A Raman Study of Potassium-Doped Double- wall Carbon Nanotubes

We report on studies of the n-type doping dependence of the Raman response of double-wall carbon nanotubes (DWCNT). The G-line is found to be shifting upon doping. The direction of the shift depends on if the exciting laser light is in resonance with mainly inner or outer tubes. The RBM response upon doping shows that a charge transfer from the dopant happens predominantly to the outer tubes at low doping. Charge transfer to the inner tubes occurs at higher doping levels. Charge transfer to the inner component is also shown to be starting earlier to the inner tube in DWCNT than to C60 in peapods.