Introducing Carbon Diffusion Barriers for Uniform, High-Quality Graphene Growth from Solid Sources

Abstract

Carbon diffusion barriers are introduced as a general and simple method to prevent premature carbon dissolution and thereby to significantly improve graphene formation from the catalytic transformation of solid carbon sources. A thin Al2O3 barrier inserted into an amorphous-C/Ni bilayer stack is demonstrated to enable growth of uniform monolayer graphene at 600 °C with domain sizes exceeding 50 μm, and an average Raman D/G ratio of <0.07. A detailed growth rationale is established via in situ measurements, relevant to solid-state growth of a wide range of layered materials, as well as layer-by-layer control in these systems.

Chemical vapour deposition of freestanding sub-60 nm graphene gyroids

“…38 When the Ni surface becomes satrurated, the additional hydrocarbon dissociation feeds graphene nucleation at the Ni surface. 39 The relatively small bulk of the gyroids compared to thicker catalyst foams, foils, and films means this point is reached at a lower temperature. Consistent with the Raman results discussed above, a higher nucleation density is thus expected as a result of the lower C diffusivity at this low nucleation temperature, 18 as well as the higher template curvature and thus an abundance of lowcoordination sites which serve as preferential graphene nucleation sites.…”

Co-catalytic Absorption Layers for Controlled Laser-Induced Chemical Vapor Deposition of Carbon Nanotubes

“…We highlight the potential of this approach by demonstrating the local growth of vertically aligned CNT forests directly on flexible polyimide substrates with potential applications ranging from flexible, integrated devices to proteomics. 37,38 by atomic layer deposition (ALD) using a Cambridge Nanotech Savannah system and a 200°C process with tri[methyl]aluminum and water both carried in a N 2 (20 sccm) flow for 200 cycles. 39,40 Ta layers are sputter deposited (100 W, 35 sccm Ar, 3.5 × 10 −3 mbar) in a custom-built DC sputter coater, using a slitshaped shadow mask 41 to create a gradual thickness profile across the sample (∼0−130 nm, measured by profilometry).…”

Protecting nickel with graphene spin-filtering membranes: A single layer is enough

“…While nickel can easily promote the growth of multilayers by CVD, an experimental process has been carefully developed here, with theoretical support, to limit the growth to monolayer graphene. [18][19][20] The graphene monolayer is directly grown on nickel ferromagnetic electrodes by CVD. First, a 150 nm-thick nickel layer is deposited onto the SiO 2 (300 nm)/ Si substrate by thermal evaporation.…”