in the repulsive regime, show that the energy dissipation on a graphene-covered substrate is lower than that on a bare one, so graphene provides certain shielding in tip-substrate interaction. Based on the obtained phase curves and their derivatives, as well as on correlation measurements based on AFM nanoindentation and force modulation microscopy, we conclude that the main dissipation channels in graphene-substrate systems are short-range hysteresis and long-range interfacial forces.
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Affiliation(s)
- Borislav Vasić
- Graphene Laboratory (GLAB) of Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
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6
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Ben Gouider Trabelsi A, Kusmartsev FV, Gaifullin MB, Forrester DM, Kusmartseva A, Oueslati M. Morphological imperfections of epitaxial graphene: from a hindrance to the generation of new photo-responses in the visible domain. NANOSCALE 2017; 9:11463-11474. [PMID: 28580975 DOI: 10.1039/c6nr08999b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the discovery of remarkable photo-physical phenomena with characteristics unique to epitaxial graphene grown on 6H-SiC (000-1). Surprisingly, the electrical resistance of graphene increases under light illumination in contrast to conventional materials where it normally decreases. The resistance shows logarithmic temperature dependences which may be attributed to an Altshuler-Aronov effect. We show that the photoresistance depends on the frequency of the irradiating light, with three lasers (red, green, and violet) used to demonstrate the phenomenon. The counterintuitive rise of the positive photoresistance may be attributed to a creation of trapped charges upon irradiation. We argue that the origin of the photoresistance is related to the texture formed by the graphene flakes. Photovoltage also exists and increases with light intensity. However, its value saturates quickly with irradiation and does not change with time. The saturation of the photovoltage may be associated with the formation of a quasi-equilibrium state of the excited electrons and holes associated with a charge redistribution between the graphene and SiC substrate. The obtained physical picture is in agreement with the photoresistance measurements: X-ray photoelectron spectrometry "XPS", atomic force microscopy "AFM", Raman spectroscopy and the magnetic dependence of photoresistance decay measurements. We also observed non-decaying photoresistance and linear magnetoresistance in magnetic fields up to 1 T. We argue that this is due to topological phases spontaneously induced by persistent current formation within the graphene flake edges by magnetic fields.
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7
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Jain SK, Juričić V, Barkema GT. Probing the shape of a graphene nanobubble. Phys Chem Chem Phys 2017; 19:7465-7470. [PMID: 28256643 DOI: 10.1039/c6cp08535k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Universal shape behavior and ∼1 GPa vdW pressure in a small ∼10 nm graphene nanobubble.
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Affiliation(s)
- Sandeep K. Jain
- Institute for Theoretical Physics
- Universiteit Utrecht
- 3584 CC Utrecht
- The Netherlands
| | - Vladimir Juričić
- Nordita
- Center for Quantum Materials
- KTH Royal Institute of Technology and Stockholm University
- S-106 91 Stockholm
- Sweden
| | - Gerard T. Barkema
- Department of Information and Computing Science
- Universiteit Utrecht
- 3584 CC Utrecht
- The Netherlands
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8
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Pierucci D, Henck H, Naylor CH, Sediri H, Lhuillier E, Balan A, Rault JE, Dappe YJ, Bertran F, Fèvre PL, Johnson ATC, Ouerghi A. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures. Sci Rep 2016; 6:26656. [PMID: 27246929 PMCID: PMC4894673 DOI: 10.1038/srep26656] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 05/03/2016] [Indexed: 11/09/2022] Open
Abstract
Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.
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Affiliation(s)
- Debora Pierucci
- Laboratoire de Photonique et de Nanostructures (CNRS- LPN),
Route de Nozay, 91460
Marcoussis, France
| | - Hugo Henck
- Laboratoire de Photonique et de Nanostructures (CNRS- LPN),
Route de Nozay, 91460
Marcoussis, France
| | - Carl H. Naylor
- Department of Physics and Astronomy, University of
Pennsylvania, 209S 33rd Street, Philadelphia,
Pennsylvania
19104, USA
| | - Haikel Sediri
- Laboratoire de Photonique et de Nanostructures (CNRS- LPN),
Route de Nozay, 91460
Marcoussis, France
| | - Emmanuel Lhuillier
- Institut des Nanosciences de Paris, UPMC, 4 place Jussieu,
boîte courrier 840, 75252
Paris cedex 05, France
| | - Adrian Balan
- Department of Physics and Astronomy, University of
Pennsylvania, 209S 33rd Street, Philadelphia,
Pennsylvania
19104, USA
- Laboratoire d’Innovation en Chimie des Surfaces et
Nanosciences, DSM/NIMBE/LICSEN (CNRS UMR 3685), CEA Saclay,
91191
Gif-sur-Yvette Cedex, France
| | - Julien E. Rault
- Synchrotron-SOLEIL, Saint-Aubin, BP48,
F91192 Gif sur Yvette Cedex, France
| | - Yannick J. Dappe
- SPEC, CEA, CNRS, Universite Paris-Saclay, CEA Saclay,
91191 Gif-sur-Yvette Cedex, France
| | - François Bertran
- Synchrotron-SOLEIL, Saint-Aubin, BP48,
F91192 Gif sur Yvette Cedex, France
| | - Patrick Le Fèvre
- Synchrotron-SOLEIL, Saint-Aubin, BP48,
F91192 Gif sur Yvette Cedex, France
| | - A. T. Charlie Johnson
- Department of Physics and Astronomy, University of
Pennsylvania, 209S 33rd Street, Philadelphia,
Pennsylvania
19104, USA
| | - Abdelkarim Ouerghi
- Laboratoire de Photonique et de Nanostructures (CNRS- LPN),
Route de Nozay, 91460
Marcoussis, France
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9
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Hajlaoui M, Sediri H, Pierucci D, Henck H, Phuphachong T, Silly MG, de Vaulchier LA, Sirotti F, Guldner Y, Belkhou R, Ouerghi A. High Electron Mobility in Epitaxial Trilayer Graphene on Off-axis SiC(0001). Sci Rep 2016; 6:18791. [PMID: 26739366 PMCID: PMC4704025 DOI: 10.1038/srep18791] [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: 07/09/2015] [Accepted: 11/09/2015] [Indexed: 11/09/2022] Open
Abstract
The van de Waals heterostructure formed by an epitaxial trilayer graphene is of particular interest due to its unique tunable electronic band structure and stacking sequence. However, to date, there has been a lack in the fundamental understanding of the electronic properties of epitaxial trilayer graphene. Here, we investigate the electronic properties of large-area epitaxial trilayer graphene on a 4° off-axis SiC(0001) substrate. Micro-Raman mappings and atomic force microscopy (AFM) confirmed predominantly trilayer on the sample obtained under optimized conditions. We used angle-resolved photoemission spectroscopy (ARPES) and Density Functional Theory (DFT) calculations to study in detail the structure of valence electronic states, in particular the dispersion of π bands in reciprocal space and the exact determination of the number of graphene layers. Using far-infrared magneto-transmission (FIR-MT), we demonstrate, that the electron cyclotron resonance (CR) occurs between Landau levels with a (B)(1/2) dependence. The CR line-width is consistent with a high Dirac fermions mobility of ~3000 cm(2)·V(-1)·s(-1) at 4 K.
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Affiliation(s)
- Mahdi Hajlaoui
- CNRS- Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis, France.,Synchrotron-SOLEIL, Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Haikel Sediri
- CNRS- Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis, France
| | - Debora Pierucci
- CNRS- Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis, France
| | - Hugo Henck
- CNRS- Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis, France
| | - Thanyanan Phuphachong
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure-PSL Research University, CNRS, Université Pierre &Marie Curie-Sorbonne Universités, 24 rue Lhomond, 75005 Paris, France
| | - Mathieu G Silly
- Synchrotron-SOLEIL, Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Louis-Anne de Vaulchier
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure-PSL Research University, CNRS, Université Pierre &Marie Curie-Sorbonne Universités, 24 rue Lhomond, 75005 Paris, France
| | - Fausto Sirotti
- Synchrotron-SOLEIL, Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Yves Guldner
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure-PSL Research University, CNRS, Université Pierre &Marie Curie-Sorbonne Universités, 24 rue Lhomond, 75005 Paris, France
| | - Rachid Belkhou
- Synchrotron-SOLEIL, Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Abdelkarim Ouerghi
- CNRS- Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis, France
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10
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Zamborlini G, Imam M, Patera LL, Menteş TO, Stojić N, Africh C, Sala A, Binggeli N, Comelli G, Locatelli A. Nanobubbles at GPa Pressure under Graphene. NANO LETTERS 2015; 15:6162-6169. [PMID: 26241631 DOI: 10.1021/acs.nanolett.5b02475] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We provide direct evidence that irradiation of a graphene membrane on Ir with low-energy Ar ions induces formation of solid noble-gas nanobubbles. Their size can be controlled by thermal treatment, reaching tens of nanometers laterally and height of 1.5 nm upon annealing at 1080 °C. Ab initio calculations show that Ar nanobubbles are subject to pressures reaching tens of GPa, their formation being driven by minimization of the energy cost of film distortion and loss of adhesion.
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Affiliation(s)
- Giovanni Zamborlini
- Department of Physics, University of Trieste , Via Valerio 2, I-34127 Trieste, Italy
- Peter Grünberg Institute (PGI-6) , Research Centre Jülich, 52425 Jülich, Germany
| | - Mighfar Imam
- Abdus Salam International Centre for Theoretical Physics , Strada Costiera 11, Trieste I-34151, Italy
| | - Laerte L Patera
- Department of Physics, University of Trieste , Via Valerio 2, I-34127 Trieste, Italy
- IOM-CNR Laboratorio TASC , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
| | - Tevfik Onur Menteş
- Elettra - Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
| | - Nataša Stojić
- Abdus Salam International Centre for Theoretical Physics , Strada Costiera 11, Trieste I-34151, Italy
- IOM-CNR Democritos , Trieste I-34151, Italy
| | - Cristina Africh
- IOM-CNR Laboratorio TASC , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
| | - Alessandro Sala
- Elettra - Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
| | - Nadia Binggeli
- Abdus Salam International Centre for Theoretical Physics , Strada Costiera 11, Trieste I-34151, Italy
- IOM-CNR Democritos , Trieste I-34151, Italy
| | - Giovanni Comelli
- Department of Physics, University of Trieste , Via Valerio 2, I-34127 Trieste, Italy
- IOM-CNR Laboratorio TASC , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
| | - Andrea Locatelli
- Elettra - Sincrotrone Trieste , S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
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11
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Jin HB, Jeon Y, Jung S, Modepalli V, Kang HS, Lee BC, Ko JH, Shin HJ, Yoo JW, Kim SY, Kwon SY, Eom D, Park K. Enhanced crystallinity of epitaxial graphene grown on hexagonal SiC surface with molybdenum plate capping. Sci Rep 2015; 5:9615. [PMID: 25905989 PMCID: PMC5386107 DOI: 10.1038/srep09615] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 03/09/2015] [Indexed: 11/20/2022] Open
Abstract
The crystallinity of epitaxial graphene (EG) grown on a Hexagonal-SiC substrate is found to be enhanced greatly by capping the substrate with a molybdenum plate (Mo-plate) during vacuum annealing. The crystallinity enhancement of EG layer grown with Mo-plate capping is confirmed by the significant change of measured Raman spectra, compared to the spectra for no capping. Mo-plate capping is considered to induce heat accumulation on SiC surface by thermal radiation mirroring and raise Si partial pressure near surface by confining the sublimated Si atoms between SiC substrate and Mo-plate, which would be the essential contributors of crystallinity enhancement.
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Affiliation(s)
- Han Byul Jin
- School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Youngeun Jeon
- School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Sungchul Jung
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Vijayakumar Modepalli
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Hyun Suk Kang
- Quantum Optics Laboratory, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Byung Cheol Lee
- Quantum Optics Laboratory, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Jae-Hyeon Ko
- Department of Physics, Hallym University, Chuncheon, Gangwondo 200-702, Republic of Korea
| | - Hyung-Joon Shin
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Sung Youb Kim
- School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Soon-Yong Kwon
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Daejin Eom
- Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
| | - Kibog Park
- 1] School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea [2] Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
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12
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Abstract
Full confinement of the leviton/anti-leviton can occur inside a potential. Bifurcations in the wavefunction show the onset of internal vortex structures. Transmission and reflection occurs as a function of a leviton energy/potential barrier ratio.
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Forrester DM, Kusmartsev FV. Graphene levitons and anti-levitons in magnetic fields. NANOSCALE 2014; 6:7594-7603. [PMID: 24893578 DOI: 10.1039/c4nr00754a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The leviton is an electron or hole wavepacket that rides the surface of the Fermi sea. When a series of Lorentzian or Gaussian time dependent pulses are applied to an ultracold system a soliton-like excitation with only one electron and no localised hole emerges. Graphene is a unique system where the Fermi surface may arise from a Dirac point and therewith the levitons character may display many interesting features. For example, the leviton formation may be associated with a chiral anomaly, and inside a single potential step an anti-leviton forms. We show that the application of weak magnetic fields may switch on and off the leviton Klein tunnelling. Also, in a moderate field negative refraction arises along a curved trajectory, whereas with a stronger field a new elementary excitation - the levity vortex - in the reflected wavefunction occurs. Herein we describe these phenomena in detail along with a complete explanation of the transmission of graphene levitons at a step potential in terms of the probability densities and a series of phase diagrams and the tunnelling times.
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