Direct observation of a widely tunable bandgap in bilayer graphene (original) (raw)

Nature volume 459, pages 820–823 (2009)Cite this article

Abstract

The electronic bandgap is an intrinsic property of semiconductors and insulators that largely determines their transport and optical properties. As such, it has a central role in modern device physics and technology and governs the operation of semiconductor devices such as p–n junctions, transistors, photodiodes and lasers1. A tunable bandgap would be highly desirable because it would allow great flexibility in design and optimization of such devices, in particular if it could be tuned by applying a variable external electric field. However, in conventional materials, the bandgap is fixed by their crystalline structure, preventing such bandgap control. Here we demonstrate the realization of a widely tunable electronic bandgap in electrically gated bilayer graphene. Using a dual-gate bilayer graphene field-effect transistor (FET)2 and infrared microspectroscopy3,4,5, we demonstrate a gate-controlled, continuously tunable bandgap of up to 250 meV. Our technique avoids uncontrolled chemical doping6,7,8 and provides direct evidence of a widely tunable bandgap—spanning a spectral range from zero to mid-infrared—that has eluded previous attempts2,[9](/articles/nature08105#ref-CR9 "Kuzmenko, A. B. et al. Infrared spectroscopy of electronic bands in bilayer graphene. Preprint at < http://arxiv.org/abs/0810.2400

              &gt; (2008)"). Combined with the remarkable electrical transport properties of such systems, this electrostatic bandgap control suggests novel nanoelectronic and nanophotonic device applications based on graphene.

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Acknowledgements

This work was supported by the Office of Basic Energy Sciences, US Department of Energy under contract DE-AC03-76SF0098 (Materials Science Division) and contract DE-AC02-05CH11231 (Advanced Light Source). F.W., Y.Z. and T.-T.T. acknowledge support from a Sloan fellowship, a Miller fellowship and a fellowship from the National Science Council of Taiwan, respectively.

Author information

Author notes

  1. Tsung-Ta Tang
    Present address: Present address: Department of Photonics and Institute of Electro-optical Engineering, National Chiao Tung University, Hsinchu, Taiwan 30010.,
  2. Yuanbo Zhang and Tsung-Ta Tang: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Physics, University of California at Berkeley,
    Yuanbo Zhang, Tsung-Ta Tang, Caglar Girit, Alex Zettl, Michael F. Crommie, Y. Ron Shen & Feng Wang
  2. Advanced Light Source Division, Lawrence Berkeley National Laboratory,
    Zhao Hao & Michael C. Martin
  3. Materials Science Division, Lawrence Berkeley National Laboratory,
    Alex Zettl, Michael F. Crommie, Y. Ron Shen & Feng Wang
  4. Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA,
    Zhao Hao

Authors

  1. Yuanbo Zhang
  2. Tsung-Ta Tang
  3. Caglar Girit
  4. Zhao Hao
  5. Michael C. Martin
  6. Alex Zettl
  7. Michael F. Crommie
  8. Y. Ron Shen
  9. Feng Wang

Corresponding author

Correspondence toFeng Wang.

Additional information

The authors declare no competing financial interests.

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Zhang, Y., Tang, TT., Girit, C. et al. Direct observation of a widely tunable bandgap in bilayer graphene.Nature 459, 820–823 (2009). https://doi.org/10.1038/nature08105

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Editorial Summary

Field-tunable bandgap in bilayer graphene

The electronic bandgap of a material refers to an energy region where electrons are not 'allowed' to reside because of quantum mechanical considerations related to the symmetries and atomic constituents of the underlying crystal structure. It is a fundamental property of semiconductors and insulators and determines their electrical and optical response, which is why it is a crucial consideration in modern device physics and technologies. Ideally, the bandgap would be tunable by electric fields, which would allow great flexibility in device design and functionality. Until now electrical tunability has proved elusive, but now Zhang et al. demonstrate such a tunable bandgap in a bilayer-graphene-based device, spanning a spectral range from zero to mid-infrared.