1,720,992 research outputs found
Metals on oxides: structure, morphology and interface chemistry
No full textIn this paper we review our recent studies on the structure, morphology andinterface chemistry of different metal systems on simple rock-salt oxides,providing a basis for the understanding of their properties.Fe on both MgO and NiO grows in the cubic structure with the(001)Fe _ (001)oxide and [110]Fe _ [100]oxide orientation.The Fe/MgO interface is sharp at the atomic level up to 400 ◦C, thusshowing that MgO can allow the growth of ‘free standing’ Fe films and lowdimensionalstructures. Submicrometric Fe dots on MgO have been preparedby FIB milling and characterized by the magneto-optical Kerr effect. Atthe Fe/NiO(001) interface an Fe–Ni body centred tetragonal alloyed phase isformed on top of a two-dimensional FeO layer situated at the interface. TheFeO layer presents an expansion of the interplanar distance at the interfaceand a buckling in the Fe and O atomic positions. The presence of thestructurally distorted FeO phase is predicted by ab initio density functionaltheory calculations to increase the spin magnetic moment of Fe atoms by 0.6 μBcompared to the ideally abrupt interface. A reduction of NiO is also induced bythe deposition of (supposedly) inert Au films, which incorporate the metallicNi atoms. The reduction takes place at the low-coordination sites at the surfaceof the NiO film. The Co/MgO(001) system has also been studied. In all theinvestigated cases, given the lower surface free energy of the oxide surfacescompared to the metal ones, the deposited metals tend to form islands, whichcoalesce above a few monolayers
Chemical reactions and interdiffusion at the Fe/NiO(001) interface
No full textThe interaction between Fe and NiO(001) surface for increasing metal deposition at RT was studied by means of Xrayphotoelectron spectroscopy and X-ray photoelectron diffraction. NiO reduces to an extent that depends on theamount of deposited Fe, up to a maximum of 1ML for Fe deposition of 5ML or larger. The overlayer initially growsin a 3D island mode, with partial intermixing between the deposited Fe atoms and the metallic Ni atoms resulting fromthe reduction process. The intermixed region extends up to about 3ML. For 5ML Fe deposition, the islands coalesceinto a continuous film. 2004 Elsevier B.V. All rights reserved
Interfacial reactivity and morphology at the Au/NiO(001) interface
No full textThe interest on metal-oxide interfaces is stimulated stimulated by the applications in many fields, such as catalysis, magnetic ecording, hard coatings. In the first stages of growth, gold nanoparticles dispersed on different oxides exhibit unusual electronic properties, depending on cluster size and gold-substrate interaction [1,2]. In particular a partial charge transfer
can occur, especially when the substrate is defective since gold tends to nucleate on oxygen vacancies. Thus the properties of goldoxide systems are critically dependent on interface reactions, in turn influenced by substrate preparation. A deeper understanding of the reactivity at the gold-oxide interface is essential to determine and control properties and behaviour of supported gold clusters. In this work we present a study of Au nucleation on top of 10 ML NiO film on Ag(001). By means of XPS, XPD and STM/AFM we studied electronic properties and morphology of the first stages of growth. It was previously reported that deposition of 15 A Au on NiO/Ag(001) causes oxide reduction [3]. We provide detailed and quantitative description
of the chemical interactions at this interface. From these results we aim to determine a relation between NiO reduction and morphological modifications (cluster formation and step decoration) in order to understand the driving force of the reduction process. Similar metal-oxide interfaces have been
also studied [4,5] to identify a general trend
in nucleation and reaction processes. In particular Fe, Pt on NiO and Fe, Pt, Au on MgO have been comparatively investigated.
[1] A. Sanchez, S. Abbet, U. Heiz, W.-D. Schneider, H. Hkkinen, R.N. Barnett, U. Landman, J. Phys. Chem. A 103(1999) 9573
[2] Z. Yang, R. Wu, D.W. Goodman, Phys. Rev. B 61 (2000) 14066
[3] R. de Masi, D. Reinicke, F. Mller, P. Steiner, S. Hfner, Surf. Sci. 515 (2002) 523
[4] S. Benedetti, P. Luches, M. Liberati, S. Valeri, Surf. Sci. 572 (2004) L348
[5] P. Luches, S. Benedetti, M. Liberati, F. Boscherini, I.I. Pronin, S. Valeri, Surf. Sci., in pres
Chromium-Doped MgO Thin Films: Morphology, Electronic Structure, and Segregation Effects
No full textIncorporation of Cr into a crystalline MgO(001) thin film has been investigated by means of scanning tunnelingmicroscopy, X-ray photoelectron spectroscopy, and diffraction. For this purpose, samples of different Cr content (0−33 at %) and postannealing treatments (300−1050 K) have been analyzed. The Cr impurities mainly adopt a 3+ oxidation state, which renders the formation of compensating Mg vacancies necessary to maintain charge neutrality. Only at 33 at % doping amount are Cr6+ species detected in the as-grown films, indicating the development of a metastable CrO3 phase. At low doping level, the Cr ions fully dissolve in the MgO lattice, while segregation toward the surface is observed for Cr-rich films. In the latter case, a new surface oxide develops that is characterized by a lower binding energy of the Mg 1s and Cr 2p core levels and a (2 × 1) superstructure with respect to weakly doped MgO. In combination with a distinct 4-fold symmetric XPD pattern, the new surface phase resembles Mg chromite (MgCr2O4) growing on top of the heavily doped MgO film. Our study provides insight into the technologically relevant transition region between doped binary and ternary oxides
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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