Figure 2.

a Optical microscope image and b AFM topographic image of as-synthesized graphene on Ni catalytic films. Lower insets of (b) show graphene wrinkles on the substrate with 3 nm height. c Schematic presentation showing the graphene transfer without a polymeric mediator. d Optical microscope image of transferred graphene on a SiO₂-covered Si wafer. e Raman spectra show the intensity enhancement after the transfer