Hydrogenation of the buffer-layer graphene on 6H-SiC (0001): A possible route for the engineering of graphene-based devices
graphene, hydrogenation, photoemission spectroscopy, electronic structure
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 °C. 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 °C), 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.
Tsinghua University Press
Yu-Pu Lin,Younal Ksari,Jean-Marc Themlin, Hydrogenation of the buffer-layer graphene on 6H-SiC (0001): A possible route for the engineering of graphene-based devices. NanoRes.2015, 8(3): 839–850