1. OM images of different copper substrates(a) Untreated copper substrate; (b) Hydrochloric acid etching treatment; (c) Hydrochloric acid etching and electrochemical polishing treatment; (d) Passivation paste etching; (e) Passivation paste etching and electrochemical polishing treatment

2. OM images of copper substrates electrochemical polished with different voltages and time(a1) 1.2 V/10 min; (a2) 1.2 V/20 min; (a3) 1.2 V/30 min; (a4) 1.2 V/40 min; (b1) 4 V/10 min; (b2) 4 V/20 min; (b3) 4 V/30 min; (b4) 4 V/40 min; (c1) 8 V/6 min; (c2) 8 V/8 min; (c3) 8 V/10 min; (c4) 8 V/12 min

3. OM images of copper substrates annealed at different temperatures for 30 min (a) 800 ℃; (b) 900 ℃; (c) 1000 ℃; (d) 1060 ℃

4. OM images of copper substrates annealed at 1000 ℃ for different time (a) 0; (b) 30 min; (c) 90 min; (d) 120 min

5. SEM image of graphene sample

6. Raman spectra of quartz substrate (a), graphene sample in gray area (b), and graphene sample in dark gray area (c)