▎ 摘　　要

Point defects in freestanding graphene monolayers such as monovacancies (MVs) and divacancies have been investigated at atomic scale with aberration-corrected transmission electron microscopy and theoretical calculations. In general, these defects can be formed simply by the absence of individual carbon atoms and carbon bond reconstructions in the graphene lattice under electron and ion irradiation. However, in this study, we found that oxygen and hydrogen atoms can be involved in the formation of these point defects caused by the simultaneous detachment of oxygen-carbon atoms. Here we report the effect of the oxygen and hydrogen atoms on the graphene surface forming the point defects under electron beam irradiation, and their role of stabilizing other MVs when composed of 13-5 ring pairs. In addition, theoretical analysis using density functional theory calculations demonstrates that the participating atoms can form the point defects in the intermediate states and stabilize 13-5 ring pairs under electron beam irradiation.