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Ruiz-Gómez S, Trapero EM, Fernández-González C, Campo AD, Granados-Miralles C, Prieto JE, Khaliq MW, Niño MA, Foerster M, Aballe L, Figuera JDL. A Platform for Addressing Individual Magnetite Islands Grown Epitaxially on Ru(0001) and Manipulating Their Magnetic Domains. CRYSTAL GROWTH & DESIGN 2023; 23:5785-5791. [PMID: 37547877 PMCID: PMC10401631 DOI: 10.1021/acs.cgd.3c00388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 06/06/2023] [Indexed: 08/08/2023]
Abstract
We have grown high-quality magnetite micrometric islands on ruthenium stripes on sapphire through a combination of magnetron sputtering (Ru film), high-temperature molecular beam epitaxy (oxide islands), and optical lithography. The samples have been characterized by atomic force microscopy, Raman spectroscopy, X-ray absorption and magnetic circular dichroism in a photoemission microscope. The magnetic domains on the magnetite islands can be modified by the application of current pulses through the Ru stripes in combination with magnetic fields. The modification of the magnetic domains is explained by the Oersted field generated by the electrical current flowing through the stripes underneath the magnetite nanostructures. The fabrication method is applicable to a wide variety of rock salt and spinel oxides.
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Affiliation(s)
- Sandra Ruiz-Gómez
- Max-Planck-Institut
für Chemische Physik fester Stoffe, Dresden 01187, Germany
| | - Eva María Trapero
- Instituto
de Química Física Blas Cabrera (IQF), CSIC, Madrid 28006, Spain
| | | | | | | | - José Emilio Prieto
- Instituto
de Química Física Blas Cabrera (IQF), CSIC, Madrid 28006, Spain
| | | | - Miguel Angel Niño
- Alba
Synchrotron Light Facility, Cerdanyola
del Valles, Barcelona 08290, Spain
| | - Michael Foerster
- Alba
Synchrotron Light Facility, Cerdanyola
del Valles, Barcelona 08290, Spain
| | - Lucía Aballe
- Alba
Synchrotron Light Facility, Cerdanyola
del Valles, Barcelona 08290, Spain
| | - Juan de la Figuera
- Instituto
de Química Física Blas Cabrera (IQF), CSIC, Madrid 28006, Spain
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2
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Masia F, Langbein W, Fischer S, Krisponeit JO, Falta J. Low-energy electron microscopy intensity-voltage data - Factorization, sparse sampling and classification. J Microsc 2023; 289:91-106. [PMID: 36288376 PMCID: PMC10108219 DOI: 10.1111/jmi.13155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 09/15/2022] [Accepted: 10/17/2022] [Indexed: 01/14/2023]
Abstract
Low-energy electron microscopy (LEEM) taken as intensity-voltage (I-V) curves provides hyperspectral images of surfaces, which can be used to identify the surface type, but are difficult to analyse. Here, we demonstrate the use of an algorithm for factorizing the data into spectra and concentrations of characteristic components (FSC3 ) for identifying distinct physical surface phases. Importantly, FSC3 is an unsupervised and fast algorithm. As example data we use experiments on the growth of praseodymium oxide or ruthenium oxide on ruthenium single crystal substrates, both featuring a complex distribution of coexisting surface components, varying in both chemical composition and crystallographic structure. With the factorization result a sparse sampling method is demonstrated, reducing the measurement time by 1-2 orders of magnitude, relevant for dynamic surface studies. The FSC3 concentrations are providing the features for a support vector machine-based supervised classification of the surface types. Here, specific surface regions which have been identified structurally, via their diffraction pattern, as well as chemically by complementary spectro-microscopic techniques, are used as training sets. A reliable classification is demonstrated on both example LEEM I-V data sets.
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Affiliation(s)
- Francesco Masia
- School of Biosciences, Cardiff University, Cardiff, UK.,School of Physics and Astronomy, Cardiff University, Cardiff, UK
| | | | - Simon Fischer
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Jon-Olaf Krisponeit
- Institute of Solid State Physics, University of Bremen, Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bremen, Germany
| | - Jens Falta
- Institute of Solid State Physics, University of Bremen, Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bremen, Germany
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3
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Grinter DC, Thornton G. Structure and reactivity of model CeO 2surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:253001. [PMID: 35287117 DOI: 10.1088/1361-648x/ac5d89] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
As a key component in many industrial heterogeneous catalysts, the surface structure and reactivity of ceria, CeO2, has attracted a lot of attention. In this topical review we discuss some of the approaches taken to form a deeper understanding of the surface physics and chemistry of this important and interesting material. In particular, we focus on the preparation of ultrathin ceria films, nanostructures and supported metal nanoparticles. Cutting-edge microscopic and spectroscopic experimental techniques are highlighted which can probe the behaviour of oxygen species and atomic defects on these model surfaces.
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Affiliation(s)
- David C Grinter
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - Geoff Thornton
- Department of Chemistry and London Centre for Nanotechnology, University College London, London WC1H 0AJ, United Kingdom
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4
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Ruiz-Gómez S, Mandziak A, Prieto JE, Aristu M, Trapero EM, Soria GD, Quesada A, Foerster M, Aballe L, de la Figuera J. A real-time XAS PEEM study of the growth of cobalt iron oxide on Ru(0001). J Chem Phys 2020; 152:074704. [PMID: 32087633 DOI: 10.1063/1.5140886] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The growth of mixed cobalt-iron oxides on Ru(0001) by high-temperature oxygen-assisted molecular beam epitaxy has been monitored in real time and real space by x-ray absorption photoemission microscopy. The initial composition is a mixed Fe-Co(II) oxide wetting layer, reflecting the ratio of the deposited materials. However, as subsequent growth of three dimensional spinel islands nucleating on this wetting layer takes place, the composition of the oxide in the wetting layer changes as iron is transferred into the spinel islands. The composition of the islands themselves also changes during growth.
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Affiliation(s)
- S Ruiz-Gómez
- Dpto. de Física de Materiales, Univ. Complutense de Madrid, Madrid E-28040, Spain
| | - A Mandziak
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
| | - J E Prieto
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
| | - M Aristu
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
| | - E M Trapero
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
| | - G D Soria
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
| | - A Quesada
- Instituto de Cerámica y Vidrio, CSIC, Madrid E-28049, Spain
| | - M Foerster
- ALBA Synchrotron Light Facility, CELLS, Cerdanyola del Vallés E-08290, Spain
| | - L Aballe
- ALBA Synchrotron Light Facility, CELLS, Cerdanyola del Vallés E-08290, Spain
| | - J de la Figuera
- Instituto de Química Física "Rocasolano," CSIC, Madrid E-28006, Spain
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5
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Shi J, Wittstock A, Mahr C, Murshed MM, Gesing TM, Rosenauer A, Bäumer M. Nanoporous gold functionalized with praseodymia-titania mixed oxides as a stable catalyst for the water-gas shift reaction. Phys Chem Chem Phys 2019; 21:3278-3286. [PMID: 30681677 DOI: 10.1039/c8cp06040a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dealloyed nanoporous metals hold great promise in the field of heterogeneous catalysis; however their tendency to coarsen at elevated temperatures or under catalytic reaction conditions sometimes limit further applications. Here, we report on a highly stable nanoporous gold catalyst (npAu) functionalized with praseodymia-titania mixed oxides as synthesized by a sol-gel method. Specifically, we used aberration-corrected transmission electron microscopy to study the morphology and the interface between the oxide deposits and the npAu substrate at the atomic level. Based on electron energy loss spectroscopy (EELS), it is concluded that Pr-TiOx mixed oxides form a solid solution. Flow reactor tests reveal that the Pr-TiOx functionalized nanoporous gold is not only highly active but also very stable for the water gas shift reaction in a large temperature range (180-400 °C). Our results demonstrate the potential of engineering the compositions of oxides coatings on npAu for advanced functional systems.
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Affiliation(s)
- Junjie Shi
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany.
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Höcker J, Krisponeit JO, Schmidt T, Falta J, Flege JI. The cubic-to-hexagonal phase transition of cerium oxide particles: dynamics and structure. NANOSCALE 2017; 9:9352-9358. [PMID: 28534898 DOI: 10.1039/c6nr09760j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cerium oxide is often applied in today's catalysts due to its remarkable oxygen storage capacity. The changes in stoichiometry during reaction are linked to structural modifications, which in turn affect its catalytic activity. We present a real-time in situ study of the structural transformations of cerium oxide particles on ruthenium(0001) at high temperatures of 700 °C in ultra-high vacuum. Our results demonstrate that the reduction from CeO2 to cubic Ce2O3 proceeds via ordered intermediary phases. The final reduction step from cubic to hexagonal Ce2O3 is accompanied by a lattice expansion, the formation of two new surface terminations, a partial dissolution of the cerium oxide particles, and a massive mass transport of cerium from the particles to the substrate. The conclusions allow for new insights into the structure, stability, and dynamics of cerium oxide nanoparticles in strongly reducing environments.
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Affiliation(s)
- Jan Höcker
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
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7
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Flege JI, Krisponeit JO, Höcker J, Hoppe M, Niu Y, Zakharov A, Schaefer A, Falta J, Krasovskii EE. Nanoscale analysis of the oxidation state and surface termination of praseodymium oxide ultrathin films on ruthenium(0001). Ultramicroscopy 2017; 183:61-66. [PMID: 28526269 DOI: 10.1016/j.ultramic.2017.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 04/18/2017] [Accepted: 05/09/2017] [Indexed: 10/19/2022]
Abstract
The complex structure and morphology of ultrathin praseodymia films deposited on a ruthenium(0001) single crystal substrate by reactive molecular beam epitaxy is analyzed by intensity-voltage low-energy electron microscopy in combination with theoretical calculations within an ab initio scattering theory. A rich coexistence of various nanoscale crystalline surface structures is identified for the as-grown samples, notably comprising two distinct oxygen-terminated hexagonal Pr2O3(0001) surface phases as well as a cubic Pr2O3(111) and a fluorite PrO2(111) surface component. Furthermore, scattering theory reveals a striking similarity between the electron reflectivity spectra of praseodymia and ceria due to very efficient screening of the nuclear charge by the extra 4f electron in the former case.
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Affiliation(s)
- J I Flege
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany.
| | - J-O Krisponeit
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - J Höcker
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - M Hoppe
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Y Niu
- MAX IV Laboratory, Box 118, 221 00 Lund, Sweden
| | - A Zakharov
- MAX IV Laboratory, Box 118, 221 00 Lund, Sweden
| | - A Schaefer
- Division of Synchrotron Radiation Research, Lund University, 221 00 Lund, Sweden
| | - J Falta
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - E E Krasovskii
- Departamento de Física de Materiales, Universidad del Pais Vasco UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain; Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain; IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
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