Effect of the 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 (SLG) and is
a model system for probing the tribology of graphene-based lubricants.
However, few studies have investigated how metal substrates affect the
interlayer interactions, as quantified by the exfoliation energy and
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 (DFT) incorporating the exchange-hole dipole
moment (XDM) dispersion model. Our results show that physisorption of
BLG on metal substrates does not significantly perturb the interlayer
interactions. Conversely, chemisorption on metal substrates increases
the exfoliation energies due to stronger dispersion contributions,
which in turn affect the sliding energy barrier of BLG.