1
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Magchiels G, Claessens N, Meersschaut J, Vantomme A. Enhanced accuracy through machine learning-based simultaneous evaluation: a case study of RBS analysis of multinary materials. Sci Rep 2024; 14:8186. [PMID: 38589457 PMCID: PMC11001917 DOI: 10.1038/s41598-024-58265-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 03/27/2024] [Indexed: 04/10/2024] Open
Abstract
We address the high accuracy and precision demands for analyzing large in situ or in operando spectral data sets. A dual-input artificial neural network (ANN) algorithm enables the compositional and depth-sensitive analysis of multinary materials by simultaneously evaluating spectra collected under multiple experimental conditions. To validate the developed algorithm, a case study was conducted analyzing complex Rutherford backscattering spectrometry (RBS) spectra collected in two scattering geometries. The dual-input ANN analysis excelled in providing a systematic analysis and precise results, showcasing its robustness in handling complex data and minimizing user bias. A comprehensive comparison with human supervision analysis and conventional single-input ANN analysis revealed a reduced susceptibility of the dual-input ANN analysis to inaccurately known setup parameters, a common challenge in material characterization. The developed multi-input approach can be extended to a wide range of analytical techniques, in which the combined analysis of measurements performed under different experimental conditions is beneficial for disentangling details of the material properties.
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Affiliation(s)
- Goele Magchiels
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium.
| | - Niels Claessens
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
- IMEC, Kapeldreef 75, 3001, Leuven, Belgium
| | | | - André Vantomme
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
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2
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Kraemer S, Moens J, Athanasakis-Kaklamanakis M, Bara S, Beeks K, Chhetri P, Chrysalidis K, Claessens A, Cocolios TE, Correia JGM, Witte HD, Ferrer R, Geldhof S, Heinke R, Hosseini N, Huyse M, Köster U, Kudryavtsev Y, Laatiaoui M, Lica R, Magchiels G, Manea V, Merckling C, Pereira LMC, Raeder S, Schumm T, Sels S, Thirolf PG, Tunhuma SM, Van Den Bergh P, Van Duppen P, Vantomme A, Verlinde M, Villarreal R, Wahl U. Observation of the radiative decay of the 229Th nuclear clock isomer. Nature 2023; 617:706-710. [PMID: 37225880 DOI: 10.1038/s41586-023-05894-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 02/28/2023] [Indexed: 05/26/2023]
Abstract
The radionuclide thorium-229 features an isomer with an exceptionally low excitation energy that enables direct laser manipulation of nuclear states. It constitutes one of the leading candidates for use in next-generation optical clocks1-3. This nuclear clock will be a unique tool for precise tests of fundamental physics4-9. Whereas indirect experimental evidence for the existence of such an extraordinary nuclear state is substantially older10, the proof of existence has been delivered only recently by observing the isomer's electron conversion decay11. The isomer's excitation energy, nuclear spin and electromagnetic moments, the electron conversion lifetime and a refined energy of the isomer have been measured12-16. In spite of recent progress, the isomer's radiative decay, a key ingredient for the development of a nuclear clock, remained unobserved. Here, we report the detection of the radiative decay of this low-energy isomer in thorium-229 (229mTh). By performing vacuum-ultraviolet spectroscopy of 229mTh incorporated into large-bandgap CaF2 and MgF2 crystals at the ISOLDE facility at CERN, photons of 8.338(24) eV are measured, in agreement with recent measurements14-16 and the uncertainty is decreased by a factor of seven. The half-life of 229mTh embedded in MgF2 is determined to be 670(102) s. The observation of the radiative decay in a large-bandgap crystal has important consequences for the design of a future nuclear clock and the improved uncertainty of the energy eases the search for direct laser excitation of the atomic nucleus.
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Affiliation(s)
- Sandro Kraemer
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium.
- Ludwig-Maximilians-Universität München, Garching, Germany.
| | - Janni Moens
- KU Leuven, Quantum Solid State Physics, Leuven, Belgium
| | | | - Silvia Bara
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | - Kjeld Beeks
- Institute for Atomic and Subatomic Physics, TU Wien, Vienna, Austria
| | | | | | - Arno Claessens
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | - João G M Correia
- Centro de Ciências e Tecnologias Nucleares, Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Bobadela, Portugal
| | - Hilde De Witte
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | - Rafael Ferrer
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | - Sarina Geldhof
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | - Niyusha Hosseini
- Institute for Atomic and Subatomic Physics, TU Wien, Vienna, Austria
| | - Mark Huyse
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | - Yuri Kudryavtsev
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | - Mustapha Laatiaoui
- Department Chemie, Johannes-Gutenberg-Universität, Mainz, Germany
- Helmholtz-Institut Mainz, Mainz, Germany
- GSI Helmholtzzentrum für Scherionenforschung, Darmstadt, Germany
| | - Razvan Lica
- CERN, Geneva, Switzerland
- Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
| | | | - Vladimir Manea
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | | | - Sebastian Raeder
- Helmholtz-Institut Mainz, Mainz, Germany
- GSI Helmholtzzentrum für Scherionenforschung, Darmstadt, Germany
| | - Thorsten Schumm
- Institute for Atomic and Subatomic Physics, TU Wien, Vienna, Austria
| | - Simon Sels
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | | | | | - Piet Van Duppen
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
| | | | | | | | - Ulrich Wahl
- Centro de Ciências e Tecnologias Nucleares, Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Bobadela, Portugal
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3
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Corte E, Andrini G, Nieto Hernández E, Pugliese V, Costa Â, Magchiels G, Moens J, Tunhuma SM, Villarreal R, Pereira LMC, Vantomme A, Correia JG, Bernardi E, Traina P, Degiovanni IP, Moreva E, Genovese M, Ditalia Tchernij S, Olivero P, Wahl U, Forneris J. Magnesium-Vacancy Optical Centers in Diamond. ACS Photonics 2023; 10:101-110. [PMID: 36691430 PMCID: PMC9855000 DOI: 10.1021/acsphotonics.2c01130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Indexed: 06/17/2023]
Abstract
We provide the first systematic characterization of the structural and photoluminescence properties of optically active centers fabricated upon implantation of 30-100 keV Mg+ ions in synthetic diamond. The structural configurations of Mg-related defects were studied by the electron emission channeling technique for short-lived, radioactive 27Mg implantations at the CERN-ISOLDE facility, performed both at room temperature and 800 °C, which allowed the identification of a major fraction of Mg atoms (∼30 to 42%) in sites which are compatible with the split-vacancy structure of the MgV complex. A smaller fraction of Mg atoms (∼13 to 17%) was found on substitutional sites. The photoluminescence emission was investigated both at the ensemble and individual defect level in the 5-300 K temperature range, offering a detailed picture of the MgV-related emission properties and revealing the occurrence of previously unreported spectral features. The optical excitability of the MgV center was also studied as a function of the optical excitation wavelength to identify the optimal conditions for photostable and intense emission. The results are discussed in the context of the preliminary experimental data and the theoretical models available in the literature, with appealing perspectives for the utilization of the tunable properties of the MgV center for quantum information processing applications.
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Affiliation(s)
- Emilio Corte
- Physics
Department, University of Torino, Torino10125, Italy
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Greta Andrini
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
- Dipartimento
di Elettronica e Telecomunicazioni, Politecnico
di Torino, Torino10129, Italy
| | - Elena Nieto Hernández
- Physics
Department, University of Torino, Torino10125, Italy
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Vanna Pugliese
- Physics
Department, University of Torino, Torino10125, Italy
| | - Ângelo Costa
- KU
Leuven, Quantum Solid State Physics, 3001Leuven, Belgium
| | | | - Janni Moens
- KU
Leuven, Quantum Solid State Physics, 3001Leuven, Belgium
| | | | | | | | - André Vantomme
- KU
Leuven, Quantum Solid State Physics, 3001Leuven, Belgium
| | - João Guilherme Correia
- Centro
de
Ciências e Tecnologias Nucleares, Departamento de Engenharia
e Ciências e Engenharias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066Bobadela LRS, Portugal
| | - Ettore Bernardi
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Paolo Traina
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Ivo Pietro Degiovanni
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Ekaterina Moreva
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Marco Genovese
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Sviatoslav Ditalia Tchernij
- Physics
Department, University of Torino, Torino10125, Italy
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Paolo Olivero
- Physics
Department, University of Torino, Torino10125, Italy
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
| | - Ulrich Wahl
- Centro
de
Ciências e Tecnologias Nucleares, Departamento de Engenharia
e Ciências e Engenharias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066Bobadela LRS, Portugal
| | - Jacopo Forneris
- Physics
Department, University of Torino, Torino10125, Italy
- Istituto
Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino10125, Italy
- Istituto
Nazionale di Ricerca Metrologica (INRiM), Torino10135, Italy
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4
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Tan Z, de Rojas J, Martins S, Lopeandia A, Quintana A, Cialone M, Herrero-Martín J, Meersschaut J, Vantomme A, Costa-Krämer JL, Sort J, Menéndez E. Frequency-dependent stimulated and post-stimulated voltage control of magnetism in transition metal nitrides: towards brain-inspired magneto-ionics. Mater Horiz 2023; 10:88-96. [PMID: 36305823 PMCID: PMC9810105 DOI: 10.1039/d2mh01087a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
Magneto-ionics, which deals with the change of magnetic properties through voltage-driven ion migration, is expected to be one of the emerging technologies to develop energy-efficient spintronics. While a precise modulation of magnetism is achieved when voltage is applied, much more uncontrolled is the spontaneous evolution of magneto-ionic systems upon removing the electric stimuli (i.e., post-stimulated behavior). Here, we demonstrate a voltage-controllable N ion accumulation effect at the outer surface of CoN films adjacent to a liquid electrolyte, which allows for the control of magneto-ionic properties both during and after voltage pulse actuation (i.e., stimulated and post-stimulated behavior, respectively). This effect, which takes place when the CoN film thickness is below 50 nm and the voltage pulse frequency is at least 100 Hz, is based on the trade-off between generation (voltage ON) and partial depletion (voltage OFF) of ferromagnetism in CoN by magneto-ionics. This novel effect may open opportunities for new neuromorphic computing functions, such as post-stimulated neural learning under deep sleep.
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Affiliation(s)
- Zhengwei Tan
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
| | - Julius de Rojas
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
| | - Sofia Martins
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
| | - Aitor Lopeandia
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Cerdanyola del Vallès, E-08193 Barcelona, Spain
| | - Alberto Quintana
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, E-08193 Barcelona, Spain
| | - Matteo Cialone
- CNR-SPIN Genova, Corso F. M. Perrone 24, 16152 Genova, Italy
| | | | | | - André Vantomme
- Quantum Solid State Physics, KU Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
| | - José L Costa-Krämer
- IMN-Instituto de Micro y Nanotecnología (CNM-CSIC), Isaac Newton 8, PTM, 28760 Tres Cantos, Madrid, Spain
| | - Jordi Sort
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, E-08010 Barcelona, Spain
| | - Enric Menéndez
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain.
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5
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Macková A, Lorenz K, Vantomme A. Editorial. EPJ Web Conf 2022. [DOI: 10.1051/epjconf/202226100001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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6
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Leemans J, Dümbgen KC, Minjauw MM, Zhao Q, Vantomme A, Infante I, Detavernier C, Hens Z. Acid–Base Mediated Ligand Exchange on Near-Infrared Absorbing, Indium-Based III–V Colloidal Quantum Dots. J Am Chem Soc 2021; 143:4290-4301. [DOI: 10.1021/jacs.0c12871] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Jari Leemans
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, 9000 Gent, Belgium
| | - Kim C. Dümbgen
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, 9000 Gent, Belgium
| | - Matthias M. Minjauw
- Department of Solid State Sciences, COCOON group, Ghent University, 9000 Gent, Belgium
| | - Qiang Zhao
- Institute for Nuclear and Radiation Physics, KU Leuven, Celestijnenlaan 200d, B-3001 Leuven, Belgium
| | - André Vantomme
- Institute for Nuclear and Radiation Physics, KU Leuven, Celestijnenlaan 200d, B-3001 Leuven, Belgium
| | - Ivan Infante
- Nanochemistry Department, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | | | - Zeger Hens
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, 9000 Gent, Belgium
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7
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Wahl U, Correia JG, Villarreal R, Bourgeois E, Gulka M, Nesládek M, Vantomme A, Pereira LMC. Direct Structural Identification and Quantification of the Split-Vacancy Configuration for Implanted Sn in Diamond. Phys Rev Lett 2020; 125:045301. [PMID: 32794782 DOI: 10.1103/physrevlett.125.045301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 05/28/2020] [Accepted: 07/01/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate formation of the ideal split-vacancy configuration of the Sn-vacancy center upon implantation into natural diamond. Using β^{-} emission channeling following low fluence ^{121}Sn implantation (2×10^{12} atoms/cm^{2}, 60 keV) at the ISOLDE facility at CERN, we directly identified and quantified the atomic configurations of the Sn-related centers. Our data show that the split-vacancy configuration is formed immediately upon implantation with a surprisingly high efficiency of ≈40%. Upon thermal annealing at 920 °C ≈30% of Sn is found in the ideal bond-center position. Photoluminescence revealed the characteristic SnV^{-} line at 621 nm, with an extraordinarily narrow ensemble linewidth (2.3 nm) of near-perfect Lorentzian shape. These findings further establish the SnV^{-} center as a promising candidate for single photon emission applications, since, in addition to exceptional optical properties, it also shows a remarkably simple structural formation mechanism.
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Affiliation(s)
- U Wahl
- KU Leuven, Quantum Solid-State Physics, 3001 Leuven, Belgium
- Centro de Ciências e Tecnologias Nucleares, Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS, Portugal
| | - J G Correia
- Centro de Ciências e Tecnologias Nucleares, Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS, Portugal
| | - R Villarreal
- KU Leuven, Quantum Solid-State Physics, 3001 Leuven, Belgium
| | - E Bourgeois
- Institute for Materials Research (IMO), Hasselt University, 3590 Diepenbeek, Belgium
- IMOMEC division, IMEC, 3590 Diepenbeek, Belgium
| | - M Gulka
- Institute for Materials Research (IMO), Hasselt University, 3590 Diepenbeek, Belgium
| | - M Nesládek
- Institute for Materials Research (IMO), Hasselt University, 3590 Diepenbeek, Belgium
- IMOMEC division, IMEC, 3590 Diepenbeek, Belgium
| | - A Vantomme
- KU Leuven, Quantum Solid-State Physics, 3001 Leuven, Belgium
| | - L M C Pereira
- KU Leuven, Quantum Solid-State Physics, 3001 Leuven, Belgium
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8
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Abstract
Copper is the conventional, broadly applied anode current collector in lithium-ion batteries, because Li does not form intermetallic alloys with Cu at room temperature. Fast diffusion and trapping of lithium in copper were, however, suggested in the past, and the involved diffusion mechanisms are still not clarified. By using three complementary methods, we determine grain boundary and lattice diffusion of lithium in copper. We show that indiffusion into copper is possible not only from metallic lithium deposits at the surface but also from a Li+-containing electrolyte. Lattice diffusion (D0 = 3.9 × 10-9 cm2/s; Ea = 0.68 eV) and grain boundary diffusion (D0 = 1.5 × 10-11 cm2/s; Ea = 0.36 eV) are found to be 13 orders of magnitude lower than previously published. Furthermore, for practical Li-ion battery considerations, lithium trapping in copper current collectors, which relies heavily on operating temperature and morphology, is discussed.
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Affiliation(s)
- Rico Rupp
- Institute of Condensed Matter and Nanosciences, UC Louvain, Place Louis Pasteur 1, B-1348 Louvain-la-Neuve, Belgium
| | - Bart Caerts
- Institute for Nuclear and Radiation Physics, KU Leuven, Celestijnenlaan 200d, B-3001 Leuven, Belgium
| | - André Vantomme
- Institute for Nuclear and Radiation Physics, KU Leuven, Celestijnenlaan 200d, B-3001 Leuven, Belgium
| | - Jan Fransaer
- Department of Materials Science, KU Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium
| | - Alexandru Vlad
- Institute of Condensed Matter and Nanosciences, UC Louvain, Place Louis Pasteur 1, B-1348 Louvain-la-Neuve, Belgium
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9
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Benetti G, Cavaliere E, Brescia R, Salassi S, Ferrando R, Vantomme A, Pallecchi L, Pollini S, Boncompagni S, Fortuni B, Van Bael MJ, Banfi F, Gavioli L. Tailored Ag-Cu-Mg multielemental nanoparticles for wide-spectrum antibacterial coating. Nanoscale 2019; 11:1626-1635. [PMID: 30644952 DOI: 10.1039/c8nr08375d] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Bactericidal nanoparticle coatings are very promising for hindering the indirect transmission of pathogens through cross-contaminated surfaces. The challenge, limiting their employment in nosocomial environments, is the ability of tailoring the coating's physicochemical properties, namely, composition, cytotoxicity, bactericidal spectrum, adhesion to the substrate, and consequent nanoparticles release into the environment. We have engineered a new family of nanoparticle-based bactericidal coatings comprising Ag, Cu, and Mg and synthesized by a green gas-phase technique. These coatings present wide-spectrum bactericidal activity on both Gram-positive and Gram-negative reference strains and tunable physicochemical properties of relevance in view of their "on-field" deployment. The link between material and functional properties is rationalized based on a multidisciplinary and multitechnique approach. Our results pave the way for engineering biofunctional, fully tunable nanoparticle coatings, exploiting an arbitrarily wide number of elements in a straightforward, eco-friendly, high-throughput, one-step process.
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Affiliation(s)
- Giulio Benetti
- Interdisciplinary Laboratories for Advanced Materials Physics (i-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy. luca.gavioli@unicatt and Laboratory of Solid State Physics and Magnetism, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Emanuele Cavaliere
- Interdisciplinary Laboratories for Advanced Materials Physics (i-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy. luca.gavioli@unicatt
| | - Rosaria Brescia
- Electron Microscopy Facility, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova, Italy
| | - Sebastian Salassi
- Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - Riccardo Ferrando
- Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - André Vantomme
- Institute for Nuclear and Radiation Physics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Lucia Pallecchi
- Department of Medical Biotechnologies, University of Siena, Viale Bracci 1, 53100 Siena, Italy
| | - Simona Pollini
- Dipartimento di Medicina Sperimentale e Clinica, Università di Firenze, Largo Brambilla 1, 50134 Firenze, Italy
| | - Selene Boncompagni
- Department of Medical Biotechnologies, University of Siena, Viale Bracci 1, 53100 Siena, Italy
| | - Beatrice Fortuni
- Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Margriet J Van Bael
- Laboratory of Solid State Physics and Magnetism, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Francesco Banfi
- FemtoNanoOptics group, Universitė de Lyon, Institut Lumière Matière (iLM), Université Lyon 1 and CNRS, 10 rue Ada Byron, 69622 Villeurbanne, France
| | - Luca Gavioli
- Interdisciplinary Laboratories for Advanced Materials Physics (i-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy. luca.gavioli@unicatt
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10
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Maes J, Balcaen L, Drijvers E, Zhao Q, De Roo J, Vantomme A, Vanhaecke F, Geiregat P, Hens Z. Light Absorption Coefficient of CsPbBr 3 Perovskite Nanocrystals. J Phys Chem Lett 2018; 9:3093-3097. [PMID: 29790351 DOI: 10.1021/acs.jpclett.8b01065] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Inductively coupled plasma mass spectrometry (ICP-MS) was combined with UV-vis absorption spectroscopy and transmission electron microscopy to determine the size, composition, and intrinsic absorption coefficient μi of 4 to 11 nm sized colloidal CsPbBr3 nanocrystals (NCs). The ICP-MS measurements demonstrate the nonstoichiometric nature of the NCs, with a systematic excess of lead for all samples studied. Rutherford backscattering measurements indicate that this enrichment in lead concurs with a relative increase in the bromide content. At high photon energies, μi is independent of the nanocrystal size. This allows the nanocrystal concentration in CsPbBr3 nanocolloids to be readily obtained by a combination of absorption spectroscopy and the CsPbBr3 sizing curve.
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Affiliation(s)
- Jorick Maes
- Physics and Chemistry of Nanostructures (PCN) , Ghent University , Krijgslaan 281-S3 , B9000 Gent , Belgium
- Center for Nano and Biophotonics , Ghent University , Technologiepark-Zwijnaarde , B9052 Gent , Belgium
| | - Lieve Balcaen
- Atomic and Mass Spectrometry (A&MS) , Ghent University , Krijgslaan 281-S12 , B9000 Gent , Belgium
| | - Emile Drijvers
- Physics and Chemistry of Nanostructures (PCN) , Ghent University , Krijgslaan 281-S3 , B9000 Gent , Belgium
- Center for Nano and Biophotonics , Ghent University , Technologiepark-Zwijnaarde , B9052 Gent , Belgium
| | - Qiang Zhao
- Instituut voor Kern- en Stralingsfysica , KU Leuven , Celestijnenlaan 200d - bus 2418 , BE-3001 Leuven , Belgium
| | - Jonathan De Roo
- Physics and Chemistry of Nanostructures (PCN) , Ghent University , Krijgslaan 281-S3 , B9000 Gent , Belgium
- Department of Chemistry , Columbia University , New York 10027 , United States
| | - André Vantomme
- Instituut voor Kern- en Stralingsfysica , KU Leuven , Celestijnenlaan 200d - bus 2418 , BE-3001 Leuven , Belgium
| | - Frank Vanhaecke
- Atomic and Mass Spectrometry (A&MS) , Ghent University , Krijgslaan 281-S12 , B9000 Gent , Belgium
| | - Pieter Geiregat
- Physics and Chemistry of Nanostructures (PCN) , Ghent University , Krijgslaan 281-S3 , B9000 Gent , Belgium
- Center for Nano and Biophotonics , Ghent University , Technologiepark-Zwijnaarde , B9052 Gent , Belgium
| | - Zeger Hens
- Physics and Chemistry of Nanostructures (PCN) , Ghent University , Krijgslaan 281-S3 , B9000 Gent , Belgium
- Center for Nano and Biophotonics , Ghent University , Technologiepark-Zwijnaarde , B9052 Gent , Belgium
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11
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Augustyns V, Trekels M, Gunnlaugsson HP, Masenda H, Temst K, Vantomme A, Pereira LMC. Multipurpose setup for low-temperature conversion electron Mössbauer spectroscopy. Rev Sci Instrum 2017; 88:053901. [PMID: 28571408 DOI: 10.1063/1.4982954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe an experimental setup for conversion electron Mössbauer spectroscopy (CEMS) at low temperature. The setup is composed of a continuous flow cryostat (temperature range of 4.2-500 K), detector housing, three channel electron multipliers, and corresponding electronics. We demonstrate the capabilities of the setup with CEMS measurements performed on a sample consisting of a thin enriched 57Fe film, with a thickness of 20 nm, deposited on a silicon substrate. We also describe exchangeable adaptations (lid and sample holder) which extend the applicability of the setup to emission Mössbauer spectroscopy as well as measurements under an applied magnetic field.
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Affiliation(s)
- V Augustyns
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - M Trekels
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - H P Gunnlaugsson
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - H Masenda
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - K Temst
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - A Vantomme
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
| | - L M C Pereira
- Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
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12
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Wahl U, Amorim LM, Augustyns V, Costa A, David-Bosne E, Lima TAL, Lippertz G, Correia JG, da Silva MR, Kappers MJ, Temst K, Vantomme A, Pereira LMC. Lattice Location of Mg in GaN: A Fresh Look at Doping Limitations. Phys Rev Lett 2017; 118:095501. [PMID: 28306281 DOI: 10.1103/physrevlett.118.095501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Indexed: 06/06/2023]
Abstract
Radioactive ^{27}Mg (t_{1/2}=9.5 min) was implanted into GaN of different doping types at CERN's ISOLDE facility and its lattice site determined via β^{-} emission channeling. Following implantations between room temperature and 800 °C, the majority of ^{27}Mg occupies the substitutional Ga sites; however, below 350 °C significant fractions were also found on interstitial positions ∼0.6 Å from ideal octahedral sites. The interstitial fraction of Mg was correlated with the GaN doping character, being highest (up to 31%) in samples doped p type with 2×10^{19} cm^{-3} stable Mg during epilayer growth, and lowest in Si-doped n-GaN, thus giving direct evidence for the amphoteric character of Mg. Implanting above 350 °C converts interstitial ^{27}Mg to substitutional Ga sites, which allows estimating the activation energy for migration of interstitial Mg as between 1.3 and 2.0 eV.
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Affiliation(s)
- U Wahl
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela, Portugal
| | - L M Amorim
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - V Augustyns
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - A Costa
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela, Portugal
| | - E David-Bosne
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela, Portugal
| | - T A L Lima
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - G Lippertz
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - J G Correia
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela, Portugal
| | - M R da Silva
- Centro de Física Nuclear da Universidade de Lisboa, 1649-003 Lisboa, Portugal
| | - M J Kappers
- Cambridge Centre for Gallium Nitride, University of Cambridge, Cambridge CB3 0FS, United Kingdom
| | - K Temst
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - A Vantomme
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
| | - L M C Pereira
- KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium
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13
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Menéndez E, Modarresi H, Petermann C, Nogués J, Domingo N, Liu H, Kirby BJ, Mohd AS, Salhi Z, Babcock E, Mattauch S, Van Haesendonck C, Vantomme A, Temst K. Lateral Magnetically Modulated Multilayers by Combining Ion Implantation and Lithography. Small 2017; 13:1603465. [PMID: 28067997 DOI: 10.1002/smll.201603465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 11/11/2016] [Indexed: 06/06/2023]
Abstract
The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co-CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au-sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature. Conversely, anisotropic magnetoresistance and GMR contributions are distinguished at low temperature (i.e., 10 K) since the O-implanted areas become exchange coupled. This planar GMR is principally ascribed to the spatial modulation of coercivity in a spring-magnet-type configuration, which results in 180° Néel extrinsic domain walls at the Co/Co-CoO interfaces. The versatility, in terms of pattern size, morphology, and composition adjustment, of this method offers a unique route to fabricate planar systems for, among others, spintronic research and applications.
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Affiliation(s)
- Enric Menéndez
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - Hiwa Modarresi
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - Claire Petermann
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - Josep Nogués
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193, Barcelona, Spain
- ICREA, Pg. Lluís Companys 23, 08010, Barcelona, Spain
| | - Neus Domingo
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - Haoliang Liu
- KU Leuven, Laboratorium voor Vaste-Stoffysica en Magnetisme, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - Brian J Kirby
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Amir Syed Mohd
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747, Garching, Germany
| | - Zahir Salhi
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747, Garching, Germany
| | - Earl Babcock
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747, Garching, Germany
| | - Stefan Mattauch
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747, Garching, Germany
| | - Chris Van Haesendonck
- KU Leuven, Laboratorium voor Vaste-Stoffysica en Magnetisme, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - André Vantomme
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, 3001, Leuven, Belgium
| | - Kristiaan Temst
- KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, 3001, Leuven, Belgium
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14
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Liu HL, Brems S, Zeng YJ, Temst K, Vantomme A, Van Haesendonck C. Interplay between magnetocrystalline anisotropy and exchange bias in epitaxial CoO/Co films. J Phys Condens Matter 2016; 28:196002. [PMID: 27092595 DOI: 10.1088/0953-8984/28/19/196002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The interplay between magnetocrystalline anisotropy and exchange bias is investigated in CoO/Co bilayer films, which are grown epitaxially on MgO (0 0 1), by magnetization reversal measurements based on the anisotropic magnetoresistance (AMR) effect. While an asymmetric magnetization reversal survives after training for cooling field (CF) along the hard axis, the magnetization reversal becomes symmetric and is dominated in both branches of the hysteresis loop by domain wall motion before and after training for CF along the easy axis. When performing an in-plane hysteresis loop perpendicular to the CF, the hysteresis loop along the easy axis becomes asymmetric: magnetization rotation dominates in the ascending branch, while there is a larger contribution of domain wall motion in the descending branch. Furthermore, the azimuthal angular dependence of the AMR shows two minima after performing a perpendicular hysteresis loop, instead of only one minimum after training. Relying on the extended Fulcomer and Charap model, these effects can be related to an increased deviation of the average uncompensated antiferromagnetic magnetization from the CF direction. This model provides a consistent interpretation of training and asymmetry of the magnetization reversal for epitaxial films with pronounced magnetocrystalline anisotropy as well as for the previously investigated polycrystalline films.
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Affiliation(s)
- Hao-Liang Liu
- Laboratorium voor Vaste-Stoffysica en Magnetisme, KU Leuven, Celestijnenlaan 200 D, BE-3001 Leuven, Belgium
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15
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Lorenz M, Wagner G, Lazenka V, Schwinkendorf P, Bonholzer M, Van Bael MJ, Vantomme A, Temst K, Oeckler O, Grundmann M. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO₃-BiFeO₃ Composite Thin Films. Materials (Basel) 2016; 9:E44. [PMID: 28787843 PMCID: PMC5456545 DOI: 10.3390/ma9010044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/18/2015] [Accepted: 12/30/2015] [Indexed: 11/17/2022]
Abstract
Epitaxial multiferroic BaTiO₃-BiFeO₃ composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO₃-BiFeO₃ superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. Probably, charge-mediated ME coupling may play a role in the composite films. Furthermore, the chemically-homogeneous composite films show an oxygen vacancy superstructure, which arises from vacancy ordering on the {111} planes of the pseudocubic BaTiO₃-type structure. This work contributes to the understanding of magnetoelectric coupling as a complex and sensitive interplay of chemical, structural and geometrical issues of the BaTiO₃-BiFeO₃ composite system and, thus, paves the way to practical exploitation of magnetoelectric composites.
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Affiliation(s)
- Michael Lorenz
- Institut für Experimentelle Physik II, Universität Leipzig, Leipzig D-04103, Germany.
| | - Gerald Wagner
- Institut für Mineralogie, Kristallographie und Materialwissenschaft, Universität Leipzig, Leipzig D-04103, Germany.
| | - Vera Lazenka
- Instituut voor Kern- en Stralingsfysica, KU Leuven, Leuven B-3001, Belgium.
| | - Peter Schwinkendorf
- Institut für Experimentelle Physik II, Universität Leipzig, Leipzig D-04103, Germany.
| | - Michael Bonholzer
- Institut für Experimentelle Physik II, Universität Leipzig, Leipzig D-04103, Germany.
| | - Margriet J Van Bael
- Laboratorium voor Vaste-Stoffysica en Magnetisme, KU Leuven, Leuven B-3001, Belgium.
| | - André Vantomme
- Instituut voor Kern- en Stralingsfysica, KU Leuven, Leuven B-3001, Belgium.
| | - Kristiaan Temst
- Instituut voor Kern- en Stralingsfysica, KU Leuven, Leuven B-3001, Belgium.
| | - Oliver Oeckler
- Institut für Mineralogie, Kristallographie und Materialwissenschaft, Universität Leipzig, Leipzig D-04103, Germany.
| | - Marius Grundmann
- Institut für Experimentelle Physik II, Universität Leipzig, Leipzig D-04103, Germany.
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16
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Cicmil D, van Ravenhorst IK, Meeuwissen J, Vantomme A, Weckhuysen BM. Structure–performance relationships of Cr/Ti/SiO2 catalysts modified with TEAl for oligomerisation of ethylene: tuning the selectivity towards 1-hexene. Catal Sci Technol 2016. [DOI: 10.1039/c5cy01512j] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ethylene oligomerisation properties of TEAl-modified Cr/Ti/SiO2 ethylene polymerisation Phillips-type catalysts studied with in situ UV-vis-NIR diffuse reflectance spectroscopy, mass spectrometry and gas chromatography.
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Affiliation(s)
- D. Cicmil
- Inorganic Chemistry and Catalysis
- Debye Institute for Nanomaterials Science
- Utrecht University
- 3584 CG Utrecht
- The Netherlands
| | - I. K. van Ravenhorst
- Inorganic Chemistry and Catalysis
- Debye Institute for Nanomaterials Science
- Utrecht University
- 3584 CG Utrecht
- The Netherlands
| | - J. Meeuwissen
- Total Research and Technology Feluy
- B-7181 Seneffe
- Belgium
| | - A. Vantomme
- Total Research and Technology Feluy
- B-7181 Seneffe
- Belgium
| | - B. M. Weckhuysen
- Inorganic Chemistry and Catalysis
- Debye Institute for Nanomaterials Science
- Utrecht University
- 3584 CG Utrecht
- The Netherlands
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17
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Dijkmans J, Dusselier M, Janssens W, Trekels M, Vantomme A, Breynaert E, Kirschhock C, Sels BF. An Inner-/Outer-Sphere Stabilized Sn Active Site in β-Zeolite: Spectroscopic Evidence and Kinetic Consequences. ACS Catal 2015. [DOI: 10.1021/acscatal.5b01822] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jan Dijkmans
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Michiel Dusselier
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Wout Janssens
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Maarten Trekels
- Nuclear
and Radiation Physics Section, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
| | - André Vantomme
- Nuclear
and Radiation Physics Section, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
| | - Eric Breynaert
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Christine Kirschhock
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Bert F. Sels
- Center
for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
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18
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Dijkmans J, Dusselier M, Gabriëls D, Houthoofd K, Magusin PCMM, Huang S, Pontikes Y, Trekels M, Vantomme A, Giebeler L, Oswald S, Sels BF. Cooperative Catalysis for Multistep Biomass Conversion with Sn/Al Beta Zeolite. ACS Catal 2015. [DOI: 10.1021/cs501388e] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jan Dijkmans
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
| | - Michiel Dusselier
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
| | - Dries Gabriëls
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
| | - Kristof Houthoofd
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
| | - Pieter C. M. M. Magusin
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
| | - Shuigen Huang
- Department
of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium
| | - Yiannis Pontikes
- Department
of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium
| | - Maarten Trekels
- Nuclear
and Radiation Physics Section, KU Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
| | - André Vantomme
- Nuclear
and Radiation Physics Section, KU Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
| | - Lars Giebeler
- Institute for
Complex Materials, Leibniz-Institute for Solid State and Material
Research, Helmholtzstraβe 20, 01069 Dresden, Germany
| | - Steffen Oswald
- Institute for
Complex Materials, Leibniz-Institute for Solid State and Material
Research, Helmholtzstraβe 20, 01069 Dresden, Germany
| | - Bert F. Sels
- Center
for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
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19
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Justo Y, Sagar LK, Flamee S, Zhao Q, Vantomme A, Hens Z. Less is more. Cation exchange and the chemistry of the nanocrystal surface. ACS Nano 2014; 8:7948-57. [PMID: 25090034 DOI: 10.1021/nn5037812] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We link the extent of Pb for Cd cation exchange reactions in PbS colloidal quantum dots (QDs) to their surface chemistry. Using PbS QDs with either a full or a partial surface coverage by excess Pb, we demonstrate the central role played by vacant cation sites on the QD surface. They facilitate the adsorption of cations from solution, and they act as a source of vacancies needed for the transport of cations through the crystal lattice. This model explains our finding that the cation exchange reaction runs to completion when using a low Cd excess in the exchange bath, while it is impeded by a high Cd excess. Whereas in the latter case, the QD surface is poisoned by surface Cd, the former conditions provide the mixture of surface Cd and vacant surface sites the exchange reaction needs to proceed. This understanding provides a missing link needed to build a unifying mechanistic picture of cation exchange reactions at nanocrystals.
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20
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Li DY, Zeng YJ, Batuk D, Pereira LMC, Ye ZZ, Fleischmann C, Menghini M, Nikitenko S, Hadermann J, Temst K, Vantomme A, Van Bael MJ, Locquet JP, Van Haesendonck C. Relaxor ferroelectricity and magnetoelectric coupling in ZnO-Co nanocomposite thin films: beyond multiferroic composites. ACS Appl Mater Interfaces 2014; 6:4737-4742. [PMID: 24598535 DOI: 10.1021/am4053877] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
ZnO-Co nanocomposite thin films are synthesized by combination of pulsed laser deposition of ZnO and Co ion implantation. Both superparamagnetism and relaxor ferroelectricity as well as magnetoelectric coupling in the nanocomposites have been demonstrated. The unexpected relaxor ferroelectricity is believed to be the result of the local lattice distortion induced by the incorporation of the Co nanoparticles. Magnetoelectric coupling can be attributed to the interaction between the electric dipole moments and the magnetic moments, which are both induced by the incorporation of Co. The introduced ZnO-Co nanocomposite thin films are different from conventional strain-mediated multiferroic composites.
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Affiliation(s)
- D Y Li
- Laboratory of Solid-State Physics and Magnetism and ‡Instituut voor Kern-en Stralingsfysica, KU Leuven , Celestijnenlaan 200 D, BE-3001 Leuven, Belgium
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21
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Menéndez E, Templier C, Garcia-Ramirez P, Santiso J, Vantomme A, Temst K, Nogués J. Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals. ACS Appl Mater Interfaces 2013; 5:10118-10126. [PMID: 24028676 DOI: 10.1021/am402773w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Ferromagnetic single crystalline [100], [110], and [111]-oriented expanded austenite is obtained by plasma nitriding of paramagnetic 316L austenitic stainless steel single crystals at either 300 or 400 °C. After nitriding at 400 °C, the [100] direction appears to constitute the magnetic easy axis due to the interplay between a large lattice expansion and the expected decomposition of the expanded austenite, which results in Fe- and Ni-enriched areas. However, a complex combination of uniaxial (i.e., twofold) and biaxial (i.e., fourfold) in-plane magnetic anisotropies is encountered. It is suggested that the former is related to residual stress-induced effects while the latter is associated to the in-plane projections of the cubic lattice symmetry. Increasing the processing temperature strengthens the biaxial in-plane anisotropy in detriment of the uniaxial contribution, in agreement with a more homogeneous structure of expanded austenite with lower residual stresses. In contrast to polycrystalline expanded austenite, single crystalline expanded austenite exhibits its magnetic easy axes along basic directions.
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Affiliation(s)
- Enric Menéndez
- Instituut voor Kern- en Stralingsfysica, KU Leuven , Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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Pereira LMC, Wahl U, Correia JG, Van Bael MJ, Temst K, Vantomme A, Araújo JP. Paramagnetism and antiferromagnetic interactions in single-phase Fe-implanted ZnO. J Phys Condens Matter 2013; 25:416001. [PMID: 24025311 DOI: 10.1088/0953-8984/25/41/416001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
As the intrinsic origin of the high-temperature ferromagnetism often observed in wide-gap dilute magnetic semiconductors becomes increasingly debated, there is a growing need for comprehensive studies on the single-phase region of the phase diagram of these materials. Here we report on the magnetic and structural properties of Fe-doped ZnO prepared by ion implantation of ZnO single crystals. A detailed structural characterization shows that the Fe impurities substitute for Zn in ZnO in a wurtzite Zn(1-x)Fe(x)O phase which is coherent with the ZnO host. In addition, the density of beam-induced defects is progressively decreased by thermal annealing up to 900 ° C, from highly disordered after implantation to highly crystalline upon subsequent annealing. Based on a detailed analysis of the magnetometry data, we demonstrate that isolated Fe impurities occupying Zn-substitutional sites behave as localized paramagnetic moments down to 2 K, irrespective of the Fe concentration and the density of beam-induced defects. With increasing local concentration of Zn-substitutional Fe, strong nearest-cation-neighbor antiferromagnetic interactions favor the antiparallel alignment of the Fe moments.
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Affiliation(s)
- L M C Pereira
- Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Leuven, Belgium. IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Universidade do Porto, 4169-007 Porto, Portugal. Instituto Tecnológico e Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 2686-953 Sacavém, Portugal
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Menéndez E, Demeter J, Van Eyken J, Nawrocki P, Jedryka E, Wójcik M, Lopez-Barbera JF, Nogués J, Vantomme A, Temst K. Improving the magnetic properties of Co-CoO systems by designed oxygen implantation profiles. ACS Appl Mater Interfaces 2013; 5:4320-4327. [PMID: 23581246 DOI: 10.1021/am400529r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Oxygen implantation in ferromagnetic Co thin films is shown to be an advantageous route to improving the magnetic properties of Co-CoO systems by forming multiple nanoscaled ferromagnetic/antiferromagnetic interfaces homogeneously distributed throughout the layer. By properly designing the implantation conditions (energy and fluence) and the structure of the films (capping, buffer, and Co layer thickness), relatively uniform O profiles across the Co layer can be achieved using a single-energy ion implantation approach. This optimized configuration results in enhanced exchange bias loop shifts, improved loop homogeneity, increased blocking temperature, reduced relative training effects and increased retained remanence in the trained state with respect to both Co/CoO bilayers and O-implanted Co films with a Gaussian-like O depth profile. This underlines the great potential of ion implantation to tailor the magnetic properties by controllably modifying the local microstructure through tailored implantation profiles.
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Affiliation(s)
- Enric Menéndez
- Instituut voor Kern- en Stralingsfysica, KU Leuven, Leuven, Belgium.
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Decoster S, Glover CJ, Johannessen B, Giulian R, Sprouster DJ, Kluth P, Araujo LL, Hussain ZS, Schnohr C, Salama H, Kremer F, Temst K, Vantomme A, Ridgway MC. Lift-off protocols for thin films for use in EXAFS experiments. J Synchrotron Radiat 2013; 20:426-432. [PMID: 23592621 DOI: 10.1107/s0909049513005049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 02/20/2013] [Indexed: 06/02/2023]
Abstract
Lift-off protocols for thin films for improved extended X-ray absorption fine structure (EXAFS) measurements are presented. Using wet chemical etching of the substrate or the interlayer between the thin film and the substrate, stand-alone high-quality micrometer-thin films are obtained. Protocols for the single-crystalline semiconductors GeSi, InGaAs, InGaP, InP and GaAs, the amorphous semiconductors GaAs, GeSi and InP and the dielectric materials SiO2 and Si3N4 are presented. The removal of the substrate and the ability to stack the thin films yield benefits for EXAFS experiments in transmission as well as in fluorescence mode. Several cases are presented where this improved sample preparation procedure results in higher-quality EXAFS data compared with conventional sample preparation methods. This lift-off procedure can also be advantageous for other experimental techniques (e.g. small-angle X-ray scattering) that benefit from removing undesired contributions from the substrate.
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Affiliation(s)
- S Decoster
- Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, Leuven, Belgium.
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Riskin A, Beale AM, Boyen HG, Vantomme A, Hardy A, Van Bael MK. The use of XAFS to determine the nature of interaction of iron and molybdenum metal salts within PS-b-P2VP micelles. Phys Chem Chem Phys 2013; 15:1675-81. [DOI: 10.1039/c2cp43046k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Zeng YJ, Pereira LMC, Menghini M, Temst K, Vantomme A, Locquet JP, Van Haesendonck C. Tuning quantum corrections and magnetoresistance in ZnO nanowires by ion implantation. Nano Lett 2012; 12:666-72. [PMID: 22214218 DOI: 10.1021/nl2034656] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Using ion implantation, the electrical as well as the magnetotransport properties of individual ZnO nanowires (NWs) can be tuned. The virgin NWs are configured as field-effect transistors which are in the enhancement mode. Al-implanted NWs reveal a three-dimensional metallic-like behavior, for which the magnetoresistance is well described by a semiempirical model that takes into account the presence of doping induced local magnetic moments and of two conduction bands. On the other hand, one-dimensional electron transport is observed in Co-implanted NWs. At low magnetic fields, the anisotropic magnetoresistance can be described in the framework of weak electron localization in the presence of strong spin-orbit scattering. From the weak localization, a large phase coherence length is inferred that reaches up to 800 nm at 2.5 K. The temperature-dependent dephasing is shown to result from a one-dimensional Nyquist noise-related mechanism. At the lowest temperatures, the phase coherence length becomes limited by magnetic scattering.
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Affiliation(s)
- Y J Zeng
- Laboratory of Solid-State Physics and Magnetism, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, BE-3001 Leuven, Belgium.
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Schaltin S, D'Urzo L, Zhao Q, Vantomme A, Plank H, Kothleitner G, Gspan C, Binnemans K, Fransaer J. Direct electroplating of copper on tantalum from ionic liquids in high vacuum: origin of the tantalum oxide layer. Phys Chem Chem Phys 2012; 14:13624-9. [DOI: 10.1039/c2cp41786c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Pereira LMC, Som T, Demeulemeester J, Van Bael MJ, Temst K, Vantomme A. Paramagnetism and antiferromagnetic interactions in Cr-doped GaN. J Phys Condens Matter 2011; 23:346004. [PMID: 21841222 DOI: 10.1088/0953-8984/23/34/346004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on the magnetic and structural properties of Cr-doped GaN prepared by ion implantation of epitaxial thin films. Based on a detailed analysis of the magnetometry data, we demonstrate that the magnetic interactions between Cr moments in GaN are antiferromagnetic (AFM). Increasing the Cr fractional concentration up to 0.35, we observe that strong nearest cation neighbor AFM coupling results in the reduction of the effective moment per Cr atom. The uncompensated Cr moments exhibit paramagnetic behavior and we discuss to what extent the effects of an anisotropic crystal field and AFM interactions can be inferred from the magnetization data. We discuss the observed changes in magnetic and structural properties induced by thermal annealing in terms of defect annealing and Cr aggregation.
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Affiliation(s)
- L M C Pereira
- Instituut voor Kern- en Stralingsfysica and INPAC, K U Leuven, 3001 Leuven, Belgium. IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Faculdade de Ciências da Universidade do Porto, 4169-007 Porto, Portugal. Instituto Tecnológico e Nuclear, UFA, 2686-953 Sacavém, Portugal
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Satta A, Beyer G, Maex K, Elers K, Haukka S, Vantomme A. Properties of Tin Thin Films Deposited by Alcvd as Barrier for Cu Metallization. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-612-d6.5.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractIn advanced multi-level metallization schemes, the application of copper as interconnect metal requires the prevention of Cu diffusion into the active area and into interlevel dielectrics by total encapsulation of Cu with barrier films. Critical requirements for diffusion barriers are very small thicknesses, low resistivity, low deposition temperature and conformality on high aspect ratio trenches and vias. For this application, we have studied TiN films deposited by atomic layer chemical vapour deposition (ALCVD) at 400°C and 350°C. This paper discusses the ALCVD TiN films properties and compares them to the properties of TiN deposited by ionized physical vapour deposition (I-PVD).The ALCVD TiN deposited at 400°C exhibits a resistivity comparable to I-PVD TiN resistivity. However, the ALCVD films deposited at 350°C show higher resistivity. The Cl residue in ALCVD films is 1.5% at 400°C and 3% at 350°C. The microstructure is fine-grained. A very high level of conformality on trenches characterizes the ALCVD TiN films. We believe this property gives a clear advantage over the sputtered I-PVD TiN since its coverage in high aspect ratio trenches and vias is expected to be limited for the future devices interconnection scheme.
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Demeter J, Teichert A, Kiefer K, Wallacher D, Ryll H, Menéndez E, Paramanik D, Steitz R, Van Haesendonck C, Vantomme A, Temst K. Simultaneous polarized neutron reflectometry and anisotropic magnetoresistance measurements. Rev Sci Instrum 2011; 82:033902. [PMID: 21456758 DOI: 10.1063/1.3541839] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A novel experimental facility to carry out simultaneous polarized neutron reflectometry (PNR) and anisotropic magnetoresistance (AMR) measurements is presented. Performing both techniques at the same time increases their strength considerably. The proof of concept of this method is demonstrated on a CoO/Co bilayer exchange bias system. Although information on the same phenomena, such as the coercivity or the reversal mechanism, can be separately obtained from either of these techniques, the simultaneous application optimizes the consistency between both. In this way, possible differences in experimental conditions, such as applied magnetic field amplitude and orientation, sample temperature, magnetic history, etc., can be ruled out. Consequently, only differences in the fundamental sensitivities of the techniques can cause discrepancies in the interpretation between the two. The almost instantaneous information obtained from AMR can be used to reveal time-dependent effects during the PNR acquisition. Moreover, the information inferred from the AMR measurements can be used for optimizing the experimental conditions for the PNR measurements in a more efficient way than with the PNR measurements alone.
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Affiliation(s)
- J Demeter
- Instituut voor Kern- en Stralingsfysica and INPAC, K.U.Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
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31
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Abstract
ABSTRACTThe template growth technique was applied to the growth of CrSi2 thin films on Si(111) by UHV E-gun evaporation. A 4He+ channeling yield of -50% was obtained for an epitaxial -2100 Å-thick film of continuous morphology grown at 450° C The heteroepitaxial relationship is CrSi2 (001) / Si (lll) with CrSi2[210] ∥ Si<110>.In the case of film formation simply via reactive deposition epitaxy (RDE, chromium evaporation onto hot substrates) a severe crystallinity-Morphology tradeoff is always observed. Continuous films are formed at low temperature but no long-range epitaxy is found. On the other hand, high temperature annealing of these films induces the formation of islands that show good epitaxial alignment with the substrate. This tradeoff was addressed with the template growth technique.
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Sree SP, Dendooven J, Smeets D, Deduytsche D, Aerts A, Vanstreels K, Baklanov MR, Seo JW, Temst K, Vantomme A, Detavernier C, Martens JA. Spacious and mechanically flexible mesoporous silica thin film composed of an open network of interlinked nanoslabs. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm10270b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rennhofer M, Kozlowski M, Laenens B, Sepiol B, Kozubski R, Smeets D, Vantomme A. Study of reorientation processes in L1 0-ordered FePt thin films. Intermetallics (Barking) 2010; 18:2069-2076. [PMID: 27087748 PMCID: PMC4819027 DOI: 10.1016/j.intermet.2010.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 05/12/2010] [Accepted: 06/17/2010] [Indexed: 06/05/2023]
Abstract
We report on the development of structural and magnetic order in epitaxially grown L10 FePt thin films. Upon annealing, the easy axis of magnetization changes from the out-of-plain into the in-plain direction. We found that the overall fraction of reoriented domains first increases but after certain time decreases before achieving a saturated state. The results are based on conversion electron Mössbauer spectroscopy studies and confirm Monte Carlo simulations in nano-layered FePt. We present a modified version of the Johnson-Mehl-Avrami (JMA) model adequately describing the experimental findings. Two dynamical processes, the first being a 2D-growth, dominate the initial state of sample annealing and the second being a 3D-growth, dominate the late stage close to saturation. From an Arrhenius plots of JMA coefficients for both processes we extracted the activation energies of the underlying dynamics which are 1.5(1) eV for disordering and 0.8(2) eV for ordering.
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Affiliation(s)
- M. Rennhofer
- Dynamics of Condensed Systems, Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Wien, Austria
| | - M. Kozlowski
- M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
| | - B. Laenens
- Instituut voor Kern- en Stralingsfysica and INPAC, K.U.Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
| | - B. Sepiol
- Dynamics of Condensed Systems, Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Wien, Austria
| | - R. Kozubski
- M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
| | - D. Smeets
- Instituut voor Kern- en Stralingsfysica and INPAC, K.U.Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
| | - A. Vantomme
- Instituut voor Kern- en Stralingsfysica and INPAC, K.U.Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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34
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Planckaert N, Demeulemeester J, Laenens B, Smeets D, Meersschaut J, L'abbé C, Temst K, Vantomme A. Artificial neural networks applied to the analysis of synchrotron nuclear resonant scattering data. J Synchrotron Radiat 2010; 17:86-92. [PMID: 20029116 DOI: 10.1107/s0909049509042824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 10/18/2009] [Indexed: 05/28/2023]
Abstract
The capabilities of artificial neural networks (ANNs) have been investigated for the analysis of nuclear resonant scattering (NRS) data obtained at a synchrotron source. The major advantage of ANNs over conventional analysis methods is that, after an initial training phase, the analysis is fully automatic and practically instantaneous, which allows for a direct intervention of the experimentalist on-site. This is particularly interesting for NRS experiments, where large amounts of data are obtained in very short time intervals and where the conventional analysis method may become quite time-consuming and complicated. To test the capability of ANNs for the automation of the NRS data analysis, a neural network was trained and applied to the specific case of an Fe/Cr multilayer. It was shown how the hyperfine field parameters of the system could be extracted from the experimental NRS spectra. The reliability and accuracy of the ANN was verified by comparing the output of the network with the results obtained by conventional data analysis.
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Affiliation(s)
- N Planckaert
- Instituut voor Kern- en Stralingsfysica and INPAC, KU Leuven, Celestijnenlaan 200 D, BE-3001 Leuven, Belgium.
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35
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Paredis K, Smeets D, Vantomme A. The Influence of an Adsorbate Layer on Adatom Diffusion and Island Nucleation: Fe on Si(111)-√3×√3-Au. Nanoscale Res Lett 2009; 4:1447-1451. [PMID: 20652140 PMCID: PMC2893974 DOI: 10.1007/s11671-009-9418-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 08/12/2009] [Indexed: 05/29/2023]
Abstract
Using scanning tunneling microscopy, the influence of a thin Au layer on the diffusion of Fe adatoms and the subsequent island nucleation on a Si(111) surface is investigated. The adsorbate induces the Si(111)-√3×√3-Au structure that increases the surface mobility of subsequently deposited Fe atoms, resulting in the formation well-defined nanoclusters. Surprisingly, the domain walls-inherent to the √3×√3-Au reconstruction-do not influence the surface diffusion, which demonstrates that the passivation is of much more importance for the self-assembly than the surface corrugation. Using the decoupling of the diffusion and nucleation on the surface and the reaction with the surface and conventional nucleation theory, the activation energy for surface diffusion E(d) = 0.61 eV and the critical cluster size i = 3 are determined, which reveal the microscopic details of the diffusion and nucleation processes.
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Affiliation(s)
- K Paredis
- Instituut voor Kern- en Stralingsfysica and INPAC, K. U. Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
| | - D Smeets
- Instituut voor Kern- en Stralingsfysica and INPAC, K. U. Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
| | - A Vantomme
- Instituut voor Kern- en Stralingsfysica and INPAC, K. U. Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
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36
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Moreels I, Lambert K, Smeets D, De Muynck D, Nollet T, Martins JC, Vanhaecke F, Vantomme A, Delerue C, Allan G, Hens Z. Size-dependent optical properties of colloidal PbS quantum dots. ACS Nano 2009; 3:3023-30. [PMID: 19780530 DOI: 10.1021/nn900863a] [Citation(s) in RCA: 426] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots), by combining the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases with the Qdot volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on epsilon in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the epsilon of PbSe Qdots. The data are related to the oscillator strength f(if) of the band gap transition and results agree well with theoretical tight-binding calculations, predicting a linear dependence of f(if) on d. For both PbS and PbSe Qdots, the exciton lifetime tau is calculated from f(if). We find values ranging between 1 and 3 mus, in agreement with experimental literature data from time-resolved luminescence spectroscopy. Our results provide a thorough general framework to calculate and understand the optical properties of suspended colloidal quantum dots. Most importantly, it highlights the significance of the local field factor in these systems.
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Affiliation(s)
- Iwan Moreels
- Physics and Chemistry of Nanostructures, Ghent University, Krijgslaan 281-S12, B-9000 Ghent, Belgium.
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Paredis K, Smeets D, Vantomme A. Iron silicide nanostructure formation on Au induced superstructures on Si(111). Nanotechnology 2009; 20:075607. [PMID: 19417428 DOI: 10.1088/0957-4484/20/7/075607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Using scanning tunnelling microscopy we have investigated the formation of low dimensional Fe-Si structures on Au covered Si(111) surfaces. The ultrathin Au layer induces a variety of surface reconstructions, depending on the coverage and temperature: Si(111)-5 x 2, [alpha-squareroot 3 x squareroot 3,beta-squareroot 3 x squareroot 3], and 6 x 6-Au. The subsequent deposition of 0.28 ML (monolayers) of Fe at 400 degrees C results in the formation of Fe-Si nanostructures whose morphological properties critically depend on the underlying surface. All Au induced reconstructions give rise to an increase in diffusion length as compared to the bare Si(111)-7 x 7 surface, thereby allowing the growth of well-separated nanostructures at considerably lower temperatures. Ultimately, the decoupling of surface diffusion and temperature, induced by the Au layer, can be exploited to tailor the island dimensions and density. With an appropriate choice of substrate, passivating layer and deposited material, nanostructures with the desired properties can be grown in a controlled way.
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Affiliation(s)
- K Paredis
- Instituut voor Kern- en Stralingsfysica and INPAC, K U Leuven, Leuven, Belgium
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38
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Decoster S, Cottenier S, De Vries B, Emmerich H, Wahl U, Correia JG, Vantomme A. Transition metal impurities on the bond-centered site in germanium. Phys Rev Lett 2009; 102:065502. [PMID: 19257601 DOI: 10.1103/physrevlett.102.065502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Indexed: 05/27/2023]
Abstract
We report on the lattice location of ion implanted Fe, Cu, and Ag impurities in germanium from a combined approach of emission channeling experiments and ab initio total energy calculations. Following common expectation, a fraction of these transition metals (TMs) was found on the substitutional Ge position. Less expected is the observation of a second fraction on the sixfold coordinated bond-centered site. Ab initio calculated heats of formation suggest this is the result of the trapping of a vacancy by a substitutional TM impurity, spontaneously forming an impurity-vacancy complex in the split-vacancy configuration. We also present an approach to displace the TM impurities from the electrically active substitutional site to the bond-centered site.
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Affiliation(s)
- S Decoster
- Instituut voor Kern- en Stralingsfysica and INPAC, KULeuven, BE-3001 Leuven, Belgium
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39
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Giraudon JM, Nguyen T, Leclercq G, Siffert S, Lamonier JF, Aboukaïs A, Vantomme A, Su BL. Chlorobenzene total oxidation over palladium supported on ZrO2, TiO2 nanostructured supports. Catal Today 2008. [DOI: 10.1016/j.cattod.2008.02.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Di Vece M, Grandjean D, Van Bael MJ, Romero CP, Wang X, Decoster S, Vantomme A, Lievens P. Hydrogen-induced Ostwald ripening at room temperature in a Pd nanocluster film. Phys Rev Lett 2008; 100:236105. [PMID: 18643522 DOI: 10.1103/physrevlett.100.236105] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Indexed: 05/26/2023]
Abstract
The structural and morphological changes occurring in an ensemble of vapor deposited palladium nanoclusters have been studied after several hydrogenation cycles with x-ray diffraction, extended x-ray-absorption fine structure spectroscopy, Rutherford backscattering spectrometry, and STM. Initial hydrogenation increased the cluster size, a result that is attributed to hydrogen-induced Ostwald ripening. This phenomenon originates from the higher mobility of palladium atoms resulting from the low sublimation energy of the palladium hydride as compared to that of the palladium metal. The universality of this phenomenon makes it important for the application of future nanostructured hydrogen storage materials.
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Affiliation(s)
- M Di Vece
- Laboratorium voor Vaste-Stoffysica en Magnetisme & INPAC-Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Leuven, Belgium
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Hosseini M, Siffert S, Tidahy H, Cousin R, Lamonier JF, Aboukais A, Vantomme A, Roussel M, Su BL. Promotional effect of gold added to palladium supported on a new mesoporous TiO2 for total oxidation of volatile organic compounds. Catal Today 2007. [DOI: 10.1016/j.cattod.2007.03.012] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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De Vries B, Wahl U, Vantomme A, Correia J, ISOLDE Collaboration T. Lattice Location of Implanted
147
Nd and
147*
Pm in GaN Using Emission Channeling. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/pssc.200390086] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- B. De Vries
- Instituut voor Kern‐ en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium
| | - U. Wahl
- Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2685 Sacavém, Portugal
| | - A. Vantomme
- Instituut voor Kern‐ en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium
| | - J.G. Correia
- Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2685 Sacavém, Portugal
- CERN‐PPE, 1211 Geneva 23, Switzerland
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43
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Wahl U, Vantomme A, Langouche G, Correia JG. Lattice location and stability of ion implanted Cu in Si. Phys Rev Lett 2000; 84:1495-1498. [PMID: 11017551 DOI: 10.1103/physrevlett.84.1495] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/1999] [Indexed: 05/23/2023]
Abstract
We report on the lattice location of ion implanted Cu in Si using the emission channeling technique. The angular distribution of beta(-) particles emitted by the radioactive isotope 67Cu was monitored following room temperature implantation into Si single crystals and annealing up to 600 degrees C. The majority of Cu was found close to substitutional sites, however, with a significant displacement, most likely 0.50(8) A along the <111> directions towards the bond center position. The activation energy for the dissociation of near-substitutional Cu is estimated to be 1.8-2.2 eV.
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Affiliation(s)
- U Wahl
- Instituut voor Kern- en Stralingsfysica, University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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Mahan JE, Vantomme A, Langouche G, Becker JP. Semiconducting Mg2Si thin films prepared by molecular-beam epitaxy. Phys Rev B Condens Matter 1996; 54:16965-16971. [PMID: 9985826 DOI: 10.1103/physrevb.54.16965] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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45
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Maltez RL, Amaral L, Behar M, Vantomme A, Langouche G, Lin XW. Mössbauer study of the magnetic character and ordering process of the cubic gamma -FeSi2 phase obtained by Fe implantation into a Si(100) matrix. Phys Rev B Condens Matter 1996; 54:11659-11665. [PMID: 9984955 DOI: 10.1103/physrevb.54.11659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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46
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Piquet JJ, Darras JA, Vantomme A, Desaulty A. [Laser microsurgery]. J Fr Otorhinolaryngol Audiophonol Chir Maxillofac 1984; 33:131-3. [PMID: 6716081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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