Ultrafast Transition of Non-Uniform Graphene to High-Quality Uniform Monolayer Film on Liquid Cu

It is essentially important to synthesize uniform graphene films with a controlled number of layers because their properties strongly depend on the number of layers. Although chemical vapor deposition (CVD) on Cu has been widely used to synthesize large-area graphene films, the growth on solid and liquid Cu (L-Cu) suffers from poor thickness uniformity with a great number of adlayers and difficulty in forming continuous films even after a long growth time of hours, respectively. Here, we found that nonuniform graphene films initially grown on solid Cu (S-Cu) foil can rapidly transform into continuously uniform monolayer graphene film on L-Cu within 3 min. Moreover, the films obtained show larger grain size, higher quality, better optical and electrical properties, and better performance in organic light-emitting diode applications than the original films grown on S-Cu foil. By using carbon isotope labeling, we revealed that the multilayer-to-monolayer transition of graphene on L-Cu experiences etching-“se...