MSA  Vol.5 No.1 , January 2014
Electronic Properties of Nanopore Edges of Ferromagnetic Graphene Nanomeshes at High Carrier Densities under Ionic-Liquid Gating

Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with honeycomb-like arrays of low-defect hexagonal nanopores by observing room-temperature ferromagnetism and spin-based phenomena arising from the zigzag-pore edges. Here, we apply extremely high electric fields to the ferromagnetic (FM) GNMs using an ionic-liquid gate. A large on/off-ratio for hole current is observed for even small applied ionic-liquid gate voltages (Vig). Observations of the magnetoresistance behavior reveal high carrier densities of ~1013 cm-2 at large Vig values. We find a maximum conductance peak in the high -Vig region and its separation into two peaks upon applying a side-gate (in-plane external) voltage (Vex). It is discussed that localized edge-π band with excess-density electrons induced by Vig and its spin splitting for majority and minority of spins by Vex (half-metallicity model) lead to these phenomena. The results must realize critical-element-free novel spintronic devices.

Cite this paper
T. Hashimoto, S. Kamikawa, Y. Yagi and J. Haruyama, "Electronic Properties of Nanopore Edges of Ferromagnetic Graphene Nanomeshes at High Carrier Densities under Ionic-Liquid Gating," Materials Sciences and Applications, Vol. 5 No. 1, 2014, pp. 1-9. doi: 10.4236/msa.2014.51001.
[1]   K. Nakada, M. Fujita, G. Dresselhaus and M. S. Dresselhaus, “Edge State in Graphene Ribbons: Nanometer Size Effect and Edge Shape Depend,” Physical Review B, Vol. 54, No. 24, 1996, pp. 17954-17961.

[2]   M. Fujita, K. Wakabayashi, K. Nakada and K. Kusakabe, “Peculiar Localized State at Zigzag Graphite Edge,” Journal of the Physical Society of Japan, Vol. 65, 1996, pp. 1920-1923.

[3]   H. Lee, Y. Son, N. Park, S. Han and J. Yu, “Magnetic Ordering at the Edges of Graphitic Fragments: Magnetic Tail Interactions between the Edge-Localized States,” Physical Review B, Vol. 72, No. 17, 2005, Article ID: 174431.

[4]   R. G. A. Veiga, R. H. Miwa and G. P. Srivastava, “Quenching of Local Magnetic Moment in Oxygen Adsorbed Graphene Nanoribbons,” The Journal of Chemical Physics, Vol. 128, 2008, Article ID: 201101.

[5]   T. Enoki and K Takai, “The Edge State of Nanographene and the Magnetism of the Edge-State Spins,” Solid State Communications, Vol. 149, No. 27-28, 2009, pp. 1144-1150.

[6]   Y. W. Son, M. L. Cohen and S. G. Louie, “Half-Metallic Graphene Nanoribbons,” Nature, Vol. 444, 2006, pp. 347-349.

[7]   L. Yang, C. Park, Y. Son, M. L. Cohen and S. G. Louie, “Quasiparticle Energies and Band Gaps in Graphene Nanoribbons,” Physical Review Letters, Vol. 99, No. 18, 2007, Article ID: 186801.

[8]   T. Shimizu, J. Haruyama, D. C. Marcano, D. V. Kosinkin, J. M. Tour, K. Hirose and K. Suenaga, “Large Intrinsic Energy Bandgaps in Annealed Nanotube-Derived Graphene Nanoribbons,” Nature Nanotechnology, Vol. 6, 2011, pp. 45-50.

[9]   X. Wang, Y. Ouyang, X. Li, H. Wang, J. Guo and H. Dai, “Room-Temperature All-Semiconducting Sub-10-nm Graphene Nanoribbon Field-Effect Transistors,” Physical Review Letters, Vol. 100, No. 20, 2008, Article ID: 206803.

[10]   K. Tada, T. Hashimoto, J. Haruyama, H. Yang and M. Chshiev, “Spontaneous Spin Polarization and Spin Pumping Effect on Edges of Graphene Antidot Lattices,” Solid State Physics, Vol. 249, No. 12, 2012, pp. 2491-2496.

[11]   I. Takesue, J. Haruyama, N. Kobayashi, S. Chiashi, S. Maruyama, T. Sugai and H. Shinohara, “Superconductivity in Entirely End-Bonded Multiwalled Carbon Nanotubes,” Physical Review Letters, Vol. 96, No. 5, 2006, Article ID: 057001.

[12]   X. Jia, M. Hofmann, V. Meunier, B. G. Sumpter, J. Campos-Delgado, J. M. Romo-Herrera, H. Son, Y. Hsieh, A. Reina, J. Kong and M. S. Dresselhaus, “Controlled Formation of Sharp Zigzag and Armchair Edges in Graphitic Nanoribbons,” Science, Vol. 323, No. 5922, 2009, pp. 1701-1705.

[13]   C. O. Girit, J. C. Meyer, R. Erni, M. D. Rossell, C. Kisielowski, L. Yang, C. Park, M. F. Crommie, M. L. Cohen and S. G. Louie, “Graphene at the Edge: Stability and Dynamics,” Science, Vol. 323, No. 5922, 2009, pp. 1705-1708.

[14]   Y. M. You, Z. H. Ni, T. Yu and Z. X. Shen, “Edge Chirality Determination of Graphene by Raman Spectroscopy,” Applied Physics Letters, Vol. 93, No. 16, 2008, Article ID: 163112.

[15]   B. Krauss, P. Nemes-Incze, V. Skakalova, L. P. Biro, K. von Klitzing and J. H. Smet, “Raman Scattering at Pure Graphene Zigzag Edges,” Nano Letters, Vol. 10, No. 11, 2010, pp. 4544-4548.

[16]   D. K. Efetov and P. Kim, “Controlling Electron-Phonon Interactions in Graphene at Ultrahigh Carrier Densities,” Physical Review Letters, Vol. 105, No. 25, 2010, Article ID: 256805.

[17]   D. K. Efetov, P. Maher, S. Glinskis and P. Kim, “Multiband Transport in Bilayer Graphene at High Carrier Densities,” Physical Review B, Vol. 84, No. 16, 2011, Article ID: 161412(R).

[18]   A. Das, A. K. Geim, et al., “Monitoring Dopants by Raman Scattering in an Electrochemically Top-Gated Graphene Transistor,” Nature Nanotechnology, Vol. 3, 2008, p. 210.

[19]   M. Panzer, et al., “Photo-Embossed Surface Relief Structures with an Increased Aspect Ratios by Addition of a Reversible Addition—Fragmentation Chain Transfer Agent,” Advanced Materials, Vol. 20, No. 16, 2008, p. 3117.

[20]   K. F. Mac, et al., “Observation of an Electric-Field-Induced Band Gap in Bilayer Graphene by Infrared Spectroscopy,” Physical Review Letters, Vol. 102, No. 25, 2009, Article ID: 256405.

[21]   A. H. R. Pasler, “Interlayer Interactions in Graphite and Carbon Nanotubes,” Chemical Physics, Vol. 1, No. 18, 1999, p. 4459.

[22]   M. Otani, M. Koshino, Y. Takagi and S. Okada, “Intrinsic Magnetic Moment on (0001) Surfaces of Rhombohedral Graphitee,” Physical Review B, Vol. 81, No. 16, 2010, Article ID: 161403 (R).

[23]   M. Otani, Y. Takagi, M. Koshino and S. Okada, “Phase Control of Magnetic State of Graphite Thin Films by Electric Field,” Appl. Phys. Lett., Vol. 96, No. 24, 2010, pp. 242504.

[24]   S. Murakami, N. Nagaosa and S. Zhang, “Dissipationless Quantum Spin Current at Room Temperature,” Science, Vol. 301, No. 5638, 2003, pp. 1348-1351.

[25]   C. L. Kane and E. J. Mele, “Quantum Spin Hall Effect in Graphene,” Physical Review Letters, Vol. 95, No. 22, 2005, pp. 226801-226804.

[26]   M. J. Schmidt and D. Loss, “Edge States and Enhanced Spin-Orbit Interaction at Graphene/Graphane Interfaces,” Physical Review B, Vol. 81, No. 16, 2010, Article ID: 165439.

[27]   D. A. Abanin, S. V. Morozov, L. A. Ponomarenko, R. V. Gorbachev, A. S. Mayorov, M. I. Katsnelson, K. Watanabe, T. Taniguchi, K. S. Novoselov and L. S. Levitov, “Giant Nonlocality near the Dirac Point in Graphene,” Science, Vol. 332, No. 6027, 2011, pp. 328-330.

[28]   T. Shimizu, J. Nakamura, K. Tada, Y. Yagi and J. Haruyama, “Magnetoresistance Oscillations Arising from Edge-Localized Electrons in Low-Defect Graphene Antidot-Lattices,” Applied Physics Letters, Vol. 100, No. 2, 2012, Article ID: 023104.

[29]   J. Bai, X. Zhong, S. Jiang, Y. Huang and X. Duan, “Graphene Nanomesh,” Nature Nanotechnology, Vol. 5, 2010, pp. 190-194.

[30]   H. Grabert and M. H. Devoret, “Single Charge Tunneling,” NATO ASI Series B, Vol. 294, Plenum, New York, 1991.

[31]   J. Haruyama I. Takesue, T. Hasegawa and Y. Sato, “Coulomb Blockade Related to a Localization Effect in a Single Tunnel-Junction/Carbon-Nanotube System,” Physical Review B, Vol. 63, No. 7, 2001, Article ID: 073406.