Measurement of Scattering Rate and Minimum Conductivity in Graphene

Tan, Yan‐Wen; Zhang, Y.; Bolotin, Kirill I.; Zhao, Yüe; Adam, Shaffique; Hwang, E. H.; Sarma, S. Das; Störmer, H. L.; Kim, Philip

doi:10.1103/physrevlett.99.246803

Cited by 975 publications

(869 citation statements)

References 24 publications

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“…at the DP becomes very sharp at low temperatures, and on the hole branch the half width at half maximum (HWHM) at the lowest temperature (δV g ~ 0.15 V, δn ~3.2 10 9 cm -2 for the sample with channel length L = 0.5 μm) is almost one order of magnitude narrower than that of the best NSG samples published so far 4,22 . This is directly seen (Figure 2a A remarkable feature of the ) (n ρ curves in SG samples is the strong temperature dependence of the maximum resistivity at the DP, in stark contrast to NSG samples.…”

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confidence: 87%

Approaching ballistic transport in suspended graphene

et al. 2008

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The recent discovery of methods to isolate graphene 1-3 , a one-atom-thick layer of crystalline carbon, has raised the possibility of a new class of nano-electronics devices based on the extraordinary electrical transport and unusual physical properties 4,5 of this material. However, the experimental realization of devices displaying these properties was, until now, hampered by the influence of the ambient environment, primarily the substrate. Here we report on the fabrication of Suspended Graphene (SG) devices and on studies of their electrical transport properties. In these devices, environmental disturbances were minimized allowing unprecedented access to the intrinsic properties of graphene close to the Dirac Point (DP) where the energy dispersion of the carriers and their density-of-states vanish linearly giving rise to a range of exotic physical properties. We show that charge inhomogeneity is reduced by almost one order of magnitude compared to that in Non-Suspended Graphene (NSG) devices. Moreover, near the DP, the mobility exceeds 100,000 cm 2 /Vs, approaching theoretical predictions for evanescent transport in the ballistic model. The low energy excitation spectrum of graphene mimics relativistic particles -massless Dirac fermions (DF) -with an electron-hole symmetric conical energy dispersion and .vanishing density of states at the DP. Such unusual spectrum is expected to produce 1 novel electronic properties such as negative index of refraction 6 , specular Andreev reflections at graphene-superconductor junctions 7,8 , evanescent transport 9 , anomalous phonon softening 10 , etc. A basic assumption behind these intriguing predictions is that the graphene layer is minimally affected by interactions with the environment. However in reality the environment 11,12 and in particular the substrate 13 , can be quite invasive for such ultra-thin films. For example, the carrier mobility in graphene deposited on a substrate such as Si/SiO 2 deteriorates due to trapped charges in the oxide or to contaminants that get trapped at the graphene-substrate interface during fabrication. The substrate-induced charge inhomogeneity is particularly deleterious near the DP where screening is weak, 14,15 leading to reduced carrier mobility there. In addition, the atomic roughness of the substrate introduces short range scattering centers and may contribute to quench-condensation of ripples within the graphene layer 16 .In order to eliminate substrate induced perturbations, graphene films were suspended from Au/Ti contacts to bridge over a trench in a SiO 2 substrate. In contrast to prior realizations of suspended graphene 17,18 which did not provide electrical contacts for transport measurements, the SG devices described here incorporate multiple electrodes that allow 4-lead transport measurements. The SG devices employed here were fabricated from conventional NSG devices using wet chemical etching (see supporting online material). In a typical SG device, shown in Figure 1b, the graphene layer is suspended from the voltage l...

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confidence: 87%

Approaching ballistic transport in suspended graphene

et al. 2008

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“…17 These doping effects are understood to play a major role in defining the transport properties of typical graphene samples. [10][11][12] However, the underlying process responsible for doping has not yet been elucidated. In particular, the relative role of doping induced by the substrate and that arising from the intrinsic environmental sensitivity of graphene 19 remains unclear.…”

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confidence: 99%

Probing the Intrinsic Properties of Exfoliated Graphene: Raman Spectroscopy of Free-Standing Monolayers

Berciaud¹,

Ryu²,

Brus³

et al. 2009

Nano Lett.

517

485

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The properties of pristine, free-standing graphene monolayers prepared by mechanical exfoliation of graphite are investigated. The graphene monolayers, suspended over open trenches, are examined by means of spatially resolved Raman spectroscopy of the G-, D-, and 2D-phonon modes. The G-mode phonons exhibit reduced energies (1580 cm -1 ) and increased widths (14 cm -1 ) compared to the response of graphene monolayers supported on the SiO 2 -covered substrate. From analysis of the G-mode Raman spectra, we deduce that the free-standing graphene monolayers are essentially undoped, with an upper bound of 2×10 11 cm -2 for the residual carrier concentration. On the supported regions, significantly higher and spatially inhomogeneous doping is observed. The free-standing graphene monolayers show little local disorder, based on the very weak Raman D-mode response. The two-phonon 2D mode of the free-standing graphene monolayers is downshifted in frequency compared to that of the supported region of the samples and exhibits a narrowed, positively skewed line shape.

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“…[1][2][3][4][5] However, charge impurities universally exist in graphene and influence its electronic properties. [6][7][8][9][10] A particular case is when approaching the Dirac point at which, because of the vanishing density of states, the transport properties of graphene are expected to be highly sensitive to 3 scattering from charged impurities. [6][7][8][9][10] Previous studies of charge carrier scattering in graphene are mainly achieved with the scattering centers introduced by physical methods, such as ion irradiation, 7, 8 adsorption of adlayers, 9 low temperature deposition 10 and spin coating [11][12][13] of nanoparticles, and atomic hydrogen adsorption.…”

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Electron–Hole Symmetry Breaking in Charge Transport in Nitrogen-Doped Graphene

Lin

Rui

et al. 2017

ACS Nano

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Graphitic nitrogen-doped graphene is an excellent platform to study scattering processes of massless Dirac fermions by charged impurities, in which high mobility can be preserved due to the absence of lattice defects through direct substitution of carbon atoms in the graphene lattice by nitrogen atoms. In this work, we report on 2 electrical and magnetotransport measurements of high-quality graphitic nitrogen-doped graphene. We show that the substitutional nitrogen dopants in graphene introduce atomically sharp scatters for electrons but long-range Coulomb scatters for holes and, thus, graphitic nitrogen-doped graphene exhibits clear electron-hole asymmetry in transport properties. Dominant scattering processes of charge carriers in graphitic nitrogen-doped graphene are analyzed. It is shown that the electron-hole asymmetry originates from a distinct difference in intervalley scattering of electrons and holes. We have also carried out the magnetotransport measurements of graphitic nitrogen-doped graphene at different temperatures and the temperature dependences of intervalley scattering, intravalley scattering and phase coherent scattering rates are extracted and discussed. Our results provide an evidence for the electron-hole asymmetry in the intervalley scattering induced by substitutional nitrogen dopants in graphene and shine a light on versatile and potential applications of graphitic nitrogen-doped graphene in electronic and valleytronic devices. KEYWORDS: graphene, charge transport, intervalley scattering, graphitic nitrogen doping, atomically sharp scattering center Graphene, a honeycomb lattice of single layer carbon atoms with a Dirac-like energy dispersion, has attracted extensive interests in recent years owing to its extraordinary charge transport properties and potential applications in electronic devices. [1][2][3][4][5] However, charge impurities universally exist in graphene and influence its electronic properties. [6][7][8][9][10] A particular case is when approaching the Dirac point at which, because of the vanishing density of states, the transport properties of graphene are expected to be highly sensitive to 3 scattering from charged impurities. [6][7][8][9][10] Previous studies of charge carrier scattering in graphene are mainly achieved with the scattering centers introduced by physical methods, such as ion irradiation, 7, 8 adsorption of adlayers, 9 low temperature deposition 10 and spin coating [11][12][13] of nanoparticles, and atomic hydrogen adsorption. 14 These methods could inevitably induce randomness and disorder in graphene and thereby largely degrade its transport properties. Compared with the physical methods, chemical doping has the advantage to achieve scattering centers in graphene with good replicability, lattice stability, and tunablity of doping concentration through the substitution of carbon atoms in the graphene lattice by dopant atoms. Among numerous dopants, nitrogen (N) atoms can be chemically incorporated into graphene forming covalent bonds with carbon (...

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Measurement of Scattering Rate and Minimum Conductivity in Graphene

Cited by 975 publications

References 24 publications

Approaching ballistic transport in suspended graphene

Approaching ballistic transport in suspended graphene

Probing the Intrinsic Properties of Exfoliated Graphene: Raman Spectroscopy of Free-Standing Monolayers

Electron–Hole Symmetry Breaking in Charge Transport in Nitrogen-Doped Graphene

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