M. A. Pimenta

Dispersive Raman spectra observed in graphite and single wall carbon nanotubes

The disorder-induced D-band and some other non-zone center Raman modes of graphite and single wall carbon nanotubes are assigned to phonon modes in their respective Brillouin zones. In disordered graphite, the weak, dispersive phonon modes, which have been known but never assigned so far, are well described by the double resonance Raman process. All weak Raman peaks observed for sp2 carbons are useful for determining the phonon dispersion relations of graphite. In carbon nanotubes, all semiconducting nanotubes and some metallic nanotubes have van Hove singular k points for their electronic and phonon energy dispersion curves at the Γ point of the Brillouin zone. A corresponding Raman process is relevant to explain the observed D-band and intermediate frequency spectra.

Raman spectroscopy of nanoscale carbons and of an isolated carbon nanotube

The use of Raman spectroscopy as a characterization tool for carbon materials is briefly reviewed with particular emphasis given to nano-carbons and carbon nanotubes. The observation of Raman spectra from one carbon nanotube is discussed, including the new physical phenomena that occur at the single nanotube level, with special emphasis given to the use of resonance Raman scattering for the structural determination of (n, m) for individual nanotubes. Examples are given to show how single nanotube spectroscopy provides insight into the use of Raman spectroscopy for characterizing nanotube bundles and for carrying out other properties measurements on individual carbon nanotubes.

Double resonance raman spectrain disordered graphite and singlewall carbon nanotubes

The Raman spectra of the disorder-induced D-band and some other non-zone-center phonon modes of graphite and single wall carbon nanotubes are discussed using double resonance Raman theory. For two-dimensional disordered graphite, two D-band peaks and one G′-band peak are predicted. The trigonal warping effect of the constant energy contours in graphite and the van Hove singularities in the electronic and phonon energy dispersion of carbon nanotubes are of importance for discussing the line width and possible numbers of Raman peaks which come from inequivalent Raman processes.

Resonance Raman Scattering in Carbon Nanotubes and Nanographites

In this work, we discuss the resonant Raman process in nanographites and carbon nanotubes, relating the most important Raman features to a first‐order (single resonance) or a second‐order (double resonance) process. We also show that, in the case of 1D systems, the term “resonance” has a more strict meaning and occurs when the energy of the photon does not simply coincide with the energy of a possible electron‐hole pair, but rather matches the separation between van Hove singularities in the valence and conduction bands.

Dependence of the Second-order G'-band Profile on the Electronic Structure of Single-wal Nanotubes

We analyze the dependence of the second-order G -band profile in terms of their ( n,m ) indices by measuring the resonance Raman spectra of several semiconducting and metalic isolated single wal carbon nanotubes. We show that this profile is very sensitive to the electronic structure, thus making it possible to get structural ( n,m ) information and to probe the splitting of the van Hove singularities in the electronic density of states due to the trigona warping effect.

Raman Spectra from One Carbon Nanotube

Dept. of Electrical Engineering and Computer Science, Dept. of Physics, Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA; Dept. de F́ısica, Univ. Federal do Ceará, Fortaleza CE, 60455-760 Brazil; Department of Electronic Engineering, University of Electro-Communications, Chofu, 182-8585 Tokyo, Japan; Dept. de F́ısica, Univ. Federal de Minas Gerais, Belo Horizonte MG, 30123-970 Brazil.