Temperature dependence of Raman scattering from single-walled carbon nanotubes: Undefined radial breathing mode peaks at high temperatures

We measured the Raman scatterings from various single-walled carbon nanotube (SWNT) samples over a wide temperature range (4-1000K). The G-band peaks showed a clear temperature dependence, namely, decrease in the Raman shift frequency and broadening of the peak width as temperature increases. The main G-band peak (G(+) peak) showed universal temperature dependence in Raman shift for the various SWNT samples and for the three excitation laser wavelengths (488.0, 514.5, and 632.8 nm), although the G-band features changed depending on the SWNT samples and excitation laser wavelengths owing to the resonance Raman effects. The Raman shift, peak width, and intensity of the radial breathing mode (RBM) peaks also exhibited temperature dependence. At high temperatures, undefined RBM peaks appeared, which could not be assigned to specific chiralities, and showed opposite temperature dependence in their intensities. The intensities of the RBM peaks are strongly enhanced by the resonance Raman effects, and the temperature may change the resonance Raman conditions.