First, highly energetic radical species are produced by radiolysis inside the ESEM through interaction of the gas species with the e-beam and with secondary electrons generated from the irradiated volume. The interaction area of the short-lived radiolysis products (in our case, those derived from H2O ) with the graphene surface is defined by the interaction volume of the e-beam. This volume depends on its elemental composition of the specimen (including any underlying substrate), the electro-optical configuration, and the acceleration voltage. With the e-beam focused on the graphene surface, radiolysis products generated in the vicinity of the irradiated area can react with the carbon atoms in the graphene lattice and hence modify or remove the atoms, thereby creating defects in graphene.