▎ 摘　　要

We report an investigation of the microscopic mechanism of hydrogen penetration and migration in the conversion process of the buffer layer on SiC into quasi-freestanding graphene. By systematically observing the initial stage, we found that hydrogen intercalation initiates locally and simultaneously throughout the terrace, followed by the expansion of the intercalated area, resulting in full graphenization of the buffer layer over the SiC surface. This suggests that hydrogen can penetrate the buffer layer. In addition, we found that the steps on the SiC surface can act as a migration barrier, hindering the migration of hydrogen at the interface across the steps. This series of experimental results provides important insights into the fundamental mechanism of hydrogen intercalation and may help to pave the way toward graphene electronics.