Charge transfer and Fermi level shift in p-doped single-walled carbon nanotubes -: art. no. 205423

The electronic properties of p-doped single-walled carbon nanotube (SWNT) bulk samples were studied by temperature-dependent resistivity and thermopower, optical reflectivity, and Raman spectroscopy. These all give consistent results for the Fermi level downshift (Delta E(F)) induced by doping. We find Delta E(F) approximate to 0.35 eV and 0.50 eV for concentrated nitric and sulfuric acid doping respectively. With these values, the evolution of Raman spectra can be explained by variations in the resonance condition as E(F) moves down into the valence band. Furthermore, we find no evidence for diameter-selective doping, nor any distinction between doping responses of metallic and semiconducting tubes.