Electrically tunable resonant scattering in fluorinated bilayer graphene

Adatom-decorated graphene offers a promising new path towards spintronics in the ultrathin limit. We combine experiment and theory to investigate the electronic properties of dilutely fluorinated bilayer graphene, where the fluorine adatoms covalently bond to the top graphene layer. We show that fluorine adatoms give rise to resonant impurity states near the charge neutrality point of the bilayer, leading to strong scattering of charge carriers and hopping conduction inside a field-induced band gap. Remarkably, the application of an electric field across the layers is shown to tune the resonant scattering amplitude from fluorine adatoms by nearly twofold. The experimental observations are well explained by a theoretical analysis combining Boltzmann transport equations and fully quantum-mechanical methods. This paradigm can be generalized to many bilayer graphene-adatom materials, and we envision that the realization of electrically tunable resonance may be a key advantage in graphene-based spintronic devices.We thank X. Hong for helpful discussions. A.S., J.L., and J.Z. are supported by ONR under Grant No. N00014-11-1-0730 and by NSF CAREER Grant No. DMR-0748604. A.F. and N.M.R.P. acknowledge EC under Graphene Flagship (Contract No. CNECT-ICT-604391). A.F. gratefully acknowledges the financial support of the Royal Society (U.K.) through a Royal Society University Research Fellowship. We acknowledge use of facilities at the PSU site of NSF NNIN