The quasi-free-standing nature of graphene on H-saturated SiC(0001)

Speck, Florian; Jobst, Johannes; Fromm, Felix; Ostler, Markus; Waldmann, Daniel; Hundhausen, Martin; Weber, Heiko B.; Seyller, Thomas

doi:10.1063/1.3643034

Cited by 254 publications

(339 citation statements)

References 27 publications

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“…Weakly interacting graphene layers such as graphene on C-face SiC exhibit a 2D peak located between those of monolayer and AB-stacked graphene. A G peak enhancement (comparable to 2D peak) is also observed 22 . Previous Raman studies on TG have attributed a narrowing and intensity increase of the 2D peak to interlayer coupling and a modified electronic band structure 16,21 .…”

Section: Resultsmentioning

confidence: 64%

Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene

et al. 2015

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Twisted graphene is of particular interest due to several intriguing characteristics, such as its the Fermi velocity, van Hove singularities and electronic localization. Theoretical studies recently suggested the possible bandgap opening and tuning. Here, we report a novel approach to producing epitaxial twisted graphene on SiC (0001) and the observation of its intrinsic bandgap behaviour. The direct deposition of C 60 on pre-grown graphene layers results in few-layer twisted graphene confirmed by angular resolved photoemission spectroscopy and Raman analysis. The strong enhanced G band in Raman and sp 3 bonding characteristic in X-ray photoemission spectroscopy suggests the existence of interlayer interaction between adjacent graphene layers. The interlayer spacing between graphene layers measured by transmission electron microscopy is 0.352 ± 0.012 nm. Thermal activation behaviour and nonlinear current-voltage characteristics conclude that an intrinsic bandgap is opened in twisted graphene. Low sheet resistance (B160 O& À 1 at 10 K) and high mobility (B2,000 cm 2 V À 1 s À 1 at 10 K) are observed.

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Section: Resultsmentioning

confidence: 64%

Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene

et al. 2015

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“…Moreover, the charge carrier mobility of MLG is temperature * Corresponding author Tel: +49 371 531-32898. E-mail: Thomas.Seyller@physik.tu-chemnitz.de (Thomas Seyller) dependent [4] and it has been observed that this is a direct consequence of the presence of the buffer layer [10]. In recent years, various elements such as gold [11], lithium [12], silicon [13], fluorine [14], germanium [15], oxygen [16][17][18][19] and hydrogen [10,[20][21][22][23] have been intercalated between the buffer layer and SiC(0001) in order to modify the interface.…”

Section: Introductionmentioning

confidence: 99%

“…Hydrogen has been shown to work well, leading to so-called quasi-free-standing monolayer graphene (QFMLG) with improved electrical properties [10,[22][23]] when compared to normal MLG which resides on the buffer layer. Hydrogen is therefore a prime candidate for the future integration of quasi-free-standing graphene into devices.…”

Section: Introductionmentioning

confidence: 99%

Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Ostler

Fromm

Koch

et al. 2014

Carbon

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Intercalation of various elements has become a popular technique to decouple the buffer layer of epitaxial graphene on SiC(0001) from the substrate. Among many other elements, oxygen can be used to passivate the SiC interface, causing the buffer layer to transform into graphene. Here, we study a gentle oxidation of the interface by annealing buffer layer and monolayer graphene samples in water vapor. X-ray photoelectron spectroscopy demonstrates the decoupling of the buffer layer from the SiC substrate. Raman spectroscopy is utilized to investigate a possible introduction of defects. Angle-resolved photoemission spectroscopy shows that the electronic structure of the water vapor treated samples. Low-energy electron microscopy (LEEM) measurements demonstrate that the decoupling takes place without changes in the surface morphology. The LEEM reflectivity spectra are discussed in terms of two different interpretations.

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“…H-QFMLG was obtained by annealing the buffer layer in molecular hydrogen [16,17], while O-QFMLG was prepared by annealing in water vapor [18]. Quasi-freestanding bilayer graphene (H-QFBLG) on Hterminated SiC(0001) was prepared by annealing MLG in hydrogen [16,19].…”

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confidence: 99%