Ref HAL: hal-00512611_v1
DOI: 10.1103/PhysRevB.75.155432
WoS: 000246075300128
Exporter : BibTex | endNote
40 Citations
Résumé:

By combining, on the same freestanding single-walled carbon nanotubes, electron diffraction and Raman experiments, we were able to obtain the resonance energy of unambiguously (n,m)-identified single-walled carbon nanotubes. We focus on the analysis of the first optical transition of metallic tubes (E-11(M)) and the third and fourth transitions of semiconducting tubes (E-33(S) and E-44(S), respectively) in comparison with calculated values using a nonorthogonal tight-binding approach. For semiconducting tubes, we find that the calculated energies E-33(S) and E-44(S) have to be corrected by non-diameter-dependent (rigid) shifts of about 0.43 eV and 0.44 eV, respectively, for tubes in the 1.4-2.4-nm-diameter range. For metallic tubes in the 1.2-1.7-nm-diameter range, we show that a rigid shift (0.32 eV) of the calculated transition energy also leads to a good estimation of E-11(M). The rather large and non-diameter-dependent shifts for the third and fourth transitions in semiconducting tubes question a recent theoretical study, which relates the shifts to electron-electron correlation and exciton binding energy and suggest that the exciton binding is very small or missing for the higher transitions E-33(S) and E-44(S), contrary to the lower transitions E-11(S) and E-22(S).

Ref HAL: hal-00498157_v1
Exporter : BibTex | endNote
Résumé:

The goal of our "complete experimental" approach was to relate the Raman response of an individual single-walled carbon nanotubes (SWNT) to its (n,m) structure determined from an independent way. In this aim, a procedure including transmission electronic microscopy (TEM), Raman spectroscopy, and electron diffraction experiments on the same SAINT has been developed. The independent determinations of both structure and Raman features of semiconducting and metallic nanotubes allows to discuss several questions concerning: (i) the relation between diameter of the tubes and the radial breathing mode (RBM) frequency, (ii) the values and the nature of the E-33(S) and E-44(S) optical transition energies. (c) 2007 WELEY-VCH Veriag GmbH & Co. KGaA, Weinheim.

Commentaires: 0370-1972

Commentaires: ISI Document Delivery No.: 007LA Times Cited: 0 Cited Reference Count: 4 Cited References: PAILLET M, 2005, PHYS REV LETT, V94 RADOSAVLJEVIC M, 2002, NANO LETTERS, V2, P761 ZDROJEK M, 2005, APPL PHYS LETT, V86, P13114 ZDROJEK M, 2006, PHYS REV LETT, V96 English Editorial Material 0031-9007 039704

Ref HAL: hal-00514936_v1
PMID 16907341
DOI: 10.1103/PhysRevLett.96.257401
WoS: 000238697000053
Exporter : BibTex | endNote
71 Citations
Résumé:

The resonant Raman spectra of (n,m) semiconducting single-walled carbon nanotubes, unambiguously identified from their electron diffraction patterns, have been measured. The diameter dependence of the frequency of the tangential modes with A symmetry has been obtained in the diameter range from 1.4 to 2.5 nm. The comparison between the excitation energies and the calculated transition energies allowed us to determine precisely the values of the Es33 and Es44 transition energies. Finally, in the debate concerning the dominant process at the origin of the first-order Raman scattering in single-walled carbon nanotubes (single resonance process or double resonance process), our results are well understood in the framework of a single resonance process.

Ref HAL: hal-00514937_v1
Exporter : BibTex | endNote
Résumé:

We have developed a versatile catalyst-assisted chemical vapor deposition (CVD) technique for the synthesis of single-walled carbon nanotubes (SWNTs) from discrete nickel nanoparticles (average diameter of 4.7 ± 1.5 nm). Atomic force microscopy (AFM), transmission electron microscopy (TEM) and electron diffraction are used to characterize these as-grown nanotubes. On a particular sample we found that the SWNTs have an average chiral angle of 25.3°. This result shows that a control of the chiral angle of SWNT with large diameters (mean diameter = 1.75 nm) and with a relatively broad diameter distribution (standard deviation = 0.5 nm) is achievable to a certain extent.

Ref HAL: hal-00514938_v1
PMID 16471515
DOI: 10.1021/jp0516137
WoS: 000234520700032
Exporter : BibTex | endNote
9 Citations
Résumé:

The radial breathing modes and tangential modes have been systematically measured on a large number of individual semiconducting single-wall carbon nanotubes (thin bundles) suspended between plots (free-standing single-wall carbon nanotubes). The strong intensity of the Raman spectra ensures the precision of the experimentally determined line shapes and frequencies of these modes. The diameter dependence of the frequencies of the tangential modes was measured. This dependence is discussed in relation with recent calculations. The present data confirm/contradict some previous interpretations.