For what is regarding the graphene edges, "a strong D peak will appear near armchair edges using an excitation laser polarized in a direction parallel to the line of the edge. This effect is significantly smaller for zigzag edges". It follows in the Childres and coworkers' article a discussion about the optical phonons active in armchair and zigzag edges. From the article, it seems that polarized Raman spectroscopy is relevant for graphene and related materials, and in fact we can find this spectroscopy mentioned by