/Si substrate.

We carried out an investigation into the mechanism for the etching of exfoliated graphene multilayer on 300nm thick SiO₂/Si substrates. A recent mechanism was proposed in which the etching was due to dissociated oxygen from the SiO₂ substrate. Oxygen is released from underneath the substrate and etches the graphene layer from below. In order to test the mechanism, we carried out electron beam irradiation on focused areas, using an SEM/e-beam lithography system at energies from 1.5 to 30 keV. We found no evidence for graphene etching. We also carried out wide area electron irradiation using a plasma electron source for graphene exfoliated on a variety of conducting and dielectric substrates. We conclude that low-energy electron etching of graphene is due to sputtering by residual gas ions in the environment.