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The hydrogenation at various temperatures of the (6√3 × 6√3)R30° reconstruction of SiC(0001), the so-called buffer layer graphene (BLG), is investigated. For the BLG, a significant concentration of remaining dangling bonds related to unsaturated Si atoms of the outermost SiC bilayer is evidenced in the inverse photoemission spectra. These dangling bonds give rise to a peak around 1 eV above the Fermi level, associated with the upper single-electron states of a Mott-Hubbard insulator, which vanishes upon hydrogenation. Hydrogen atoms adsorbed at ambient temperature remain covalently bound to BLG (H-BLG) up to temperatures of ~500 ℃. They induce additional C-Si bonds at the BLG/SiC interface that saturate the remaining Si dangling bonds, as evidenced in both IPES and Auger electron spectra. The H-BLG further shows a large energy gap and an excess n-type doping in comparison to the pristine BLG. Upon hydrogen exposure at higher temperature (> 700 ℃), hydrogen atoms intercalate at the BLG/SiC interface, inducing the formation of a single layer of quasi-free-standing graphene (QFSG) lying on top of a hydrogenated (√3 × √3)R30° reconstruction as supported by IPES. We suggest that the high-stability and the distinct electronic structure of both BLG-derived structures, H-BLG and QFSG, may open a route for the engineering of graphene-based devices.

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Publication history

Received: 06 June 2014
Revised: 07 August 2014
Accepted: 18 August 2014
Published: 25 September 2014
Issue date: March 2015

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© Tsinghua University Press and Springer-Verlag Heidelberg 2014

Acknowledgements

Acknowledgements

This work is supported by the project ANR-10-BLAN 1017 ChimiGraphN.

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Reprints and Permission requests may be sought directly from editorial office.
Email: nanores@tup.tsinghua.edu.cn

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