Why graphene growth is very different on the C face than on the Si face of SiC: Insights from surface equilibria and the (3$times$3)-3C-SiC($bar{text{1}}bar{text{1}}bar{text{1}}$) reconstruction

We address the stability of the surface phases that occur on the C-side of 3C-SiC($bar{1} bar{1} bar{1}$) 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$times$3) reconstruction, the known (2$times$2)$_{C}$ adatom phase, and the graphene covered (2$times$2)$_{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.

Thermodynamic equilibrium conditions of graphene films on SiC

First-principles surface phase diagrams reveal that epitaxial monolayer graphene films on the Si side of 3C-SiC(111) can exist as thermodynamically stable phases in a narrow range of experimentally controllable conditions, defining a path to the highest-quality graphene films. Our calculations are based on a van der Waals corrected density functional. The full, experimentally observed (6 sqrt(3)x 6 sqrt(3))-R30 supercells for zero- to trilayer graphene are essential to describe the correct interface geometries and the relative stability of surface phases and possible defects.