Effect of quantized electronic states on the dispersive Raman features in individual single-wall carbon nanotubes (original) (raw)
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Resonant Raman study of the structure and electronic properties of single-wall carbon nanotubes
Chemical Physics Letters, 2000
. We investigate the laser-energy dependence of the Raman profile of single-wall carbon nanotube SWNT samples with various distributions of diameters. We show that resonant Raman is an efficient tool for the study of the structure and electronic properties of SWNT. The tube diameter distribution is derived from the comparison between the experimental Ž . frequencies of the radial A breathing mode range RBM and the calculated RBM frequency of SWNT bundles. Metallic 1g or semi-conducting tubes are identified in the light of calculations of allowed optical transitions. The assignments are Ž . confirmed by the observation absence of a Breit-Wigner-Fano-like lineshape for the tangential graphite-like modes of Ž . metallic semiconducting nanotubes. q
Raman spectroscopy of carbon nanotubes
Physics Reports, 2005
The use of Raman spectroscopy to reveal the remarkable structure and the unusual electronic and phonon properties of single wall carbon nanotubes (SWNTs) is reviewed comprehensively. The various types of Raman scattering processes relevant to carbon nanotubes are reviewed, and the theoretical foundations for these topics are presented. The most common experimental techniques used to probe carbon nanotubes are summarized, followed by a review of the novel experimental findings for each of the features in the first order and second order Raman spectra for single wall carbon nanotubes. These results are presented and discussed in connection with theoretical considerations. Raman spectra for bundles of SWNTs, for SWNTs surrounded by various common wrapping agents, and for isolated SWNTs at the single nanotube level are reviewed. Some of the current research challenges facing the field are briefly summarized.
Nanoscale research letters, 2016
Micro-Raman spectra of single-walled carbon nanotubes in the range of two-phonon 2D bands are investigated in detail. The fine structure of two-phonon 2D bands in the low-temperature Raman spectra of the mixture and individual single-walled carbon nanotubes is considered as the reflection of structure of their π-electron zones. The dispersion behavior of 2D band fine structure components in the resonant Raman spectra of single-walled carbon nanotube mixture is studied depending on the energy of excitating photons. The role of incoming and outgoing electron-phonon resonances in the formation of 2D band fine structure in Raman spectra of single-walled carbon nanotubes is analyzed. The similarity of dispersion behavior of 2D phonon bands in single-walled carbon nanotubes, one-layer graphene, and bulk graphite is discussed.
Diameter-Selective Raman Scattering from Vibrational Modes in Carbon Nanotubes
Science, 1997
Single wall carbon nanotubes (SWNTs) that are found as close-packed arrays in crystalline ropes have been studied by using Raman scattering techniques with laser excitation wavelengths in the range from 514.5 to 1320 nanometers. Numerous Raman peaks were observed and identified with vibrational modes of armchair symmetry (n, n) SWNTs. The Raman spectra are in good agreement with lattice dynamics calculations based on CC force constants used to fit the two-dimensional, experimental phonon dispersion of a single graphene sheet. Calculated intensities from a nonresonant, bond polarizability model optimized for sp 2 carbon are also in qualitative agreement with the Raman data, although a resonant Raman scattering process is also taking place. This resonance results from the one-dimensional quantum confinement of the electrons in the nanotube.
Diameter dependence of the Raman D-band in isolated single-wall carbon nanotubes
Physical Review B, 2001
Raman D-band spectra are reported for several different SWNTs using two different laser energies (E laser ϭ1.58 and 2.41 eV͒. At a fixed E laser , individual isolated SWNTs exhibit different diameter-dependent D-band frequencies D around an average value. For both semiconducting and metallic tubes, D decreases with decreasing nanotube diameter, though D for isolated metallic SWNTs is higher than for isolated semiconducting SWNTs. The average D-band frequency depends linearly on E laser , as previously observed for SWNT bundles, suggesting that the D-band in SWNTs is activated by defects or by the finite size of the SWNTs.
G-band resonant Raman study of 62 isolated single-wall carbon nanotubes
2002
We report G-band resonance Raman spectra of single-wall carbon nanotubes ͑SWNTs͒ at the singlenanotube level. By measuring 62 different isolated SWNTs resonant with the incident laser, and having diameters d t ranging between 0.95 nm and 2.62 nm, we have conclusively determined the dependence of the two most intense G-band features on the nanotube structure. The higher-frequency peak is not diameter dependent ( G ϩ ϭ1591 cm Ϫ1 ), while the lower-frequency peak is given by G Ϫ ϭ G ϩ ϪC/d t 2 , with C being different for metallic and semiconducting SWNTs (C M ϾC S ). The peak frequencies do not depend on nanotube chiral angle. The intensity ratio between the two most intense features is in the range 0.1ϽI G Ϫ /I G ϩϽ 0.3 for most of the isolated SWNTs (ϳ90%). Unusually high or low I G Ϫ /I G ϩ ratios are observed for a few spectra coming from SWNTs under special resonance conditions, i.e., SWNTs for which the incident photons are in resonance with the E 44 S interband transition and scattered photons are in resonance with E 33 S . Since the E ii values depend sensitively on both nanotube diameter and chirality, the (n,m) SWNTs that should exhibit such a special G-band spectra can be predicted by resonance Raman theory. The agreement between theoretical predictions and experimental observations about these special G-band phenomena gives additional support for the (n,m) assignment from resonance Raman spectroscopy.
Fine structure of the low-frequency Raman phonon bands of single-wall carbon nanotubes
Chemical Physics Letters, 2000
The Raman _:pectr:-,.. of siugle-wall carbon, nr, notubes (SWNT) produced by laser aud arc process were studied between 5 and 500 K. The line width vs t.emperatme dependence of the low-fl'equonc_, Ramao bands between 150 and '200 cm-1 deviates i_-om that expe,:ted fc,r ph,.-,n,.-,n decay through pl+onon-phonoli scattering mechanism. The cxperin;eutal t_uult.s: and their analy.;is provide convii,,.:m.g evidence t]-jat each of the low-frequency Ft.aman lines is z_ supcrp,.',siliot_, of several narrower Rz, m.ar_ !ines corresponding to tul:,es of nearly the same diameter. The .-applicatiou u[ ithi-_man spectroscopy to probe the distribution of SWNT by both diameter and chiraLitv is discussed.
Raman spectroscopy on isolated single wall carbon nanotubes
Carbon, 2002
A review is presented on the resonance Raman spectra from one isolated single wall carbon nanotube. The reasons why it is possible to observe the spectrum from only one nanotube are given and the important structural information that is provided by single nanotube spectroscopy is discussed. Emphasis is given to the new physics revealed by the various phonon features found in the single nanotube spectra and their connection to spectra observed for single wall nanotube bundles. The implications of this work on single wall carbon nanotube research generally are also indicated.