Fibers of aligned single-walled carbon nanotubes: Polarized Raman spectroscopy

To probe the one-dimensional nature of single-wall carbon nanotubes (SWNTs) in bulk samples, we have devised a simple method for generating fibers of aligned SWNTs. We measured polarization-dependent Raman spectra on the oriented fibers. Contrary to what is expected from their theoretically assigned vibration-mode symmetries, all the Raman line intensities are observed to decrease in nearly equal amounts for the 647.1 nm laser excitation polarized perpendicular to the fiber axis versus that polarized parallel to the fiber axis. The effect is explained as a loss of resonance Raman scattering for the perpendicular polarization case.