1：Experimental Design and Method Selection:

A two-step CVD method was designed. Step 1: Growth of non-uniform continuous graphene films on solid Cu (S-Cu) foil at 1,070 °C under H2 and Ar flow with CH4 as carbon source. Step 2: Transformation on liquid Cu (L-Cu) by raising temperature above the melting point of Cu (1,084 °C) to 1,090 °C for 3 min under continuous CH4 supply. The method leverages the uniform surface of L-Cu to achieve etching-‘self-aligning’-coalescence processes.

2：Sample Selection and Data Sources:

A 25-μm-thick Cu foil (99.999 wt.% purity) placed on a 50-μm-thick W foil (99.5 wt.% purity) was used as the substrate. Graphene films were characterized after transfer to SiO2/Si substrates, PET, or TEM grids.

3：999 wt.% purity) placed on a 50-μm-thick W foil (5 wt.% purity) was used as the substrate. Graphene films were characterized after transfer to SiO2/Si substrates, PET, or TEM grids. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: CVD system with fused-silica reaction tube, Cu foil, W foil, CH4, H2, Ar, PMMA, (NH4)2S2O8, acetone, ethanol, nitrogen, TEM grids, SiO2/Si wafers, PET.

4：Experimental Procedures and Operational Workflow:

(1) Heat S-Cu substrate to 1,070 °C under H2 (200 sccm) and Ar (500 sccm). (2) Introduce CH4 (1.5 sccm) for 20 min to grow graphene on S-Cu. (3) Raise temperature to 1,090 °C in 2 min to melt Cu, maintain for 3 min on L-Cu. (4) Cool to room temperature under Ar (100 sccm). Transfer involved spin-coating PMMA, etching Cu with (NH4)2S2O8, and cleaning with acetone.

5：5 sccm) for 20 min to grow graphene on S-Cu. (3) Raise temperature to 1,090 °C in 2 min to melt Cu, maintain for 3 min on L-Cu. (4) Cool to room temperature under Ar (100 sccm). Transfer involved spin-coating PMMA, etching Cu with (NH4)2S2O8, and cleaning with acetone. Data Analysis Methods:

5. Data Analysis Methods: Characterization using SEM, optical microscopy, Raman spectroscopy, AFM, HRTEM, SAED, sheet resistance measurements, transmittance measurements, FET electrical properties, and OLED performance analysis.