RESUMO
Single-layer chemical vapor deposition (CVD)-grown graphene was transferred onto a ZnO (0001) substrate forming a large-area, low-defect density, protective layer. The quality of the graphene layer and its effect on the interaction between the ZnO support and vapor-deposited cobalt particles was investigated by spectroscopic and microscopic techniques. We demonstrate that the in-between graphene layer influences both the oxidation state and the morphology of cobalt upon annealing in vacuum. In particular, cobalt strongly interacts with the bare ZnO substrate forming flat particles, which are readily oxidized and redispersed upon annealing in ultrahigh vacuum conditions. In contrast, in the presence of the graphene interlayer, cobalt forms highly dispersed nanoparticles, which are resistant to oxidation, but prone to surface diffusion and agglomeration. The graphene layer exhibits remarkable stability upon cobalt deposition and vacuum annealing, while interaction with reactive gases can facilitate the formation of defects.
