Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10610903 | Carbon | 2005 | 6 Pages |
Abstract
The second order Raman signals around the Gâ²-band region of graphite and carbon nanotubes have been investigated at more than 15 excitation laser lines. Two distinct Raman bands have been observed around 2700 cmâ1; a prominent one is due to the so-called Gâ²-band and the other is a weak band around 2450 cmâ1. Both two bands can be from the double resonance process involving two phonons around the K-point in the phonon dispersion of a two-dimensional graphite. The 2450 cmâ1-band has exhibited little power dependence, whereas the intensity of Gâ²-band has shown large photon energy dependence as already reported. The 2450 cmâ1-band and the Gâ²-band correspond to non-dispersive q = 0 and fully-dispersive q = 2k, respectively. From the phonon dispersion and the corresponding phonon frequency, the 2450 cmâ1-band can be assigned as an overtone mode of LO phonon (i.e. 2LO). This is revealed by calculated Raman spectra of graphite with proper electron-phonon matrix elements. The present study is the first report on the origin and assignment of the 2450 cmâ1-band, which is based on the double resonance Raman scattering.
Related Topics
Physical Sciences and Engineering
Energy
Energy (General)
Authors
T. Shimada, T. Sugai, C. Fantini, M. Souza, L.G. Cançado, A. Jorio, M.A. Pimenta, R. Saito, A. Grüneis, G. Dresselhaus, M.S. Dresselhaus, Y. Ohno, T. Mizutani, H. Shinohara,