Raman study of damage extent in graphene nanostructures carved by high energy helium ion beam

We performed spatial Raman mapping on supported monolayer graphene carved by 30 keV He+ beam. A tilted beam was introduced to effectively eliminate the substrate swelling. The ratio between D and G peak intensities shows that Stage 1 and Stage 2 disorder are introduced over a wider range on both sides of the 35 nm etched line. The mean defect distance LD was estimated in these regions using the local activation model. Vacancies and amorphisations are dominant types of defects as suggested by the ratio of D and D′ peak intensities. Monte Carlo simulation on stopping range of ions was accomplished to explain the asymmetric defect formation in graphene.