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Zhenyu Zhang

Bio: Zhenyu Zhang is an academic researcher from Oak Ridge National Laboratory. The author has contributed to research in topics: Scanning tunneling microscope & Kinetic Monte Carlo. The author has an hindex of 26, co-authored 51 publications receiving 3135 citations. Previous affiliations of Zhenyu Zhang include Cray & University of Wisconsin-Madison.


Papers
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Journal ArticleDOI
18 Apr 1997-Science
TL;DR: The atomic nature of the most important kinetic mechanisms of film growth is explored, which include adatom diffusion on terraces, along steps, and around island corners; nucleation and dynamics of the stable nucleus; atom attachment to and detachment from terraces and islands; and interlayer mass transport.
Abstract: Growth of thin films from atoms deposited from the gas phase is intrinsically a nonequilibrium phenomenon governed by a competition between kinetics and thermodynamics. Precise control of the growth and thus of the properties of deposited films becomes possible only after an understanding of this competition is achieved. Here, the atomic nature of the most important kinetic mechanisms of film growth is explored. These mechanisms include adatom diffusion on terraces, along steps, and around island corners; nucleation and dynamics of the stable nucleus; atom attachment to and detachment from terraces and islands; and interlayer mass transport. Ways to manipulate the growth kinetics in order to select a desired growth mode are briefly addressed.

814 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a novel electronic growth model for metallic thin films on semiconductor substrates, where the competition between the effects of quantum confinement, charge spilling and interface-induced Friedel oscillations is defined, as characterized by the existence of critical/magic thicknesses for smooth growth.
Abstract: We present a novel {open_quotes}electronic growth{close_quotes} model for metallic thin films on semiconductor substrates. Depending on the competition between the effects of quantum confinement, charge spilling, and interface-induced Friedel oscillations, different types of film stability are defined, as characterized by the existence of critical/magic thicknesses for smooth growth. In particular, smooth growth can be achieved only above a few monolayers for noble metals, and only for the first layer for alkali metals. {copyright} {ital 1998} {ital The American Physical Society}

288 citations

Journal ArticleDOI
TL;DR: On a vicinal surface under stress, elastic relaxation at steps produces a long-range attractive interaction between the steps, but the surface is unstable against step bunching, driven by the energetics of the system rather than by the kinetics of step flow.
Abstract: On a vicinal surface under stress, elastic relaxation at steps produces a long-range attractive interaction between the steps. As a result, the surface is unstable against step bunching, driven by the energetics of the system rather than by the kinetics of step flow. This bunching instability differs from the predictions of previous continuum models by its lack of a characteristic wavelength. Instead, it evolves by progressive coalescence of step bunches. Flux can dramatically modify this evolution, limiting the growth of step bunches.

265 citations

Journal ArticleDOI
TL;DR: In situ scanning tunneling microscopy analysis of In clusters, combined with first-principles total energy calculations, unveils unique initial-stage atomic structures of the surface-supported clusters and the vital steps that lead to the success of this method.
Abstract: A method, by which periodic two-dimensional arrays of identical metal clusters of nanometer size and spacing could be spontaneously obtained by taking advantage of surface mediated clustering, is reported. The versatility of the method is demonstrated for a broad range of metals on $\mathrm{Si}(111)\ensuremath{-}(7\ifmmode\times\else\texttimes\fi{}7)$ substrates. In situ scanning tunneling microscopy analysis of In clusters, combined with first-principles total energy calculations, unveils unique initial-stage atomic structures of the surface-supported clusters and the vital steps that lead to the success of this method. A strong interaction between the clusters and the surface holds the key to the observed cluster sizes.

255 citations

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TL;DR: In this article, the diffusion and coarsening of two-dimensional homoepitaxial islands on Cu(100) and Ag (100) surfaces have been studied at room temperature with time-sequenced scanning tunneling microscopy.
Abstract: The diffusion and coarsening of two-dimensional homoepitaxial islands on Cu(100) and Ag(100) surfaces have been studied at room temperature with time-sequenced scanning tunneling microscopy. Quantitative analyses of the dependence of island diffusion coefficient $D$ vs the island side length $L$, $D\ensuremath{\propto}{L}^{\ensuremath{-}\ensuremath{\alpha}}$, yield noninteger scaling exponents which are consistent with island coalescence. Moreover, the near absence of island decay shows that the island diffusion occurs via mass transport along the island periphery.

158 citations


Cited by
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Journal ArticleDOI
TL;DR: A comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals, including a brief introduction to nucleation and growth within the context of metal Nanocrystal synthesis, followed by a discussion of the possible shapes that aMetal nanocrystal might take under different conditions.
Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

4,927 citations

Journal ArticleDOI
TL;DR: Fractional dynamics has experienced a firm upswing during the past few years, having been forged into a mature framework in the theory of stochastic processes as mentioned in this paper, and a large number of research papers developing fractional dynamics further, or applying it to various systems have appeared since our first review article on the fractional Fokker-Planck equation.
Abstract: Fractional dynamics has experienced a firm upswing during the past few years, having been forged into a mature framework in the theory of stochastic processes. A large number of research papers developing fractional dynamics further, or applying it to various systems have appeared since our first review article on the fractional Fokker–Planck equation (Metzler R and Klafter J 2000a, Phys. Rep. 339 1–77). It therefore appears timely to put these new works in a cohesive perspective. In this review we cover both the theoretical modelling of sub- and superdiffusive processes, placing emphasis on superdiffusion, and the discussion of applications such as the correct formulation of boundary value problems to obtain the first passage time density function. We also discuss extensively the occurrence of anomalous dynamics in various fields ranging from nanoscale over biological to geophysical and environmental systems.

2,119 citations

Journal ArticleDOI
29 Sep 2005-Nature
TL;DR: This work presents an autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces that combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed.
Abstract: The fabrication methods of the microelectronics industry have been refined to produce ever smaller devices, but will soon reach their fundamental limits. A promising alternative route to even smaller functional systems with nanometre dimensions is the autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces. This approach combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials.

2,013 citations

Journal ArticleDOI
TL;DR: This report introduces briefly some concepts and materials on crystal growth presented by Dr. Zhen-yu Zhang from the Oak Ridge (TN) National Laboratory, and Dr. En-ge Wang from the Institute of Physics, Chinese Academy of Sciences in a session on Crystal growth at the first Chinese-American Frontiers of Science Symposium.
Abstract: This report introduces briefly some concepts and materials on crystal growth presented by Dr. Zhen-yu Zhang from the Oak Ridge (TN) National Laboratory, and Dr. En-ge Wang from the Institute of Physics, Chinese Academy of Sciences, in a session on crystal growth at the first Chinese-American Frontiers of Science Symposium. Crystal growth involves a variety of research fields ranging from surface physics, crystallography, and material sciences to condenser mater physics. Though it has been studied extensively more than 100 years, crystal growth still plays an important role in both theoretical and experimental research fields, as well as in applications. For example, how to growth ideal high Tc superconductor crystal has become an dominant subject both for testing of superconductor theories and physical properties. Furthermore, carbon 60 and carbon nano-tubes have opened a new field to both condensed mater physics and chemistry. From the recent discoveries in high Tc superconductors and C60, which brought the Nobel prize to the pioneer researchers in this field, one can understand the importance of crystal growth today. As the development of scientific instruments and analytical methods, such as x-rays, electron microscopy, NMR, and scanning tunneling microscopy continues, research on crystal growth and structure characterization has entered an atomic level, which makes it possible for further understanding of the physical, chemical, and other properties of the structure nature of various crystals. Especially for the crystals with low dimension and nano-structures, such as carbon nanotubes, blue-light emitting GaN thin films, and magnetic multilayers with giant magneto-resistance, their abnormal properties that have great potential in application can be understood only with the knowledge of structure at the atomic level. Moreover, a further improvement of crystal quality also depends on the structure characterizations. Based on its importance described above, crystal growth had been chosen as one of the topics …

1,958 citations

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TL;DR: The facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick are reported, using carbon monoxide as a surface confining agent and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region.
Abstract: Ultrathin sheets of palladium exhibit a tunable surface plasmon resonance in the near infrared and useful catalytic properties.

1,337 citations