We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.

Structural (n,m) determination of isolated single wall carbon nanotubes by resonant Raman scattering

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=907346

Evaluating the characteristics of multiwall carbon nanotubes

This paper reviews progress that has been made in the use of Raman spectroscopy to study graphene and carbon nanotubes These are two nanostructured forms of sp2 carbon materials that are of major current interest These nanostructured materials have attracted particular attention because of their simplicity, small physical size and the exciting new science they have introduced This review focuses on each of these materials systems individually and comparatively as prototype examples of nanostructured materials In particular, this paper discusses the power of Raman spectroscopy as a probe and a characterization tool for sp2 carbon materials, with particular emphasis given to the field of photophysics Some coverage is also given to the close relatives of these sp2 carbon materials, namely graphite, a three-dimensional (3D) material based on the AB stacking of individual graphene layers, and carbon nanoribbons, which are one-dimensional (1D) planar structures, where the width of the ribbon is on the nano

Raman spectroscopy of graphene and carbon nanotubes

A review of double resonance Raman spectroscopy is presented. Non-zone centre phonon modes in solids can be observed in the double resonance Raman spectra, in which weak Raman signals appear in a wide frequency region and their combination or overtone modes can be assigned. By changing the excitation laser energy, we can derive the phonon dispersion relations of a single nanotube.

https://iopscience.iop.org/article/10.1088/1367-2630/5/1/157/pdf

Double resonance Raman spectroscopy of single-wall carbon nanotubes

Influence of the growth temperature on the first and second-order Raman band ratios and widths of carbon nanotubes and fibers

Solid State Properties: From Bulk to Nano

The electronic properties of exohedrally doped double-walled carbon nanotubes (DWNTs) have been investigated using density functional theory and resonance Raman spectroscopy (RRS) measurements. First-principles calculations elucidate the effects of exohedral doping on the M@S and S@M systems, where a metallic (M) tube is either inside or outside a semiconducting (S) one. The results demonstrate that metallic nanotubes are extremely sensitive to doping even when they are inner tubes, in sharp contrast to semiconducting nanotubes, which are not affected by doping when the outer shell is a metallic nanotube (screening effects). The theoretical predictions are in agreement with RRS data on Br2- and H2SO4-doped DWNTs. These results pave the way to novel nanoscale electronics via exohedral doping.

Selective tuning of the electronic properties of coaxial nanocables through exohedral doping.

Resonant Raman scattering for one single wall carbon nanotube spectroscopy is overviewed. First-order resonance Raman spectra of the radial breathing mode of one carbon nanotube is of importance for assigning (n,m) values to the nanotube. This assignment of (n,m) values is confirmed by the chirality dependence of other phonon modes. Second-order, one-phonon emission, and the inter-valley scattering processes of two dimensional graphite and of single wall carbon nanotubes are relevant to disorder-induced D-band Raman spectra. The dispersive nature of the D-band Raman spectra is explained by double resonance processes. Many weak Raman spectra appearing in the intermediate frequency range, which have been observed for a long time but never assigned so far, have recently been assigned as double resonance Raman peaks. The second-order Raman phonon frequencies can be used as a new fundamental tool for determining the phonon energy dispersion relations, especially for disordered materials and for zone boundary phonons.

https://iopscience.iop.org/article/10.1143/JJAP.41.4878/pdf

First and Second-Order Resonance Raman Process in Graphite and Single Wall Carbon Nanotubes

We theoretically investigate the electric rectification in an organic two terminal push-pull molecular device using a combination of ab initio techniques. Our main finding is that the electric rectification is extremely sensitive to the length of the chain, undergoing a complete switching after a specific chain length. This unique process occurs for betainelike donor- bridge-acceptor systems and is directly associated with a conjugated bridge in the presence of an external electric field. The conjugated bridge between the donor and acceptor groups is composed of oligoethylene with sizes ranging from zero to ten C=C units. The appearance of electric rectification occurs when the bridge size is equal to 5 units and is complete for those larger than 6 units (i.e. full inversion). This new electronic effect is advantageous for the design of large hybrid organic/inorganic circuits with anincreased majority carrier flow that is necessary for the emerging needs of nanotechnology.

Electrical Rectification in Betaine Derivatives

In this work, we use an extended tight-binding approach for calculating the Fermi-energy dependence of the structural deformation of chiral single-wall carbon nanotubes (SWNTs). We show that, in general, nanotube strains occur in such a way as to avoid a net charge from being accumulated on the nanotube. We also investigate the effect of the Fermi-energy-induced strains on the electronic structure of SWNTs, showing that the optical transition energies change by up to 0.5 eV due to the induced strains and that this change is nearly independent of how the nanotube is deformed. Finally, we also consider the contribution of the electron-electron Coulomb repulsion to the total energy by using an effective regularized potential energy model. We show that the inclusion of the Coulomb repulsion leads to larger strains and smaller net charges transferred to the nanotube.

Antonio G. Souza Filho

Papers

Solid State Properties: From Bulk to Nano

Selective tuning of the electronic properties of coaxial nanocables through exohedral doping.

First and Second-Order Resonance Raman Process in Graphite and Single Wall Carbon Nanotubes

Electrical Rectification in Betaine Derivatives

Fermi-Energy-Dependent Structural Deformation of Chiral Single-Wall Carbon Nanotubes