Europhys. Lett, 47 (5), pp. 601-607 (1999)
Electron backscattering on single-wall carbon nanotubes observed by scanning tunneling microscopy
D. J. Bergeron, M. Freitag, C. L. Kane
E. J. Mele and A. T. Johnson
Department of Physics and Astronomy,
University of Pennsylvania
Philadelphia, Pennsylvania 19104, USA
(received 23 March 1999; accepted in final form 5 July 1999)
PACS. 72.80Rj - Fullerenes and related materials.
PACS. 73.40Gk - Tunneling.
PACS. 61.16Ch - Scanning probe microscopy: scanning tunneling, atomic force, scanning optical, magnetic force, etc.
Single-wall carbon nanotubes, seamless cylindrical molecules formed from a graphene sheet, are either conducting or semiconducting, depending on the particular "wrapping vector'' that defines the waist of the tube. Scanning tunneling microscopy experiments have tested this idea by simultaneously measuring a tube's lattice structure and electronic properties. Here we present a series of STM images of single-wall carbon nanotubes with a strikingly rich set of superstructures. The observed patterns can be understood as due to interference between propagating electron waves that are reflected from defects on the tube walls and ends, or as intrinsic to states propagating on semiconducting tubes. The measured broken symmetries can be used to directly probe electronic backscattering on the tube and provide a key element in the understanding of low-energy electron transport on these structures.
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