Abstract
By measuring the anti-Stokes (AS) and Stokes (S) Raman spectra on the same isolated single-wall carbon nanotube (SWNT), we here determine the electronic transition energies experimentally and then we compare these with the values obtained with theoretical predictions In such an approach, the nanotube structure identification depends on the theory parameters, but the experimental determination of does not, and depends only on the experimental AS/S intensity ratio and the laser energy used in the experiment. We measured the radial breathing mode frequency and for specific tubes, and we then performed the identification by using the diameter dependence of the electronic transitions. We present such an analysis for a wide nanotube diameter range, focusing primarily on small diameter SWNTs where there are very few possibilities for SWNTs that can be in resonance with the appropriate laser energy This allows an experimental determination of values to be made for a variety of SWNTs. Our experimental results indicate that: (i) the large curvature in small diameter tubes induces a hybridization, thus lowering the electronic band energies, and (ii) the simple formulation of the tight binding model to determine starts to deviate from for tubes with but the deviation remains smaller than 20 meV for A comparison between data obtained from Raman and photoluminescence is made, and a comparison is also made between data for SWNTs and double-wall carbon nanotubes.
- Received 10 May 2003
DOI:https://doi.org/10.1103/PhysRevB.69.115428
©2004 American Physical Society