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Charge transfer and Fermi level shift in p -doped single-walled carbon nanotubes

2005; American Physical Society; Volume: 71; Issue: 20 Linguagem: Inglês

10.1103/physrevb.71.205423

1550-235X

Wei Zhou, J. Vavro, N. M. Nemes, J. E. Fischer, Ferenc Borondics, K. Kamarás, D. B. Tanner,

Mechanical and Optical Resonators

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 $(\ensuremath{\Delta}{E}_{F})$ induced by doping. We find $\ensuremath{\Delta}{E}_{F}\ensuremath{\approx}0.35\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $0.50\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ 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.