The alignment-dependent properties and applications of graphene moiré superstructures on the Ru(0001) surface

The moiré superstructure of graphene on a lattice-mismatched metal substrate has profound effects on the electronic properties of graphene and can be used for many applications. Here, we propose to systematically tune the moiré superstructure of graphene on the Ru(0001) surface by rotating the graphene layer. Our study reveals two kinds of graphene moiré superstructures: (i) the ultra-flat graphene layers with height variations of less than 0.1 A for rotation angles greater than 20° that have the same structural and electronic properties everywhere, and (ii) the highly corrugated graphene moiré superstructures with height variations from 0.4 to 1.6 A for rotation angles less than 20°, whose electronic properties are highly modulated by the interaction with the substrate. Moreover, these rotated graphene moiré superstructures can serve as templates to produce matrices of size-tunable metal clusters from a few to ∼100 atoms. This study reveals the causes of the structural fluctuation of moiré superstructures of graphene on the transition metal surface and suggests a pathway to tune graphene's electronic properties for various applications.