Conductivity of multiwall carbon nanotubes: Role of multiple shells and defects

We report on laterally resolved measurements of the current-induced gradient in the electrochemical potential of multiwall carbon nanotubes. Nanotubes with different classes of defects were studied at room temperature. The potential profile of the outermost shell along the tube was measured in a local as well as in a nonlocal geometry. The data have been used to separate the contributions of various shells to the total resistance of the whole tube. For this purpose, a classical resistivity model was used that describes the measured potential profiles well. Additionally, the influence of structural defects on the conductivity has been quantified. Particularly, defects such as an ending outermost shell, an intratube junction, and a plastically stretched tube with a kink were investigated.