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Vialla F, Del Fatti N. Time-Domain Investigations of Coherent Phonons in van der Waals Thin Films. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2543. [PMID: 33348750 PMCID: PMC7766349 DOI: 10.3390/nano10122543] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 01/31/2023]
Abstract
Coherent phonons can be launched in materials upon localized pulsed optical excitation, and be subsequently followed in time-domain, with a sub-picosecond resolution, using a time-delayed pulsed probe. This technique yields characterization of mechanical, optical, and electronic properties at the nanoscale, and is taken advantage of for investigations in material science, physics, chemistry, and biology. Here we review the use of this experimental method applied to the emerging field of homo- and heterostructures of van der Waals materials. Their unique structure corresponding to non-covalently stacked atomically thin layers allows for the study of original structural configurations, down to one-atom-thin films free of interface defect. The generation and relaxation of coherent optical phonons, as well as propagative and resonant breathing acoustic phonons, are comprehensively discussed. This approach opens new avenues for the in situ characterization of these novel materials, the observation and modulation of exotic phenomena, and advances in the field of acoustics microscopy.
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Affiliation(s)
- Fabien Vialla
- Institut Lumière Matière UMR 5306, Université Claude Bernard Lyon 1, CNRS, Université de Lyon, F-69622 Villeurbanne, France;
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2
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Arca F, Mendez JP, Ortiz M, Ariza P. Steric Interference in Bilayer Graphene with Point Dislocations. NANOMATERIALS 2019; 9:nano9071012. [PMID: 31337141 PMCID: PMC6669646 DOI: 10.3390/nano9071012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/02/2019] [Accepted: 07/05/2019] [Indexed: 12/04/2022]
Abstract
We present evidence of strong steric interference in bilayer graphene containing offset point dislocations. Calculations are carried out with Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) using the Long-Range Carbon Bond-Order Potential (LCBOP) potential of Los et al.. We start by validating the potential in the harmonic response by comparing the predicted phonon dispersion curves to experimental data and other potentials. The requisite force constants are derived by linearization of the potential and are presented in full form. We then continue to validate the potential in applications involving the formation of dislocation dipoles and quadrupoles in monolayer configurations. Finally, we evaluate a number of dislocation quadrupole configurations in monolayer and bilayer graphene and document strong steric interactions due to out-of-plane displacements when the dislocations on the individual layers are sufficiently offset with respect to each other.
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Affiliation(s)
- Francisco Arca
- Escuela Técnica Superior de Ingeniería, University of Seville, 41092 Seville, Spain
| | - Juan Pedro Mendez
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA
| | - Michael Ortiz
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA
| | - Pilar Ariza
- Escuela Técnica Superior de Ingeniería, University of Seville, 41092 Seville, Spain.
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Electron-Phonon Coupling as the Source of 1/f Noise in Carbon Soot. Sci Rep 2019; 9:947. [PMID: 30700741 PMCID: PMC6353950 DOI: 10.1038/s41598-018-36544-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/22/2018] [Indexed: 11/25/2022] Open
Abstract
Two 1/f noise peaks were found in a carbon soot resistor at voltages characteristic of Kohn anomalies in graphite. The ratio of the electron-phonon coupling matrix elements at the anomalies calculated from the noise peak intensities is the same as the one obtained from the Raman frequencies. This demonstrates that the electron-phonon coupling is the microscopic source of 1/f noise in carbon soot. A new, very general formula was deduced for the frequency exponent, wherein nonlinearity and dispersion are the only ingredients. The interplay between nonlinearity and dispersion in this formula describes the sublinear-supralinear transitions experimentally observed at both anomalies in the voltage dependence of the frequency exponent. A quadratic dependence of the 1/f noise parameter on the matrix element is proposed and applied to explain the M-shape of the 1/f noise in graphene. We found that the frequency exponent mimics the dependence of the noise intensity in the whole voltage range, while both are the image of the graphite phonon spectrum. This implies that the source of nonlinearity is in the electron-phonon coupling which modulates the slope of the spectrum. It requires the presence of 1/f noise in the thermal noise background of the resistor till phonon frequencies.
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4
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Al Taleb A, Farías D. Phonon dynamics of graphene on metals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:103005. [PMID: 26886508 DOI: 10.1088/0953-8984/28/10/103005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The study of surface phonon dispersion curves is motivated by the quest for a detailed understanding of the forces between the atoms at the surface and in the bulk. In the case of graphene, additional motivation comes from the fact that thermal conductivity is dominated by contributions from acoustic phonons, while optical phonon properties are essential to understand Raman spectra. In this article, we review recent progress made in the experimental determination of phonon dispersion curves of graphene grown on several single-crystal metal surfaces. The two main experimental techniques usually employed are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS). The different dispersion branches provide a detailed insight into the graphene-substrate interaction. Softening of optical modes and signatures of the substrate's Rayleigh wave are observed for strong graphene-substrate interactions, while acoustic phonon modes resemble those of free-standing graphene for weakly interacting systems. The latter allows determining the bending rigidity and the graphene-substrate coupling strength. A comparison between theory and experiment is discussed for several illustrative examples. Perspectives for future experiments are discussed.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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5
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Nai CT, Xu H, Tan SJR, Loh KP. Analyzing Dirac Cone and Phonon Dispersion in Highly Oriented Nanocrystalline Graphene. ACS NANO 2016; 10:1681-1689. [PMID: 26713552 DOI: 10.1021/acsnano.5b07662] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Chemical vapor deposition (CVD) is one of the most promising growth techniques to scale up the production of monolayer graphene. At present, there are intense efforts to control the orientation of graphene grains during CVD, motivated by the fact that there is a higher probability for oriented grains to achieve seamless merging, forming a large single crystal. However, it is still challenging to produce single-crystal graphene with no grain boundaries over macroscopic length scales, especially when the nucleation density of graphene nuclei is high. Nonetheless, nanocrystalline graphene with highly oriented grains may exhibit single-crystal-like properties. Herein, we investigate the spectroscopic signatures of graphene film containing highly oriented, nanosized grains (20-150 nm) using angle-resolved photoemission spectroscopy (ARPES) and high-resolution electron energy loss spectroscopy (HREELS). The robustness of the Dirac cone, as well as dispersion of its phonons, as a function of graphene's grain size and before and after film coalescence, was investigated. In view of the sensitivity of atomically thin graphene to atmospheric adsorbates and intercalants, ARPES and HREELS were also used to monitor the changes in spectroscopic signatures of the graphene film following exposure to the ambient atmosphere.
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Affiliation(s)
- Chang Tai Nai
- Department of Chemistry and Centre for Advanced 2D Materials (CA2DM), National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences , #05-01, 28 Medical Drive, Singapore 117456, Singapore
| | - Hai Xu
- Department of Chemistry and Centre for Advanced 2D Materials (CA2DM), National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
| | - Sherman J R Tan
- Department of Chemistry and Centre for Advanced 2D Materials (CA2DM), National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences , #05-01, 28 Medical Drive, Singapore 117456, Singapore
| | - Kian Ping Loh
- Department of Chemistry and Centre for Advanced 2D Materials (CA2DM), National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
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Mann S, Rani P, Kumar R, Dubey GS, Jindal VK. Thermodynamic properties of pure and doped (B, N) graphene. RSC Adv 2016. [DOI: 10.1039/c5ra25239c] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ab initio density functional perturbation theory (DFPT) has been employed to study the thermodynamical properties of pure and doped graphene sheet and the results have been compared with available theoretical and experimental data.
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Affiliation(s)
- Sarita Mann
- Department of Physics
- Panjab University
- Chandigarh-160014
- India
| | - Pooja Rani
- D.A.V. College Sec-10
- Chandigarh-160010
- India
| | - Ranjan Kumar
- Department of Physics
- Panjab University
- Chandigarh-160014
- India
| | - Girija S. Dubey
- Department of Earth & Physical Sciences
- York College-CUNY
- Jamaica
- USA
| | - V. K. Jindal
- Department of Physics
- Panjab University
- Chandigarh-160014
- India
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7
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Tamtögl A, Bahn E, Zhu J, Fouquet P, Ellis J, Allison W. Graphene on Ni(111): Electronic Corrugation and Dynamics from Helium Atom Scattering. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:25983-25990. [PMID: 26617683 PMCID: PMC4655418 DOI: 10.1021/acs.jpcc.5b08284] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/22/2015] [Indexed: 06/05/2023]
Abstract
Using helium atom scattering, we have studied the structure and dynamics of a graphene layer prepared in situ on a Ni(111) surface. Graphene/Ni(111) exhibits a helium reflectivity of ∼20% for a thermal helium atom beam and a particularly small surface electron density corrugation ((0.06 ± 0.02) Å peak to peak height). The Debye-Waller attenuation of the elastic diffraction peaks of graphene/Ni(111) and Ni(111) was measured at surface temperatures between 150 and 740 K. A surface Debye temperature of θD = (784 ± 14) K is determined for the graphene/Ni(111) system and θD = (388 ± 7) K for Ni(111), suggesting that the interlayer interaction between graphene and the Ni substrate is intermediary between those for strongly interacting systems like graphene/Ru(0001) and weakly interacting systems like graphene/Pt(111). In addition we present measurements of low frequency surface phonon modes on graphene/Ni(111) where the phonon modes of the Ni(111) substrate can be clearly observed. The similarity of these findings with the graphene/Ru(0001) system indicates that the bonding of graphene to a metal substrate alters the dynamic properties of the graphene surface strongly and is responsible for the high helium reflectivity of these systems.
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Affiliation(s)
- Anton Tamtögl
- Cavendish
Laboratory, J. J. Thompson
Avenue, Cambridge CB3 0HE, United Kingdom
| | - Emanuel Bahn
- Institut
Laue-Langevin, 71 Avenue
des Martyrs, 38000 Grenoble, France
| | - Jianding Zhu
- Cavendish
Laboratory, J. J. Thompson
Avenue, Cambridge CB3 0HE, United Kingdom
| | - Peter Fouquet
- Institut
Laue-Langevin, 71 Avenue
des Martyrs, 38000 Grenoble, France
| | - John Ellis
- Cavendish
Laboratory, J. J. Thompson
Avenue, Cambridge CB3 0HE, United Kingdom
| | - William Allison
- Cavendish
Laboratory, J. J. Thompson
Avenue, Cambridge CB3 0HE, United Kingdom
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8
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Bandura AV, Porsev VV, Evarestov RA. Application of zone-folding approach to the first-principles estimation of thermodynamic properties of carbon and ZrS2-based nanotubes. J Comput Chem 2015; 37:641-52. [DOI: 10.1002/jcc.24243] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 10/15/2015] [Accepted: 10/17/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Andrei V. Bandura
- Quantum Chemistry Department; Saint-Petersburg State University, 7/9 Universitetskaya nab.; St. Petersburg 199034 Russia
| | - Vitaly V. Porsev
- Quantum Chemistry Department; Saint-Petersburg State University, 7/9 Universitetskaya nab.; St. Petersburg 199034 Russia
| | - Robert A. Evarestov
- Quantum Chemistry Department; Saint-Petersburg State University, 7/9 Universitetskaya nab.; St. Petersburg 199034 Russia
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9
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Li F, Tu K, Zhang H, Chen Z. Flexible structural and electronic properties of a pentagonal B2C monolayer via external strain: a computational investigation. Phys Chem Chem Phys 2015; 17:24151-6. [DOI: 10.1039/c5cp03885e] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A pentagonal B2C monolayer shows flexible structural and electronic properties under external strain.
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Affiliation(s)
- Fengyu Li
- Department of Chemistry
- The Institute for Functional Nanomaterials
- University of Puerto Rico
- San Juan
- USA
| | - Kaixiong Tu
- Department of Chemistry
- The Institute for Functional Nanomaterials
- University of Puerto Rico
- San Juan
- USA
| | - Haijun Zhang
- Department of Chemistry
- The Institute for Functional Nanomaterials
- University of Puerto Rico
- San Juan
- USA
| | - Zhongfang Chen
- Department of Chemistry
- The Institute for Functional Nanomaterials
- University of Puerto Rico
- San Juan
- USA
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10
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Li F, Jiang DE, Chen Z. Computational quest for spherical C12B68 fullerenes with “magic” π-electrons and quasi-planar tetra-coordinated carbon. J Mol Model 2014; 20:2085. [DOI: 10.1007/s00894-014-2085-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/03/2013] [Indexed: 10/25/2022]
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11
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Zhang X, Rajaraman BRS, Liu H, Ramakrishna S. Graphene's potential in materials science and engineering. RSC Adv 2014. [DOI: 10.1039/c4ra02817a] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Materials have become an indispensable part of our modern life, which was tailored such as good mechanical, electrical, thermal properties, establish the basis and fundamentals and the governing rules for every modern technology.
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Affiliation(s)
- Xiang Zhang
- Centre of Nanofibers & Nanotechnology
- Department of Mechanical Engineering
- Faculty of Engineering
- National University of Singapore
- Singapore 117576, Singapore
| | - Bhavatharini R. S. Rajaraman
- Centre of Nanofibers & Nanotechnology
- Department of Mechanical Engineering
- Faculty of Engineering
- National University of Singapore
- Singapore 117576, Singapore
| | - Huihui Liu
- Department of Medicine
- Yong Loo Lin School of Medicine
- National University of Singapore
- Singapore 119260, Singapore
| | - Seeram Ramakrishna
- Centre of Nanofibers & Nanotechnology
- Department of Mechanical Engineering
- Faculty of Engineering
- National University of Singapore
- Singapore 117576, Singapore
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12
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Politano A, Marino AR, Chiarello G. Phonon dispersion of quasi-freestanding graphene on Pt(111). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:104025. [PMID: 22354008 DOI: 10.1088/0953-8984/24/10/104025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
High-resolution electron energy loss spectroscopy has been used to probe phonon dispersion in quasi-freestanding graphene epitaxially grown on Pt(111). Loss spectra clearly show different dispersing features related to both acoustic and optical phonons. The present results have been compared with graphene systems which strongly interact with the substrate, i.e. the nearly-flat monolayer graphene (MLG)/Ni(111) and the corrugated MLG/Ru(0001). We found that the phonon dispersion of graphene/Pt(111) reproduces well the behavior of pristine graphite. This could be taken as an indication of the negligible interaction between the graphene sheet and the underlying Pt substrate. The softening of out-of-plane modes observed for interacting graphene/metal interfaces does not occur for the nearly-free-standing graphene/Pt(111).
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Affiliation(s)
- Antonio Politano
- Dipartimento di Fisica, Università degli Studi della Calabria, 87036 Rende (Cs), Italy.
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13
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Adamyan V, Zavalniuk V. Phonons in graphene with point defects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:015402. [PMID: 21406824 DOI: 10.1088/0953-8984/23/1/015402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The phonon density of states (DOS) of graphene with different types of point defects (carbon isotopes, substitution atoms, vacancies) is considered. Using a solvable model which is based on the harmonic approximation and the assumption that the elastic forces act only between nearest neighboring ions we calculate corrections to the graphene DOS dependent on the type and concentration of defects. In particular the correction due to isotopic dimers is determined. It is shown that a relatively small concentration of defects may lead to significant and specific changes in the DOS, especially at low frequencies, near the Van Hove points and in the vicinity of the K points of the Brillouin zone. In some cases defects generate one or several narrow gaps near the critical points of the phonon DOS as well as resonance states in the Brillouin zone regular points. All types of defects are characterized by the appearance of one or more additional Van Hove peaks near the (Dirac) K points and their singular contribution may be comparable with the effect of electron-phonon interaction. Besides, for low frequencies and near the critical points the relative change in density of states may be many times higher than the concentration of defects.
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Affiliation(s)
- Vadym Adamyan
- Department of Theoretical Physics, Odessa I I Mechnikov National University, 2 Dvoryanskaya Street, Odessa 65026, Ukraine.
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14
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Pascal TA, Karasawa N, Goddard WA. Quantum mechanics based force field for carbon (QMFF-Cx) validated to reproduce the mechanical and thermodynamics properties of graphite. J Chem Phys 2010; 133:134114. [DOI: 10.1063/1.3456543] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Sakong S, Kratzer P. Hydrogen vibrational modes on graphene and relaxation of the C–H stretch excitation from first-principles calculations. J Chem Phys 2010; 133:054505. [DOI: 10.1063/1.3474806] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Shishir RS, Ferry DK, Goodnick SM. Room temperature velocity saturation in intrinsic graphene. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/193/1/012118] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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17
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Shishir RS, Ferry DK. Velocity saturation in intrinsic graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:344201. [PMID: 21715776 DOI: 10.1088/0953-8984/21/34/344201] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We study the transport of carriers in intrinsic graphene by means of an ensemble Monte Carlo technique. Scattering by acoustic and optical phonons dominates the transport. We find that velocity 'saturation' sets in at relatively low values of the electric field, but that the value is dependent upon the carrier density. Velocity overshoot is also observed to occur in these simulations.
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Affiliation(s)
- R S Shishir
- Department of Electrical Engineering and Center for Solid State Electronics Research, Arizona State University, Tempe, AZ 85287, USA
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18
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Shishir RS, Ferry DK. Intrinsic mobility in graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:232204. [PMID: 21825578 DOI: 10.1088/0953-8984/21/23/232204] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent studies have shown that a high K dielectric solvent screens the impurities for room temperature transport in graphene and the mobility has been found to increase by orders of magnitude. This gives what is probably the intrinsic, phonon limited mobility at room temperature, and we have confirmed this with simulation. Mobility as high as 44 000 cm(2) V(-1) s(-1) was achieved. At very low density, impurity scattering still is the determining factor for mobility, but this is significantly reduced in the recent experiments due to the dielectric screening. At high density, impurity scattering becomes negligible.
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Affiliation(s)
- R S Shishir
- Department of Electrical Engineering and Center for Solid State Electronics Research, Arizona State University, Tempe, AZ 85287, USA
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19
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Theory and measurements of room temperature transport in graphene using SiO[sub 2] backgate and electrochemical gate. ACTA ACUST UNITED AC 2009. [DOI: 10.1116/1.3156733] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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Tanaka I, Oba F. First principles calculations for modern ceramic science and engineering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:064215. [PMID: 21693877 DOI: 10.1088/0953-8984/20/6/064215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The free energy of compounds can be theoretically obtained as a function of temperature, pressure and chemical potentials by a combination of a first principles method including phonon calculations and statistical approaches using cluster expansion and Monte Carlo simulations. The information is quite useful in ceramic science and engineering since experimental data are not abundantly available. As an example of phonon calculations, results for graphite in comparison to diamond are presented. The free energy difference among polymorphs of Ga(2)O(3) is shown as a function of temperature as well. Theoretical calculations of x-ray absorption near edge structures (XANES) and electron energy loss near edge structures (ELNES) are also demonstrated. Proper inclusion of the core-hole effect is mandatory in the calculation. For 3d transition element L(2,3) XANES/ELNES, a configuration interaction approach to take account of the correlation among the core-hole and the excited electron satisfactorily reproduces experimental spectra. As an example, results for Mn-doped ZnO are shown.
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Affiliation(s)
- Isao Tanaka
- Department of Materials Science and Engineering, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501, Japan
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Gupta A, Chen G, Joshi P, Tadigadapa S, Eklund PC. Raman scattering from high-frequency phonons in supported n-graphene layer films. NANO LETTERS 2006; 6:2667-73. [PMID: 17163685 DOI: 10.1021/nl061420a] [Citation(s) in RCA: 302] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Results of room-temperature Raman scattering studies of ultrathin graphitic films supported on Si (100)/SiO2 substrates are reported. The results are significantly different from those known for graphite. Spectra were collected using 514.5 nm radiation on films containing from n = 1 to 20 graphene layers, as determined by atomic force microscopy. Both the first- and second-order Raman spectra show unique signatures of the number of layers in the film. The nGL film analogue of the Raman G-band in graphite exhibits a Lorentzian line shape whose center frequency shifts linearly relative to graphite as approximately 1/n (for n = 1 omegaG approximately 1587 cm-1). Three weak bands, identified with disorder-induced first-order scattering, are observed at approximately 1350, 1450, and 1500 cm-1. The approximately 1500 cm-1 band is weak but relatively sharp and exhibits an interesting n-dependence. In general, the intensity of these D-bands decreases dramatically with increasing n. Three second-order bands are also observed (approximately 2450, approximately 2700, and 3248 cm-1). They are analogues to those observed in graphite. However, the approximately 2700 cm-1 band exhibits an interesting and dramatic change of shape with n. Interestingly, for n < 5 this second-order band is more intense than the G-band.
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Affiliation(s)
- A Gupta
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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