  The effect of contact architecture, graphene defect density and
metal-semiconductor work function difference on resistivity of metal-graphene
contacts have been investigated. An architecture with metal on the bottom of
graphene is found to yield resistivities that are lower, by a factor of 4, and
most consistent as compared to metal on top of graphene. Growth defects in
graphene film were found to further reduce resistivity by a factor of 2. Using
a combination of method and metal used, the contact resistivity of graphene has
been decreased by a factor of 10 to 1200 +- 250 Ohm-um using Palladium as the
contact metal. While the improved consistency is due to the metal being able to
contact uncontaminanted graphene in the metal on the bottom architecture, lower
contact resistivities observed on defective graphene with the same metal is
attributed to the increased number of modes of quantum transport in the
channel.
