A tool box to ascertain the nature of doping and photoresponse in single-walled 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.
Spectro-electrochemical studies of single wall carbon nanotubes films
Chemical Physics Letters, 2004
The dependence of the resonance Raman spectra of single wall carbon nanotubes (SWNTs) on an externally applied potential (V ap ) was studied in different media. The spectro-electrochemical data indicate that the reaching of van Hove singularities (vHSs) of SWNTs occurs at a different V ap for each electrolyte, and that there is a dependence of the charge transfer and intercalation processes on the chemical nature of the media. We present evidence to suggest that the position of the vHSs of SWNTs is perturbed by V ap . Asymmetry between empty and filled vHSs is revealed by the spectroscopic response upon electrochemical p-and n-doping.
Electrochemical and Raman measurements on single-walled carbon nanotubes
Chemical Physics Letters, 2003
Electrochemical measurements were performed on a carbon nanotube mat as a working electrode using different salt solutions. The gravimetric capacitance of the nanotube material was estimated and its effective surface area was determined in a purely electrochemical way. We also studied the Raman response upon electrochemical p-doping of carbon nanotubes. The frequency shifts and the Raman intensities of the radial breathing mode and the high-energy stretching-like mode were examined as a function of doping level.
2001
This work reports how resonance Raman experiments are used to study details of the electronic structure of individual single-wall carbon nanotubes ͑SWNTs͒ by measuring the phonon spectra and how the quantized electronic structure affects the dispersive Raman features of SWNTs. We focus our analysis on the dispersive D and GЈ bands observed in the Raman spectra of isolated semiconducting nanotubes. By using a laser excitation energy of 2.41 eV, we show that both the D-band and GЈ-band frequencies are dependent on the wave vector k ii where the electrons are confined in the one-dimensional subband i of the electronic structure of SWNTs. By making use of the (n,m) assignment for each tube, we theoretically correlate the observed frequency dependences for the D-and GЈ-band modes with the electronic structure predicted for each (n,m) pair and we determine the dependence of D and G Ј on the diameter and chirality for individual electronic transitions E ii for nanotube bundles. We use the D-and GЈ-band dependence on electron wave vector k ii to predict the dominant phonon wave vector q selected by the quantum-confined electronic state k ii and to explain the anomalous dispersion observed for D and G Ј in SWNT bundles as a function of laser excitation energy, yielding excellent agreement between experiment and theory.
Spectroscopic Investigation of Modified Single Wall Carbon Nanotube (SWCNT
We have investigated the effects of chemical treatment on Single Wall Carbon Nanotube (SWCNT) before and after being modified with HNO 3 /H 2 SO 4 by Raman, FTIR and UV-Vis-NIR spectroscopy. The results show successful carboxylation of the CNT sidewalls as observed from FTIR and UV-Vis-NIR spectroscopy. This successful functionalization is achieved in 6-8 hrs of refluxing. We also report changes in the first and second order Raman spectra of SWNTs functionalized with oxygenated groups. During the experiment, we observe some important Raman features: Radial breathing mode (RBM), Tangential mode (G-band), and Disordered mode (D-band); which are affected due to the chemical oxidation of carbon nanotubes. We found that the ratio of D-to the G-band intensity (I d /I g ), increase after functionalization and the RBM mode in acid treated SWCNTs is almost disappeared.
Raman spectroscopy on one isolated carbon nanotube
Physica B: Condensed Matter, 2002
The use of Raman spectroscopy to elucidate the vibrational and electronic structure of single wall carbon nanotubes is reviewed. The special role played by single nanotube spectroscopy in the ðn; mÞ structural characterization of individual nanotubes and in the elucidation of the spectra of nanotube bundles is emphasized. r
Optoelectronic Properties of Single-Wall Carbon Nanotubes
Advanced Materials, 2012
diffraction is a powerful technique for the determination of atomic structure of individual nano-objects, as was demonstrated in Iijima's original work on multiwall [ 187 ] and singlewall [ 1 ] carbon nanotubes. However, it is not suited for studying a large number of carbon nanotubes. Therefore, optical spectroscopy has emerged in the last decade as the most convenient means for determining the chirality indices (n , m) of SWCNTs in macroscopic ensembles of SWCNTs. There is now a wellestablished correlation between optical transition energies, diameters, and (n , m) indices, as shown in Figure 2 a. [ 188 ] RRS spectroscopy has served as the most commonly used tool for (n , m) determination for both metallic and semiconducting SWCNTs for many years. [ 189 ] For semiconducting, or ν = ± 1, SWCNTs, PLE spectroscopy [ 24-35 ] can provide accurate information on the E 11 and E 22 energies from the emission and excitation photon energies, respectively, as shown in Figure 2 b. One can also combine PLE and RRS spectroscopies to determine E 33 and E 44 in semiconducting nanotubes. [ 190 ] Furthermore, as detailed in Section 3, coherent phonon spectroscopy has several advantages for simultaneously determining (n , m) indices and phonon frequencies for both semiconducting and metallic SWCNTs (see Figure 2 c). Finally, Section 4 presents how aligned SWCNT fi lms can be used to develop optoelectronic devices, ranging from state-of-the-art terahertz polarizers to large-area, broadband photodetectors. 2. Enrichment and Spectroscopy of Armchair Carbon Nanotubes Because of their excellent electrical properties, metallic SWCNTs are considered to be promising candidates for a variety of future electronic applications such as nanocircuit interconnects and power transmission cables. In particular, (n , n)-chirality, or 'armchair,' metallic nanotubes are theoretically predicted to be truly gapless and intrinsically insensitive to disorder, [ 191-192 ] consistent with experimentally observed ballistic conduction behavior at the single-tube level. Unfortunately, progress towards creating such ballistic-conducting armchair devices in bulk quantities has been slowed by the inherent problem of nanotube synthesis, whereby both semiconducting and metallic nanotubes are produced. Sébastien Nanot received his Ph.D. from Université de Toulouse (France) in 2009 under supervision by Profs. Bertrand Raquet and Jean-Marc Broto. His thesis focused on individual carbon nanotube properties under a very high magnetic fi eld. He moved to Rice University where he is appointed as a postdoctoral researcher in Prof. Junichiro Kono's group. His current research focuses on optoelectronic properties of carbon nanotubes ensembles.