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 re...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.展开更多
文摘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.
