Direct observation of a widely tunable bandgap in bilayer graphene

Yuanbo Zhang, Tsung-Ta Tang, Caglar Girit, Zhao Hao, Michael C. Martin, Alex Zettl, Michael F. Crommie, Y. Ron Shen, Feng Wang

Nature, 459, 820-823 (Jun 2009). 1.4.4

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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 lasers. 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) and infrared microspectroscopy, we demonstrate a gate-controlled, continuously tunable bandgap of up to 250 meV. Our technique avoids uncontrolled chemical doping and provides direct evidence of a widely tunable bandgap -- spanning a spectral range from zero to mid-infrared -- that has eluded previous attempts. 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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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.

BibTex references

@Article\{ZTGHMZCSW09,
  author       = "Zhang, Yuanbo and Tang, Tsung-Ta and Girit, Caglar and Hao, Zhao and Martin, Michael C. and Zettl, Alex and Crommie, Michael F. and Shen, Y. Ron and Wang, Feng",
  title        = "Direct observation of a widely tunable bandgap in bilayer graphene",
  journal      = "Nature",
  volume       = "459",
  pages        = "820-823",
  month        = "Jun",
  year         = "2009",
  note         = "1.4.4",
  keywords     = "electrically gated bandgap bilayer graphene dual-gate gate-controlled, transport, nanophotonic",
  url          = "http://infrared.als.lbl.gov/Publications/2009/ZTGHMZCSW09"
}

Other ALS IR beamlines publications by these authors

» Yuanbo Zhang
» Tsung-Ta Tang
» Caglar Girit
» Zhao Hao
» Michael C. Martin
» Alex Zettl
» Michael F. Crommie
» Y. Ron Shen
» Feng Wang

Direct observation of a widely tunable bandgap in bilayer graphene

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See also

Field-tunable bandgap in bilayer graphene

BibTex references

Other ALS IR beamlines publications by these authors