▎ 摘　　要

We show using scanning tunneling microscopy, spectroscopy, and ab initio calculations that two intercalation structures coexist for Na in epitaxial graphene on SiC(0001). Intercalation takes place at room temperature, and Na electron dopes the graphene. It inserts in between single-layer graphene and the interfacial layer and also penetrates beneath the interfacial layer and decouples it to form a second graphene layer. Decoupling is accelerated by annealing and is verified by Na deposition onto the interface layer combined with computational modeling of the two new decoupled buffer layer structures.