显示 1 条，共 50 条
作者: Novoselov, KS; Geim, AK; Morozov, SV; Jiang, D; Zhang, Y; Dubonos, SV; Grigorieva, IV; Firsov, AA
标题: Electric field effect in atomically thin carbon films
来源出版物: SCIENCE, 306 (5696): 666-669 OCT 22 2004
摘要: We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10(13) per square centimeter and with room-temperature mobilities of similar to10,000 square centimeters per volt-second can be induced by applying gate voltage.
显示 2 条，共 50 条
作者: Thess, A; Lee, R; Nikolaev, P; Dai, HJ; Petit, P; Robert, J; Xu, CH; Lee, YH; Kim, SG; Rinzler, AG; Colbert, DT; Scuseria, GE; Tomanek, D; Fischer, JE; Smalley, RE
标题: Crystalline ropes of metallic carbon nanotubes
来源出版物: SCIENCE, 273 (5274): 483-487 JUL 26 1996
摘要: Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200 degrees C. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform. in diameter and thai they self-organize into ''ropes,'' which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form. factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C-5v symmetry and an open edge stabilized by triple bonds.
显示 3 条，共 50 条
作者: Novoselov, KS; Geim, AK; Morozov, SV; Jiang, D; Katsnelson, MI; Grigorieva, IV; Dubonos, SV; Firsov, AA
标题: Two-dimensional gas of massless Dirac fermions in graphene
来源出版物: NATURE, 438 (7065): 197-200 NOV 10 2005
摘要: Quantum electrodynamics ( resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry(1-3). The ideas underlying quantum electrodynamics also influence the theory of condensed matter(4,5), but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrodinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon(6,7)) in which electron transport is essentially governed by Dirac's ( relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* approximate to 10(6) m s(-1). Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m(c) of massless carriers in graphene is described by E = m(c)c(*)(2). This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.
显示 4 条，共 50 条
作者: Geim, AK (Geim, A. K.); Novoselov, KS (Novoselov, K. S.)
标题: The rise of graphene
来源出版物: NATURE MATERIALS, 6 (3): 183-191 MAR 2007
摘要: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.
显示 5 条，共 50 条
作者: Zhang, YB; Tan, YW; Stormer, HL; Kim, P
标题: Experimental observation of the quantum Hall effect and Berry's phase in graphene
来源出版物: NATURE, 438 (7065): 201-204 NOV 10 2005
摘要: When electrons are confined in two-dimensional materials, quantum-mechanically enhanced transport phenomena such as the quantum Hall effect can be observed. Graphene, consisting of an isolated single atomic layer of graphite, is an ideal realization of such a two-dimensional system. However, its behaviour is expected to differ markedly from the well-studied case of quantum wells in conventional semiconductor interfaces. This difference arises from the unique electronic properties of graphene, which exhibits electron - hole degeneracy and vanishing carrier mass near the point of charge neutrality(1,2). Indeed, a distinctive half-integer quantum Hall effect has been predicted(3-5) theoretically, as has the existence of a non-zero Berry's phase ( a geometric quantum phase) of the electron wavefunction - a consequence of the exceptional topology of the graphene band structure(6,7). Recent advances in micromechanical extraction and fabrication techniques for graphite structures(8-12) now permit such exotic two-dimensional electron systems to be probed experimentally. Here we report an experimental investigation of magneto-transport in a high-mobility single layer of graphene. Adjusting the chemical potential with the use of the electric field effect, we observe an unusual half-integer quantum Hall effect for both electron and hole carriers in graphene. The relevance of Berry's phase to these experiments is confirmed by magneto-oscillations. In addition to their purely scientific interest, these unusual quantum transport phenomena may lead to new applications in carbon-based electronic and magneto-electronic devices.
显示 6 条，共 50 条
作者: Hu, JT; Odom, TW; Lieber, CM
标题: Chemistry and physics in one dimension: Synthesis and properties of nanowires and nanotubes
来源出版物: ACCOUNTS OF CHEMICAL RESEARCH, 32 (5): 435-445 MAY 1999
显示 7 条，共 50 条
作者: SAITO, R; FUJITA, M; DRESSELHAUS, G; DRESSELHAUS, MS
标题: ELECTRONIC-STRUCTURE OF CHIRAL GRAPHENE TUBULES
来源出版物: APPLIED PHYSICS LETTERS, 60 (18): 2204-2206 MAY 4 1992
摘要: The electronic structure for graphene monolayer tubules is predicted as a function of the diameter and helicity of the constituent graphene tubules. The calculated results show that approximately 1/3 of these tubules are a one-dimensional metal which is stable against a Peierls distortion, and the other 2/3 are one-dimensional semiconductors. The implications of these results are discussed.
显示 8 条，共 50 条
作者: Rao, AM; Richter, E; Bandow, S; Chase, B; Eklund, PC; Williams, KA; Fang, S; Subbaswamy, KR; Menon, M; Thess, A; Smalley, RE; Dresselhaus, G; Dresselhaus, MS
标题: Diameter-selective Raman scattering from vibrational modes in carbon nanotubes
来源出版物: SCIENCE, 275 (5297): 187-191 JAN 10 1997
摘要: Single wall carbon nanotubes (SWNTs) that are found as close-packed arrays in crystalline ropes have been studied by using Raman scattering techniques with laser excitation wavelengths in the range from 514.5 to 1320 nanometers. Numerous Raman peaks were observed and identified with vibrational modes of armchair symmetry (n, n) SWNTs. The Raman spectra are in good agreement with lattice dynamics calculations based on C-C force constants used to fit the two-dimensional, experimental phonon dispersion of a single graphene sheet. Calculated intensities from a nonresonant, bond polarizability model optimized for sp(2) carbon are also in qualitative agreement with the Raman data, although a resonant Raman scattering process is also taking place. This resonance results from the one-dimensional quantum confinement of the electrons in the nanotube.
显示 9 条，共 50 条
作者: Odom, TW; Huang, JL; Kim, P; Lieber, CM
标题: Atomic structure and electronic properties of single-walled carbon nanotubes
来源出版物: NATURE, 391 (6662): 62-64 JAN 1 1998
摘要: Carbon nanotubes(1) are predicted to be metallic or semiconducting depending on their diameter and the helicity of the arrangement of graphitic rings in their walls(2-5). Scanning tunnelling microscopy (STM) offers the potential to probe this prediction, as it can resolve simultaneously both atomic structure and the electronic density of states. Previous STM studies of multi-walled nanotubes(6-9) and single-walled nanotubes (SWNTs)(10) have provided indications of differing structures and diameter-dependent electronic properties, but have not revealed any explicit relationship between structure and electronic properties, Here we report STM measurements of the atomic structure and electronic properties of SWNTs. We are able to resolve the hexagonal-ring structure of the walls, and show that the electronic properties do indeed depend on diameter and helicity. We find that the SWNT samples exhibit many different structures, with no one species dominating.
显示 10 条，共 50 条
作者: Castro Neto, AH (Castro Neto, A. H.); Guinea, F (Guinea, F.); Peres, NMR (Peres, N. M. R.); Novoselov, KS (Novoselov, K. S.); Geim, AK (Geim, A. K.)
标题: The electronic properties of graphene
来源出版物: REVIEWS OF MODERN PHYSICS, 81 (1): 109-162 JAN-MAR 2009
摘要: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.
显示 11 条，共 50 条
作者: Berger, C (Berger, Claire); Song, ZM (Song, Zhimin); Li, XB (Li, Xuebin); Wu, XS (Wu, Xiaosong); Brown, N (Brown, Nate); Naud, C (Naud, Cecile); Mayou, D (Mayou, Didier); Li, TB (Li, Tianbo); Hass, J (Hass, Joanna); Marchenkov, AN (Marchenkov, Atexei N.); Conrad, EH (Conrad, Edward H.); First, PN (First, Phillip N.); de Heer, WA (de Heer, Wait A.)
标题: Electronic confinement and coherence in patterned epitaxial graphene
来源出版物: SCIENCE, 312 (5777): 1191-1196 MAY 26 2006
摘要: Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged.
显示 12 条，共 50 条
作者: RINZLER, AG; HAFNER, JH; NIKOLAEV, P; LOU, L; KIM, SG; TOMANEK, D; NORDLANDER, P; COLBERT, DT; SMALLEY, RE
标题: UNRAVELING NANOTUBES - FIELD-EMISSION FROM AN ATOMIC WIRE
来源出版物: SCIENCE, 269 (5230): 1550-1553 SEP 15 1995
摘要: Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1 microampere were readily obtained at room temperature with bias voltages of less than 80 volts, The emitting structures are concluded to be linear chains of carbon atoms, C-n (n = 10 to 100), pulled out from the open edges of the graphene wall layers of the nanotube by the force of the electric field, in a process that resembles unraveling the sleeve of a sweater.
显示 13 条，共 50 条
作者: Collins, PC; Arnold, MS; Avouris, P
标题: Engineering carbon nanotubes and nanotube circuits using electrical breakdown
来源出版物: SCIENCE, 292 (5517): 706-709 APR 27 2001
摘要: Carbon nanotubes display either metallic or semiconducting properties. Both Large, multiwalled nanotubes (MWNTs), with many concentric carbon shells, and bundles or "ropes" of aligned single-walled nanotubes (SWNTs), are complex composite conductors that incorporate many weakly coupled nanotubes that each have a different electronic structure. Here we demonstrate a simple and reliable method for selectively removing single carbon shells from MWNTs and SWNT ropes to tailor the properties of these composite nanotubes. We can remove shells of MWNTs stepwise and individually characterize the different shells. By choosing among the shells, we can convert a MWNT into either a metallic or a semiconducting conductor, as well as directly address the issue of multiple-shell transport. With SWNT ropes, similar selectivity allows us to generate entire arrays of nanoscale field-effect transistors based solely on the fraction of semiconducting SWNTs.
显示 14 条，共 50 条
作者: Stankovich, S (Stankovich, Sasha); Dikin, DA (Dikin, Dmitriy A.); Dommett, GHB (Dommett, Geoffrey H. B.); Kohlhaas, KM (Kohlhaas, Kevin M.); Zimney, EJ (Zimney, Eric J.); Stach, EA (Stach, Eric A.); Piner, RD (Piner, Richard D.); Nguyen, ST (Nguyen, SonBinh T.); Ruoff, RS (Ruoff, Rodney S.)
标题: Graphene-based composite materials
来源出版物: NATURE, 442 (7100): 282-286 JUL 20 2006
摘要: Graphene sheets - one- atom-thick two-dimensional layers of sp(2)-bonded carbon - are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (similar to 3,000 W m(-1) K-1 and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects(1-3); and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties(4-8). One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite(9) and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene - graphene composite formed by this route exhibits a percolation threshold(10) of similar to 0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes(11); at only 1 volume per cent, this composite has a conductivity of similar to 0.1 S m(-1), sufficient for many electrical applications(12). Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.
显示 15 条，共 50 条
作者: Nakada, K; Fujita, M; Dresselhaus, G; Dresselhaus, MS
标题: Edge state in graphene ribbons: Nanometer size effect and edge shape dependence
来源出版物: PHYSICAL REVIEW B, 54 (24): 17954-17961 DEC 15 1996
摘要: Finite graphite systems having a zigzag edge exhibit a special edge state. The corresponding energy bands are almost flat at the Fermi level and thereby give a sharp peak in the density of states. The charge density in the edge state is strongly localized on the zigzag edge sites. No such localized state appears in graphite systems having an armchair edge. By utilizing the graphene ribbon model, we discuss the effect of the system size and edge shape on the special edge state. By varying the width of the graphene ribbons, we find that the nanometer size effect is crucial for determining the relative importance of the edge state. We also have extended the graphene ribbon to have edges of a general shape, which is defined as a mixture of zigzag and armchair sites. Examining the relative importance of the edge state for graphene ribbons with general edges, we find that a non-negligible edge state survives even in graphene ribbons with less developed zigzag edges. We demonstrate that such an edge shape with three or four zigzag sites per sequence is sufficient to show an edge state, when the system size is on a nanometer scale. The special characteristics of the edge state play a large role in determining the density of states near the Fermi level for graphite networks on a nanometer scale.
显示 16 条，共 50 条
作者: Novoselov, KS; Jiang, D; Schedin, F; Booth, TJ; Khotkevich, VV; Morozov, SV; Geim, AK
标题: Two-dimensional atomic crystals
来源出版物: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 102 (30): 10451-10453 JUL 26 2005
摘要: We report free-standing atomic crystals that are strictly 2D and can be viewed as individual atomic planes pulled out of bulk crystals or as unrolled single-wall nanotubes. By using micromechanical cleavage, we have prepared and studied a variety of 2D crystals including single layers of boron nitride, graphite, several dichalcogenicles, and complex oxides. These atomically thin sheets (essentially gigantic 2D molecules unprotected from the immediate environment) are stable under ambient conditions, exhibit high crystal quality, and are continuous on a macroscopic scale.
显示 17 条，共 50 条
作者: SAITO, R; FUJITA, M; DRESSELHAUS, G; DRESSELHAUS, MS
标题: ELECTRONIC-STRUCTURE OF GRAPHENE TUBULES BASED ON C-60
来源出版物: PHYSICAL REVIEW B, 46 (3): 1804-1811 JUL 15 1992
摘要: The electronic structures of some possible carbon fibers nucleated from the hemisphere of a C60 molecule are presented. A one-dimensional electronic band-structure model of such carbon fibers, having not only rotational symmetry but also screw axes, is derived by folding the two-dimensional energy bands of graphite. A simple tight-binding model shows that some fibers are metallic and are stable against perturbations of the one-dimensional energy bands and the mixing of sigma and pi-bands due to the curvature of the circumference of the fiber.
显示 18 条，共 50 条
作者: Berber, S; Kwon, YK; Tomanek, D
标题: Unusually high thermal conductivity of carbon nanotubes
来源出版物: PHYSICAL REVIEW LETTERS, 84 (20): 4613-4616 MAY 15 2000
摘要: Combining equilibrium and nonequilibrium molecular dynamics simulations with accurate carbon potentials, we determine the thermal conductivity lambda of carbon nanotubes and its dependence on temperature. Our results suggest an unusually high value, lambda approximate to 6600 W/m K, for an isolated (10, 10) nanotube at room temperature, comparable to the thermal conductivity of a hypothetical isolated graphene monolayer or diamond. Our results suggest that these high values of lambda are associated with the large phonon mean free paths in these systems; substantially lower values are predicted and observed for the basal plane of bulk graphite.
显示 19 条，共 50 条
作者: Han, MY (Han, Melinda Y.); Ozyilmaz, B (Oezyilmaz, Barbaros); Zhang, YB (Zhang, Yuanbo); Kim, P (Kim, Philip)
标题: Energy band-gap engineering of graphene nanoribbons
来源出版物: PHYSICAL REVIEW LETTERS, 98 (20): Art. No. 206805 MAY 18 2007
摘要: We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge carriers creates an energy gap near the charge neutrality point. Individual graphene layers are contacted with metal electrodes and patterned into ribbons of varying widths and different crystallographic orientations. The temperature dependent conductance measurements show larger energy gaps opening for narrower ribbons. The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temperatures. We find that the energy gap scales inversely with the ribbon width, thus demonstrating the ability to engineer the band gap of graphene nanostructures by lithographic processes.
显示 20 条，共 50 条
作者: Ferrari, AC (Ferrari, A. C.); Meyer, JC (Meyer, J. C.); Scardaci, V (Scardaci, V.); Casiraghi, C (Casiraghi, C.); Lazzeri, M (Lazzeri, M.); Mauri, F (Mauri, F.); Piscanec, S (Piscanec, S.); Jiang, D (Jiang, D.); Novoselov, KS (Novoselov, K. S.); Roth, S (Roth, S.); Geim, AK (Geim, A. K.)
标题: Raman spectrum of graphene and graphene layers
来源出版物: PHYSICAL REVIEW LETTERS, 97 (18): Art. No. 187401 NOV 3 2006
摘要: Graphene is the two-dimensional building block for carbon allotropes of every other dimensionality. We show that its electronic structure is captured in its Raman spectrum that clearly evolves with the number of layers. The D peak second order changes in shape, width, and position for an increasing number of layers, reflecting the change in the electron bands via a double resonant Raman process. The G peak slightly down-shifts. This allows unambiguous, high-throughput, nondestructive identification of graphene layers, which is critically lacking in this emerging research area.
显示 21 条，共 50 条
作者: Dresselhaus, MS; Eklund, PC
标题: Phonons in carbon nanotubes
来源出版物: ADVANCES IN PHYSICS, 49 (6): 705-814 SEP 2000
摘要: A broad review of the unusual one-dimensional properties of phonons in carbon nanotubes is presented, including phonons in isolated nanotubes and in crystalline arrays of nanotubes in nanotube bundles. The main technique for probing the phonon spectra has been Raman spectroscopy and the many unique and unusual features of the Raman spectra of carbon nanotubes are reviewed. Also included is a brief review of the thermal properties of carbon nanotubes in relation to their unusual phonon dispersion relations and density of states.
显示 22 条，共 50 条
作者: Berger, C; Song, ZM; Li, TB; Li, XB; Ogbazghi, AY; Feng, R; Dai, ZT; Marchenkov, AN; Conrad, EH; First, PN; de Heer, WA
标题: Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics
来源出版物: JOURNAL OF PHYSICAL CHEMISTRY B, 108 (52): 19912-19916 DEC 30 2004
摘要: We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically three graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOmega to 225 kOmega at 4 K, with positive magnetoconductance). Low-resistance samples show characteristics of weak localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 10(12) cm(-2) per graphene sheet. The most highly ordered sample exhibits Shubnikov-de Haas oscillations that correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic techniques, and we demonstrate modulation of the film conductance using a top-gate electrode. These key elements suggest electronic device applications based on nanopatterned epitaxial graphene (NPEG), with the potential for large-scale integration.
显示 23 条，共 50 条
作者: Son, YW (Son, Young-Woo); Cohen, ML (Cohen, Marvin L.); Louie, SG (Louie, Steven G.)
标题: Half-metallic graphene nanoribbons
来源出版物: NATURE, 444 (7117): 347-349 NOV 16 2006
摘要: Electrical current can be completely spin polarized in a class of materials known as half- metals, as a result of the coexistence of metallic nature for electrons with one spin orientation and insulating nature for electrons with the other. Such asymmetric electronic states for the different spins have been predicted for some ferromagnetic metals - for example, the Heusler compounds(1) and were first observed in a manganese perovskite (2). In view of the potential for use of this property in realizing spin- based electronics, substantial efforts have been made to search for half-metallic materials(3,4). However, organic materials have hardly been investigated in this context even though carbon- based nanostructures hold significant promise for future electronic devices (5). Here we predict half- metallicity in nanometre- scale graphene ribbons by using first- principles calculations. We show that this phenomenon is realizable if in- plane homogeneous electric fields are applied across the zigzag- shaped edges of the graphene nanoribbons, and that their magnetic properties can be controlled by the external electric fields. The results are not only of scientific interest in the interplay between electric fields and electronic spin degree of freedom in solids 6,7 but may also open a new path to explore spintronics(3) at the nanometre scale, based on graphene(8 - 11).
显示 24 条，共 50 条
作者: Son, YW (Son, Young-Woo); Cohen, ML (Cohen, Marvin L.); Louie, SG (Louie, Steven G.)
标题: Energy gaps in graphene nanoribbons
来源出版物: PHYSICAL REVIEW LETTERS, 97 (21): Art. No. 216803 NOV 24 2006
摘要: Based on a first-principles approach, we present scaling rules for the band gaps of graphene nanoribbons (GNRs) as a function of their widths. The GNRs considered have either armchair or zigzag shaped edges on both sides with hydrogen passivation. Both varieties of ribbons are shown to have band gaps. This differs from the results of simple tight-binding calculations or solutions of the Dirac's equation based on them. Our ab initio calculations show that the origin of energy gaps for GNRs with armchair shaped edges arises from both quantum confinement and the crucial effect of the edges. For GNRs with zigzag shaped edges, gaps appear because of a staggered sublattice potential on the hexagonal lattice due to edge magnetization. The rich gap structure for ribbons with armchair shaped edges is further obtained analytically including edge effects. These results reproduce our ab initio calculation results very well.
显示 25 条，共 50 条
作者: Li, XL (Li, Xiaolin); Wang, XR (Wang, Xinran); Zhang, L (Zhang, Li); Lee, SW (Lee, Sangwon); Dai, HJ (Dai, Hongjie)
标题: Chemically derived, ultrasmooth graphene nanoribbon semiconductors
来源出版物: SCIENCE, 319 (5867): 1229-1232 FEB 29 2008
摘要: We developed a chemical route to produce graphene nanoribbons ( GNR) with width below 10 nanometers, as well as single ribbons with varying widths along their lengths or containing lattice- defined graphene junctions for potential molecular electronics. The GNRs were solution-phase - derived, stably suspended in solvents with noncovalent polymer functionalization, and exhibited ultrasmooth edges with possibly well- defined zigzag or armchair- edge structures. Electrical transport experiments showed that, unlike single- walled carbon nanotubes, all of the sub - 10- nanometer GNRs produced were semiconductors and afforded graphene field effect transistors with on- off ratios of about 10(7) at room temperature.
显示 26 条，共 50 条
作者: BLASE, X; BENEDICT, LX; SHIRLEY, EL; LOUIE, SG
标题: HYBRIDIZATION EFFECTS AND METALLICITY IN SMALL RADIUS CARBON NANOTUBES
来源出版物: PHYSICAL REVIEW LETTERS, 72 (12): 1878-1881 MAR 21 1994
摘要: Hybridization of the sigma* and pi* states of the graphene network is shown to be as important as band-folding effects in determining the metallicity of small radius carbon nanotubes. Using detailed plane-wave ab initio pseudopotential local density functional (LDA) calculations, we find that the electronic properties of small tubes are significantly altered from those obtained in previous tight-binding calculations. Strongly modified low-lying conduction band states are introduced into the band gap of insulating tubes because of strong sigma*-pi* hybridization. As a result, the LDA gaps of some tubes are lowered by more than 50%, and a tube previously predicted to be semiconducting is shown to be metallic.
显示 27 条，共 50 条
作者: Dresselhaus, MS; Dresselhaus, G; Saito, R; Jorio, A
标题: Raman spectroscopy of carbon nanotubes
来源出版物: PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 409 (2): 47-99 MAR 2005
摘要: The use of Raman spectroscopy to reveal the remarkable structure and the unusual electronic and phonon properties of single wall carbon nanotubes (SWNTs) is reviewed comprehensively. The various types of Raman scattering processes relevant to carbon nanotubes are reviewed, and the theoretical foundations for these topics are presented. ne most common experimental techniques used to probe carbon nanotubes are summarized, followed by a review of the novel experimental findings for each of the features in the first order and second order Raman spectra for single wall carbon nanotubes. These results are presented and discussed in connection with theoretical considerations. Raman spectra for bundles of SWNTs, for SWNTs surrounded by various common wrapping agents, and for isolated SWNTs at the single nanotube level are reviewed. Some of the current research challenges facing the field are briefly summarized. (c) 2004 Elsevier B.V. All rights reserved.
显示 28 条，共 50 条
作者: Katsnelson, MI (Katsnelson, M. I.); Novoselov, KS (Novoselov, K. S.); Geim, AK (Geim, A. K.)
标题: Chiral tunnelling and the Klein paradox in graphene
来源出版物: NATURE PHYSICS, 2 (9): 620-625 SEP 2006
摘要: The so-called Klein paradox - unimpeded penetration of relativistic particles through high and wide potential barriers - is one of the most exotic and counterintuitive consequences of quantum electrodynamics. The phenomenon is discussed in many contexts in particle, nuclear and astro-physics but direct tests of the Klein paradox using elementary particles have so far proved impossible. Here we show that the effect can be tested in a conceptually simple condensed-matter experiment using electrostatic barriers in single- and bi-layer graphene. Owing to the chiral nature of their quasiparticles, quantum tunnelling in these materials becomes highly anisotropic, qualitatively different from the case of normal, non-relativistic electrons. Massless Dirac fermions in graphene allow a close realization of Klein's gedanken experiment, whereas massive chiral fermions in bilayer graphene offer an interesting complementary system that elucidates the basic physics involved.
显示 29 条，共 50 条
作者: Hernandez, E; Goze, C; Bernier, P; Rubio, A
标题: Elastic properties of C and BxCyNz composite nanotubes
来源出版物: PHYSICAL REVIEW LETTERS, 80 (20): 4502-4505 MAY 18 1998
摘要: We present a comparative study of the energetic, structural, and elastic properties of carbon and composite single-wall nanotubes, including BN, BC3, and BC2N nanotubes, using a nonorthogonal tight-binding formalism. Our calculations predict that carbon nanotubes have a higher Young modulus than any of the studied composite nanotubes, and of the same order as that found for defect-free graphene sheets. We obtain good agreement with the available experimental results.
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作者: Schedin, F (Schedin, F.); Geim, AK (Geim, A. K.); Morozov, SV (Morozov, S. V.); Hill, EW (Hill, E. W.); Blake, P (Blake, P.); Katsnelson, MI (Katsnelson, M. I.); Novoselov, KS (Novoselov, K. S.)
标题: Detection of individual gas molecules adsorbed on graphene
来源出版物: NATURE MATERIALS, 6 (9): 652-655 SEP 2007
摘要: The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity(1-4). The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects(5), which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here, we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required.
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作者: Ohta, T (Ohta, Taisuke); Bostwick, A (Bostwick, Aaron); Seyller, T (Seyller, Thomas); Horn, K (Horn, Karsten); Rotenberg, E (Rotenberg, Eli)
标题: Controlling the electronic structure of bilayer graphene
来源出版物: SCIENCE, 313 (5789): 951-954 AUG 18 2006
摘要: We describe the synthesis of bilayer graphene thin films deposited on insulating silicon carbide and report the characterization of their electronic band structure using angle-resolved photoemission. By selectively adjusting the carrier concentration in each layer, changes in the Coulomb potential led to control of the gap between valence and conduction bands. This control over the band structure suggests the potential application of bilayer graphene to switching functions in atomic-scale electronic devices.
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作者: Rao, AM; Eklund, PC; Bandow, S; Thess, A; Smalley, RE
标题: Evidence for charge transfer in doped carbon nanotube bundles from Raman scattering
来源出版物: NATURE, 388 (6639): 257-259 JUL 17 1997
摘要: Single-walled carbon nanotubes(1) (SWNTs) are predicted to be metallic for certain diameters and pitches of the twisted graphene ribbons that make up their walls(2). Chemical doping is expected to substantially increase the density of free charge carriers and thereby enhance the electrical (and thermal) conductivity. Here we use Raman spectroscopy to study the effects of exposing SWNT bundles(1) to typical electron-donor (potassium, rubidium) and electron-acceptor (iodine, bromine) dopants. We find that the high-frequency tangential vibrational modes of the carbon atoms in the SWNTs shift substantially to lower (for K, Rb) or higher (for Br-2) frequencies. Little change is seen for I-2 doping. These shifts provide evidence for charge transfer between the dopants and the nanotubes, indicating an ionic character of the doped samples. This, together with conductivity measurements(3), suggests that doping does increase the carrier concentration of the SWNT bundles.
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作者: Peres, NMR; Guinea, F; Neto, AHC
标题: Electronic properties of disordered two-dimensional carbon
来源出版物: PHYSICAL REVIEW B, 73 (12): Art. No. 125411 MAR 2006
摘要: Two-dimensional carbon, or graphene, is a semimetal that presents unusual low-energy electronic excitations described in terms of Dirac fermions. We analyze in a self-consistent way the effects of localized (impurities or vacancies) and extended (edges or grain boundaries) defects on the electronic and transport properties of graphene. On the one hand, point defects induce a finite elastic lifetime at low energies with the enhancement of the electronic density of states close to the Fermi level. Localized disorder leads to a universal, disorder independent, electrical conductivity at low temperatures, of the order of the quantum of conductance. The static conductivity increases with temperature and shows oscillations in the presence of a magnetic field. The graphene magnetic susceptibility is temperature dependent (unlike an ordinary metal) and also increases with the amount of defects. Optical transport properties are also calculated in detail. On the other hand, extended defects induce localized states near the Fermi level. In the absence of electron-hole symmetry, these states lead to a transfer of charge between the defects and the bulk, the phenomenon we call self-doping. The role of electron-electron interactions in controlling self-doping is also analyzed. We also discuss the integer and fractional quantum Hall effect in graphene, the role played by the edge states induced by a magnetic field, and their relation to the almost field independent surface states induced at boundaries. The possibility of magnetism in graphene, in the presence of short-range electron-electron interactions and disorder is also analyzed.
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作者: Meyer, JC (Meyer, Jannik C.); Geim, AK (Geim, A. K.); Katsnelson, MI (Katsnelson, M. I.); Novoselov, KS (Novoselov, K. S.); Booth, TJ (Booth, T. J.); Roth, S (Roth, S.)
标题: The structure of suspended graphene sheets
来源出版物: NATURE, 446 (7131): 60-63 MAR 1 2007
摘要: The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles(1-3). However, the physical structure of graphene - a single layer of carbon atoms densely packed in a honeycomb crystal lattice - is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. On the other hand, perfect two-dimensional crystals cannot exist in the free state, according to both theory and experiment(4-9). This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix(1-3,9-12). Here we report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range crystalline order. However, our studies by transmission electron microscopy also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the observed corrugations in the third dimension may provide subtle reasons for the stability of two-dimensional crystals(13-15).
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作者: Stankovich, S (Stankovich, Sasha); Dikin, DA (Dikin, Dmitriy A.); Piner, RD (Piner, Richard D.); Kohlhaas, KA (Kohlhaas, Kevin A.); Kleinhammes, A (Kleinhammes, Alfred); Jia, Y (Jia, Yuanyuan); Wu, Y (Wu, Yue); Nguyen, ST (Nguyen, SonBinh T.); Ruoff, RS (Ruoff, Rodney S.)
标题: Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide
来源出版物: CARBON, 45 (7): 1558-1565 JUN 2007
摘要: Reduction of a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high-surface-area carbon material which consists of thin graphene-based sheets. The reduced material was characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, NMR spectroscopy, Raman spectroscopy, and by electrical conductivity measurements. (c) 2007 Elsevier Ltd. All rights reserved.
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作者: Dai, HJ
标题: Carbon nanotubes: opportunities and challenges
来源出版物: SURFACE SCIENCE, 500 (1-3): 218-241 MAR 10 2002
摘要: Carbon nanotubes are graphene sheets rolled-up into cylinders,with diameters as small as one nanometer. Extensive work carried out worldwide in recent years has revealed the intriguing electrical and mechanical properties of these novel molecular scale wires. It is now well established that carbon nanotubes are ideal model systems for studying the physics in one-dimensional solids and have significant potential as building blocks for various practical nanoscale devices. Nanotubes have been shown to be useful for miniaturized electronic, mechanical, electromechanical, chemical and scanning probe devices and materials for macroscopic composites. Progress in nanotube growth has facilitated the fundamental study and applications of nanotubes. Gaining control over challenging nanotube growth issues is critical to the future advancement of nanotube science and technology, and is being actively pursued by researchers. (C) 2001 Elsevier Science B.V. All rights reserved.
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作者: Girifalco, LA; Hodak, M; Lee, RS
标题: Carbon nanotubes, buckyballs, ropes, and a universal graphitic potential
来源出版物: PHYSICAL REVIEW B, 62 (19): 13104-13110 NOV 15 2000
摘要: The potential energies of interaction between two parallel, infinitely long carbon nanotubes of the same diameter, and between C-60 and a nanotube in various arrangements, were computed by assuming a continuous distribution of atoms on the tube and ball surfaces and using a Lennard-Jones (LJ) carbon-carbon potential. The constants in the LJ potential are different for graphene-graphene and C-60-C-60 interactions. From these, the constants for tube-C-60 interactions were estimated using averaging rules from the theory of dispersion forces. For tubes in ropes, the cohesive energy per unit length, the compressibility, and the equilibrium separation distance were computed as a function of tube radius. For a C-60 molecule interacting with tubes, the binding energy inside a tube was much higher than on a tube or at the tube mouth. Within a tube, the binding energy was highest at a spherically capped end. The potential energies for tubes of all radii, as well as for interactions between C-60 molecules, for a C-60 molecule outside of a nanotube, between a C-60 molecule and a graphene sheet, and between graphene sheets, all fell on the same curve when plotted in terms of certain reduced parameters. Because of this, all the potentials can be represented by a simple analytic form, thereby greatly simplifying all computations of van der Waals interactions in graphitic systems. Binding-energy results were all consistent with the recently proposed mechanism of peapod formation based on transmission electron microscopy experiments.
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作者: Novoselov, KS; McCann, E; Morozov, SV; Fal'ko, VI; Katsnelson, MI; Zeitler, U; Jiang, D; Schedin, F; Geim, AK
标题: Unconventional quantum Hall effect and Berry's phase of 2 pi in bilayer graphene
来源出版物: NATURE PHYSICS, 2 (3): 177-180 MAR 2006
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作者: Li, D (Li, Dan); Muller, MB (Mueller, Marc B.); Gilje, S (Gilje, Scott); Kaner, RB (Kaner, Richard B.); Wallace, GG (Wallace, Gordon G.)
标题: Processable aqueous dispersions of graphene nanosheets
来源出版物: NATURE NANOTECHNOLOGY, 3 (2): 101-105 FEB 2008
摘要: Graphene sheets offer extraordinary electronic, thermal and mechanical properties and are expected to find a variety of applications. A prerequisite for exploiting most proposed applications for graphene is the availability of processable graphene sheets in large quantities. The direct dispersion of hydrophobic graphite or graphene sheets in water without the assistance of dispersing agents has generally been considered to be an insurmountable challenge. Here we report that chemically converted graphene sheets obtained from graphite can readily form. stable aqueous colloids through electrostatic stabilization. This discovery has enabled us to develop a facile approach to large-scale production of aqueous graphene dispersions without the need for polymeric or surfactant stabilizers. Our findings make it possible to process graphene materials using low-cost solution processing techniques, opening up enormous opportunities to use this unique carbon nanostructure for many technological applications.
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作者: McCann, E; Fal'ko, VI
标题: Landau-level degeneracy and quantum hall effect in a graphite bilayer
来源出版物: PHYSICAL REVIEW LETTERS, 96 (8): Art. No. 086805 MAR 3 2006
摘要: We derive an effective two-dimensional Hamiltonian to describe the low-energy electronic excitations of a graphite bilayer, which correspond to chiral quasiparticles with a parabolic dispersion exhibiting Berry phase 2 pi. Its high-magnetic-field Landau-level spectrum consists of almost equidistant groups of fourfold degenerate states at finite energy and eight zero-energy states. This can be translated into the Hall conductivity dependence on carrier density, sigma(xy)(N), which exhibits plateaus at integer values of 4e(2)/h and has a double 8e(2)/h step between the hole and electron gases across zero density, in contrast to (4n+2)e(2)/h sequencing in a monolayer.
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作者: Helveg, S; Lopez-Cartes, C; Sehested, J; Hansen, PL; Clausen, BS; Rostrup-Nielsen, JR; Abild-Pedersen, F; Norskov, JK
标题: Atomic-scale imaging of carbon nanofibre growth
来源出版物: NATURE, 427 (6973): 426-429 JAN 29 2004
摘要: The synthesis of carbon nanotubes with predefined structure and functionality plays a central role in the field of nanotechnology(1,2), whereas the inhibition of carbon growth is needed to prevent a breakdown of industrial catalysts for hydrogen and synthesis gas production(3). The growth of carbon nanotubes and nanofibres has therefore been widely studied(4-10). Recent advances in in situ techniques now open up the possibility of studying gas - solid interactions at the atomic level(11-12). Here we present time-resolved, high-resolution in situ transmission electron microscope observations of the formation of carbon nanofibres from methane decomposition over supported nickel nanocrystals. Carbon nanofibres are observed to develop through a reaction-induced reshaping of the nickel nanocrystals. Specifically, the nucleation and growth of graphene layers are found to be assisted by a dynamic formation and restructuring of mono-atomic step edges at the nickel surface. Density-functional theory calculations indicate that the observations are consistent with a growth mechanism involving surface diffusion of carbon and nickel atoms. The finding that metallic step edges act as spatio-temporal dynamic growth sites may be important for understanding other types of catalytic reactions and nanomaterial syntheses.
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作者: Kane, CL; Mele, EJ
标题: Quantum spin Hall effect in graphene
来源出版物: PHYSICAL REVIEW LETTERS, 95 (22): Art. No. 226801 NOV 25 2005
摘要: We study the effects of spin orbit interactions on the low energy electronic structure of a single plane of graphene. We find that in an experimentally accessible low temperature regime the symmetry allowed spin orbit potential converts graphene from an ideal two-dimensional semimetallic state to a quantum spin Hall insulator. This novel electronic state of matter is gapped in the bulk and supports the transport of spin and charge in gapless edge states that propagate at the sample boundaries. The edge states are nonchiral, but they are insensitive to disorder because their directionality is correlated with spin. The spin and charge conductances in these edge states are calculated and the effects of temperature, chemical potential, Rashba coupling, disorder, and symmetry breaking fields are discussed.
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作者: Kim, KS (Kim, Keun Soo); Zhao, Y (Zhao, Yue); Jang, H (Jang, Houk); Lee, SY (Lee, Sang Yoon); Kim, JM (Kim, Jong Min); Kim, KS (Kim, Kwang S.); Ahn, JH (Ahn, Jong-Hyun); Kim, P (Kim, Philip); Choi, JY (Choi, Jae-Young); Hong, BH (Hong, Byung Hee)
标题: Large-scale pattern growth of graphene films for stretchable transparent electrodes
来源出版物: NATURE, 457 (7230): 706-710 FEB 5 2009
摘要: Problems associated with large- scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications(1). Recently, macroscopic- scale graphene films were prepared by two- dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides(2,3). However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large- scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of similar to 280 Omega per square, with 80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm(2) V-1 s(-1) and exhibit the half- integer quantum Hall effect(4,5), implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene(6). Employing the outstanding mechanical properties of graphene(7), we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics(8,9).
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