Figure 2. Morphology and structure characterization of as-grown GNM.

(a) SEM image of the close-packed monolayer of PS nanosphere with the diameter of 230 nm. (b) SEM image of PS nanosphere with ~40 nm gap after O₂ plasma etching. (c) SEM image of periodic SiO₂ mask on Cu foil after CF₄ plasma etching of the exposed SiO₂ and removing of PS nanosphere. (d) OM image of the large-area and homogeneous GNM on Si substrate with 300 nm SiO₂ after graphene growth on patterned Cu foil, removing of SiO₂ mask and the transfer of sample. (e) Low-magnification SEM image of the as-grown GNM showing the existence of boundary line resulted from the configuration of PS nanosphere film. (f) High-magnification SEM image of the GNM morphology. (g) AFM image of GNM structure with the thickness of ~1.1 nm except some PMMA residues from transfer process. (h) AC-HRTEM image and the corresponding Fourier transform of the single-crystal GNM neck. (i) Fourier enhanced TEM micrograph of the marked area in (h) showing a single set of a hexagonal spot pattern.