Effect of copper substrate oxidation and crystals orientations on nucleation of triangular graphene domains

In graphene fabrication by chemical vapor deposition (CVD), substrate crystal structure and orientation play an essential role in the formation of graphene shapes. This work gives experimental evidence and creates a better understanding of the role of oxygen on graphene domains' shape. It explains for the first time how triangular-shaped graphene is formed on copper. The experimental results verify that the growth of the triangular graphene is self-limited, and it is as a result of Cu substrate oxidation. In this work, the copper substrate and graphene were studied before and after growth by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoemission spectroscopy (XPS). The results reveal that the triangular-shaped graphene is multilayered and covalent with oxygen. It shows that this type of graphene is grown on Cu2O grains of (111) facets. This work confirms that the nucleation mechanism and the angles of triangular shape graphene are affected by structure of substrate crystals, facets, and orientations.