▎ 摘　　要

Ultraclean graphene is essential for studying its intrinsic transport properties or fabricating high-performance electronic devices. Unfortunately, the contamination on graphene is unavoidable after. microelectromechanical system. processing. Here, we report an in situ current-annealing method for achieving ultraclean suspended monolayer graphene. The charge mobility of cleaned graphene reached a. surprising 3.8. x. 10(5) cm(2) V-1 s(-1), one of the highest values ever. reported. For the first time, the process of current annealing was recorded under a high-resolution electron scanning microscope. It was demonstrated that temperature was the only dominant factor of the current-annealing process. Meanwhile, the mobility of suspended graphene was found to be highly sensitive to. structural defects. The mobility decreased by a factor of over 100 after ion irradiation on graphene. The results revealed the underlying mechanism of current annealing on graphene and provided an effective means of preparing ultraclean graphene membranes.