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1. Excellent electronic transport in heterostructures of graphene and monoisotopic boron-nitride grown at atmospheric pressure

Author

Christoph Stampfer, Jiahan Li, James H. Edgar, Julien Barjon, Alexandre Plaud, Jens Sonntag, Annick Loiseau, RWTH Aachen University, Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Kansas State University, Groupe d'Etude de la Matière Condensée (GEMAC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), LEM, UMR 104, CNRS-ONERA, Université Paris-Saclay (Laboratoire d'étude des microstructures), and ONERA-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
FOS: Physical sciences, Cathodoluminescence, 02 engineering and technology, Substrate (electronics), Quantum Hall effect, 7. Clean energy, law.invention, 03 medical and health sciences, chemistry.chemical_compound, symbols.namesake, Condensed Matter::Materials Science, law, Ballistic conduction, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Materials Science, ddc:530, 030304 developmental biology, Physics, 0303 health sciences, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Graphene, business.industry, Mechanical Engineering, Materials Science (cond-mat.mtrl-sci), Heterojunction, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 3. Good health, chemistry, Mechanics of Materials, Boron nitride, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, 0210 nano-technology, Raman spectroscopy, business
Abstract

Hexagonal boron nitride (BN), one of the very few layered insulators, plays a crucial role in 2D materials research. In particular, BN grown with a high pressure technique has proven to be an excellent substrate material for graphene and related 2D materials, but at the same time very hard to replace. Here we report on a method of growth at atmospheric pressure as a true alternative for producing BN for high quality graphene/BN heterostructures. The process is not only more scalable, but also allows to grow isotopically purified BN crystals. We employ Raman spectroscopy, cathodoluminescence, and electronic transport measurements to show the high-quality of such monoisotopic BN and its potential for graphene-based heterostructures. The excellent electronic performance of our heterostructures is demonstrated by well developed fractional quantum Hall states, ballistic transport over distances around $10\,\mathrm{\mu m}$ at low temperatures and electron-phonon scattering limited transport at room temperature., Comment: 7 pages, 4 figures

Published
2020

2. Electrostatic potential mapping at ferroelectric domain walls by low-temperature photoemission electron microscopy

Author

Claus M. Schneider, Dennis Meier, Jakob Schaab, Konstantin Shapovalov, Edith Bourret, Mario Hentschel, Zewu Yan, Johanna Hackl, Muhammad Imtiaz Khan, Slavomír Nemšák, Peggy Schoenherr, Andres Cano, Massimiliano Stengel, Department of Materials [ETH Zürich] (D-MATL), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institut de Ciència de Materials de Barcelona (ICMAB), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Universität Stuttgart [Stuttgart], Department of Physics [ETH Zürich] (D-PHYS), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Institució Catalana de Recerca i Estudis Avançats (ICREA), Théorie de la Matière Condensée (TMC ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Norwegian University of Science and Technology [Trondheim] (NTNU), and Norwegian University of Science and Technology (NTNU)

Subjects
Image formation, Technology, Materials science, Physics and Astronomy (miscellaneous), Electrostatic force microscope, FOS: Physical sciences, Bioengineering, 02 engineering and technology, 01 natural sciences, Molecular physics, Scanning probe microscopy, Engineering, 0103 physical sciences, Image resolution, Nanoscopic scale, ComputingMilieux_MISCELLANEOUS, Applied Physics, 010302 applied physics, Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Ferroelectricity, cond-mat.mtrl-sci, Photoemission electron microscopy, Physical Sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Electric potential, 0210 nano-technology
Abstract

Low-temperature X-ray photoemission electron microscopy (X-PEEM) is used to measure the electric potential at domain walls in improper ferroelectric Er0.99Ca0.01MnO3. By combining X-PEEM with scanning probe microscopy and theory, we develop a model that relates the detected X-PEEM contrast to the emergence of uncompensated bound charges, explaining the image formation based on intrinsic electronic domain-wall properties. In contrast to previously applied low-temperature electrostatic force microscopy (EFM), X-PEEM readily distinguishes between positive and negative bound charges at domain walls. Our study introduces an X-PEEM based approach for low-temperature electrostatic potential mapping, facilitating nanoscale spatial resolution and data acquisition times in the order of 0.1-1 sec., Comment: 15 pages, 6 figures

Published
2020
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3. Targets for high repetition rate laser facilities: needs, challenges and perspectives

Author

N. J. Hartley, Keiji Nagai, Rosa Letizia Zaffino, Arie Irman, Thomas Kluge, Mihail Octavian Cernaianu, Daniele Margarone, Cs. Vass, Douglass Schumacher, M. De Marco, Richard B. Stephens, L. G. Huang, P. Fitzsimmons, Neil Alexander, Sven Steinke, Irene Prencipe, Julien Fuchs, Tuomas Wiste, A. Pelka, Richard Briggs, Karl Zeil, J. Metzkes, Matteo Passoni, Daniel Papp, Dominik Kraus, Markus Büscher, C.C. Gheorghiu, R. Torchio, Sakura Pascarelli, Joachim Schulz, Jürgen Fassbender, J. Hund, Wigen Nazarov, Michal Smid, V. Leca, Artur Erbe, P. Lutoslawski, Jean-Paul Perin, Andrei Choukourov, C. Spindloe, Thomas E. Cowan, Stephan Kraft, Zuzana Konôpková, Guillaume Fiquet, Thomas Tschentscher, Marion Harmand, Ulrich Schramm, Institute of Radiation Physics [Dresden], Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), Ohio State University [Columbus] (OSU), University of Pennsylvania, General Atomics [San Diego], Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Heinrich Heine Universität Düsseldorf = Heinrich Heine University [Düsseldorf], IFIN-HH, Charles University [Prague] (CU), Institute of Ion Beam Physics and Materials Research [Dresden], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Deutsches Elektronen-Synchrotron [Zeuthen] (DESY), Helmholtz-Gemeinschaft = Helmholtz Association, University of St Andrews [Scotland], Politecnico di Milano [Milan] (POLIMI), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Laboratoire de Cryogénie pour la Fusion (LCF ), Service des Basses Températures (SBT ), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Spanish National Research Council (CSIC), European Project: 654220,H2020,H2020-INFRADEV-1-2014-1,EUCALL(2015), European Project: 637748,H2020,ERC-2014-STG,NanoSOFT(2015), European Project: 647554,H2020,ERC-2014-CoG,ENSURE(2015), and University of Pennsylvania [Philadelphia]

Subjects
target design and fabrication, Nuclear and High Energy Physics, high-energy density physics, High energy density physics, 01 natural sciences, 7. Clean energy, Bottleneck, 010305 fluids & plasmas, law.invention, Target design and fabrication < High power laser related laser components, law, Atomic and Molecular Physics, 0103 physical sciences, Electronic, Optical and Magnetic Materials, 010306 general physics, 01.03. Fizikai tudományok, Repetition (rhetorical device), Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Nuclear Energy and Engineering, Laser, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Systems engineering, and Optics, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract

International audience; A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.

Published
2017

4. Activation of surface oxygen sites on an iridium-based model catalyst for the oxygen evolution reaction

Author

Matthieu Saubanère, Walid Dachraoui, Jean-Marie Tarascon, Marie-Liesse Doublet, Martial Duchamp, Arnaud Demortière, Alexis Grimaud, Réseau sur le stockage électrochimique de l'énergie (RS2E), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Aix Marseille Université (AMU)-Université de Pau et des Pays de l'Adour (UPPA)-Université de Nantes (UN)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Chaire Chimie du solide et énergie, Chimie du solide et de l'énergie (CSE), Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU), Laboratoire réactivité et chimie des solides - UMR CNRS 7314 (LRCS), Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Aix Marseille Université (AMU)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Université de Picardie Jules Verne (UPJV)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Collège de France - Chaire Chimie du solide et énergie, Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)

Subjects
Renewable Energy, Sustainability and the Environment, Oxygen evolution, Energy Engineering and Power Technology, chemistry.chemical_element, 02 engineering and technology, Active surface, 010402 general chemistry, 021001 nanoscience & nanotechnology, Photochemistry, Electrocatalyst, 01 natural sciences, Oxygen, Ruthenium oxide, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Catalysis, Fuel Technology, chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM]Chemical Sciences, Iridium, 0210 nano-technology, Surface reconstruction
Abstract

International audience; The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices, however, deeper mechanistic understanding is required in order to design enhanced electrocatalysts for the reaction. Current understanding of the OER mechanism based on oxygen adsorption on a metallic surface site fails to fully explain the activity of iridium and ruthenium oxide surfaces, and the drastic surface reconstruction observed for the most active OER catalysts. Here we demonstrate, using La 2 LiIrO 6 as a model catalyst, that the exceptionally high activity found for Ir-based catalysts arises from the formation of active surface oxygen atoms that act as electrophilic centres for water to react. Moreover, we observe with the help of transmission electron microscopy drastic surface reconstruction and iridium migration from the bulk to the surface. Therefore, we establish a correlation between surface activity and surface stability for OER catalysts which is rooted in the formation of surface reactive oxygen.

Published
2016
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5. Spectroscopic XPEEM of highly conductive SI-doped GaN wires

Author

Vitaliy Feyer, Christian Schneider, Nicolas Chevalier, Julien Pernot, Olivier Renault, J. Morin, Pierre Tchoulfian, Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Semi-conducteurs à large bande interdite (SC2G), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Peter Grünberg Institut, Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Semi-conducteurs à large bande interdite (NEEL - SC2G), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), and Peter Grünberg Institut (PGI)

Subjects
Materials science, Applied physics, Silicon, Doping, Analytical chemistry, chemistry.chemical_element, Scanning capacitance microscopy, Nitride, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Band bending, chemistry, Interstitial defect, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Electrical measurements, Instrumentation
Abstract

International audience; Using soft X-ray photoelectron emission microscopy (XPEEM), complemented by scanning Auger microscopy (SAM) and scanning capacitance microscopy, we have quantitatively studied the incorporation of silicon and band bending at the surface (m-facet) of an individual, highly conductive Si-doped GaN micro-wires (Tchoulfian et al., Applied Physics Letters 102 (12), 2013). Electrically active n-dopants Si atoms in Ga interstitial sites are detected as nitride bonding states in the high-resolution Si2p core level spectra, and represent only a small fraction (

Published
2015

6. Imaging and characterization of conducting ferroelectric domain walls by photoemission electron microscopy

Author

I. P. Krug, Andres Cano, Mario Hentschel, Daniel M. Gottlob, Zewu Yan, Edith Bourret, Jakob Schaab, Ramamoorthy Ramesh, Claus M. Schneider, Hatice Doğanay, Dennis Meier, F. Nickel, Department of Materials, Institut für Optik und Atomare Physik, Technische Universität Berlin (TU), Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich Peter Grünberg Institute, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), Materials Science Division [LBNL Berkeley], Lawrence Berkeley National Laboratory [Berkeley] (LBNL), 4th Physics Institute and Research Center SCoPE, University of Stuttgart, and Department of Materials Science and Engineering [Berkeley]

Subjects
Condensed Matter - Materials Science, Materials science, Physics and Astronomy (miscellaneous), business.industry, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Photoelectric effect, Ferroelectricity, Domain (software engineering), Characterization (materials science), law.invention, Photoemission electron microscopy, X-ray photoelectron spectroscopy, law, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, ddc:530, Electron microscope, business, Image resolution
Abstract

International audience; High-resolution X-ray photoemission electron microscopy (X-PEEM) is a well-established method for imaging ferroelectric domain structures. Here, we expand the scope of application of X-PEEM and demonstrate its capability for imaging and investigating domain walls in ferroelectrics with high-spatial resolution. Using ErMnO3 as test system, we show that ferroelectric domain walls can be visualized based on photo-induced charging effects and local variations in their electronic conductance can be mapped by analyzing the energy distribution of photoelectrons. Our results open the door for non-destructive, contract-free, and element-specific studies of the electronic and chemical structure at domain walls in ferroelectrics.

Published
2014

8. Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd$_2$Si$_2$ single crystal

Author

Li, Hai-Feng, Cao, Chongde, Wildes, Andrew, Schmidt, Wolfgang, Schmalzl, Karin, Hou, Binyang, Regnault, Louis-Pierre, Zhang, Cong, Meuffels, Paul, Loeser, Wolfgang, Roth, Georg, Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, Northwestern Polytechnical University [Xi'an] (NPU), Institut Laue-Langevin (ILL), ILL, European Synchrotron Radiation Facility (ESRF), Magnétisme et Diffusion Neutronique (MDN), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institute of Crystallography [Aachen], Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), Forschungszentrum Jülich Peter Grünberg Institute, Leibniz Institute for Solid State and Materials Research (IFW Dresden), Leibniz Association, Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH)

Subjects
[PHYS]Physics [physics], Condensed Matter - Materials Science, Neutron-Diffraction, Strongly Correlated Electrons (cond-mat.str-el), Condensed Matter - Superconductivity, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Magnetic-Properties, Article, Superconductivity (cond-mat.supr-con), Condensed Matter - Strongly Correlated Electrons, UPd2Al3, ddc:000, Condensed Matter::Strongly Correlated Electrons, Iron-Based Superconductors
Abstract

Identifying the nature of magnetism, itinerant or localized, remains a major challenge in condensed-matter science. Purely localized moments appear only in magnetic insulators, whereas itinerant moments more or less co-exist with localized moments in metallic compounds such as the doped-cuprate or the iron-based superconductors, hampering a thorough understanding of the role of magnetism in phenomena like superconductivity or magnetoresistance. Here we distinguish two antiferromagnetic modulations with respective propagation wave vectors of $Q_{\pm}$ = ($H \pm 0.557(1)$, 0, $L \pm 0.150(1)$) and $Q_\text{C}$ = ($H \pm 0.564(1)$, 0, $L$), where $\left(H, L\right)$ are allowed Miller indices, in an ErPd$_2$Si$_2$ single crystal by neutron scattering and establish their respective temperature- and field-dependent phase diagrams. The modulations can co-exist but also compete depending on temperature or applied field strength. They couple differently with the underlying lattice albeit with associated moments in a common direction. The $Q_{\pm}$ modulation may be attributed to localized 4\emph{f} moments while the $Q_\text{C}$ correlates well with itinerant conduction bands, supported by our transport studies. Hence, ErPd$_2$Si$_2$ represents a new model compound that displays clearly-separated itinerant and localized moments, substantiating early theoretical predictions and providing a unique platform allowing the study of itinerant electron behavior in a localized antiferromagnetic matrix., 7 pages, 7 Figures, 1 Table

Published
2015

9. Boron-Doped Graphene Nanoribbons: Electronic Structure and Raman Fingerprint

Author

Chaoyu Chen, Moritz Hoesch, Tomas Marangoni, Niels Ehlen, Danny Haberer, Timur K. Kim, Andrei Varykhalov, Nicolae Atodiresei, Alexander V. Fedorov, Alexei Nefedov, Maria C. Asensio, Shigeru Tsukamoto, Gianni Profeta, José Avila, Alexander Grüneis, Vasile Caciuc, Cesare Tresca, Boris V. Senkovskiy, Christof Wöll, Felix R. Fischer, Dmitry Yu. Usachov, II. Physikalisches Institut [Köln], Universität zu Köln, St Petersburg State University (SPbU), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Dipartimento di Fisica [L'Aquila], Università degli Studi dell'Aquila (UNIVAQ), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Forschungszentrum Jülich Peter Grünberg Institute, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Karlsruher Institut für Technologie (KIT), DIAMOND Light source, Photone Sciences, Deutsches Elektronen-Synchrotron (DESY), and Materials Science Division [LBNL Berkeley]

Subjects
Materials science, graphene nanoribbons, boron doping, electronic structure, ARPES, Raman, substrate interaction, Photoemission spectroscopy, General Physics and Astronomy, Angle-resolved photoemission spectroscopy, 02 engineering and technology, Electronic structure, 010402 general chemistry, 01 natural sciences, 7. Clean energy, Molecular physics, law.invention, symbols.namesake, Physics and Astronomy (all), Effective mass (solid-state physics), Engineering (all), law, Physics::Atomic and Molecular Clusters, General Materials Science, ddc:530, Nanoscience & Nanotechnology, [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, Valence (chemistry), Graphene, General Engineering, Materials Science (all), 021001 nanoscience & nanotechnology, 0104 chemical sciences, ddc:540, symbols, 0210 nano-technology, Raman spectroscopy, Graphene nanoribbons
Abstract

International audience; We investigate the electronic and vibrational properties of bottom-up synthesized aligned armchair graphene nanoribbons of N = 7 carbon atoms width periodically doped by substitutional boron atoms (B-7AGNRs). Using angle-resolved photoemission spectroscopy and density functional theory calculations, we find that the dopant-derived valence and conduction band states are notably hybridized with electronic states of Au substrate and spread in energy. The interaction with the substrate leaves the bands with pure carbon character rather unperturbed. This results in an identical effective mass of ≈0.2 m0 for the next-highest valence band compared with pristine 7AGNRs. We probe the phonons of B-7AGNRs by ultrahigh-vacuum (UHV) Raman spectroscopy and reveal the existence of characteristic splitting and red shifts in Raman modes due to the presence of substitutional boron atoms. Comparing the Raman spectra for three visible lasers (red, green, and blue), we find that interaction with gold suppresses the Raman signal from B-7AGNRs and the energy of the green laser (2.33 eV) is closer to the resonant E22 transition. The hybridized electronic structure of the B-7AGNR–Au interface is expected to improve electrical characteristics of contacts between graphene nanoribbon and Au. The Raman fingerprint allows the easy identification of B-7AGNRs, which is particularly useful for device fabrication.

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10. Extremely low-energy ARPES of quantum well states in cubic-GaN/AlN and GaAs/AlGaAs heterostructures.

Author

Hajlaoui M, Ponzoni S, Deppe M, Henksmeier T, As DJ, Reuter D, Zentgraf T, Springholz G, Schneider CM, Cramm S, and Cinchetti M

Abstract

Quantum well (QW) heterostructures have been extensively used for the realization of a wide range of optical and electronic devices. Exploiting their potential for further improvement and development requires a fundamental understanding of their electronic structure. So far, the most commonly used experimental techniques for this purpose have been all-optical spectroscopy methods that, however, are generally averaging in momentum space. Additional information can be gained by angle-resolved photoelectron spectroscopy (ARPES), which measures the electronic structure with momentum resolution. Here we report on the use of extremely low-energy ARPES (photon energy ~ 7 eV) to increase depth sensitivity and access buried QW states, located at 3 nm and 6 nm below the surface of cubic-GaN/AlN and GaAs/AlGaAs heterostructures, respectively. We find that the QW states in cubic-GaN/AlN can indeed be observed, but not their energy dispersion, because of the high surface roughness. The GaAs/AlGaAs QW states, on the other hand, are buried too deep to be detected by extremely low-energy ARPES. Since the sample surface is much flatter, the ARPES spectra of the GaAs/AlGaAs show distinct features in momentum space, which can be reconducted to the band structure of the topmost surface layer of the QW structure. Our results provide important information about the samples' properties required to perform extremely low-energy ARPES experiments on electronic states buried in semiconductor heterostructures., (© 2021. The Author(s).)

Published
2021
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11. Graphene-multiferroic interfaces for spintronics applications.

Author

Zanolli Z

Abstract

Graphene and magnetoelectric multiferroics are promising materials for spintronic devices with high performance and low energy consumption. A very long spin diffusion length and high carrier mobility make graphene attractive for spintronics. The coupling between ferroelectricity and magnetism, which characterises magnetoelectrics, opens the way towards unique device architectures. In this work, we combine the features of both materials by investigating the interface between graphene and BaMnO3, a magnetoelectric multiferroic. We show that electron charge is transferred across the interface and magnetization is induced in the graphene sheet due to the strong interaction between C and Mn. Depending on the relative orientation of graphene and BaMnO3, a quasi-half-metal or a magnetic semiconductor can be obtained. A remarkably large proximity induced spin splitting of the Dirac cones (~300 meV) is achieved. We also show how doping with acceptors can make the high-mobility region of the electronic bands experimentally accessible. This suggests a series of possible applications in spintronics (e.g. spin filters, spin injectors) for hybrid organic-multiferroic materials and reveals hybrid organic-multiferroics as a new class of materials that may exhibit exotic phenomena such as the quantum anomalous Hall effect and a Rashba spin-orbit induced topological gap.

Published
2016
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12. Platinum-Containing Polyoxometalates: syn- and anti-[Pt(II)2(α-PW11O39)2](10-) and Formation of the Metal-Metal-Bonded di-Pt(III) Derivatives.

Author

Lin Z, Izarova NV, Kondinski A, Xing X, Haider A, Fan L, Vankova N, Heine T, Keita B, Cao J, Hu C, and Kortz U

Abstract

The first examples of dimeric, di-Pt(II) -containing heteropolytungstates are reported. The two isomeric di-platinum(II)-containing 22-tungsto-2-phosphates [anti-Pt(II)2(α-PW11O39)2](10-) (1 a) and [syn-Pt(II)2(α-PW11O39)2](10-) (2 a) were synthesized in aqueous pH 3.5 medium using one-pot procedures. Polyanions 1 a and 2 a contain a core comprising two face-on PtO4 units, with a Pt⋅⋅⋅Pt distance of 2.9-3 Å. Both polyanions were investigated by single-crystal XRD, IR, TGA, UV/Vis, (31) P NMR, ESI-MS, CID-MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt2(II)} moiety in 1 a and 2 a can undergo fully reversible two-electron oxidation to {Pt2(III)}, accompanied by formation of a single Pt-Pt bond. Hence we have discovered the novel subclass of Pt(III)-containing heteropolytungstates., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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