  The effects of Au grains on graphene conduction and doping are investigated
in this report. To obtain a clean Au-graphene contact, Au grains are deposited
over graphene at elevated temperature and in high vacuum, before any chemical
processing. The bulk and the effective contact resistance versus gate voltage
demonstrate that Au grains cause p-doping in graphene. The Fermi level shift is
in agreement with first principles calculations, but the equilibrium separation
we find between the graphene and the top-most Au layer is larger than
predicted. Nonequilibrium electron transport displays giant-phonon thresholds
observed in graphene tunnel junctions, demonstrating the tunneling nature of
the contact, even though there are no dielectrics involved.
