Figure 1. Morphology of as-synthesized N-doped graphene (NG) sheets.

(a) Photograph of as-synthesized NG sample on Cu foil. (b) PMMA-coated NG with Cu residues floating on FeCl₃/HCl aqueous solution, which is used as Cu etchant. Cu foil can be completely etched away within ~20 min. (c) NG sheet (1cm×1cm) on silicon wafer with 300 nm-thick SiO₂ coating. This NG sheet was only part of the prepared NG sample shown in (a). It could be any size depending on the dimension of original NG-covered Cu foil for transfer. (d-e) Typical HRTEM images of as-synthesized monolayer NG. The inset of (e) is the corresponding fast Fourier transform (FFT) depicting the hexagonal pattern characteristic of the graphene framework.