Near-static dielectric polarization of individual carbon nanotubes.

Low-frequency dielectric responses of carbon nanotubes are important for their manipulation, separation, and electronic applications. Here we report the first experimental measurement of near-dc polarization of individual carbon nanotubes by using modified scanning force microscopy techniques. The transverse polarizability of carbon nanotubes is equivalent to solid cylindrical media with a dielectric constant of about 10, irrespective of tube diameter and chirality. The longitudinal polarization is also observed and used to distinguish metallic from semiconducting nanotubes.