▎ 摘　　要

We study the selective preparation of graphene zigzag edges by crystallographically anisotropic etching processes. Exfoliated graphene on a set of substrates is heated at various temperatures in argon atmospheres with different oxygen concentrations in the ppm range. The removal of carbon atoms from armchair sites at predefined antidots is studied by scanning electron and force microscopy. The anisotropy of etching is determined by the choice of the substrate, graphene's layer thickness and sample conditioning. We show that under all experimental conditions, gaseous oxygen at low concentrations is responsible for graphene etching. SEM image of anisotropically etched antidots in graphene and dependence of etch rate on added oxygen concentration.