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Ab initio study of graphene on SiC
Alexander Mattausch1, Oleg Pankratov
1Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstrasse 7, 91058 Erlangen, Germany. Alexander.Mattausch@physik.uni-erlangen.de
Physical Review Letters
|October 13, 2007
Summary
The second carbon layer on silicon carbide (SiC) surfaces exhibits weak bonding, revealing the freestanding graphene electronic spectrum. The first carbon layer covalently bonds to SiC, differing from prior assumptions.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Surface Science
Background:
- Graphene on silicon carbide (SiC) is crucial for electronic applications.
- Previous studies assumed the first graphene layer dictated electronic properties.
Purpose of the Study:
- To investigate the electronic properties of single and double graphene layers on Si- and C-terminated 6H-SiC surfaces.
- To clarify the bonding mechanisms and their impact on graphene's electronic spectrum.
Main Methods:
- Density-functional theory (DFT) calculations were employed.
- Analysis of single and double graphene layers on specific SiC surface terminations.
Main Results:
- The first carbon layer covalently bonds to the SiC substrate, not producing the graphene spectrum.
- The second carbon layer shows weak van der Waals bonding, responsible for the observed graphene-type electronic spectrum.
- Si-terminated substrates result in a metallic interface.
- C-terminated substrates yield semiconducting (single layer) or semimetallic (double layer) interfaces.
Conclusions:
- The second graphene layer is key to the experimentally observed electronic spectrum on SiC.
- Interface electronic properties are highly dependent on the SiC termination and graphene coverage.
