▎ 摘　　要

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 L-D 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. (C) 2014 Elsevier Ltd. All rights reserved.