We investigate the effects of transition metals (TM) on the electronic doping and scattering in graphene using molecular-beam epitaxy combined with in situ transport measurements. The room-temperature deposition of TM onto graphene produces clusters that dope $n$ type for all TM investigated (Ti, Fe, and Pt). We also find that the scattering by TM clusters exhibits different behavior compared to $1/r$ Coulomb scattering. At high coverage, Pt films are able to produce doping that is either $n$ type or weakly $p$ type, which provides experimental evidence for a strong interfacial dipole favoring $n$-type doping as predicted theoretically.

• Received 10 June 2009

DOI:https://doi.org/10.1103/PhysRevB.80.075406