Strong enhancement of the Breit-Wigner-Fano Raman line in carbon nanotube bundles caused by plasmon band formation

We investigate the origin of the Breit-Wigner-Fano line in the Raman spectra of individual single-walled carbon nanotubes and their bundles. Using confocal Raman microscopy and atomic-force microscopy we found that the Breit-Wigner-Fano line intensity increases strongly with the bundle thickness. We confirmed this result by Raman investigations of partially decomposed bundles, which were additionally investigated by transmission electron microscopy. Our random-phase approximation based theory, which identifies the Breit-Wigner-Fano line as an excited band of plasmon-phonon modes, is fully consistent with the experimental results.

Electrical Transport and Confocal Raman Studies of Electrochemically Modified Individual Carbon Nanotubes

Raman investigation of single oxidized carbon nanotubes

The oxidation process of single-walled carbon nanotubes via nitric acid treatment was followed by IR-, UV-Vis-NIR, and single bundle Raman spectroscopy. The introduction of functional, oxygen-containing groups is revealed by an additional absorption band at 1725 cm−1, characteristic of carbonyl stretch vibrations. No significant shift of the optical absorption bands could be detected after oxidation. The combination of atomic force microscopy and confocal scanning resonance-enhanced Raman microscopy was used to investigate thin bundles and, eventually, individual nanotubes in detail. These experiments enabled determination of the dependence of the Raman intensity of the G-line (around 1590 …

Combination of Confocal Raman Spectroscopy and Electron Microscopy on the Same Individual Bundles of Single-Walled Carbon Nanotubes

We report a method to investigate the same individual single-walled carbon nanotube (SWNT) bundles with both transmission electron microscopy (TEM) and Raman spectroscopy. Free-standing individual bundles are obtained by depositing a solution of suspend SWNTs on a carbon film with a regular pattern of holes, which can be localized by TEM and also by confocal Raman microscopy. While most of the TEM images predict that the bundles consist of tubes with a similar diameter, we will show that occasionally a certain tube diameter can be associated with a particular radial breathing mode frequency of the Raman spectrum. Single-walled carbon nanotubes (SWNTs) are one-dimensional molecular structure…

Raman imaging and spectroscopy of heterogeneous individual carbon nanotubes

Isolated single-walled carbon nanotubes (CNTs) were grown by chemical vapor deposition methods on Fe/Mo/Al2O3 catalysts, which were patterned by microcontact printing. The pattern allowed us to trace back and investigate the same isolated CNT by atomic-force (AFM) and confocal Raman microscopy with different excitation wavelengths. A change of the Raman intensity could be correlated with structural defects revealing that the molecular structure of the tubes is changing along the tube axis. By investigating the same tube segments with different excitation energies, we found that the D-line of isolated tubes shows a strong dispersive effect of 45−50 cm-1/eV. In contrast, the spectral position…