Dilute fluorinated graphene and bilayer graphene: resonant impurity scattering, anomalous magneto-transport and local spin-orbit coupling

Graphene is a high-mobility semi-metal with weak spin-orbit coupling (SOC). I will discuss the striking effects of a dilute coverage of chemisorbed fluorine adatoms (F:C $<0.1\%$) on charge transport and magneto-transport of graphene and bilayer graphene. We show that electron scattering with the F-adatoms can be quantitatively described by resonant impurity scattering. The T-dependence of conductivity reveals strong quantum corrections not yet understood, which differs qualitatively between F-monolayer and F-bilayer. Both F-monolayer and F-bilayer exhibit weak localization in a magnetic field. The dephasing rate $\tau_{\phi}^{-1}$ is dramatically enhanced in fluorined samples, compared to pristine and defluorinated control samples. It is further tunable by a perpendicular electric field in dual-gated F-bilayer devices. Strikingly, the ratio of $\tau_{\phi}^{-1}$ over the transport relaxation rate $\tau_p^{-1}$ is independent of $n_F$ and scales with the carrier density n as $n^{-1}$ in both F-monolayer and F-bilayer. Strong local SOC induced by the F-adatoms, combined with the unusual effect of SOC on the magneto-resistance of WL, is likely to play a key role. Fluorine induced SOC has important implications on spin relaxation and spin Hall current in these engineered materials.