Effect of a Metal Substrate on Interlayer Interactions in Bilayer Graphene

Bilayer graphene (BLG) has been shown to have advantageous electronic and physical properties relative to single-layer graphene and is a model system for probing the tribology of graphene-based lubricants. However, few studies have investigated how metal substrates affect interlayer interactions, as quantified by the exfoliation energy and the sliding barrier of the upper graphene layer. In this work, we present a study of adsorbed BLG on several transition-metal surfaces using density-functional theory incorporating the exchange-hole dipole moment dispersion model. Our results show that physisorption of BLG on a surface does not significantly perturb the interlayer interactions, exfoliation, or sliding. Conversely, chemisorption of BLG increases the exfoliation energy and decreases the sliding barriers because of stronger dispersion contributions from the metal substrate. Changes in translational and rotational orientations massively impact the sliding friction for Ni group metals that can facilitate both chemisorption and physisorption