Figure 2.

Raman spectra of graphene sheets before and after CF₄plasma treatment. ( a) Raman spectra of a single-layer graphene sheet before (lower panel) and after (upper panel) 2 s of CF₄ plasma treatment. (b) Raman spectra of a few-layer graphene sheet before (lower panel) and after (upper panel) 5 s of CF₄ plasma treatment. A thinning effect is obvious.