Synthesis of large-area graphene layers on nickel film by chemical vapor deposition: Wrinkle formation

Highly crystalline few-graphene layers were synthesized on poly-nickel, Ni(111) and Ni-deposited substrates by optimizing the mixing ratio of C ₂H₂/H₂ and C₂H₄/H ₂ and growth time. The hydrogen effect was investigated to minimize defects and maintain uniformity of the synthesized few-layer graphenes. Using the optimized ratio of hydrogen and acetylene mixture, few graphene layers with large sizes of up to 4 inches in diameter were also synthesized on Ni evaporated Si substrate with different thicknesses and were transferred successfully onto PET film. We also found that the wrinkles, different from inherent ripples, were formed in the graphene layer independent of the location of the grain boundary of poly-Ni substrate and growth conditions. This was attributed to the formation of a step terrace followed by the terrace bunching to result in higher wrinkles due to the thermal mismatch existing between Ni substrate and graphene layers during thermal quenching. A sheet resistance of 233 ω/sq was obtained at a transmittance of 65%.