Optical Determination of Gate--Tunable Bandgap in Bilayer Graphene

Journal Article · Tue Aug 11 04:00:00 EDT 2009 · Nature

DOI:https://doi.org/10.1038/nature08105· OSTI ID:974550

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

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.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Advanced Light Source Division; Earth Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 974550
• Report Number(s): LBNL-2786E
• Journal Information: Nature, Journal Name: Nature
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
77 NANOSCIENCE AND NANOTECHNOLOGY
DESIGN
ELECTRIC FIELDS
ELECTROSTATICS
FIELD EFFECT TRANSISTORS
FLEXIBILITY
LASERS
OPTICAL PROPERTIES
OPTIMIZATION
P-N JUNCTIONS
PHOTODIODES
PHYSICS
SEMICONDUCTOR DEVICES
TRANSISTORS
TRANSPORT
electrically gated bandgap bilayer graphene dual-gate gate-controlled
transport
nanophotonic