Epitaxial graphene

2010

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Plasmon-phonon strongly coupled mode in epitaxial graphene

Yu Liu* and R. F. Willis

Phys. Rev. B 81, 081406(R) (2010)

We report the dispersion measurements, using angle-resolved reflection electron-energy-loss spectroscopy, on two-dimensional (2D) plasmons in single and multilayer graphene which couple strongly to surface optical phonon (FK-phonon) modes of silicon carbide substrate. The coupled modes show discrete dispersion behaviors in the single and bilayer graphene. With increasing graphene layers on SiC(0001), a transition from plasmonlike dispersion to phononlike dispersion is observed. For plasmonlike modes, the dispersion is strongly damped by electron-hole pair excitations at entering single-particle continuum, while phononlike mode is undamped. In the region free of coupling, the graphene 2D plasmon exhibits acoustic behavior with linear dispersion with slope and damping determined by the Fermi-surface topology.

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2009

Quasi-Free-Standing Epitaxial Graphene on SiC Obtained by Hydrogen Intercalation

C. Riedl, C. Coletti, T. Iwasaki, A. A. Zakharov, and U. Starke

Phys. Rev. Lett. 103, 246804 (2009)

Quasi-free-standing epitaxial graphene is obtained on SiC(0001) by hydrogen intercalation. The hydrogen moves between the (6?3×6?3)R30° reconstructed initial carbon layer and the SiC substrate. The topmost Si atoms which for epitaxial graphene are covalently bound to this buffer layer, are now saturated by hydrogen bonds. The buffer layer is turned into a quasi-free-standing graphene monolayer with its typical linear ? bands. Similarly, epitaxial monolayer graphene turns into a decoupled bilayer. The intercalation is stable in air and can be reversed by annealing to around 900?°C.

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Observation of quantum-Hall effect in gated epitaxial graphene grown on SiC (0001)

T. Shen, J. J. Gu, M. Xu, Y. Q. Wu, M. L. Bolen, M. A. Capano, L. W. Engel, and P. D. Ye

Appl. Phys. Lett. 95, 172105 (2009)

Epitaxial graphene films examined were formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. A high-k gate stack on the epitaxial graphene was realized by inserting a fully oxidized nanometer thin aluminum film as a seeding layer, followed by an atomic-layer deposition process. The electrical properties of epitaxial graphene films are retained after gate stack formation without significant degradation. At low temperatures, the quantum-Hall effect in Hall resistance is observed along with pronounced Shubnikov–de Haas oscillations in diagonal magnetoresistance of gated epitaxial graphene on SiC (0001).

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Epitaxial graphene: How silicon leaves the scene

Peter Sutter

 

Nature Materials 8, 171–172

 

Since it was first isolated in 2004, graphene, a sheet of pure carbon just one atom thick, has generated a flurry of research activities. Although much of the initial 'gold rush' has focused on the fascinating properties of this two-dimensional crystal — which have as much to do with fundamental quantum electrodynamics and particle physics as with solid state physics and materials science — researchers have recently begun addressing the more mundane question of how some of these characteristics might be harnessed in applications ranging from post-Moore's law electronics over ultra-responsive sensors and actuators to transparent solar cell contacts.

 

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Half integer quantum Hall effect in high mobility single layer epitaxial graphene

Xiaosong Wu, Yike Hu, Ming Ruan, Nerasoa K Madiomanana, John Hankinson, Mike Sprinkle, Claire Berger, and Walt A. de Heer

 

he quantum Hall effect, with a Berry's phase of pi is demonstrated here on a single graphene layer grown on the C-face of 4H silicon carbide. The mobility is ~20 000 cm2/V·s at 4 K and 15 000 cm2/V·s at 300 K despite contamination and substrate steps. This is comparable to the best exfoliated graphene flakes on SiO2 and an order of magnitude larger than Si-face epitaxial graphene monolayers. These and other properties indicate that C-face epitaxial graphene is a viable platform for graphene-based electronics.

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