Electronic mean free path in as-produced and purified single-wall carbon   nanotubes
  The effect of purification on room temperature electronic transport properties of single-wall carbon nanotubes (SWNT) was studied by submerging samples into liquid mercury. The conductance plots of purified SWNTs showed plateaus, indicating weak dependence of the electrical resistance on the length of the tube connecting the electrodes, providing evidence of quasi-ballistic conduction in SWNTs. The electronic mean free path of the purified SWNTs reached a few microns, which is longer than that of the as-produced SWNTs, and which is consistent with the calculation based on the scattering by acoustic phonons. 
H.Kajiura, A.Nandyala, U.C.Coskun, A.Bezryadin, M.Shiraishi, M.Ata