Absence of Broad G$^{-}$ Feature in Resonant Raman Spectra of Armchair Carbon Nanotubes

ORAL

Abstract

Unlike the radial breathing mode in carbon nanotubes (CNTs), the G-band Raman feature does not display a strong frequency dependence on nanotube structure. The appearance of a broad G$^ {-}$ peak in CNT Raman spectra has been attributed to numerous phenomena including the presence of metallic nanotubes, although a consensus has yet to be achieved amongst researchers. Here, we present resonant Raman measurements on macroscopic ensembles enriched in armchair CNTs produced by density gradient ultracentrifugation. Our G-band data clearly show that the broad, lower-frequency G$^{-}$ mode is absent for armchair structures, in contrast with recent theoretical and experimental results, and only occurs with resonance of non- armchair metals. This forms a generalized correlation between G-band lineshape and nanotube structure due to the sampling of a large number of nanotubes of several armchair species.

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Authors

  • E.H. Haroz

    • Department of Electrical \& Computer Engineering, Rice University
    • Rice Univ.

  • William Rice

    • Department of Electrical \& Computer Engineering, Rice University
    • Dept. of Electrical and Computer Engineering, Rice University

  • J. Kono

    • Department of Electrical \& Computer Engineering, Rice University
    • Rice University
    • Department of Electrical and Computer Engineering, Rice University
    • Department of Electrical Engineering, Rice University, Houston, Texas 77005
    • ECE Dept., Rice University
    • Dept. of Electrical and Computer Engineering, Rice University
    • Rice Univ.

  • J.G. Duque

    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory

  • C.G. Densmore

    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory

  • S.K. Doorn

    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory