Improving Graphene Conductivity through Selective Atomic Layer Deposition
Here we report a technique to electrically heal and connect graphene flakes via selective atomic layer deposition (ALD) of conductive materials. We have demonstrated selective growth of ALD aluminum-doped zinc oxide, ruthenium and platinum on pristine graphene surface prepared from exfoliated highly ordered pyrolytic graphite (HOPG). ALD materials nucleate on graphene cracks and edges but exhibit a significant nucleation barrier on intact basal planes due to the chemical inertness from delocalized π-orbitals. We also present a high-throughput fabrication method to create graphene patterns via metal shadow mask and O2 plasma. This model system of patterned CVD graphene islands demonstrates electrical connection of separated graphnene flakes by selective ALD processes. In addition, shadow-mask-patterned CVD graphene field effect transistors (FETs) are used to monitor graphene carrier density and mobility variation after ALD growth. We found considerable carrier density and conductivity increase of a single graphene flake after V2O5 ALD, which can be explained by p-doping of graphene due to the high work function V2O5.