Figure 2. Graphene growth on Ni(111).

(a) An SEM image, obtained with an in-lens detector, reveals the surface morphology of the continuous nickel thin film composed of steps and terraces post-graphene growth at 1000 °C. The red arrow shows a prominent step edge. (b) An SEM image of the same region shown in (a), taken with a low angle secondary electron detector that is more sensitive to the graphene layers. The red outline serves to show the same step-edge depicted in (a). The areas of dark contrast correspond to thicker graphene layers due to attenuation of the secondary electrons emitted from the underlying nickel. The nickel thin film is entirely covered with graphene as evidenced by the presence of graphene wrinkles, which appear as bright contrast (blue arrows). (c) A cross-sectional TEM image that exemplifies a graphene growth mechanism on nickel. The red line shows the nickel and graphene interface where the dark region underneath is the nickel substrate. The faceted step edge serves as a nucleation region for thicker multilayer graphene while the higher terrace is covered by bilayer graphene.