Epitaxial graphene

Heer, Walt A. de; Berger, Claire; Wu, Xiaosong; First, Phillip N.; Conrad, E. H.; Li, Xuebin; Li, Tianbo; Sprinkle, M.; Hass, Joanna; Sadowski, M. L.; Potemski, M.; Martinez, G.

doi:10.1016/j.ssc.2007.04.023

Cited by 838 publications

(622 citation statements)

References 38 publications

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“…[9], where, by deploying a continuum approximation, the small angle limit was investigated and v F found to be suppressed. Experimentally, the evidence for this seems uncertain as a suppression of v F is found for graphene stacks grown on both the C and Si faces of SiC, whereas twist boundary faults appear only during growth on the C face [17]. This disagreement between the continuum approximation for the (singular) !…”

Section: 056803 (2008) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 98%

Quantum Interference at the Twist Boundary in Graphene

2008

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We explore the consequences of a rotation between graphene layers for the electronic spectrum. We derive the commensuration condition in real space and show that the interlayer electronic coupling is governed by an equivalent commensuration in reciprocal space. The larger the commensuration cell, the weaker the interlayer coupling, with exact decoupling for incommensurate rotations and in the ! 0 limit. Furthermore, from first-principles calculations we determine that even for the smallest possible commensuration cell the decoupling is effectively perfect, and thus graphene layers will be seen to decouple for all rotation angles.

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Section: 056803 (2008) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 98%

Quantum Interference at the Twist Boundary in Graphene

2008

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“…We observe cooling of the photogenerated carrier distribution as well as electronhole recombination in graphene in real time. Our results indicate that the recombination times in graphene depend on the carrier density and material disorder.The epitaxial graphene samples used in this work were grown on the carbon face of semi-insulating 6H-SiC wafers using techniques that have been reported previously [12]. As discussed in [8,11], X-ray photoemission, Raman, and optical/IR/THz transmission spectroscopy were used to characterize each sample to determine the number of carbon atom layers and the carrier momentum relaxation time.…”

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confidence: 99%

Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene

et al. 2008

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The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on sub-picosecond time scales and that interband recombination times are carrier density dependent.Graphene is a 2D lattice of carbon atoms arranged in a honeycomb crystal structure with a zero (or nearzero) bandgap and a linear energy-momentum dispersion relation for both electrons and holes [1,2]. The unique electronic and optical properties of graphene make it a promising material for the development of high-speed electron devices, including field-effect transistors, pn-diodes, Terahertz oscillators, and electronic and optical sensors [2,3,4,5,6,7]. The realization of graphene-based devices requires understanding the nonequilibrium carrier dynamics as well as the rate at which electron-hole recombination occurs.Measurements of the ultrafast intraband relaxation dynamics of photogenerated electrons and holes in epitaxial graphene using both degenerate [8] and non-degenerate [9] optical-pump optical-probe spectroscopy have been previously reported. Similar measurements for exfoliated graphene mono-and multi-layers have also been carried out [10]. These measurements were sensitive to the interband conductivity of graphene and probed the time evolution of the carrier occupation at specific energies in the bands. Consequently, they were not able to directly measure the time scales associated with carrier recombination. At room temperature, the optical response of graphene in the THz frequency range is described by the intraband conductivity -the free carrier responsewhich depends not only on the total carrier concentration but also on the carrier distribution in energy [11]. Therefore, THz radiation can be used to study the carrier relaxation and recombination dynamics in graphene. In this paper, we present results obtained from opticalpump THz-probe spectroscopy of epitaxial graphene in which the time-dependent conductivity of graphene that has been excited with an optical pump pulse is probed with a few-cycle THz pulse. We observe cooling of the photogenerated carrier distribution as well as electronhole recombination in graphene in real time. Our results indicate that the recombination times in graphene depend on the carrier density and material disorder.The epitaxial graphene samples used in this work were grown on the carbon face of semi-insulating 6H-SiC wafers using techniques that have been reported previously [12]. As discussed in [8,11], X-ray photoemission, Raman, and optical/IR/THz transmission spectroscopy ...

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“…Advances in the epitaxial growth of graphene films on SiC have the potential to open new classes of device applications that may revolutionize the semiconductor road map for future decades [1][2][3][4][5][6][7][8][9]. However, this progress will require an in-depth understanding and utilization of the electronic processes that take place at the nanoscale, in particular, the role of the interface buffer layer, where most of the electronic properties of the system can be controlled [10].…”

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confidence: 99%

Band Engineering and Magnetic Doping of Epitaxial Graphene on SiC (0001)

et al. 2010

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Using calculations from first principles we show how specific interface modifications can lead to a finetuning of the doping and band alignment in epitaxial graphene on SiC. Upon different choices of dopants, we demonstrate that one can achieve a variation of the valence band offset between the graphene Dirac point and the valence band edge of SiC up to 1.5 eV. Finally, via appropriate magnetic doping one can induce a half-metallic behavior in the first graphene monolayer. These results clearly establish the potential for graphene utilization in innovative electronic and spintronic devices.

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Epitaxial graphene

Cited by 838 publications

References 38 publications

Quantum Interference at the Twist Boundary in Graphene

Quantum Interference at the Twist Boundary in Graphene

Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene

Band Engineering and Magnetic Doping of Epitaxial Graphene on SiC (0001)

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