Extended Data Fig. 4: ICP post-treatment of different graphene films on Cu(111).
a, AFM image of weakly defective graphene films after UHV annealing, subsequent H2 annealing and H2 ICP with light (see Methods) treatment. Inset, the related AFM phase images. The bubbles apparently occur only after ICP treatment. b, Raman spectra of a collected at similar position. The Raman frequencies show an obvious shift after H2 ICP treatment. c, AFM image of films with a medium defect level, after UHV annealing, subsequent H2 annealing, H2 ICP @ dark treatment and H2 ICP with light treatment. d, Raman spectra of c collected at the similar position, showing almost no shift. e, AFM image of the heavily defective films after UHV annealing, subsequent H2 annealing, H2 ICP with dark treatment and H2 ICP with light treatment. f, Raman spectra of e collected at similar position, showing no obvious shift. g, AFM image of the as-grown wrinkled graphene films on Cu(111), after He ICP treatment at 400 °C and 650 °C. h, Raman spectra collected from the similar position of g. i, Raman shifts collected from five different positions, showing random shift and no defects formed (no increase in the intensity at ~1,350 cm−1 of the D band). All the above results show that the atomic hydrogen, molecular hydrogen, He and He+ are not helpful in decoupling the defect-free graphene or weakly defective graphene, so only protons (and electrons) in an H2 plasma will permeate CVD-grown graphene to fully decouple it from the substrates. Scale bars in a, c, e and g are all 1 μm.
