Why graphene growth is very different on the C face than on the Si face of SiC: Insights from surface equilibria and the (3×3)-3C-SiC(111) reconstruction

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We address the stability of the surface phases that occur on the C-side of 3C-SiC(1 1 1) at the onset of graphene formation. In this growth range, experimental reports reveal a coexistence of several surface phases. This coexistence can be explained by a Si-rich model for the unknown (3×3) reconstruction, the known (2×2)C adatom phase, and the graphene covered (2×2)C phase. By constructing an ab initio surface phase diagram using a van der Waals corrected density functional, we show that the formation of a well defined interface structure like the "buffer-layer" on the Si side is blocked by Si-rich surface reconstructions.