Theoretical Study of Cu Intercalation through a Defect in Zero-Layer Graphene on SiC Surface

Cu atom penetration through a defect in zero-layer graphene (ZLG) epitaxially grown on an SiC substrate was theoretically investigated, using density functional theory calculations, as a possible mechanism for pure single-layer graphene formation by Cu intercalation on an SiC surface. Our model calculation predicted that a Cu monolayer formed by Cu intercalation causes a lift of the graphene surface of about 0.2 nm, which supports our previous experimental observation. Our calculations on Cu intercalation through a graphene defect implied the possibility that a transition of the defect shape from a 5-8-5 to a double-vacancy model causes the timing of the passage of the Cu atom through the ZLG surface to reduce the potential barrier for the penetration. In addition, it was found that the SiC substrate stabilizes the Cu atom after penetration via an Si-Cu interaction. Furthermore, a preceding intercalated Cu atom was found to be capable of facilitating subsequent Cu penetration by suppressing its inverse reaction and cooperatively stabilizing newly intercalated Cu atoms via both Cu-Cu and Si-Cu interactions. This conclusion supports the possibility that deposited Cu atoms on the ZLG can subsequently pass through defects in order to be energetically stabilized.