Theoretical STM signatures and transport properties of native defects in carbon nanotubes

We have investigated theoretically the STM images and conductance signatures of defective carbon nanotubes. The defects considered are those that form on nanotubes under tension, both in the absence and presence of additional carbon atoms. The most prominent features observed in the STM images are a set of bright rings, whose positions correlate with the location of the pentagons within the defect. These features are useful, as they enable the ready identification of many of the defects. By contrast, most of the defects have only a relatively modest effect on the transport properties of the nanotubes. While there is a general decrease in the conductance of the nanotube due to scattering effects, there appears to be no unique feature that can be associated with any of the defects investigated. This unfortunately precludes the use of transport measurements as a means of defect identification. The STM images and conductances of nanotube heterojunctions, as well as tubes under different bias voltages, have also been explored.