Combinatorial CuNi alloy thin film catalysts for layer number regulation in CVD grown graphene

In this work, synthesis of combinatorial library of Cu_xNi_1-x (copper nickel) alloy thin films via co-sputtering from Cu (copper) and Ni (nickel) targets as catalysts for chemical vapor deposition (CVD) growth of graphene is reported. The gradient alloy morphology, composition and microstructure were characterized via scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD), respectively. Subsequently, the Cu_xNi_1-x alloy thin films were used to grow graphene in a CH₄-Ar-H₂ (methane-argon-hydrogen) ambient in thermal CVD tube furnace. The underlying rationale is to adjust the Cu_xNi_1-x alloy carbon solubility at a fixed temperature (~1000 ^oC) to control the graphene layer number as the solubility limit of carbon in Cu is approximately 75 +/- 0.5 ppm and C in Ni is 1.3 at.%.

The energy dispersive x-ray spectroscopy (EDS) analysis revealed that a continuous gradient of Cu_xNi_1-x (25.29%68.95%, bilayer growth dominates from 47.56%=3) growth occurs for x<47.56%. Thus, we have overviewed the Raman analysis of the CVD grown graphene layers.

Finally, we show large area bi-layer graphene can be grown via the thin film catalyst with optimized catalyst composition.