▎ 摘　　要

We have determined the growth mode of graphene on SiC(0001) and SiC(000 (1) over bar) using ultrathin, isotopically labeled (SiC)-C-13 "marker layers" grown epitaxially on the (SiC)-C-12 surfaces. Few-layer graphene overlayers were formed via thermal decomposition at elevated temperature. For both surface terminations (Si face and C face), we find that the C-13 is located mainly in the outermost graphene layers, indicating that, during decomposition, new graphene layers form underneath existing ones.