Figure 2: AFM images of graphene oxide patterns produced on the sapphire.

(a) Surface topography of graphene oxide patterns before thermal reduction process. The graphene oxide film is piled up (as high as 200 nm) around the circular hole pattern during the photoresist removal process. (b) Representative surface topography of a graphene oxide film subjected to annealing at 1100 °C for 10 min in a metal-organic chemical vapour deposition reactor. The height profiles obtained along the solid black lines marked in the images are provided under respective images. The red arrows in each image represent two selected points at which the vertical height difference gives a direct measure of the graphene oxide thickness.