In this work, we present a detailed Raman spectroscopy study of graphitic foams probing the spatial and laser excitation energy dependences of the double resonance Raman peaks. We have observed a spatial dependence of the $D$ to $G$ band intensity ratio $(I_D∕I_G)$ and of the relative contribution from the two-dimensional (2D) and three-dimensional (3D) graphite regions to the $G^{\prime }$ band in the Raman spectra. The $D$ band integrated intensity was found to decrease linearly with increasing laser energy $\left(E_L\right)$, in contrast with recent experiments on nanographite, which showed an $E_L^{-4}$ dependence for the $I_D∕I_G$ ratio. The calculation of the skewness of the $G^{\prime }$ band was found to be a good qualitative measure of the relative density of 2D and 3D graphite in a given region of the sample. The direct comparison between the spatial distribution of defects, given by the $I_D∕I_G$ ratio, and the presence of the 2D graphite phase, given by the skewness of the $G^{\prime }$ band, suggests a correlation between the presence of defects and the high density of 2D graphite.

• Received 17 October 2006

DOI:https://doi.org/10.1103/PhysRevB.76.035444