title: Contrasting behavior of carbon nucleation in the initial stages of graphene epitaxial growth on stepped metal surfaces.
abstract: Using first-principles calculations within density functional theory, we study the energetics and kinetics of C nucleation in the early stages of epitaxial graphene growth on three representative stepped metal surfaces: Ir(111), Ru(0001), and Cu(111). We find that on the flat surfaces of Ir(111) and Ru(0001), two C atoms repel each other, while they prefer to form a dimer on Cu(111). Moreover, the step edges on Ir and Ru surfaces cannot serve as effective trapping centers for single C adatoms, but can readily facilitate the formation of C dimers. These contrasting behaviors are attributed to the delicate competition between C-C bonding and C-metal bonding, and a simple generic principle is proposed to predict the nucleation sites of C adatoms on many other metal substrates with the C-metal bond strengths as the minimal inputs.
authors.affiliation: Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
authors.forename: Wenguang
authors.initials: W
authors.lastname: Zhu
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Zhang