Tuning the doping type and level of graphene with different gold configurations.

Au nanoparticles and films are deposited onto clean graphene surfaces to study the doping effect of different Au configurations. Micro-Raman spectra show that both the doping type and level of graphene can be tuned by fine control of the Au deposition. The morphological structures of Au on graphene are imaged by transmission electron microscopy, which indicate a size-dependent electrical characteristic: isolated Au nanoparticles produce n-type doping of graphene, while continuous Au films produce p-type doping. Accordingly, graphene field-effect transistors are fabricated, with the in situ measurements suggesting the tunable conductivity type and level by contacting with different Au configurations. For interpreting the experimental observations, the first-principles approach is used to simulate the interaction within graphene-Au systems. The results suggest that, different doping properties of Au-graphene systems are induced by the chemical interactions between graphene and the different Au configurations (isolated nanoparticle and continuous film).