Abstract
Interactions of graphene with 6H-SiC {0001} surfaces are numerically investigated from first principles. In order to describe the bulk structure and its 6 bilayer thick surfaces correctly, bare and dipole-corrected atomic relaxations are considered. The obtained lattice parameters and bulk modulus are in good agreement with experimental values. The calculated indirect band gap width of 2.10 eV is smaller than the experimental value due to the nature of the computational method. Geometrical optimization of the surfaces, where dipole correction is applied, reveals that the first two bilayers displace significantly, where the relaxations of the very top bilayer is more pronounced. Band structures of the {0001} surfaces possess two flat bands around the Fermi level due to unsaturated bonds on opposite faces. When one layer of C atoms are introduced on the Si-terminated surface, it behaves as a tightly-bound buffer layer. This is also the case for the C-terminated surface when van der Waals interactions are taken into account. In contrast, disregarding these interactions yields free-standing graphene like behavior for the first C overlayer. On both surfaces, the second C overlayer is free-standing where the corresponding band structures incorporate Dirac-cone like features.
Highlights
GRAPHENE, monolayer of graphite, was first obtained in 2004 by mechanical exfoliation from graphite [1]
Epitaxial growth on substrates such as silicon carbide (SiC) with 8% lattice mismatch [8] and boron nitride (BN) with 2% lattice mismatch [9] are preferred for large-scale crystal quality growth of graphene
Density-functional theory calculations of graphene on 6H silicon carbide {0001} surfaces reveal that the free-standing graphene behavior is observed starting from the second carbon overlayer on either surface
Summary
GRAPHENE, monolayer of graphite, was first obtained in 2004 by mechanical exfoliation from graphite [1]. Since it has been extensively studied both theoretically and experimentally. Among the most common methods for obtaining few-layer graphene are mechanical exfoliation from graphite [1], arc discharge [6] and intercalation of graphite by active elements https://orcid.org/0000-0002-7686-0045. Epitaxial graphene growth can be achieved on metallic substrates such as nickel (Ni), cobalt (Co), copper (Cu), rubidium (Ru) and platinum (Pt) [10,11,12,13,14]. {0001} surfaces of hexagonal 4H-SiC [15,16,17] or 6H-SiC [18, 19] are preferred for high-quality graphene growth
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