Large intrinsic energy bandgaps in annealed nanotube-derived graphene nanoribbons


The usefulness of graphene for electronics has been limited because it does not have an energy bandgap. Although graphene nanoribbons have non-zero bandgaps, lithographic fabrication methods introduce defects that decouple the bandgap from electronic properties, compromising performance. Here we report direct measurements of a large intrinsic energy bandgap of 50 meV in nanoribbons (width, 100 nm) fabricated by high-temperature hydrogen-annealing of unzipped carbon nanotubes. The thermal energy required to promote a charge to the conduction band (the activation energy) is measured to be seven times greater than in lithographically defined nanoribbons, and is close to the width of the voltage range over which differential conductance is zero (the transport gap). This similarity suggests that the activation energy is in fact the intrinsic energy bandgap. High-resolution transmission electron and Raman microscopy, in combination with an absence of hopping conductance and stochastic charging effects, suggest a low defect density.

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Figure 1: Characterization of graphene nanoribbons.
Figure 2: Electronic characteristics of a graphene-nanoribbon FET.
Figure 3: Source–drain current versus backgate voltage.
Figure 4: Temperature dependence of minimum conductance around the charge neutrality point and activation energy.
Figure 5: Single-electron spectroscopy—half part of a Coulomb diamond measured at T = 1.5 K.


  1. 1

    Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science 306, 666–669 (2004).

    CAS  Article  Google Scholar 

  2. 2

    Geim, A. K. & Novoselov, K. S. The rise of graphene, Nature Mater. 6, 183–191 (2007).

    CAS  Article  Google Scholar 

  3. 3

    Zhao, Y. et al. Symmetry breaking of the zero energy Landau level in bilayer graphene. Phys. Rev. Lett. 104, 066801 (2010).

    CAS  Article  Google Scholar 

  4. 4

    Zhang, Y. et al. Direct observation of a widely tunable bandgap in bilayer graphene. Nature 459, 820–823 (2009).

    CAS  Article  Google Scholar 

  5. 5

    Craciun, M. F. et al. Trilayer graphene is a semimetal with a gate-tunable band overlap. Nature Nanotech. 4, 383–388 (2009).

    CAS  Article  Google Scholar 

  6. 6

    Han, M. Y. et al. Electron transport in disordered graphene nanoribbons. Phys. Rev. Lett. 104, 056801 (2010).

    Article  Google Scholar 

  7. 7

    Han, M. Y. et al. Energy band-gap engineering of graphene nanoribbons. Phys. Rev. Lett. 98, 206805 (2007).

    Article  Google Scholar 

  8. 8

    Stampfe, C. et al. Energy gaps in etched graphene nanoribbons. Phys. Rev. Lett. 102, 056403 (2009).

    Article  Google Scholar 

  9. 9

    Cresti, A. & Roche, S. Edge-disorder-dependent transport length scales in graphene nanoribbons: from Klein defects to the superlattice limit. Phys. Rev. B 79, 233404 (2009).

    Article  Google Scholar 

  10. 10

    Evaldsson, M. et al. Edge-disorder-induced Anderson localization and conduction gap in graphene nanoribbons. Phys. Rev. B 78, 161407(R) (2008).

    Article  Google Scholar 

  11. 11

    Mucciolo, E. R. et al. Conductance quantization and transport gaps in disordered graphene nanoribbons. Phys. Rev. B 79, 075407 (2009).

    Article  Google Scholar 

  12. 12

    Lherbier, A. et al. Transport length scales in disordered graphene-based materials: strong localization regimes and dimensionality effects. Phys. Rev. Lett. 100, 036803 (2008).

    Article  Google Scholar 

  13. 13

    Yang, L. et al. Quasiparticle energies and band gaps in graphene nanoribbons. Phys. Rev. Lett. 99, 186801 (2007).

    Article  Google Scholar 

  14. 14

    Son, Y-W., Cohen, M. L. & Louie, S. G. Energy gaps in graphene nanoribbons. Phys. Rev. Lett. 97, 216803 (2006).

    Article  Google Scholar 

  15. 15

    Son, Y-W., Cohen, M. L. & Louie, S. G. Half-metallic graphene nanoribbons. Nature 444, 347–349 (2006).

    CAS  Article  Google Scholar 

  16. 16

    Nakada, K., Fujita, M., Dresselhaus, G. & Dresselhaus, M. S. Edge state in graphene ribbons: nanometer size effect and edge shape dependence. Phys. Rev. B 54, 17954–17961 (1996).

    CAS  Article  Google Scholar 

  17. 17

    CastroNeto, H. et al. The electronic properties of graphene. Rev. Mod. Phys. 81, 109–163 (2009).

    CAS  Article  Google Scholar 

  18. 18

    Jiao, L. et al. Facile synthesis of high-quality graphene nanoribbons. Nature Nanotech. 5, 321–325 (2010).

    CAS  Article  Google Scholar 

  19. 19

    Li, X. et al. Chemically derived, ultrasmooth graphene nanoribbon semiconductors. Science 319, 1229–1232 (2008).

    CAS  Article  Google Scholar 

  20. 20

    Wang, X. et al. Room-temperature all-semiconducting sub-10-nm graphene nanoribbon field-effect transistors. Phys. Rev. Lett. 100, 206803 (2008).

    Article  Google Scholar 

  21. 21

    Kosynkin, D. V. et al. Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons. Nature 458, 872–877 (2009).

    CAS  Article  Google Scholar 

  22. 22

    Higginbotham, A. L. et al. Low-defect graphene oxide nanoribbons from multiwalled carbon nanotubes. ACS Nano 4, 2059–2069 (2010).

    CAS  Article  Google Scholar 

  23. 23

    Takesue, I. et al. Superconductivity in entirely end-bonded multiwalled carbon nanotubes. Phys. Rev. Lett. 96, 057001 (2006).

    CAS  Article  Google Scholar 

  24. 24

    Bail, J. et al. Graphene nanomesh. Nature Nanotech. 5, 190–194 (2010).

    Article  Google Scholar 

  25. 25

    Girit, C. O. et al. Graphene at the edge: stability and dynamics. Science 323, 1705–1708 (2009).

    CAS  Article  Google Scholar 

  26. 26

    Grabert, H. & Devoret, M. H. (eds) Single Charge Tunneling, NATO ASI Series B, Vol. 294 (Plenum, 1991).

    Google Scholar 

  27. 27

    Haruyama, J. et al. Coulomb blockade related to a localization effect in a single tunnel-junction carbon nanotubes system. Phys. Rev. B 63, 073406 (2001).

    Article  Google Scholar 

  28. 28

    Jia, X. M. et al. Controlled formation of sharp zigzag and armchair edges in graphitic nanoribbons. Science 323, 1701–1705 (2009).

    CAS  Article  Google Scholar 

  29. 29

    Niimi, Y. et al. Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surface near monoatomic step edges. Phys. Rev. B 73, 085421 (2006).

    Article  Google Scholar 

  30. 30

    Cervenka, J., Katsnelson, M. I. & Flipse, C. F. J. Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects. Nature Phys. 5, 840–844 (2009).

    CAS  Article  Google Scholar 

  31. 31

    Rangel, N. L., Sotelo, J. C. & Seminario, J. M. Mechanism of carbon nanotubes unzipping into graphene ribbons. J. Chem. Phys. 131, 031105 (2009).

    Article  Google Scholar 

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The authors thank S. Tarucha, M. Yamamoto, T. Otsuka, Y. Iye, S. Katsumoto, T. Osada, H. Fukuyama, T. Ando, A. Endo, Y. Hashimoto, N. Miyazaki, Y. Yagi, H. Kodama, A. Sawabe, X.M. Jia, M.S. Dresselhaus, M.H. Han, J. Kohno and P. Kim for technical support, fruitful discussions and encouragement. The work at Aoyama Gakuin was partly supported by a Grant-in-aid for Scientific Research and a High-Technology Research Center Project for private universities in MEXT. The work at Rice University was supported by the AFOSR (FA9550-09-1-0581), the Alliance for Nanohealth, the AFRL through the University Technology Corporation (09-S568-064-01-C1) and the Office of Naval Research Multidisciplinary Research Program of the University Research Initiative (MURI) program.

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J.H., J.M.T. and K.S conceived and designed the experiments. T.S., D.C.M., D.V.K., and K.H. performed the experiments. J.H. analysed the data. J.H. and J.M.T. co-wrote the paper.

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Correspondence to J. Haruyama or J. M. Tour.

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The authors declare no competing financial interests.

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Shimizu, T., Haruyama, J., Marcano, D. et al. Large intrinsic energy bandgaps in annealed nanotube-derived graphene nanoribbons. Nature Nanotech 6, 45–50 (2011).

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