Figure 1

Raman spectra of two individual single-walled nanotubes obtained with 473-nm excitation. The spectra are displayed in a log-linear plot. The upper spectrum is displaced for clarity ($\times 10$). Most peaks (indicated by the dashed lines) in the spectra can be assigned to different combinations of the zone-center $G$ mode and even numbers of the zone-boundary $D$ modes (see Table ). There are a few weaker features common to all nanotubes (denoted by *) and a few others specific to individual nanotubes (denoted by ▽).Reuse & Permissions

Figure 2

Comparison of the Raman and Rayleigh excitation spectra for an individual SWNT to illustrate the effect of resonant enhancement in the Raman process. (a) Raman spectrum of the SWNT for laser excitation at a wavelength of 473 nm. The Raman modes are labeled in accordance with Table . (b) Raman spectrum for laser excitation at 532 nm. (c) Excitation spectrum for Rayleigh (elastic) light scattering from the same nanotube. The two peaks at 650 and 784 nm in the Rayleigh spectrum arise from the $E_{44}$ and $E_{33}$ excitonic transitions of a 2.2 nm semiconducting SWNT [17]. Raman modes with outgoing wavelengths close to these two transitions [peaks 7 and 11 in (a) and peaks 3 and 7 in (b)] exhibit a pronounced resonant enhancement.Reuse & Permissions

Figure 3

Comparison of relative strengths of multiphonon Raman modes observed in graphite [21] (black squares) and in several individual SWNTs (other symbols). The mode intensities for each spectrum are normalized against their respective $G$-mode strength. The multiphonon Raman signals from different nanotubes vary, but on the average are much stronger than the corresponding peaks for graphite.Reuse & Permissions