Transformation of chemical vapor deposited individual graphene crystal with oxidation of copper substrate

Here, we reveal the structural transformation process of as-synthesized individual graphene crystals with oxidation of a copper (Cu) foil. We found that the transformation of a graphene crystal with Cu oxidation is significantly different for the thermal annealing and room temperature long-term atmospheric oxidation. Annealing creates large cracks in an individual graphene crystal due to the thermal stress and strain created by rapid oxidation of Cu surface. The cracks are further enhanced with longer annealing duration enabling oxygen diffusion through cracks, thereby accelerating oxidization of Cu. Eventually, the graphene crystals are completely damaged, leaving behind the highly oxidized Cu surface. On the other hand, in case of room temperature long-term atmospheric oxidation, oxygen diffusion occurs underneath of a graphene crystal through the reactive edge without any large cracks formation. The graphene crystals decouple from Cu surface during the oxygen diffusion and oxidation process, however no structural deformation is observed. This finding shows the significant contrast of structural change of graphene crystal and oxidation behaviors of Cu surface with thermal annealing and room temperature atmospheric oxidation. (C) 2014 Elsevier Ltd. All rights reserved.