Figure 4.

Synthesis of graphene. (A) Major fabrication methods of graphene. Top-down methods include mechanical cleavage and liquid-phase exfoliation of graphite. Additionally, the chemical exfoliation of graphite produces GO, which is then reduced to rGO. CVD is a representative bottom-up method that involves the decomposition of carbon sources and the subsequent deposition of carbon atoms onto substrates. (B) Photograph of a multilayer graphene flake fabricated by micromechanical cleavage. Reproduced with permission from ref (34). Copyright 2004 American Association for the Advancement of Science. (C) TEM images of a typical monolayer graphene flake fabricated by the liquid-phase exfoliation method. Inset: a diffraction pattern taken from a monolayer. Reproduced with permission from ref (165). Copyright 2010 Wiley-VCH. (D) SEM image of rGO flakes on Si/SiO₂ substrate. Reproduced with permission from ref (178). Copyright 2013 Wiley-VCH. (E) SEM images of graphene on Cu grown by CVD. Reproduced from ref (185). Copyright 2011 American Chemical Society.