Fluorine Adsorption on Single and Bilayer Graphene: Role of Sublattice and Layer Decoupling

The fluorination of mono- and bilayer graphene has been studied by means of ab initio DFT calculations. The stability of CFx systems is found to depend on both the F coverage and the position of the F atoms regarding the C sublattices. When F atoms are chemisorbed onto C atoms belonging to the same sublattice, low coverage is preferred. Otherwise, large F coverage is more stable (up to C4F for one-side fluorination). The difference of charge distribution between the two carbon sublattices explains this finding that is confirmed by the analysis of the diffusion barriers. The binding energy of F on bilayer systems is found to be slightly smaller than that on monolayer systems, and electronic decoupling is observed when only one of the layers is exposed to fluorine.