Sardinha and coworkers are referring, among many others, to the work by . Let us consider this article because of the interpretation we can find in it of D and G bands. As told by Ferrari and Robertson in their introduction, the "versatility of carbon materials" is due to their properties related to the ratio in them of sp 2graphite-like to sp 3 -diamond-like bonds. The sp 2 -bonded carbons are producing a graphitic order, "ranging from microcrystalline graphite to glassy carbon". An amorphous carbon can be considered as a mixture of sp 3 , sp 2 , and also sp 1 sites, with the presence of hydrogen up to 60%, resulting in compositions as in the ternary phase diagram shown in the Fig. given by Ferrari and Robertson. In this diagram we can find the diamond-like carbon (DLC) defined as the amorphous carbon "with a significant fraction of sp 3 bonds" (for other materials, see please the discussion in Ferrari and Robertson).