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

TL;DR

This study investigates why graphene growth differs on the C face versus the Si face of SiC by analyzing surface phase stability and reconstructions using ab initio calculations, revealing that Si-rich reconstructions hinder buffer-layer formation on the C face.

Contribution

The paper provides a detailed surface phase diagram explaining the distinct graphene growth behaviors on SiC faces, highlighting the role of surface reconstructions.

Findings

Si-rich surface reconstructions prevent buffer-layer formation on the C face.

Multiple surface phases coexist during initial graphene growth.

Ab initio calculations elucidate surface stability and phase coexistence.

Abstract

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.