Electron backscattering on single-wall carbon nanotubes\nobserved by scanning tunneling microscopy

Abstract

\n \nSingle-wall carbon nanotubes, seamless cylindrical molecules\nformed from a graphene sheet, are either conducting or semiconducting,\ndepending on the particular "wrapping vector” that defines the waist of\nthe tube. Scanning tunneling\nmicroscopy experiments have tested this idea by simultaneously\nmeasuring a tube's lattice structure and electronic properties. Here we\npresent a series of STM images of single-wall carbon nanotubes with a\nstrikingly rich set of superstructures. The observed patterns can be\nunderstood as due to interference between\npropagating electron waves that are reflected from defects on the tube\nwalls and ends, or as intrinsic to states propagating on semiconducting\ntubes. The measured broken symmetries can be used to directly probe\nelectronic backscattering on the tube and provide a key element in the\nunderstanding of low-energy electron transport on these structures.\n \n