Invited Paper GR+AS+TF+MI-ThA6
Imperfect Graphene: Point Defects, Edges, Dislocations and Grain Boundaries

Thursday, October 21, 2010, 3:40 pm, Room Brazos

In two dimensions, properties of materials can be heavily affected by defects. In this talk, I will review our recent efforts directed towards understanding various types of structural irregularities in graphene.

Firstly, I will present the results of theoretical studies of the magnetism induced by point defects and edges in graphene and graphite. We show that in graphene single-atom defects such as vacancies and hydrogen chemisorption induce the spin-polarized defect states [1, 2]. The coupling between the magnetic moments is either ferromagnetic or antiferromagnetic, depending on whether the defects correspond to the same or to different sublattices of the graphene lattice, respectively. These results are able to clarify some experimental observations of high-temperature ferromagnetism in proton-irradiated graphite. Similarly, zigzag edges of graphene are predicted to induce spin-polarized edge states which can serve as a basis for novel spintronic devices. We address the question of the spin correlation length at finite temperatures in this one-dimensional magnetic system and establish the limitations of the proposed spintronic devices [3].

Then, I will talk about our latest results on dislocations and grain boundaries in graphene [4], topological defects which are still not well understood despites the growing number of experimental observations. We introduce a general approach for constructing dislocations in graphene characterized by arbitrary Burgers vectors as well as grain boundaries, covering the whole range of possible misorientation angles. By using ab initio calculations we investigate thermodynamic, electronic and transport properties of grain boundaries, finding energetically favorable large-angle symmetric configurations, strong tendency towards out-of-plane deformation in the small-angle regimes, pronounced effects on the electronic structure, and two distinct behaviors in the electronic transport [5] - either perfect reflection or high transparency for low-energy charge carriers depending on the grain boundary structure. Our results show that dislocations and grain boundaries are important intrinsic defects in graphene which may be used for engineering graphene-based functional devices.

[1] O. V. Yazyev and L. Helm, Phys. Rev. B 75, 125408 (2007).

[2] O. V. Yazyev, Phys. Rev. Lett. 101, 037203 (2008).

[3] O. V. Yazyev and M. I. Katsnelson, Phys. Rev. Lett. 100, 047209 (2008).

[4] O. V. Yazyev and S. G. Louie, arXiv:1004.2031 (2010).

[5] O. V. Yazyev and S. G. Louie, submitted.