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Your search keyword '"Constance, Toulouse"' showing total 4 results
Start Over Author "Constance, Toulouse" Topic 02 engineering and technology
4 results on '"Constance, Toulouse"'

1. Patterning enhanced tetragonality in BiFeO3 thin films with effective negative pressure by helium implantation

Author

Pierre Fertey, Vincent Garcia, Jean-Nicolas Audinot, E. Elkaim, Jens Kreisel, S. Farokhipoor, I. Peral Alonso, Lluís Yedra, F. Carla, Tom Wirtz, J. Fischer, Mael Guennou, Beatriz Noheda, Amélie Jarnac, Constance Toulouse, and Stéphane Fusil

Subjects
Phase transition, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, chemistry.chemical_element, 02 engineering and technology, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, chemistry.chemical_compound, symbols.namesake, chemistry, Phase (matter), 0103 physical sciences, symbols, General Materials Science, Deformation (engineering), Thin film, 010306 general physics, 0210 nano-technology, Raman spectroscopy, Helium, Bismuth ferrite
Abstract

Helium implantation in epitaxial thin films is a way to control the out-of-plane deformation independently from the in-plane strain controlled by epitaxy. In particular, implantation by means of a helium microscope allows for local implantation and patterning down to the nanometer resolution, which is of interest for device applications. We present here a study of bismuth ferrite (BiFeO3) films where strain was patterned locally by helium implantation. Our combined Raman, XRD and TEM study shows that the implantation causes an elongation of the BiFeO3 unit cell and ultimately a transition towards the so-called super-tetragonal polymorph via states with mixed phases. In addition, TEM reveals the onset of amorphization at a threshold dose that does not seem to impede the overall increase in tetragonality. The phase transition from the R-like to T-like BiFeO3 appears as first-order in character, with regions of phase coexistence and abrupt changes in lattice parameters.

Published
2021
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2. Single crystal growth of BaZrO3 from the melt at 2700 °C using optical floating zone technique and growth prospects from BaB2O4 flux at 1350 °C

Author

Alain Maillard, Michaël Josse, Jens Kreisel, Monica Ciomaga Hatnean, Geetha Balakrishnan, Daniel Rytz, Matias Velázquez, Mael Guennou, Raphael Haumont, Constance Toulouse, Philippe Veber, Nathalie Valle, Romuald Saint Martin, Cong Xin, Mario Maglione, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Luxembourg Institute of Science and Technology (LIST), Luminescence (LUMINESCENCE), Institut Lumière Matière [Villeurbanne] (ILM), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, University of Warwick [Coventry], Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire Matériaux Optiques, Photonique et Systèmes (LMOPS), CentraleSupélec-Université de Lorraine (UL), FEE Gmbh, FEE GmBh, Physics and Materials Science Research Unit, University of Luxembourg [Luxembourg], This work was supported by the Innovative Training Networks (ITN) – Marie Skłodowska-Curie Actions-European Joint Doctorate in Functional Material Research (EJD-FunMat) project (no. 641640). The work at the University of Warwick was supported by the EPSRC, UK, Grant EP/M028771/1. Cong Xin, Dr. Mael Guennou, Dr Constance Toulouse and Prof. Jens Kreisel acknowledge support from the National Research Fund Luxembourg through a Pearl Grant (FNR/P12/4853155)., European Project: 641640,H2020,H2020-MSCA-ITN-2014,EJD-FunMat(2015), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Flux method, Materials science, Glow Discharge Mass Spectrometry, Band gap, Analytical chemistry, 02 engineering and technology, General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 0104 chemical sciences, Secondary ion mass spectrometry, symbols.namesake, Impurity, Melting point, symbols, General Materials Science, 0210 nano-technology, Raman spectroscopy, Spectroscopy
Abstract

International audience; We report the growth of BaZrO3 single crystals by the optical floating zone technique and the investigation on its flux growth using BaB2O4 as a solvent. 6 mm long colorless and transparent single crystals were obtained with a mirror furnace without the need for post-treatment annealing. Its properties are determined and compared with those of two commercial crystals grown by the tri-arc Czochralski method. The chemical composition was investigated using glow discharge mass spectrometry (GDMS) and secondary ion mass spectrometry (SIMS), which indicate minor impurities of Sr, Hf, Ca and Ti, with maximal concentrations for Sr and Hf in the range of 0.3–0.5% at. The optical band gap determined by UV-visible spectroscopy is found to be ∼4.8 eV and indicates the high quality of the BaZrO3 crystals grown by the optical floating zone technique. Raman spectroscopy at ambient conditions and at low temperatures down to 4.2 K reveals a relatively sharp second-order spectrum and does not reveal any structural phase transition. Prospective high-temperature solution growth using BaB2O4 self-flux was investigated and led to 150–200 μm BaZrO3 crystals. This solvent opens the way to grow BaZrO3 at half its melting point by the flux method.

Published
2019
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3. Crossover between distinct symmetries in solid solutions of rare earth nickelates

Author

Duncan T. L. Alexander, Alexander Schober, Jennifer Fowlie, Constance Toulouse, Mael Guennou, Bernat Mundet, C. Dominguez, Jean-Marc Triscone, Jens Kreisel, Marta Gibert, University of Zurich, and Fowlie, Jennifer

Subjects
Materials science, 530 Physics, QC1-999, Crossover, Oxide, perovskites, Physics [G04] [Physical, chemical, mathematical & earth Sciences], 02 engineering and technology, ddc:500.2, 10192 Physics Institute, 01 natural sciences, chemistry.chemical_compound, symbols.namesake, Phase (matter), 0103 physical sciences, Scanning transmission electron microscopy, General Materials Science, metal-insulator, Thin film, phase, 010306 general physics, Physics, General Engineering, Space group, tool, 021001 nanoscience & nanotechnology, 2500 General Materials Science, rnio3 r, chemistry, Physique [G04] [Physique, chimie, mathématiques & sciences de la terre], Chemical physics, charge disproportionation, symbols, 2200 General Engineering, films, 0210 nano-technology, Raman spectroscopy, transitions, TP248.13-248.65, Solid solution, Biotechnology
Abstract

A strong coupling of the lattice to functional properties is observed in many transition metal oxide systems, such as the ABO(3) perovskites. In the quest for tailor-made materials, it is essential to be able to control the structural properties of the compound(s) of interest. Here, thin film solid solutions that combine NdNiO3 and LaNiO3, two materials with the perovskite structure but distinct space groups, are analyzed. Raman spectroscopy and scanning transmission electron microscopy are combined in a synergistic approach to fully determine the mechanism of the structural crossover with chemical composition. It is found that the symmetry transition is achieved by phase coexistence in a way that depends on the substrate selected. These results carry implications for analog-tuning of physical properties in future functional materials based on these compounds.

Published
2021

4. Lattice dynamics and Raman spectrum of BaZrO3 single crystals

Author

Philippe Veber, Danila Amoroso, Mario Maglione, Monica Ciomaga Hatnean, Geetha Balakrishnan, Mael Guennou, Jens Kreisel, Philippe Ghosez, Cong Xin, Constance Toulouse, Physics and Materials Science Research Unit, University of Luxemburg, Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Theoretical Materials Physics, Quantum Materials Center (Q-MAT), Université de Liège, CNR SPIN, Luminescence (LUMINESCENCE), Institut Lumière Matière [Villeurbanne] (ILM), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, University of Warwick [Coventry], This work was supported by the Innovative Training Networks (ITN) Marie Sklodowska-Curie Actions-European Joint Doctorate in Functional Material Research (EJD-FunMat) (Project No. 641640). DFT-based calculations have been performed on the NIC4 cluster hosted at the University of Liège, within the ‘Consortium des Équipements de Calcul Intensif’ (CÉCI), funded by F.R.S-FNRS (Grant No. 2.5020.1) and by the Walloon Region. C.T., M.G., J.K. acknowledge financial support from the Fond National de Recherche Luxembourg through a PEARL Grant (No. FNR/P12/4853155/Kreisel). The work at the University of Warwick was supported by the EPSRC, UK (Grant No. EP/M028771/1)., Fonds National de la Recherche - FnR [sponsor], EPSCR [sponsor], and Luxembourg Institute of Science & Technology - LIST [research center]

Subjects
Materials science, Phonon, Physics [G04] [Physical, chemical, mathematical & earth Sciences], FOS: Physical sciences, 02 engineering and technology, Cubic crystal system, 01 natural sciences, symbols.namesake, Condensed Matter::Materials Science, [SPI]Engineering Sciences [physics], Phase (matter), 0103 physical sciences, [CHIM]Chemical Sciences, 010306 general physics, QC, Perovskite (structure), [PHYS]Physics [physics], Condensed Matter - Materials Science, Condensed matter physics, Materials Science (cond-mat.mtrl-sci), Atmospheric temperature range, 021001 nanoscience & nanotechnology, Physique [G04] [Physique, chimie, mathématiques & sciences de la terre], Octahedron, symbols, 0210 nano-technology, Raman spectroscopy, Raman scattering
Abstract

${\mathrm{BaZrO}}_{3}$ is a perovskite that remains in the simple cubic phase at all temperatures, hence with no first-order Raman-active phonon mode allowed by symmetry. Yet, it exhibits an intense Raman spectrum with sharp and well-defined features. Here, we report the evolution of the Raman spectrum of ${\mathrm{BaZrO}}_{3}$ single crystals in a broad temperature range (4--1200 K) and discuss its origin with the support of detailed first-principle calculations of the lattice dynamics. Phonon calculations are performed not only for the cubic phase of ${\mathrm{BaZrO}}_{3}$, but also for the low-symmetry phases with octahedra tilts that have been suspected to exist at the nanoscale. We show that the Raman spectrum shows no direct evidence for these nanodomains, but can instead be explained by classical second-order Raman scattering. We provide an assignment of the dominant features to phonon mode combinations. In particular, we show that the high frequency range of the spectrum is dominated by overtones and shows an image of the phonon density of states corresponding to the stretching modes of the oxygen octahedra.

Published
2019
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