▎ 摘　　要

We report on the properties of defects in exfoliated graphene on SiO2 produced by electron irradiation at 25 keV and dosages from 4.96 x 10(15) to 9.56 x 10(17) electrons/cm(2). With increasing dosage, graphene exhibits the two-stage amorphization trajectory reported for the Ar ion bombardment of graphene. Initially, the ratio of the D-peak height, I-D, to the G peak height, I-G, increases as new defects are formed. In the second stage, I-D/I-G decreases as defects cover most of the sample. In the second stage, we find that the full width at half maximum of the Raman 2D, D, and G peaks increases by 3, 3, and 6 cm(-1), respectively. These values are less by factors of about 10, 5, and 10, respectively, than those reported for amorphous graphene produced by Ar ion bombardment. We find that I-D/I-G monotonically decreases in the second stage as the annealing temperature increases from 80 to 220 degrees C. Assuming that I-D/I-G is proportional to the defect density, we find an activation energy for defect healing, E-a = 0.48 eV, which is significantly less than E-a= 0.95 eV reported for vacancies and closer to E-a= 0.29 and 0.58 eV reported for hydrogen and hydroxyl group adsorbates, respectively. We propose that, in the second stage, graphene does not become amorphous, and the defects responsible for the D peak are adsorbates. Published under an exclusive license by the AVS.