Theory has predicted rich and very distinct physics for graphene nanodevices with boundaries that follow either the armchair or the zigzag crystallographic directions. We have demonstrated that hexagonal holes obtained by anisotropic etching of graphene are bounded predominantly by zigzag edges which do not contribute to the D peak in Raman spectroscopy.

http://www.mfa.kfki.hu/int/nano/reprint/nanolett_10_4544_zigzagraman2010.pdf