  We investigate the effect of gold (Au) atoms in the form of both point-like
charged impurities and clusters on the transport properties of graphene.
Cryogenic deposition (18 K) of Au decreases the mobility and shifts the Dirac
point in a manner that is consistent with scattering from point-like charged
impurities. Increasing the temperature to room temperature promotes the
formation of clusters, which is verified with atomic force microscopy. We find
that for a fixed amount of Au impurities, the formation of clusters enhances
the mobility and causes the Dirac point to shift back towards zero.
