Towards high quality CVD graphene growth and transfer

Among the different graphene synthesis methods, chemical vapor deposition of graphene on low cost copper foil shows great promise for large scale applications. Here, we present growth experiments to obtain high quality graphene and its clean transfer onto any substrates. Bilayer-free monolayer graphene was obtained by a careful pre-annealing step and by optimizing the H₂ flow during growth. The as-grown graphene was transferred using an improved wet chemical graphene transfer process. Some major flaws in the conventional wet chemical, polymethyl methacrylate (PMMA) assisted, graphene transfer process are addressed. The transferred graphene on arbitrary substrates was found to be free of metallic contaminants, defects (cracks, holes or folds caused by water trapped beneath graphene) and PMMA residues. The high quality of the transferred graphene was further evidenced by angle resolved photoelectron spectroscopy studies, for which the linear dependency of the electronic band structure characteristic of graphene was measured at the Dirac point. This is the first Dirac cone observation on the CVD grown graphene transferred on some 3D bulk substrate.