calque

Workshops

Computational Studies of Defects in Nanoscale Carbon Materials

May 11, 2009 to May 13, 2009
Location : CECAM-HQ-EPFL, Lausanne, Switzerland
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Edge reconstructions and gold in-plane of graphene



Abstract

In applications for nanoscale materials and devices, it is often the atomic and electronic structure of boundaries and surfaces that is responsible for mechanical, electronic, and chemical properties. Also interactions of carbon nanostructures with metal atoms is interesting because of their fundamental relevance to many applications. This presentation combines two separate studies related to defects in graphene, the first concentrates on edge reconstructions in graphene [1] and the second on gold atom adsorption and diffusion in plane of graphene [2].

In the first study [1], we investigated planar reconstruction patterns at the zigzag and armchair edges of graphene with density-functional theory. We unexpectedly found that the zigzag edge is metastable and a planar reconstruction spontaneously takes place at room temperature. The reconstruction changes electronic structure and self-passivates the edge with respect to adsorption of atomic hydrogen from a molecular atmosphere. With help of recent TEAM-images [3], the existence of this reconstructed zigzag edge can be also seen experimentally.

In the second study [2], we investigated the bonding and diffusion of Au in graphene vacancies using density-functional theory. Energetics show that Au adsorbs preferably to double vacancies, steadily in-plane with graphene. All diffusion barriers for the complex of Au in double vacancy are above 4 eV, whereas the barriers for larger vacancies are below 2 eV. Our results support the main results of a recent experiment [4], but suggest that the observed diffusion mechanism is not thermally activated but radiation enhanced.



References

[1] P. Koskinen, S. Malola, and H. Häkkinen, Phys. Rev. Lett. 101, 115502 (2008)
[2] S. Malola, H. Häkkinen, and P. Koskinen, Appl. Phys. Lett. 94, 043106 (2009)
[3] C. Ö. Girit, J. C. Meyer, R. Erni, M. D. Rossell, C. Kisielowski, L. Yang, C.-H. Park, M. F. Crommie, M. L. Cohen, S. G. Louie, and A. Zettl, Science 323, 1705 (2009)
[4] Y. Gan, L. Sun, and F. Banhart, Small 4, 587 (2008)