Fig. 3

Structural characterization of the oxidation behavior of Cu at the presence of multilayer graphene flakes and folded wrinkles. a A representative SEM image of Gr islands grown on a Cu(100) grain, followed by annealing at ~200 °C for 120 min in air. The inset is a higher magnification SEM image of the black-dotted square in a (scale bar=1 μm). Typical SEM images of the fully grown Gr/Cu sample after annealing at ~200 °C in air for b 120 and c 240 min. Blue arrows in b and c indicate the nucleation points of Gr covered by multilayer flakes. d–f An OM image and corresponding Raman G/2D and D map images of a Gr island with a multilayer flake in the center, after being transferred onto SiO₂/Si (from left to right). White arrows in e and f indicate the position of a multilayer Gr flake. g A typical SEM image of the fully grown, air-annealed Gr/Cu sample containing folded wrinkles, after annealing at ~200 °C in air. The right is a higher magnified SEM image of the blue-dotted square, and the red arrows indicate the presence of a kink in the oxidation line features at the folded-wrinkle regions. Scale bars=5 µm a–c, 2 µm d–g. h Schematic diagram represents the effective anti-oxidation mechanism of Cu because of the presence of folded wrinkles in Gr