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Direct observation of a widely tunable bandgap in bilayer graphene

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. 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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Figure 1: Dual-gated bilayer graphene.
Figure 2: Bilayer energy gap opening at strong electrical gating.
Figure 3: Bilayer energy gap opening at weak electrical gating.
Figure 4: Electric-field dependence of tunable energy bandgap in graphene bilayer.

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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

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  1. Yuanbo Zhang
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Corresponding author

Correspondence to Feng Wang.

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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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