Electrical Control of the Chemical Bonding of Fluorine on Graphene
  We study the electronic structure of diluted F atoms chemisorbed on graphene using density functional theory calculations. We show that the nature of the chemical bonding of a F atom adsorbed on top of a C atom in graphene strongly depends on carrier doping. In neutral samples the F impurities induce a sp^3-like bonding of the C atom below, generating a local distortion of the hexagonal lattice. As the graphene is electron-doped, the C atom retracts back to the graphene plane and for high doping (10^14 cm^-2) its electronic structure corresponds to a nearly pure sp^2 configuration. We interpret this sp^3-sp^2 doping-induced crossover in terms of a simple tight binding model and discuss the physical consequences of this change. 
J. O. Sofo, A. M. Suarez, Gonzalo Usaj, P. S. Cornaglia, A. D.   Hern\'andez-Nieves, C. A. Balseiro
cond-mat.mes-hall