Growth Mechanism and Controlled Synthesis of AB-Stacked Bilayer Graphene on Cu–Ni Alloy Foils

Abstract

Strongly coupled bilayer graphene (<i>i.e.</i>, AB stacked) grows particularly well on commercial “90–10” Cu–Ni alloy foil. However, the mechanism of growth of bilayer graphene on Cu–Ni alloy foils had not been discovered. Carbon isotope labeling (sequential dosing of ¹²CH₄ and ¹³CH₄) and Raman spectroscopic mapping were used to study the growth process. It was learned that the mechanism of graphene growth on Cu–Ni alloy is by precipitation at the surface from carbon dissolved in the bulk of the alloy foil that diffuses to the surface. The growth parameters were varied to investigate their effect on graphene coverage and isotopic composition. It was found that higher temperature, longer exposure time, higher rate of bulk diffusion for ¹²C <i>vs</i> ¹³C, and slower cooling rate all produced higher graphene coverage on this type of Cu–Ni alloy foil. The isotopic composition of the graphene layer(s) could also be modified by adjusting the cooling rate. In addition, large-area, AB-stacked bilayer graphene transferrable onto Si/SiO₂ substrates was controllably synthesized