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 rep...

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Bibliographic Details
Published in:	Nature nanotechnology Vol. 6; no. 1; pp. 45 - 50
Main Authors:	Haruyama, J, Tour, J. M, Shimizu, T, Marcano, D. C, Kosinkin, D. V, Hirose, K, Suenaga, K
Format:	Journal Article
Language:	English
Published:	London Nature Publishing Group UK 01-01-2011 Nature Publishing Group
Subjects:	639/925/350/2251 639/925/357/551 639/925/357/918/1052 Annealing Carbon Chemistry and Materials Science Conductance Electronics Electrons Energy Fabrication Graphene Graphite - chemistry High temperature Materials Science Microscopy Microscopy, Electron, Transmission Models, Theoretical Nanotechnology Nanotechnology - methods Nanotechnology and Microengineering Nanotubes, Carbon Physical properties Quantum dots Spectrum Analysis, Raman Thermal energy Japan
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Summary:	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. Graphene nanoribbons manufactured by annealing unzipped carbon nanotubes have been measured to have a large energy bandgap of ∼50 meV, even for widths of ∼100 nm.
ISSN:	1748-3387 1748-3395
DOI:	10.1038/nnano.2010.249