Temperature Dependence of Raman Scattering from Single-walled Carbon Nanotubes -Undefined Radial Breathing Mode Peaks at High Temperatures-

We measured Raman scatterings from various single-walled carbon nanotube (SWNT) samples over a wide temperature range (4-1000 K). The G-band peaks showed clear temperature dependence, namely decrement 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 SWNT samples and excitation laser wavelengths owing to resonance Raman effects. The Raman shift, peak width, and intensity of the RBM (radial breathing mode) 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. Intensities of RBM peaks are strongly enhanced by resonance Raman effects, and the temperature may change the resonance Raman conditions.