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

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