Fig. 2.

Polarized Raman on monolayer graphene. (A) Optical image of an exfoliated graphene flake with straight edges, separated by a 30^° corner. (Scale bar: 20 $\mathrm{\mu }$m.) (B) Raman spectra taken at the edges of the flake. Location of laser spot and direction of laser polarization for each spectrum are indicated by the solid black points and colored arrows in (A). The D peak on Edge 1 that vanishes when the laser is polarized perpendicular to the edge indicates that edge 1 of (A) is likely armchair. Edge 2 is offset from edge 1 by 30^°, and shows no D peak signal, so is likely zigzag.