▎ 摘　　要

The stability and reactivity of steps in the initial stage of the graphene growth by sublimating the SiC(0001) surface is theoretically studied by the first-principles calculation. The steps are not necessarily unstable and reactive during the formation of the zeroth graphene layer. Temperature, Si pressure, and C coverage affect the stability and reactivity of the step. The growth mode shows a phase transition. The step is unstable and reactive after the zeroth graphene layer is formed. These findings are tightly related to the graphene formation mechanism on this surface. They are discussed with experimental results and suggest a way to control the quality of graphene.