Pt–Graphene Contacts Fabricated by Plasma Functionalization and Atomic Layer Deposition

Abstract Pt–graphene contacts are fabricated by atomic layer deposition (ALD) on H₂ and O₂ plasma functionalized graphene. The plasma functionalization of graphene enables the growth of uniform Pt layers on graphene by ALD and improves the Pt–graphene interaction, which results in a reduced Pt–graphene contact resistance. Devices created using a H₂ plasma treatment before Pt ALD perform considerably better than the ones created using O₂ plasma treatments (R_c = 0.4 ± 0.2 kΩ µm and R_c = 1.2 ± 0.1 kΩ µm, respectively). The lower performance of the O₂ plasma treatments is attributed to a less favorable Pt–graphene oxide interaction and the amorphization of graphene due to the O₂ plasma interaction. Supporting the latter, density functional theory calculations indicate that the CH groups created by a H₂ plasma treatment leave the π‐conjugation (by C‐p_z orbitals) of graphene largely intact, resulting in good in‐plane and out‐of‐plane conductivity. The CO groups formed by an O₂ plasma treatment however disturb the C‐p_z character, deteriorating the in‐plane conduction of graphene, despite the good out‐of‐plane conduction. The results indicate that the treatment of graphene by H₂ plasma is a straightforward approach to improve the ALD growth on graphene and reduce the Pt–graphene contact resistance.