Temperature effects in the Raman spectra of bundled single-wall carbon nanotubes

The Raman modes of single-walled carbon nanotubes (SWCNTs) exhibit negative temperature shift, which is reversible for the G band and partially irreversible for the radial breathing modes (RBMs). The softening of the RBMs is larger for larger diameter tubes, resulting in better separation of the constituent peaks and a residual softening after high temperature treatment (HTT). The dependence of the RBM residual softening on the treatment temperature demonstrates threshold-like behavior. The figure depicts the dependence of the residual softening of the RBM peaks on the treatment temperature.