Surface structures of single-crystal graphene on Cu/Ni(111) and Ge(110) substrates studied by scanning tunneling microscopy

The success in the synthesis of wafer-size single-crystal graphene enables a tremendous breakthrough in the development of graphene-based devices. Understanding the growth mechanism is essential for the design of suitable substrates to meet the demand of various applications. Here, we investigate the detailed growth process of the monolayer single-crystal graphene on Cu/Ni(111) and Ge(110) surfaces using scanning tunneling microscopy. The ( 3 × 3 ) R 30 ° surface structure on Cu/Ni(111) and 1 × 1 atomic structure on Ge(110) are found to match the graphene lattice along the armchair direction. These specific atomic arrangements dictate the quasiepitaxial nature of graphene growth on both substrates despite their apparent differences in native lattice geometry.