Chemically Induced Formation of C-Cu Covalent Bonds at the CVD-Graphene/Single Crystal Cu(111) Interface

Partial hydrogenation of the open surface of graphene, epitaxially grown by chemical vapor deposition (CVD) on a Cu(111) substrate, leads to the formation of a crystalline sp³ hybridized carbon monolayer stabilized by interface C-Cu covalent bonding. This transition is reversible, with heating yielding almost complete restoration of the original graphene-copper structure. The graphene-Cu system is characterized by weak van der Waals interactions and this is the first transformation to yield C-Cu bonding. Through extensive spectroscopic characterization (Raman, X-ray photoelectron, X-ray absorption fine structure and valence-band photoemission spectroscopies) and theoretical analysis based on density functional theory (DFT), we find transformation from weak van der Waals binding in the graphene-Cu system to covalent bonding between partially (topside) hydrogenated graphene and the Cu(111) surface, with the potential to revert back to its initial physisorbed state via dehydrogenation through heating. This reversible control over the graphene-Cu interaction opens new avenues for the design and manipulation of graphene-based devices. Furthermore, this sp³ hybridized carbon monolayer, with its C-metal substrate bonds, could potentially serve as a seed layer for the growth of large-area diamond films.