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

We have investigated theoretically the STM images and conductance signature s 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 pe ntagons within the defect. These features are useful, as they enable the re ady identification of many of the defects. By contrast, most of the defects have only a relatively modest effect on the transport properties of the na notubes. While there is a general decrease in the conductance of the nanotu be due to scattering effects, there appears to be no unique feature that ca n be associated with any of the defects investigated. This unfortunately pr ecludes the use of transport measurements as a means of defect identificati on. The STM images and conductances of nanotube heterojunctions, as well as tubes under different bias voltages, have also been explored.