|AVS 57th International Symposium & Exhibition|
|Graphene Focus Topic||Tuesday Sessions|
|Session:||Graphene Focus Topic Poster Session|
|Presenter:||Y. Fujii, The University of Electro-Communications (UEC-Tokyo), Japan|
|Authors:||Y. Fujii, The University of Electro-Communications (UEC-Tokyo), Japan
J. Nakamura, The University of Electro-Communications (UEC-Tokyo), Japan
|Correspondent:||Click to Email|
Oxidation and reduction are the basic and most important processes for the carbon-based materials as initial processes for producing very thin graphitic materials composed of a single or several graphene layers . Recently, Kosynkin et al. have reported that the graphene nano-ribbons (GNRs) can be produced using an oxidative process, and the edges of these GNRs are functionalized by carboxylic acids even after the reduction treatment . On the other hand, it has been well-known that a certain type of GNR with zigzag edges exhibits the so-called flat-band magnetism, which stems from the localized states at the edges [3,4]. In this study, we reveal the electronic and magnetic properties of zigzag GNRs functionalized by carboxyl groups using the first-principles total-energy calculations within the spin density functional theory.
The zigzag GNRs employed in this study have widths from N=2 to N=8. We have found that the ground state of the GNR with the zigzag edges functionalized by the carboxyl groups is ferromagnetic, if N is even. For the GNR with N=4, the ferromagnetic state is more stable by 17 meV per unit cell than the anti-ferromagnetic one. However, if N is odd, the ground state of the functionalized GNR becomes the anti-ferromagnetic: e.g., for N=3, the anti-ferromagnetic state is more stable by 12 meV per unit cell than the ferromagnetic one. We have also investigated the energy dispersions of the GNRs. In the anti-ferromagnetic states, the energy bands for both spins are degenerate, and their dispersions near the Fermi level are nearly-flat at the edge of the Brillouin zone, while for the ferromagnetic states, the up-spin and down-spin bands split from each other. The spin density for the ferromagnetic states is localized near the GNR edges. Thus, the onset of the finite magnetic moment of the functionalized GNR is due to the so-called flat-band magnetism.
 S. Horiuchi et al., Appl. Phys. Lett. 84, 2403 (2004)
 D. V. Kosynkin et al., Nature lett. 458, 872 (2009)
 M. Fujita et al., J. Phys. Soc. Jpn. 65, 1920 (1996) J. Nakamura, T. Nitta, and A. Natori, Phus. Rev. B, 72, 205429 (2005)