  Theory has predicted rich and very distinct physics for graphene devices with
boundaries that follow either the armchair or zigzag crystallographic
directions. A prerequisite to disclose this physics in experiment is to be able
to produce devices with boundaries of pure chirality. Exfoliated flakes
frequently exhibit corners with an odd multiple of 30{\deg}, which raised
expectations that their boundaries follow pure zigzag and armchair directions.
The predicted Raman behavior at such crystallographic edges however failed to
confirm pure edge chirality. Here, we perform confocal Raman spectroscopy on
hexagonal holes obtained after the anisotropic etching of prepatterned pits
using carbothermal decomposition of SiO2. The boundaries of the hexagonal holes
are aligned along the zigzag crystallographic direction and leave hardly any
signature in the Raman map indicating unprecedented purity of the edge
chirality. This work offers the first opportunity to experimentally confirm the
validity of the Raman theory for graphene edges.
