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Lui CH, Cappelluti E, Li Z, Heinz TF. Tunable infrared phonon anomalies in trilayer graphene. PHYSICAL REVIEW LETTERS 2013; 110:185504. [PMID: 23683217 DOI: 10.1103/physrevlett.110.185504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Indexed: 06/02/2023]
Abstract
Trilayer graphene in both ABA (Bernal) and ABC (rhombohedral) stacking sequences is shown to exhibit intense infrared absorption from in-plane optical phonons. The phonon feature, lying at ~1580 cm(-1), changes strongly with electrostatic gating. For ABC-stacked graphene trilayers, we observed a large enhancement in phonon absorption amplitude, as well as softening of the phonon mode, as the Fermi level is tuned away from charge neutrality. A similar, but substantially weaker, effect is seen in samples with the more common ABA stacking order. The strong infrared response of the optical phonons and the pronounced variation with electrostatic gating and stacking order reflect the interactions of the phonons and electronic excitations in the two systems. The key experimental findings can be reproduced within a simplified charged-phonon model that considers the influence of charging through Pauli blocking of the electronic transitions.
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Affiliation(s)
- Chun Hung Lui
- Department of Physics and Electrical Engineering, Columbia University, 538 West 120th Street, New York, New York 10027, USA
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52
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McCann E, Koshino M. The electronic properties of bilayer graphene. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:056503. [PMID: 23604050 DOI: 10.1088/0034-4885/76/5/056503] [Citation(s) in RCA: 201] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We review the electronic properties of bilayer graphene, beginning with a description of the tight-binding model of bilayer graphene and the derivation of the effective Hamiltonian describing massive chiral quasiparticles in two parabolic bands at low energies. We take into account five tight-binding parameters of the Slonczewski-Weiss-McClure model of bulk graphite plus intra- and interlayer asymmetry between atomic sites which induce band gaps in the low-energy spectrum. The Hartree model of screening and band-gap opening due to interlayer asymmetry in the presence of external gates is presented. The tight-binding model is used to describe optical and transport properties including the integer quantum Hall effect, and we also discuss orbital magnetism, phonons and the influence of strain on electronic properties. We conclude with an overview of electronic interaction effects.
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Affiliation(s)
- Edward McCann
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
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53
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Fang W, Hsu AL, Caudillo R, Song Y, Birdwell AG, Zakar E, Kalbac M, Dubey M, Palacios T, Dresselhaus MS, Araujo PT, Kong J. Rapid identification of stacking orientation in isotopically labeled chemical-vapor grown bilayer graphene by Raman spectroscopy. NANO LETTERS 2013; 13:1541-1548. [PMID: 23470052 DOI: 10.1021/nl304706j] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The growth of large-area bilayer graphene has been of technological importance for graphene electronics. The successful application of graphene bilayers critically relies on the precise control of the stacking orientation, which determines both electronic and vibrational properties of the bilayer system. Toward this goal, an effective characterization method is critically needed to allow researchers to easily distinguish the bilayer stacking orientation (i.e., AB stacked or turbostratic). In this work, we developed such a method to provide facile identification of the stacking orientation by isotope labeling. Raman spectroscopy of these isotopically labeled bilayer samples shows a clear signature associated with AB stacking between layers, enabling rapid differentiation between turbostratic and AB-stacked bilayer regions. Using this method, we were able to characterize the stacking orientation in bilayer graphene grown through Low Pressure Chemical Vapor Deposition (LPCVD) with enclosed Cu foils, achieving almost 70% AB-stacked bilayer graphene. Furthermore, by combining surface sensitive fluorination with such hybrid (12)C/(13)C bilayer samples, we are able to identify that the second layer grows underneath the first-grown layer, which is similar to a recently reported observation.
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Affiliation(s)
- Wenjing Fang
- Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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54
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Lapointe F, Gaufrès E, Tremblay I, Tang NYW, Martel R, Desjardins P. Fano resonances in the midinfrared spectra of single-walled carbon nanotubes. PHYSICAL REVIEW LETTERS 2012; 109:097402. [PMID: 23002881 DOI: 10.1103/physrevlett.109.097402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Indexed: 06/01/2023]
Abstract
This work revisits the physics giving rise to the carbon nanotube phonon bands in the midinfrared. Our measurements of doped and undoped samples of single-walled carbon nanotubes in Fourier transform infrared spectroscopy show that the phonon bands exhibit an asymmetric line shape and that their effective cross section is enhanced upon doping. We relate these observations to electron-phonon coupling or, more specifically, to a Fano resonance phenomenon. We note that the dopant-induced intraband (not interband) continuum couples strongly to the phonon modes, and that defects created on the sidewall are scattering centers that increase the spectral amplitude of the resonance.
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Affiliation(s)
- François Lapointe
- Regroupement Québécois sur les Matériaux de Pointe (RQMP) and Département de Chimie, Université de Montréal, Montréal, Québec, Canada
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55
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Mattson EC, Nasse MJ, Rak M, Gough KM, Hirschmugl CJ. Restoration and Spectral Recovery of Mid-Infrared Chemical Images. Anal Chem 2012; 84:6173-80. [DOI: 10.1021/ac301080h] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eric C. Mattson
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211,
United States
| | - Michael J. Nasse
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211,
United States
- Synchrotron
Radiation Center,
University of Wisconsin, Wisconsin 53589,
United States
| | - Margaret Rak
- Department
of Chemistry, University of Manitoba, Winnipeg,
Canada, R3T 2N2
| | - Kathleen M. Gough
- Department
of Chemistry, University of Manitoba, Winnipeg,
Canada, R3T 2N2
| | - Carol J. Hirschmugl
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211,
United States
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56
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Li Z, Lui CH, Cappelluti E, Benfatto L, Mak KF, Carr GL, Shan J, Heinz TF. Structure-dependent Fano resonances in the infrared spectra of phonons in few-layer graphene. PHYSICAL REVIEW LETTERS 2012; 108:156801. [PMID: 22587273 DOI: 10.1103/physrevlett.108.156801] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Indexed: 05/31/2023]
Abstract
The in-plane optical phonons around 200 meV in few-layer graphene are investigated utilizing infrared absorption spectroscopy. The phonon spectra exhibit unusual asymmetric features characteristic of Fano resonances, which depend critically on the layer thickness and stacking order of the sample. The phonon intensities in samples with rhombohedral (ABC) stacking are significantly higher than those with Bernal (AB) stacking. These observations reflect the strong coupling between phonons and interband electronic transitions in these systems and the distinctive variation in the joint density of electronic states in samples of differing thickness and stacking order.
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Affiliation(s)
- Zhiqiang Li
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
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57
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Laskar JM, Raj B, Philip J. Enhanced transmission with tunable Fano-like profile in magnetic nanofluids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051403. [PMID: 22181413 DOI: 10.1103/physreve.84.051403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 07/27/2011] [Indexed: 05/31/2023]
Abstract
We observe a Fano-like resonance in a magnetically polarizable nanofluid. Under an external magnetic field, the transmittance spectrum of a ferrofluid emulsion containing droplet size of ~220 nm shows an enhanced peak with a Fano-like profile, which is attributed to a localized waveguide resonance from random array of tubes with charged inner surface that are formed by the alignment of the droplets. Furthermore, by varying the magnetic field, the Fano profile is tuned and an opaque emulsion is turned into a transparent one. This finding may have interesting applications in tunable photonic devices.
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Affiliation(s)
- Junaid M Laskar
- SMARTS, Metallurgy and Materials Group Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu, India
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58
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Bermudez VM, Robinson JT. Effects of molecular adsorption on the electronic structure of single-layer graphene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:11026-11036. [PMID: 21812417 DOI: 10.1021/la201669j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The interaction of small molecules (CCl(4), CS(2), H(2)O, and acetone) with single-layer graphene (SLG) has been studied under steady-state conditions using infrared multiple-internal-reflection spectroscopy. Adsorption results in a broad and intense absorption band, spanning the ∼200 to 500 meV range, which is attributed to electronic excitation. This effect, which has not previously been reported for SLG, has been further investigated using dispersion-corrected density functional theory to model the adsorption of H(2)O on SLG supported on an SiO(2) substrate. However, the ideal and defect-free model does not reproduce the observed adsorption-induced electronic transition. This and other observations suggest that the effect is extrinsic, possibly the result of an adsorption-induced change in the in-plane strain, with important differences arising between species that form liquid-like layers under steady-state conditions and those that do not. Furthermore, the C-H stretching modes of CH(2) groups, incorporated in the SLG as defects, undergo nonadiabatic coupling to the electronic transition. This leads to pronounced antiresonance effects in the line shapes, which are analyzed quantitatively. These results are useful in understanding environmental effects on graphene electronic structure and in demonstrating the use of the vibrational spectroscopy of H-containing defects in characterizing SLG structure.
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Affiliation(s)
- V M Bermudez
- Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375-5347, USA.
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59
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Doughty B, Haber LH, Hackett C, Leone SR. Photoelectron angular distributions from autoionizing 4s¹4p⁶6p¹ states in atomic krypton probed with femtosecond time resolution. J Chem Phys 2011; 134:094307. [PMID: 21384969 DOI: 10.1063/1.3547459] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Photoelectron angular distributions (PADs) are obtained for a pair of 4s(1)4p(6)6p(1) (a singlet and a triplet) autoionizing states in atomic krypton. A high-order harmonic pulse is used to excite the pair of states and a time-delayed 801 nm ionization pulse probes the PADs to the final 4s(1)4p(6) continuum with femtosecond time resolution. The ejected electrons are detected with velocity map imaging to retrieve the time-resolved photoelectron spectrum and PADs. The PAD for the triplet state is inherently separable by virtue of its longer autoionization lifetime. Measuring the total signal over time allows for the PADs to be extracted for both the singlet state and the triplet state. Anisotropy parameters for the triplet state are measured to be β(2)=0.55 ± 0.17 and β(4)=-0.01 ± 0.10, while the singlet state yields β(2)=2.19 ± 0.18 and β(4)=1.84 ± 0.14. For the singlet state, the ratio of radial transition dipole matrix elements, X, of outgoing S to D partial waves and total phase shift difference between these waves, Δ, are determined to be X=0.56 ± 0.08 and Δ=2.19 ± 0.11 rad. The continuum quantum defect difference between the S and D electron partial waves is determined to be -0.15 ± 0.03 for the singlet state. Based on previous analyses, the triplet state is expected to have anisotropy parameters independent of electron kinetic energy and equal to β(2)=5∕7 and β(4)=-12∕7. Deviations from the predicted values are thought to be a result of state mixing by spin-orbit and configuration interactions in the intermediate and final states; theoretical calculations are required to quantify these effects.
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Affiliation(s)
- Benjamin Doughty
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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60
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Wu C, Feng J, Peng L, Ni Y, Liang H, He L, Xie Y. Large-area graphene realizing ultrasensitive photothermal actuator with high transparency: new prototype robotic motions under infrared-light stimuli. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm13311j] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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61
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Acik M, Lee G, Mattevi C, Chhowalla M, Cho K, Chabal YJ. Unusual infrared-absorption mechanism in thermally reduced graphene oxide. NATURE MATERIALS 2010; 9:840-5. [PMID: 20852618 DOI: 10.1038/nmat2858] [Citation(s) in RCA: 332] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 08/18/2010] [Indexed: 05/24/2023]
Abstract
Infrared absorption of atomic and molecular vibrations in solids can be affected by electronic contributions through non-adiabatic interactions, such as the Fano effect. Typically, the infrared-absorption lineshapes are modified, or infrared-forbidden modes are detectable as a modulation of the electronic absorption. In contrast to such known phenomena, we report here the observation of a giant-infrared-absorption band in reduced graphene oxide, arising from the coupling of electronic states to the asymmetric stretch mode of a yet-unreported structure, consisting of oxygen atoms aggregated at the edges of defects. Free electrons are induced by the displacement of the oxygen atoms, leading to a strong infrared absorption that is in phase with the phonon mode. This new phenomenon is only possible when all other oxygen-containing chemical species, including hydroxyl, carboxyl, epoxide and ketonic functional groups, are removed from the region adjacent to the edges, that is, clean graphene patches are present.
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Affiliation(s)
- M Acik
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
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