Observation of localized charge transport in isolated microscopic mats of single-wall carbon nanotubes

We have formulated a composite consisting of a low dielectric permittivity, low loss granular organic crystal, and 0.1% single-walled carbon nanotubes (SWNTs). The composite morphology was electrically isolated mats of SWNTs distributed on the surface of individual crystals having a typical particle size of 20 mu m. The real part of the composite permittivity (relative) was not significantly different from that of the matrix material (similar to 2.0), while the dielectric loss increased from 0.0035 to 0.3 at 2.45 GHz. We used Maxwell-Garnett mixing theory, which accounts for interfacial polarization, to calculate complex permittivity and conductivity of the SWNT mats. The results indicated weak electrical contact between SWNTs within the mats, implying that localized electron transport was the primary dielectric loss mechanism. (c) 2007 American Institute of Physics.