  The possibility to control the commensurability and distance between graphene
layers separated by a dielectric spacer is considered by the example of a
heterostructure consisting of double-layer graphene separated by atomic layers
of argon. Van der Waals corrected density functional theory (DFT-D) is applied
to study structural, energetic and tribological characteristics of this
heterostructure. It is found that in the ground state, monolayer and bilayer
argon spacers are incommensurate with the graphene layers, whereas submonolayer
argon spacers which are commensurate with the graphene layers can exist only as
metastable states. The calculations show that this incommensurability provides
negligibly small static friction for relative motion of argon-separated
graphene layers and, therefore, such a heterostructure holds great promise for
the use in nanoelectromechanical systems. A scheme and operational principles
of the nanorelay based on the revealed tribological properties of the
heterostructure are proposed.
