Raman spectra of lithium doped single-walled 0.4 nm carbon nanotubes

Using the vapor phase adsorption method, we show that it is possible to intercalate lithium atoms into 0.4-nm diameter single-walled carbon nanotubes. The charge-transfer behavior is studied by resonant Raman spectra. With increasing doping concentration, the radial breathing mode of these tubes shifts to higher frequency by about 18 cm because the vibration perpendicular to the tube axis is depressed. The G band exhibits conventional softening and downshift behavior. By decomposing the G band by one Breit-WignerFano line shape and three Lorentzians, we found that the softening and downshift is due to the intensity competition between four components. The BWF component at 1558 cm couples with the electronic continuum and survives until the saturated doping stage.