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Recent interest in functionalised graphene has been motivated by the
prospect of creating a two-dimensional semiconductor with a tunable
band gap. Various approaches to band gap engineering have been made
over the last decade, one of which is chemical functionalisation. In
this work, a predictive physical model of the self-assembly of
halogenated carbene layers on graphene is suggested. Self-assembly
of the adsorbed layer is found to be governed by a combination of
the curvature of the graphene sheet, local distortions, as
introduced by molecular adsorption, and short-range intermolecular
repulsion. The thermodynamics of bidental covalent molecular
adsorption and the resultant electronic structure are computed using
density functional theory. It is predicted that a direct band gap is
opened that is tunable by varying coverages and is dependent on the
ripple amplitude. This provides a mechanism for the controlled
engineering of graphene’s electronic structure and thus its use in
semiconductor technologies.