  The performance of graphene-based transistors is often limited by the large
electrical resistance across the metal-graphene contact. We report an approach
to achieve ultra-low resistance metal contacts to graphene transistors. Through
a process of metal-catalyzed etching in hydrogen, multiple nano-sized pits with
zigzag edges are created in the graphene that form strong chemical bonds with
deposited nickel metallization for source-drain contacts without the need for
further annealing. This facile contact treatment prior to electrode
metallization results in contact resistance as low as 100 ohm-um in
single-layer graphene field-effect transistors, and 11 ohm-um in bilayer
graphene transistors. The treatment is compatible with complementary
metal-oxide-semiconductor fabrication processes, and holds great promise to
meet the contact performance required for the integration of graphene in future
integrated circuits.
