Chemical Vapor Deposition of Graphene on Cu-Ni Alloys: The Impact of Carbon Solubility

Chemical vapour deposition (CVD) is the most promising graphene synthesis route for film and electronic applications but the growth mechanism is still not fully understood. Herein, we investigate the role of the solubility of carbon in the underlying growth substrate on the CVD growth of graphene. A range of Cu-Ni alloys compositions that cover the carbon (C) solubility range between low C solubility (pure Cu) and high C solubility (pure Ni) were used as the catalytic growth substrates. The CVD of graphene on Cu-Ni alloys showed a transition from bilayer graphene (BLG) to few-layer graphene (FLG) at a substrate Ni concentration of 45 wt.%, which was attributed to an increase in the bulk diffusion of C. The Cu-rich alloys had a high graphene coverage (BLG) at a fast-cooling rate (367 °C/min), while the Ni-rich alloys had a low coverage (FLG) under the same cooling condition. In contrast, at slow cooling rates (27 °C/min), the Cu-rich alloys had a low coverage of graphene (BLG) and the Ni-rich alloys had a high coverage of graphene (FLG). Glow discharge optical emission spectroscopy (GDOES) was used to profile the subsurface composition, particularly the C concentration, as a function of depth.