322 research outputs found
Universal temperature dependence of optical excitation life-time and band-gap in chirality assigned semiconducting single-wall carbon nanotubes
The temperature dependence of optical excitation life-time, Gamma, and
transition energies, E_ii, were measured for bucky-papers of single-wall carbon
nanotubes (SWCNTs) and inner tubes in double-wall carbon nanotubes (DWCNTs)
using resonant Raman scattering. The temperature dependence of Gamma and E_ii
is the same for both types of samples and is independent of tube chirality. The
data proves that electron-phonon interaction is responsible for temperature
dependence of E_ii(T). The temperature independent inhomogeneous contribution
to Gamma is much larger in the SWCNT samples, which is explained by the
different SWCNT environment in the two types of samples. Gamma of the inner
tubes for the bucky-paper DWCNT sample is as low as \sim 30 meV, which is
comparable to that found for individual SWCNTs
Interaction between concentric Tubes in DWCNTs
A detailed investigation of the Raman response of the inner tube radial
breathing modes (RBMs) in double-wall carbon nanotubes is reported. It revealed
that the number of observed RBMs is two to three times larger than the number
of possible tubes in the studied frequency range. This unexpected increase in
Raman lines is attributed to a splitting of the inner tube response. It is
shown to originate from the possibility that one type of inner tube may form in
different types of outer tubes and the fact that the inner tube RBM frequency
depends on the diameter of the enclosing tube. Finally, a comparison of the
inner tube RBMs and the RBMs of tubes in bundles gave clear evidence that the
interaction in a bundle is stronger than the interaction between inner and
outer tubes.Comment: 6 pages, 7 figures, submitted to Eur. Phys. J.
Fine Structure of the Radial Breathing Mode in Double-Wall Carbon Nanotubes
The analysis of the Raman scattering cross section of the radial breathing
modes of double-wall carbon nanotubes allowed to determine the optical
transitions of the inner tubes. The Raman lines are found to cluster into
species with similar resonance behavior. The lowest components of the clusters
correspond well to SDS wrapped HiPco tubes. Each cluster represents one
particular inner tube inside different outer tubes and each member of the
clusters represents one well defined pair of inner and outer tubes. The number
of components in one cluster increases with decreasing of the inner tube
diameter and can be as high as 14.Comment: 5 pages, 3 figure
Diameter selective characterization of single-wall carbon nanotubes
A novel method is presented which allows the characterization of diameter
selective phenomena in SWCNTs. It is based on the transformation of fullerene
peapod materials into double-wall carbon nanotubes and studying the diameter
distribution of the latter. The method is demonstrated for the diameter
selective healing of nanotube defects and yield from C peapod samples.
Openings on small diameter nanotubes are closed first. The yield of very small
diameter inner nanotubes from C peapods is demonstrated. This challenges
the theoretical models of inner nanotube formation. An anomalous absence of
mid-diameter inner tubes is observed and explained by the suppressed amount of
C peapods due to the competition of the two almost equally stable
standing and lying C peapod configurations
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