Structural properties and site specific interactions of Pt with the graphene/Ru(0001) moiré overlayer

The coherence of graphene layers on Ru(0001) over extended distances has been employed to identify fcc and hcp regions of the associated moire superstructure. These findings can be used as a straightforward method to discriminate between fcc and hcp hollow sites of Ru(0001). Our approach thereby makes use of the "magnifying lens" characteristics of the graphene/Ru(0001) overlayer and its coherence across several monatomic steps of the substrate. We demonstrate that the individual regions of the graphene/Ru(0001) overlayer exhibit pronounced variations in interaction strengths with deposited metal atoms. Specifically, Pt clusters have been grown at 140-180 K and they are found to organize in a well-ordered periodic array defined by the moire superlattice. Their preferred location within the graphene/Ru(0001) moiré unit cell is identified to be the fcc region.