Mesoscale Scanning Electron and Tunneling Microscopy Study of the Surface Morphology of Thermally Annealed Copper Foils for Graphene Growth

摘要

The evolution of the surface morphology of thermally annealed copper foils utilized for graphene growth by Chemical Vapor Deposition (CVD) has been studied by Scanning Tunneling Microscopy, Scanning Electron Microscopy, and optical microscopy to determine the effect of pretreatment and preannealing steps that aimed to increase grain size and reduce surface roughness for subsequent graphene growth. The results of the study show that (a) Fe(NO3)3 etch pretreatment leaves residue and etch quarries on the Cu surface even after thermal annealing, (b) certain preannealing processes yield a crust layer on the foil that can peel off, (c) graphene film can preserve an imprint of the Cu film grain structure after being transferred onto SiO2 substrate, and (d) graphene/Cu surface height variations remain much larger than the diameter of the carbon atom over micrometer length scales. Nevertheless, good quality graphene can be grown on the rough Cu surface, and a layer of graphene on top of the copper reduces its apparent surface roughness.