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Growth of ultra-uniform graphene using a Ni/W bilayer metal catalyst Appl. Phys. Lett. 106, 043110 (2015); 10.1063/1.4907166 Improvement of graphene field-effect transistors by hexamethyldisilazane surface treatment

We fabricated graphene/Ni patterns directly on sapphire substrates through a self-forming process utilizing the pattern-controlled catalyst metal agglomeration technique, which was accomplished via a thermal annealing process of rectangular Ni patterns preformed on thin amorphous carbon films on sapphire. It was confirmed that graphene films were synthesized along with the preformed Ni patterns as a result of the progress of Ni agglomeration. Notably, a few-layer graphene film was observed in specific areas along the periphery of the preformed Ni patterns. The self-forming graphene/Ni patterns showed ohmic conductivity with a contact resistance ranging from 4 × 104 to 7 × 104 Ω μm.