Efficient chemical vapor deposition (CVD) synthesis of super long (7 mm) aligned carbon nanotubes (CNTs) with highdensity is reported here. Activity of catalyst nanoparticles has been achieved for very long time periods (ca. 12 h) by optimization of experimental parameters. The relative levels of ethylene and water, as well as those of ethylene and H 2 , were found to be most important for achieving extended-time activity of the catalyst. Transmission electron microscope (TEM) images revealed that the nanotubes were mainly double-walled, but very few single-walled and multi-walled nanotubes were also present in the sample.

We have studied the resistance of a metal and carbon nanotube contact formed in a scanning electron microscope. This contact often has high resistive polymer-like amorphous carbon that is formed by electron beam-induced deposition from residual gas molecules. Results of this study revealed that the contact resistance comprises a tunneling resistance and an ohmic resistance. The current-induced Joule heating reduces the barrier for the tunneling resistance at a low current level and then the ohmic resistance at a high level. This variation is discussed in terms of compositional and structural changes of the amorphous carbon caused by Joule heating.

We have investigated the current-induced transformation from elastically buckled carbon nanotubes into plastically bent nanotubes with a large bending angle. For this study, C60-encapsulated single wall nanotubes were used, enabling the estimation of energy barriers in the process from the well known coalescence reactions. Increasing the current caused a sequential change: (a) coalescence of C60 molecules to form tube structures; (b) merging of the newly formed tubes with the original nanotube; (c) disappearance of buckling to form a plastic bend; and finally (d) sublimation of the nanotube. The order of the energy barriers for (a), (b), and (d) is consistent with the experimental results, which suggests that the observed structural change is caused by thermally activated reactions. The barrier for the disappearance of buckling to form the plastic bend is between 6.0 and 6.9 eV.

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