Figure 4. Characterization of monolayer and bilayer graphene synthesized by C-ion implantation. a) Schematic sketch of physically peeling off the Cu-Ni alloy using a thermal release tape. b) Raman spectra of the monolayer graphene grown on SiO2, Si, glass, and sapphire substrates, synthesized by C-ion implantation with a fluence of 4 × 1015 atoms/cm2. c) Raman spectra of the monolayer and bilayer graphene structures on SiO2 substrate, respectively. The monolayer (bilayer) graphene synthesized by C ion implantation with a fluence of 4 × 1015 (8 × 1015) atoms/cm2. d, g) STM of the monolayer and bilayer graphene, respectively, and the insets correspond to the enlarged images of the selected regions. e, h) SAED patterns of the monolayer and bilayer graphene and HR-TEM image revealing that the graphene is monolayer and bilayer, respectively, and the inserts show the profiles of diffraction spot intensities along a line in e) and h), respectively. f, i) Raman I2D/IG peak intensity ratio maps obtained from the monolayer and bilayer graphene films, respectively.