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