title: Defect-like structures of graphene on copper foils for strain relief investigated by high-resolution scanning tunneling microscopy.
abstract: Understanding of the continuity and the microscopic structure of as-grown graphene on Cu foils through the chemical vapor deposition (CVD) method is of fundamental significance for optimizing the growth parameters toward high-quality graphene. Because of the corrugated nature of the Cu foil surface, few experimental efforts on this issue have been made so far. We present here a high-resolution scanning tunneling microscopy (STM) study of CVD graphene directly on Cu foils. Our work indicates that graphene can be grown with a perfect continuity extending over both crystalline and noncrystalline regions, highly suggestive of weak graphene-substrate interactions. Due to thermal expansion mismatch, defect-like wrinkles and ripples tend to evolve either along the boundaries of crystalline terraces or on noncrystalline areas for strain relief. Furthermore, the strain effect arising from the conforming of perfect two-dimensional graphene to the highly corrugated surface of Cu foils is found to induce local bonding configuration change of carbon from sp(2) to sp(3), evidenced by the formation of "three-for-six" lattices.
authors.affiliation: Center for Nanochemistry (CNC), Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Teng
authors.initials: T
authors.lastname: Gao
authors.forename: Yabo
authors.initials: Y
authors.lastname: Gao
authors.forename: Shubao
authors.initials: S
authors.lastname: Xie
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Ji
authors.forename: Kai
authors.initials: K
authors.lastname: Yan
authors.forename: Hailin
authors.initials: H
authors.lastname: Peng
authors.forename: Zhongfan
authors.initials: Z
authors.lastname: Liu
mesh_terms: D055119:Elastic Modulus; D006108:Graphite / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D046911:Macromolecular Substances; D006108:Graphite