Temperature Dependence of G− Mode in Raman Spectra of Metallic Single-Walled Carbon Nanotubes

The temperature evolution of G mode in the Raman spectra of surface grown single-walled carbon nanotubes (SWNTs) is investigated. It is revealed that the intensity of G− mode in Raman spectra varies with the measurement temperature. The intensity variation of the G− mode is synchronized to that of the radial breathing mode, which is sensitive to the resonance condition (). Such an intensity evolution is associated with the temperature-induced change of . That is, the intensity of G−, an indication of electron-phonon coupling in metallic SWNTs, can be greatly enhanced only when the laser energy well matches the transition energy of nanotubes (). In other words, the window for observing asymmetric and broad G− mode is very narrow. This work further confirms that the G− mode in the Raman spectrum mainly arises from metallic SWNTs, and caution should be paid when using the intensity ratio of G−/G