Nondestructive characterization of graphene defects

An effective method is reported for oxidizing graphene/copper film in which air oxidation of the underlying copper film occurs through the grain boundary lines of graphene without oxidizing graphene. This oxidation is realized by partially immersing the graphene/copper film in sodium chloride solution. Electrons generated during etching of the graphene/copper film in electrolyte diffuse into the film in contact with air, which eventually enhances air oxidation of copper through the graphene layer. While the graphene layer acts as a protective layer against oxidation of the copper film, oxidation of the underlying Cu film near graphene grain boundary lines is observed by optical microscopy. This observation could be attributed to the selective diffusion of oxygen radicals through isolated defects and graphene grain boundaries. The process involves no appreciable oxidation of the graphene layer including the graphene grain boundary, as confirmed by use of detailed Raman and X-ray photoelectron spectroscopy. An effective method for nondestructive characterization of graphene defects is shown by enhancing oxidation of a Cu film underneath graphene through the graphene grain boundaries in air by electron injection supplied from electrochemical reaction of the graphene/Cu film. This process involves no appreciable oxidation of the graphene layer or the graphene grain boundary, as confirmed by detailed Raman and X-ray photoelectron spectroscopy.