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Hershberger MT, Hupalo M, Thiel PA, Wang CZ, Ho KM, Tringides MC. Nonclassical "explosive" nucleation in Pb/Si(111) at low temperatures. PHYSICAL REVIEW LETTERS 2014; 113:236101. [PMID: 25526139 DOI: 10.1103/physrevlett.113.236101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Indexed: 06/04/2023]
Abstract
Classically, the onset of nucleation is defined in terms of a critical cluster of the condensed phase, which forms from the gradual aggregation of randomly diffusing adatoms. Experiments in Pb/Si(111) at low temperature have discovered a dramatically different type of nucleation, with perfect crystalline islands emerging "explosively" out of the compressed wetting layer after a critical coverage Θ_{c}=1.22 ML is reached. The unexpectedly high island growth rates, the directional correlations in the growth of neighboring islands and the persistence in time of where mass is added in individual islands, suggest that nucleation is a result of the highly coherent motion of the wetting layer, over mesoscopic distances.
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Affiliation(s)
- M T Hershberger
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - M Hupalo
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
| | - P A Thiel
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA and Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - C Z Wang
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
| | - K M Ho
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - M C Tringides
- Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Menteş TO, Zamborlini G, Sala A, Locatelli A. Cathode lens spectromicroscopy: methodology and applications. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:1873-86. [PMID: 25383299 PMCID: PMC4222408 DOI: 10.3762/bjnano.5.198] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/25/2014] [Indexed: 05/28/2023]
Abstract
The implementation of imaging techniques with low-energy electrons at synchrotron laboratories allowed for significant advancement in the field of spectromicroscopy. The spectroscopic photoemission and low energy electron microscope, SPELEEM, is a notable example. We summarize the multitechnique capabilities of the SPELEEM instrument, reporting on the instrumental aspects and the latest developments on the technical side. We briefly review applications, which are grouped into two main scientific fields. The first one covers different aspects of graphene physics. In particular, we highlight the recent work on graphene/Ir(100). Here, SPELEEM was employed to monitor the changes in the electronic structure that occur for different film morphologies and during the intercalation of Au. The Au monolayer, which creeps under graphene from the film edges, efficiently decouples the graphene from the substrate lowering the Dirac energy from 0.42 eV to 0.1 eV. The second field combines magnetism studies at the mesoscopic length scale with self-organized systems featuring ordered nanostructures. This example highlights the possibility to monitor growth processes in real time and combine chemical characterization with X-ray magnetic circular dichroism-photoemission electron microscopy (XMCD-PEEM) magnetic imaging by using the variable photon polarization and energy available at the synchrotron source.
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Affiliation(s)
- T O Menteş
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy
| | - G Zamborlini
- Department of Physics, University of Trieste, Via Valerio 2, Trieste 34137, Italy
- Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich, Germany
| | - A Sala
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy
| | - A Locatelli
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy
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Matetskiy AV, Bondarenko LV, Gruznev DV, Zotov AV, Saranin AA, Tringides MC. Structural transformations in Pb/Si(111) phases induced by C₆₀ adsorption. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:395006. [PMID: 24013200 DOI: 10.1088/0953-8984/25/39/395006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Structural transformations at the Pb/Si(111) surface occurring upon C₆₀ adsorption onto Pb/Si(111)1 × 1 phase at room temperature and Pb/Si(111)[Formula: see text] at low temperatures between 30 and 210 K, have been studied using scanning tunneling microscopy and low-energy electron diffraction observations. Typically, C₆₀ fullerenes agglomerate into random molecular islands nucleated at the surface defects. C₆₀ island formation is accompanied by expelling Pb atoms to the surrounding surface area where more dense Pb/Si(111) phases form. Productivity of C₆₀-induced expelling of Pb atoms is controlled by surface defects and is suppressed dramatically when regular ('crystalline') C₆₀ islands self-assemble at the defect-free Pb/Si(111) surface. When Pb atoms are ejected by the random C₆₀ islands, extended structural transformations involving reordering of numerous Pb atoms are fully completed at the surface within the shortest possible time (a few dozen seconds) to reapproach and image the surface after C₆₀ deposition. Estimations show that the observed transformations cannot be controlled by random walk diffusion of Pb adatoms, which implies a highly correlated motion of the Pb atom displacements within the layer.
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Affiliation(s)
- A V Matetskiy
- Institute of Automation and Control Processes FEB RAS, 690041 Vladivostok, Russia. School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok, Russia
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Stojić N, Menteş TO, Binggeli N. Self-organization in Pd/W(110): interplay between surface structure and stress. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:355010. [PMID: 23920010 DOI: 10.1088/0953-8984/25/35/355010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
It has recently been shown that submonolayer Pd on W(110) forms highly ordered linear mesoscopic stripes at high temperatures. The stripes display an internal Pd superstructure with a nano-scale periodicity along the direction perpendicular to the periodicity of the stripes. The same type of superstructure is also observed in a wide range of temperatures below the stripe formation temperature. We present a combined experimental and theoretical study of this superstructure of Pd on W(110) and investigate its influence on the appearance of the linear mesoscopic stripes. By means of low-energy electron diffraction and low-energy electron microscopy we show that it has a far more peculiar dependence on temperature and coverage than expected from a regular surface reconstruction. Using density-functional theory, we model the Pd superstructures as periodic vacancy-line type configurations and investigate their energetics and elastic properties. From our calculated surface stresses and anisotropies for the vacancy-line configurations, and based on the continuum elasticity theory, we demonstrate quantitatively that the vacancy-line type of structure is a prerequisite for the formation of the linear mesoscopic stripes. Moreover, we show that the physics driving the formation of the internal superstructure is very similar to the one at play in forming the mesoscopic stripes themselves.
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Affiliation(s)
- N Stojić
- Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Trieste I-34151, Italy. IOM-CNR Democritos, Trieste, I-34151, Italy.
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Menteş T, Locatelli A, Aballe L, Niño M, Bauer E. Growth of magnetic nanowires on self-organized stripe templates: Fe on Pd–O/W(110). Ultramicroscopy 2013; 130:82-6. [DOI: 10.1016/j.ultramic.2013.03.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 03/14/2013] [Accepted: 03/18/2013] [Indexed: 10/27/2022]
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Mendoza-Coto A, Stariolo DA. Coarse-grained models of stripe forming systems: phase diagrams, anomalies, and scaling hypothesis. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:051130. [PMID: 23214761 DOI: 10.1103/physreve.86.051130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Indexed: 06/01/2023]
Abstract
Two coarse-grained models which capture some universal characteristics of stripe forming systems are studied. At high temperatures, the structure factors of both models attain their maxima on a circle in reciprocal space, as a consequence of generic isotropic competing interactions. Although this is known to lead to some universal properties, we show that the phase diagrams have important differences, which are a consequence of the particular k dependence of the fluctuation spectrum in each model. The phase diagrams are computed in a mean field approximation and also after inclusion of small fluctuations, which are shown to modify drastically the mean field behavior. Observables like the modulation length and magnetization profiles are computed for the whole temperature range accessible to both models and some important differences in behavior are observed. A stripe compression modulus is computed, showing an anomalous behavior with temperature as recently reported in related models. Also, a recently proposed scaling hypothesis for modulated systems is tested and found to be valid for both models studied.
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Affiliation(s)
- Alejandro Mendoza-Coto
- Departamento de Física, Universidade Federal do Rio Grande do Sul, CP 15051, 91501-970 Porto Alegre, Brazil
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Altman MS. Trends in low energy electron microscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:084017. [PMID: 21389393 DOI: 10.1088/0953-8984/22/8/084017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Low energy electron microscopy (LEEM) and spin polarized LEEM (SPLEEM) are two powerful in situ techniques for the study of surfaces, thin films and other surface-supported nanostructures. Their real-time imaging and complementary diffraction capabilities allow the study of structure, morphology, magnetism and dynamic processes with high spatial and temporal resolution. Progress in methods, instrumentation and understanding of novel contrast mechanisms that derive from the wave nature and spin degree of freedom of the electron continue to advance applications of LEEM and SPLEEM in these areas and beyond. We review here the basic imaging principles and recent developments that demonstrate the current capabilities of these techniques and suggest potential future directions.
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Affiliation(s)
- M S Altman
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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