Structure and electronic states of a graphene double vacancy with an embedded Si dopant

Reed Nieman, Adelia J. A. Aquino, T.P. Hardcastle, Jani Kotakoski, Toma Susi, Hans Lischka

Silicon represents a common intrinsic impurity in graphene, bonding to either three or four carbon neighbors, respectively, in a single or double carbon vacancy. We investigate the effect of the latter defect (Si-C

4) on the structural and electronic properties of graphene using density functional theory. Calculations based both on molecular models and with periodic boundary conditions have been performed. The two-carbon vacancy was constructed from pyrene (pyrene-2C) which was then expanded to circumpyrene-2C. The structural characterization of these cases revealed that the ground state is slightly non-planar, with the bonding carbons displaced from the plane by up to ±0.2 Å. This non-planar structure was confirmed by embedding the defect into a 10 × 8 supercell of graphene, resulting in 0.22 eV lower energy than the previously considered planar structure. Natural bond orbital analysis showed sp

3 hybridization at the silicon atom for the non-planar structure and sp

2d hybridization for the planar structure. Atomically resolved electron energy loss spectroscopy and corresponding spectrum simulations provide a mixed picture: a flat structure provides a slightly better overall spectrum match, but a small observed pre-peak is only present in the corrugated simulation. Considering the small energy barrier between the two equivalent corrugated conformations, both structures could plausibly exist as a superposition over the experimental time scale of seconds.

Physics of Nanostructured Materials
External organisation(s)
Texas Tech University, Tianjin University, SuperSTEM Laboratory, University of Leeds
Journal of Chemical Physics
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
104017 Physical chemistry, 103009 Solid state physics
ASJC Scopus subject areas
Physics and Astronomy(all), Physical and Theoretical Chemistry
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