Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 83: Graphene: Adsorption, Intercalation, Doping (O jointly with DS, HL, MA, TT)
O 83.4: Vortrag
Donnerstag, 3. April 2014, 16:45–17:00, WIL C107
H-adsorption and H2-splitting on graphene/SiC(0001) — •Gabriele Sclauzero and Alfredo Pasquarello — École Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland)
High-quality graphene grown epitaxially on SiC(0001) can be regarded as a convenient template for the realization of graphene-based electronics. However, the presence of a carbon “buffer” layer buried at the interface between the SiC surface and the epitaxial graphene is detrimental to the electronic transport properties of graphene. Hydrogen intercalation at high temperatures can be used to convert the buffer layer into a quasi-free standing graphene lying directly above a H-saturated SiC(0001) surface, which provides a much more effective decoupling from the substrate.
Here, the processes of H-adsorption and H2-splitting at the graphene/SiC(0001) interface is addressed through first-principles atomistic simulations based on realistic interface models, including the experimentally observed 6√(3) × 6 √(3) R30∘ reconstruction. Our main finding is a great enhancement of the chemical reactivity of the carbon buffer layer with respect to pristine graphene, as a result of the partial sp2 to sp3 rehybridization of the C atoms in the buffer. H-binding energies on threefold-coordinated C atoms of the buffer are three-to-four times larger than on graphene and H2-splitting becomes an exothermic process, with activation barriers that can be up to four times smaller than on graphene. On favorable sites, energy barriers can become as low as 1 eV and are in agreement with the observation of atomic-H intercalation also when H2 is used as hydrogen source.