Affiliation:
1. Department of Chemistry and Chemical Biology,
2. Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Abstract
Metallic single-walled carbon nanotubes have been proposed to be good one-dimensional conductors. However, the finite curvature of the graphene sheet that forms the nanotubes and the broken symmetry due to the local environment may modify their electronic properties. We used low-temperature atomically resolved scanning tunneling microscopy to investigate zigzag and armchair nanotubes, both thought to be metallic. “Metallic” zigzag nanotubes were found to have energy gaps with magnitudes that depend inversely on the square of the tube radius, whereas isolated armchair tubes do not have energy gaps. Additionally, armchair nanotubes packed in bundles have pseudogaps, which exhibit an inverse dependence on tube radius. These observed energy gaps suggest that most “metallic” single-walled nanotubes are not true metals, and they have implications for our understanding of the electronic properties and potential applications of carbon nanotubes.
Publisher
American Association for the Advancement of Science (AAAS)
Reference25 articles.
1. A SWNT can be viewed as a cylinder formed by rolling up a strip cut from an infinite graphene sheet. The geometric structure of SWNTs is represented by an index ( n m ) which corresponds to the roll-up vector C h = n a 1 + m a 2 where a 1 and a 2 are the unit vectors of the graphene sheet [M. S. Dresselhaus G. Dresselhaus P. C. Ekund Science of Fullerenes and Carbon Nanotubes (Academic Press San Diego CA 1996)].
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5. Hybridization effects and metallicity in small radius carbon nanotubes
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