Conductivity and atomic structure of isolated multiwalled carbon nanotubes

We report associated high-resolution transmission electron microscopy (HRTEM) and transport measurements on a series of isolated multiwalled carbon nanotubes. HRTEM observations, by revealing relevant structural features of the tubes, shed some light on the variety of observed transport behaviors, from semiconducting to quasi-metallic type. Non-Ohmic behavior is observed for certain samples which exhibit "bamboo-like" structural defects. The resistance of the most conducting sample exhibits a pronounced maximum at 0.6 K and strong positive magnetoresistance.