Wednesday June 29, 2005
Thursday June 30, 2005

"Near-field Raman Scattering "
Mr. Bradley Deutsch
University of Rochester

Neil Anderson, Brad Deutsch, Lukas Novotny We use tip-enhanced spectroscopy to study the spatial variation of phonon modes along single-walled carbon nanotubes (SWNTs) produced by two distinct processes, namely: arc-discharge and chemical vapor deposition (CVD). Our technique relies on the enhanced field of a laser-irradiated gold tip (dia. ≈ 25nm). Using this confined field as a nanoscale light source we produce near-field Raman images of SWNTs with high spatial resolution. We address many different SWNT structures, assigned from RBM frequencies, and map the spatial variation of the main 1st and 2nd order Raman modes. In the case of arc-discharge nanotubes we observe that both RBM and intermediate frequency modes (IFMs) are highly localized over length scales of (≈ 20 – 60nm). In studying SWNTs produced by CVD we observe a uniform spatial distribution of the RBM. However, our results show that for many such nanotubes both IFM and disorder-induced (D-band) Raman scattering are localized at the same location along the nanotube.