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 orie nted 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 polarize d perpendicular to the fiber axis versus that polarized parallel to the fib er axis. The effect is explained as a loss of resonance Raman scattering fo r the perpendicular polarization case. (C) 2000 American Institute of Physi cs. [S0021-8979(00)00517-X].