Résumé
In this communication we report the efficiency of Raman spectroscopy to characterize carbon-based nanostructures: single-walled carbon nanotubes and graphene. First, by combining Raman spectroscopy and electron diffraction experiments on individual freestanding single-walled carbon nanotube (SWNTs), we have been able to define Raman criteria allowing the identification of SWNTs from their Raman features only. We present and discuss these criteria which concern [1] (i) the radial breathing mode (RBM) vs diameter relationship, (ii) the profile of the G-modes and the diameter dependence of the frequency of the LO and TO G-mode of metallic and semiconducting SWNTs respectively [2,3] , (iii) The values of the optical transition energies EM11, ES33 and ES44 for individual freestanding SWNTs [4]. We show the efficiency of this metrological approach: (i) to assign the (n,m) indices of individual freestanding single-walled carbon nanotubes, and (ii) to identify the (n,m) tubes organized in a small bundle [5]. On the other hand, the main features of the Raman spectra of single layer graphene, Bernal bilayer and bilayer in which the two layers are arbitrary misoriented are compared. We found, in agreement with recent calculations [6], that the profile of the 2D band of misoriented bilayer graphene is similar to that of single layer graphene, and clearly opposite to the four components found in Bernal bilayer. By contrast with previous statement, we conclude that a unique thin peak of the Raman 2D spectrum is not enough to unambiguously identify single layer graphene [7]. [1] J.C. Meyer et al., Phys. Rev. Lett. . 95 (2005) 217401 [2] M. Paillet, et al., Phys. Rev. Lett. 96 (2006) 257401 [3] S. Piscanec et al., Phys. Rev. B 75 (2007) 35427 [4] T. Michel et al., Phys. Rev. B 75 (2007) 155432 [5] T. Michel et al., Phys. Rev. B (2008) submitted [6] S. Latil et al., Phys. Rev. B 76 (2007) 201402 [7] P. Poncharal et al., Phys. Rev. B 78 (2008) 113407