title: Energetics and kinetics of Cu atoms and clusters on the Si(111)-7 × 7 surface: first-principles calculations.
abstract: Exploring the properties of noble metal atoms and nano- or subnano-clusters on the semiconductor surface is of great importance in many surface catalytic reactions, self-assembly processes, crystal growth, and thin film epitaxy. Here, the energetics and kinetic properties of a single Cu atom and previously reported Cu magic clusters on the Si(111)-(7 × 7) surface are re-examined by the state-of-the-art first-principles calculations based on density functional theory. First of all, the diffusion path and high diffusion rate of a Cu atom on the Si(111)-(7 × 7) surface are identified by mapping out the total potential energy surface of the Cu atom as a function of its positions on the surface, supporting previous experimental hypothesis that the apparent triangular light spots observed by scanning tunneling microscopy (STM) are resulted from a single Cu atom frequently hopping among adjacent adsorption sites. Furthermore, our findings confirm that in the low coverage of 0.15 monolayer (ML) the previously proposed hexagonal ring-like Cu6 cluster configuration assigned to the STM pattern is considerably unstable. Importantly, the most stable Cu6/Si(111) complex also possesses a distinct simulated STM pattern with the experimentally observed ones. Instead, an energetically preferred solid-centered Cu7 structure exhibits a reasonable agreement between the simulated STM patterns and the experimental images. Therefore, the present findings convincingly rule out the tentative six-atom model and provide new insights into the understanding of the well-defined Cu nanocluster arrays on the Si(111)-(7 × 7) surface.
authors.affiliation: International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China. niuchunyao@zzu.edu.cn.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Ren
authors.forename: Chun-Yao
authors.initials: CY
authors.lastname: Niu
authors.forename: Wei-Guang
authors.initials: WG
authors.lastname: Chen
authors.forename: Ming-Sheng
authors.initials: MS
authors.lastname: Tang
authors.forename: Jun-Hyung
authors.initials: JH
authors.lastname: Cho