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1. Large‐Area Artificial van der Waals 'Mille‐Feuille' Superlattices

Author

Hao Wei, Simon Dubois, Frederic Brunnett, Julian Peiro, Florian Godel, Cécile Carrétéro, Federico Panciera, Sophie Collin, Fayçal Bouamrane, Victor Zatko, Marta Galbiati, Etienne Carré, Gilles Patriarche, Frédéric Petroff, Jean‐Christophe Charlier, Marie‐Blandine Martin, Bruno Dlubak, and Pierre Seneor

Subjects
2D semiconductors, pulsed laser deposition, quantum heterostructures, transition metal dichalcogenides, van der Waals heterostructures, Physics, QC1-999, Technology
Abstract

Abstract Van der Waals heterostructures are set as strong contenders for post‐CMOS quantum materials engineering. A major step for their systematic exploration and exploitation of technological component demonstrators resides in their eased large‐scale design. In this direction, the growth of artificial van der Waals 2D superlattices is presented here such as (MoS2/WS2)n, (WS2/WSe2)n, and (MoS2/WSe2)n with unit cells repetitions reaching n > 10. The fabrication of these materials is enabled by a fully automated in‐situ pulsed laser deposition (PLD) tool. This approach provides cm2 scale homogeneous superlattices with on‐demand material parameters tailoring (layer number, order, and composition). The process is rapid and simple compared to manual pickup exfoliation methods or to sequential transfers of single layers grown by techniques such as chemical vapor deposition, allowing a large repetition of the unit cells in a “mille‐feuille” cake configuration. The computational exploration of this family of superlattice materials sheds light on the potential for optoelectronic property design by shaping the band‐structure landscape while taking into account the influential effects induced by proximity. Overall, this large‐area approach is proposed as an entry point for the systematic design of complex van der Waals heterostructures.

Published
2024
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2. Three-dimensional skyrmionic cocoons in magnetic multilayers

Author

Matthieu Grelier, Florian Godel, Aymeric Vecchiola, Sophie Collin, Karim Bouzehouane, Albert Fert, Vincent Cros, and Nicolas Reyren

Subjects
Science
Abstract

Three dimensional topological spin textures, such as hopfions and skyrmion tubes, have seen a surge of interest for their potential technological applications. They offer greater flexibility than their two dimensional counterparts, but have been hampered by the limited material platforms. Here, Grelier et al. look at aperiodic multilayers, and observe a three dimensional skyrmionic cocoon.

Published
2022
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3. Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

Author

Maëlis Piquemal-Banci, Regina Galceran, Simon M.-M. Dubois, Victor Zatko, Marta Galbiati, Florian Godel, Marie-Blandine Martin, Robert S. Weatherup, Frédéric Petroff, Albert Fert, Jean-Christophe Charlier, John Robertson, Stephan Hofmann, Bruno Dlubak, and Pierre Seneor

Subjects
Science
Abstract

2D materials are foreseen as an opportunity to tailor spintronics devices interfaces, a.k.a spinterfaces. Here, using state-of-the-art large-scale integration in spin-valves, authors demonstrate that hybridization of graphene with a metallic spin source results in strong spin filtering effects.

Published
2020
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6. Ferroelectric phase transitions in epitaxial antiferroelectric PbZrO3 thin films

Author

Pauline Dufour, Thomas Maroutian, Maxime Vallet, Kinnary Patel, André Chanthbouala, Charlotte Jacquemont, Lluis Yedra, Vincent Humbert, Florian Godel, Bin Xu, Sergey Prosandeev, Laurent Bellaiche, Mojca Otoničar, Stéphane Fusil, Brahim Dkhil, Vincent Garcia, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Structures, Propriétés et Modélisation des solides (SPMS), Institut de Chimie du CNRS (INC)-CentraleSupélec-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Arkansas [Fayetteville], Soochow University, Jozef Stefan Institute [Ljubljana] (IJS), ANR-21-CE09-0033,TATOO,Contrôle des états topologiques dans les multiferroïques(2021), ANR-17-CE24-0032,EXPAND,Exploration des oxydes antiferroélectritriques comme nouvel brique technologique pour de futurs dispositifs nanoélectroniques(2017), and European Project: 964931,TSAR

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Physics and Astronomy
Abstract

International audience; The archetypical antiferroelectric, PbZrO3, is currently attracting a lot of interest, but no consensus can be clearly established on the nature of its ground state as well as on the influence of external stimuli over its physical properties. Here, the antiferroelectric state of 45-nm-thick epitaxial thin films of PbZrO3 is established by observing the characteristic structural periodicity of antiparallel dipoles at the atomic scale, combined with clear double hysteresis of the polarization-electric field response related to antiferroelectric–to–ferroelectric phase transitions. Surprisingly, while the antiferroelectric state is identified as the ground state, temperature-dependent measurements show that a transition to a ferroelectric-like state appears in a large temperature window (100 K). Atomistic simulations further confirm the existence, and provides the origin, of such ferroelectric state in the films. Electric-field-induced ferroelectric transitions are also detected by the divergence of the piezoresponse force microscopy response. Using this technique, we further reveal the signature of a ferroelectric ground state for 4-nm-thick PbZrO3 films. Compared with bulk crystals, these results suggest a more complex competition between ferroelectric and antiferroelectric phases in epitaxial thin films of PbZrO3.

Published
2023
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7. Artificial Graphene Spin Polarized Electrode for Magnetic Tunnel Junctions

Author

Victor Zatko, Regina Galceran, Marta Galbiati, Julian Peiro, Florian Godel, Lisa-Marie Kern, David Perconte, Fatima Ibrahim, Ali Hallal, Mairbek Chshiev, Benjamin Martinez, Carlos Frontera, Lluìs Balcells, Piran R. Kidambi, John Robertson, Stephan Hofmann, Sophie Collin, Frédéric Petroff, Marie-Blandine Martin, Bruno Dlubak, Pierre Seneor, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), ICN2 - Institut Catala de Nanociencia i Nanotecnologia (ICN2), Universitat Autònoma de Barcelona (UAB), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-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 (UGA), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Institut de Ciència de Materials de Barcelona (ICMAB), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Vanderbilt University [Nashville], University of Cambridge [UK] (CAM), ANR-19-CE09-0028,MIXES,Hétérostructures de van der Waals à dimensions mixtes pour l'électronique et la spintronique(2019), ANR-19-CE24-0015,STEM2D,Emetteurs THz de type synchrotron à base de matériaux 2D ondulés(2019), European Commission, Engineering and Physical Sciences Research Council (UK), Agence Nationale de la Recherche (France), Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Ciencia e Innovación (España), Zatko, Victor, Godel, Florian, Kern, Lisa-Marie, Chshiev, Mairbek, Frontera, Carlos, Kidambi, Piran R., Hofmann, Stephan, and Dlubak, Bruno

Subjects
Mechanical Engineering, graphene, General Materials Science, Bioengineering, General Chemistry, proximity effects, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, Condensed Matter Physics, 2D materials, spin polarization
Abstract

2D materials offer the ability to expose their electronic structure to manipulations by a proximity effect. This could be harnessed to craft properties of 2D interfaces and van der Waals heterostructures in devices and quantum materials. We explore the possibility to create an artificial spin polarized electrode from graphene through proximity interaction with a ferromagnetic insulator to be used in a magnetic tunnel junction (MTJ). Ferromagnetic insulator/graphene artificial electrodes were fabricated and integrated in MTJs based on spin analyzers. Evidence of the emergence of spin polarization in proximitized graphene layers was observed through the occurrence of tunnel magnetoresistance. We deduced a spin dependent splitting of graphene's Dirac band structure (∼15 meV) induced by the proximity effect, potentially leading to full spin polarization and opening the way to gating. The extracted spin signals illustrate the potential of 2D quantum materials based on proximity effects to craft spintronics functionalities, from vertical MTJs memory cells to logic circuits., This work has received funding from the European Union’s H2020 Future and Emerging Technologies “Graphene Flagship” (Grant Core3 No. 881603), “SINFONIA” (No. 881603) projects and a Grant Agreement Marie Skłodowska Curie “ITN Spinograph” (No. 697904), as well as from EPSRC (EP/P005152/1, EP/K016636/1). This research is supported by a public grant overseen by the French National Research Agency (ANR) as part of the “Investissements d’Avenir” program Labex NanoSaclay (ANR-10-LABX-0035), as well as grants STEM2D (ANR-19-CE24-0015), MIXES (ANR-19-CE09-0028), and by the Flag-ERA JTC 2019 project “SOGraphMEM” (ANR-19-GRFI-0001-07). This work has also received fundings from the “Spanish ministry of Science and Innovation” through “Severo Ochoa” (CEX2019-000917-S) and “OXISOT” (PID2021-128410OB-I00)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Published
2022
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8. Almost Perfect Spin Filtering in Graphene-Based Magnetic Tunnel Junctions

Author

Victor Zatko, Simon M.-M. Dubois, Florian Godel, Marta Galbiati, Julian Peiro, Anke Sander, Cécile Carretero, Aymeric Vecchiola, Sophie Collin, Karim Bouzehouane, Bernard Servet, Frédéric Petroff, Jean-Christophe Charlier, Marie-Blandine Martin, Bruno Dlubak, Pierre Seneor, and UCL - SST/IMCN/MODL - Modelling

Subjects
General Engineering, General Physics and Astronomy, General Materials Science
Abstract

We report on large spin-filtering effects in epitaxial graphene-based spin valves, strongly enhanced in our specific multilayer case. Our results were obtained by the effective association of chemical vapor deposited (CVD) multilayer graphene with a high quality epitaxial Ni(111) ferromagnetic spin source. We highlight that the Ni(111) spin source electrode crystallinity and metallic state are preserved and stabilized by multilayer graphene CVD growth. Complete nanometric spin valve junctions are fabricated using a local probe indentation process, and spin properties are extracted from the graphene-protected ferromagnetic electrode through the use of a reference Al2O3/Co spin analyzer. Strikingly, spin-transport measurements in these structures give rise to large negative tunnel magneto-resistance TMR = −160%, pointing to a particularly large spin polarization for the Ni(111)/Gr interface PNi/Gr, evaluated up to −98%. We then discuss an emerging physical picture of graphene−ferromagnet systems, sustained both by experimental data and ab initio calculations, intimately combining efficient spin filtering effects arising (i) from the bulk band structure of the graphene layers purifying the extracted spin direction, (ii) from the hybridization effects modulating the amplitude of spin polarized scattering states over the first few graphene layers at the interface, and (iii) from the epitaxial interfacial matching of the graphene layers with the spin-polarized Ni surface selecting well-defined spin polarized channels. Importantly, these main spin selection effects are shown to be either cooperating or competing, explaining why our transport results were not observed before. Overall, this study unveils a path to harness the full potential of low Resitance. Area (RA) graphene interfaces in efficient spin-based devices.

Published
2022

9. Unveiling a Chemisorbed Crystallographically Heterogeneous Graphene

Author

Hiroshi, Naganuma, Masahiko, Nishijima, Hayato, Adachi, Mitsuharu, Uemoto, Hikari, Shinya, Shintaro, Yasui, Hitoshi, Morioka, Akihiko, Hirata, Florian, Godel, Marie-Blandine, Martin, Bruno, Dlubak, Pierre, Seneor, and Kenta, Amemiya

Abstract

A crystallographically heterogeneous interface was fabricated by growing hexagonal graphene (Gr) using chemical vapor deposition (CVD) on a tetragonal FePd epitaxial film grown by magnetron sputtering. FePd was alternately arranged with Fe and Pd in the vertical direction, and the outermost surface atom was identified primarily as Fe rather than Pd. This means that FePd has a high degree of

Published
2022

10. Origin of the anomalous Hall effect at the magnetic insulator/heavy metals interface

Author

Sajid Husain, Nicholas Figueiredo-Prestes, Olivier Fayet, Sophie Collin, Florian Godel, Eric Jacquet, Nicolas Reyren, Henri Jaffrès, and Jean-Marie George

Subjects
Physics and Astronomy (miscellaneous)
Abstract

Ferrimagnetic insulators (FIMIs) are considered to be promising candidates in spin–orbit torque (SOT) devices due to their ability to propagate a spin current by magnons without Ohmic losses owing to the absence of electronic scattering. Moreover, any electrical current shunt is avoided in magnetic insulating materials. On the other hand, SOT-induced magnetization switching is generally measured through the anomalous Hall effect (AHE) in FIMI/heavy metal (HM) systems. However, the origin of AHE in FIMI/HM remains elusive since charges flow only in the HM. Here, we experimentally demonstrate that the AHE has the same origin as the spin Hall magnetoresistance (SMR). To this end, we have studied two bilayer heterostructures, Tm3Fe5O12(TmIG)/W and TmIG/Pt, where we ensure opposite spin Hall effect (SHE) signs for two heavy metals (W and Pt). The magnitudes of AHE and SMR are found to be larger for TmIG/W than TmIG/Pt. We have also evidenced the identical polarity of AHE hysteresis in both systems revealing a square dependency on the spin Hall angle whereas the current-induced magnetization switching polarity in TmIG/W is opposite to that of TmIG/Pt as expected for opposite spin Hall angle signs. Our results establish that the AHE and the spin-Hall magnetoresistance in TmIG insulating ferromagnets and heavy metal bilayers originate from the same mechanism.

Published
2023
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11. X-ray magnetic dichroism and tunnel magneto-resistance study of the magnetic phase in epitaxial CrVO

Author

Loïc, Joly, Fabrice, Scheurer, Philippe, Ohresser, Brice, Kengni-Zanguim, Jean-François, Dayen, Pierre, Seneor, Bruno, Dlubak, Florian, Godel, and David, Halley

Abstract

Epitaxial clusters of chromium and chromium-vanadium oxides are studied by tunnel magneto-resistivity measurements, x-ray absorption spectrometry and circular magnetic circular dichroism. They turn out to carry a small magnetic moment that follows a super-paramagnetic behavior. The chromium ion contribution to this magnetization is mainly due to an original magnetic Cr

Published
2021

12. Nonreciprocal Transport in a Rashba Ferromagnet, Delafossite PdCoO

Author

Jin Hong, Lee, Takayuki, Harada, Felix, Trier, Lourdes, Marcano, Florian, Godel, Sergio, Valencia, Atsushi, Tsukazaki, and Manuel, Bibes

Abstract

Rashba interfaces yield efficient spin-charge interconversion and give rise to nonreciprocal transport phenomena. Here, we report magnetotransport experiments in few-nanometer-thick films of PdCoO

Published
2021

13. 0D/2D Heterostructures Vertical Single Electron Transistor

Author

L. Simon, Ulrich Nguétchuissi Noumbé, Louis Donald Notemgnou Mouafo, Walid Baaziz, Florian Godel, Bernard Doudin, Ovidiu Ersen, Pierre Seneor, Marie-Blandine Martin, Stéphane Berciaud, Bruno Dlubak, Etienne Lorchat, Jean-Francois Dayen, Yannick J. Dappe, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Institut de Science des Matériaux de Mulhouse (IS2M), Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC), Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), ANR-19-CE09-0028,MIXES,Hétérostructures de van der Waals à dimensions mixtes pour l'électronique et la spintronique(2019), ANR-19-CE24-0022,COPIN,Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge(2019), ANR-19-CE24-0015,STEM2D,Emetteurs THz de type synchrotron à base de matériaux 2D ondulés(2019), ANR-19-GRF1-0001,SOgraphMEM,Spin Orbit functionalized GRAPHene for resistive-magnetic MEMories(2019), ANR-11-LABX-0058,NIE,Nanostructures en Interaction avec leur Environnement(2011), ANR-10-LABX-0035,Nano-Saclay,Paris-Saclay multidisciplinary Nano-Lab(2010), ANR-10-IDEX-0002,UNISTRA,Par-delà les frontières, l'Université de Strasbourg(2010), univOAK, Archive ouverte, Hétérostructures de van der Waals à dimensions mixtes pour l'électronique et la spintronique - - MIXES2019 - ANR-19-CE09-0028 - AAPG2019 - VALID, Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge - - COPIN2019 - ANR-19-CE24-0022 - AAPG2019 - VALID, Emetteurs THz de type synchrotron à base de matériaux 2D ondulés - - STEM2D2019 - ANR-19-CE24-0015 - AAPG2019 - VALID, Spin Orbit functionalized GRAPHene for resistive-magnetic MEMories - - SOgraphMEM2019 - ANR-19-GRF1-0001 - FLAG-ERA JTC 2019 - VALID, Nanostructures en Interaction avec leur Environnement - - NIE2011 - ANR-11-LABX-0058 - LABX - VALID, Paris-Saclay multidisciplinary Nano-Lab - - Nano-Saclay2010 - ANR-10-LABX-0035 - LABX - VALID, Initiative d'excellence - Par-delà les frontières, l'Université de Strasbourg - - UNISTRA2010 - ANR-10-IDEX-0002 - IDEX - VALID, Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, and Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE)

Subjects
Materials science, 2D heterostructures, single electron transistors, [SPI.NANO] Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Nanoclusters, Biomaterials, nanoelectronics, Condensed Matter::Materials Science, Electric field, Electrochemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Spintronics, business.industry, Electric potential energy, transition metal dichalcogenides, Coulomb blockade, Heterojunction, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Nanoelectronics, Quantum dot, Optoelectronics, nanoparticles, multifunctional materials, 0210 nano-technology, business, [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat]
Abstract

Mixed-dimensional heterostructures formed by the stacking of 2D materials with nanostructures of distinct dimensionality constitute a new class of nanomaterials that offers multifunctionality that goes beyond those of single dimensional systems. An unexplored architecture of single electron transistor (SET) is developed that employs heterostructures made of nanoclusters (0D) grown on a 2D molybdenum disulfide (MoS2) channel. Combining the large Coulomb energy of the nanoclusters with the electronic capabilities of the 2D layer, the concept of 0D–2D vertical SET is unveiled. The MoS2 underneath serves both as a charge tunable channel interconnecting the electrode, and as bottom electrode for each v-SET cell. In addition, its atomic thickness makes it thinner than the Debye screening length, providing electric field transparency functionality that allows for an efficient electric back gate control of the nanoclusters charge state. The Coulomb diamond pattern characteristics of SET are reported, with specific doping dependent nonlinear features arising from the 0D/2D geometry that are elucidated by theoretical modeling. These results hold promise for multifunctional single electron device taking advantage of the versatility of the 2D materials library, with as example envisioned spintronics applications while coupling quantum dots to magnetic 2D material, or to ferroelectric layers for neuromorphic devices.

Published
2021
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14. Long-range propagation and interference of d-wave superconducting pairs in graphene

Author

Juan Trastoy, Pierre Seneor, Piran R. Kidambi, Victor Zatko, F. S. Bergeret, Stephan Hofmann, Anke Sander, X. P. Zhang, Florian Godel, K. Seurre, Dario Bercioux, Christian Ulysse, Javier E. Villegas, D. Perconte, Bruno Dlubak, V. Humbert, Centre National de la Recherche Scientifique (France), European Commission, European Research Council, Agence Nationale de la Recherche (France), Japan Society for the Promotion of Science, Agencia Estatal de Investigación (España), Eusko Jaurlaritza, Ministerio de Ciencia, Innovación y Universidades (España), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Universidad Autonoma de Madrid (UAM), Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Vanderbilt University [Nashville], Department of Engineering [Cambridge], University of Cambridge [UK] (CAM), Departamento de Fisica de Materieles and Centro Mixto CSIC-UPV/EHU, Facultad de Ciencias Quimicas, Donostia International Physics Center (DIPC), University of the Basque Country/Euskal Herriko Unibertsitatea (UPV/EHU), and Ikerbasque - Basque Foundation for Science

Subjects
Dirac (software), FOS: Physical sciences, General Physics and Astronomy, Physics::Optics, 02 engineering and technology, Interference (wave propagation), 01 natural sciences, law.invention, Superconductivity (cond-mat.supr-con), law, Condensed Matter::Superconductivity, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, [PHYS]Physics [physics], Superconductivity, Physics, Quantum Physics, Range (particle radiation), Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Series (mathematics), Graphene, Condensed Matter - Superconductivity, Conductance, 021001 nanoscience & nanotechnology, Quantum Physics (quant-ph), 0210 nano-technology
Abstract

Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here, we demonstrate that those correlations propagate hundreds of nanometers, allowing for the unique observation of d-wave Andreev-pair interferences in YBa2Cu3O7-graphene devices that behave as a Fabry-Perot cavity. The interferences show as a series of pronounced conductance oscillations analogous to those originally predicted by de Gennes–Saint-James for conventional metal-superconductor junctions. The present demonstration is pivotal to the study of exotic directional effects expected for nodal superconductivity in Dirac materials., Work at Unite Mixte de Physique CNRS/Thales supported by the ERC Grant No. 647100 “SUSPINTRONICS,” French ANR Grants No. ANR-15-CE24-0008-01 “SUPERTRONICS” and No. ANR-17-CE30-0018-04 “OPTOFLUXONICS,” Labex NanoSaclay No. ANR-10-LABX-0035, European COST action 16218 “Nanocohybri”, European Union's H2020 Excellent Science (Grants No. 785219 and No. 881603), and JSPS core-to-core program A. Advanced Research Networks. This work was supported by the French RENATECH network (French national nanofabrication platform). X. P. Z., D. B., and F. S. B. acknowledge support from Ministerio de Ciencia e Innovacion (MICINN) through Project No. FIS2017-82804-P. F. S. B. acknowledges Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT1249-19).

Published
2021

15. Large‐Scale‐Compatible Stabilization of a 2D Semiconductor Platform toward Discrete Components

Author

Florian Godel, Bernard Servet, Pierre Brus, Sophie Collin, Victor Zatko, Patrick Garabedian, Pierre Seneor, Marie-Blandine Martin, Odile Bezencenet, Raphaël Aubry, Stéphane Xavier, Bruno Dlubak, Marta Galbiati, Thales Research and Technologies [Orsay] (TRT), THALES, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), and Centre National de la Recherche Scientifique (CNRS)-THALES

Subjects
Materials science, Passivation, Scale (ratio), business.industry, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Engineering physics, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, [SPI.TRON]Engineering Sciences [physics]/Electronics, Semiconductor, visual_art, Electronic component, visual_art.visual_art_medium, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, business
Abstract

International audience; Atomically thin 2D materials have drawn considerable attention in the past years with potential ranging from transistors to optoelectronics. As such, they are now foreseen as strong candidates for epitaxy-free technologies and the tetrad of size-weight-power-and-cost (SWAP-C) reduction. Targeting radiofrequency (RF) applications, the 2D semiconducting transition metal dichalcogenides (TMDC) family can offer the opportunity of wide tunability of their electronic properties, providing a large variety of band gaps. However, evaluation and integration of those materials into discrete components requires a stabilization of their properties. This work focuses on the evaluation of a large-scale compatible fabrication/passivation process on large area (>1000 μm2) monolayers of the prototypical 2D semiconductor MoS2. The process is developed including pre- and post-patterning protection/passivation layers. It is shown to reduce the initial natural p-doping of the sample, leading to lower transistor threshold voltages, a 10^6 ION/IOFF ratio, and an effective averaged field-effect mobility under ambient conditions of 20 cm2 V−1 s−1 (up to 35 cm2 V−1 s−1 for some devices), which represents an increase by a 40-fold factor compared to a conventional process carried on the large scale platform. This work represents an important step toward the integration of 2D TMDCs in discrete RF circuits and components.

Published
2021
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16. Ultrafast spin-currents and charge conversion at 3 d -5 d interfaces probed by time-domain terahertz spectroscopy

Author

Daniel Dolfi, Sophie Collin, Paolo Bortolotti, T. H. Dang, G. G. Baez Flores, Hanond Nong, J.-M. George, Maxen Cosset-Cheneau, Florian Godel, Jérôme Tignon, Juliette Mangeney, D. Q. To, Pierre Seneor, Juan-Carlos Rojas-Sánchez, E. Rongione, Albert Fert, Kirill D. Belashchenko, Sukhdeep Dhillon, M. Anane, J. Hawecker, Romain Lebrun, Laurent Vila, Henri Jaffrès, Manuel Bibes, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Nano-THz, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), University of Nebraska [Lincoln], University of Nebraska System, Université Grenoble Alpes (UGA), Thales Research and Technology [Palaiseau], THALES, Centre National de la Recherche Scientifique (CNRS)-THALES, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
Materials science, Terahertz radiation, General Physics and Astronomy, FOS: Physical sciences, 02 engineering and technology, Applied Physics (physics.app-ph), 01 natural sciences, Ab initio quantum chemistry methods, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Spectroscopy, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Spin-½, 010302 applied physics, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Spintronics, Materials Science (cond-mat.mtrl-sci), Physics - Applied Physics, 021001 nanoscience & nanotechnology, Ferromagnetic resonance, 3. Good health, Ferromagnetism, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, Ultrashort pulse
Abstract

Spintronic structures are extensively investigated for their spin orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to their inverse spin-Hall effect properties. In particular the intrinsic inverse spin Hall effect of Pt-based systems and extrinsic inverse spin-Hall effect of Au:W and Au:Ta in NiFe/Au:(W,Ta) bilayers are investigated. The spin-charge conversion is probed by complementary techniques -- ultrafast THz time domain spectroscopy in the dynamic regime for THz pulse emission and ferromagnetic resonance spin-pumping measurements in the GHz regime in the steady state -- to determine the role played by the material properties, resistivities, spin transmission at metallic interfaces and spin-flip rates. These measurements show the correspondence between the THz time domain spectroscopy and ferromagnetic spin-pumping for the different set of samples in term of the spin mixing conductance. The latter quantity is a critical parameter, determining the strength of the THz emission from spintronic interfaces. This is further supported by ab-initio calculations, simulations and analysis of the spin-diffusion and spin relaxation of carriers within the multilayers in the time domain, permitting to determine the main trends and the role of spin transmission at interfaces. This work illustrates that time domain spectroscopy for spin-based THz emission is a powerful technique to probe spin-dynamics at active spintronic interfaces and to extract key material properties for spin-charge conversion., Comment: 20 pages

Published
2020
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17. Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

Author

Robert S. Weatherup, Simon M-M Dubois, Frédéric Petroff, Victor Zatko, Pierre Seneor, Bruno Dlubak, Jean-Christophe Charlier, Regina Galceran, Albert Fert, Stephan Hofmann, John Robertson, Marie-Blandine Martin, Florian Godel, Maëlis Piquemal-Banci, Marta Galbiati, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, UCL - SST/IMCN/MODL - Modelling, Galbiati, Marta [0000-0002-6021-5156], Godel, Florian [0000-0003-1741-2741], Weatherup, Robert S [0000-0002-3993-9045], Charlier, Jean-Christophe [0000-0002-5749-1328], Hofmann, Stephan [0000-0001-6375-1459], Dlubak, Bruno [0000-0001-5696-8991], Apollo - University of Cambridge Repository, and Weatherup, Robert S. [0000-0002-3993-9045]

Subjects
120, Materials science, Science, General Physics and Astronomy, Genetics and Molecular Biology, 02 engineering and technology, Materials science Nanoscience and technology, 010402 general chemistry, 01 natural sciences, Signal, Article, General Biochemistry, Genetics and Molecular Biology, law.invention, Engineering, Nanoscience and technology, law, Monolayer, Proximity effect (superconductivity), 128, 639/925, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], lcsh:Science, Spin-½, [PHYS]Physics [physics], 639/166, 639/301, Multidisciplinary, Spintronics, Condensed matter physics, Nanotecnologia, Graphene, Physics, 639/766, General Chemistry, Ciència dels materials, 5104 Condensed Matter Physics, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Ferromagnetism, General Biochemistry, Density of states, lcsh:Q, Condensed Matter::Strongly Correlated Electrons, 119, 0210 nano-technology, 51 Physical Sciences
Abstract

We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR > 80% in junctions with low resistance × area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization effects need to be taken into account to fully grasp the spin properties (such as spin dependent density of states) when 2D materials are used as ultimately thin interfaces. While this is only a first demonstration, we thus introduce the fruitful potential of spin manipulation by proximity effect at the hybridized 2D material / ferromagnet interface for 2D-MTJs., 2D materials are foreseen as an opportunity to tailor spintronics devices interfaces, a.k.a spinterfaces. Here, using state-of-the-art large-scale integration in spin-valves, authors demonstrate that hybridization of graphene with a metallic spin source results in strong spin filtering effects.

Published
2020
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18. Ultrafast Spin-Charge Conversion in Rashba states probed by Terahertz time-domain emission spectroscopy

Author

Henri Jaffrès, P. Bortolotti, E. Rongione, Jérôme Tignon, J.-M. George, L. Moreno, Manuel Bibes, Juliette Mangeney, Pierre Seneor, J. Hawecker, Romain Lebrun, Stéphane Collin, Hanond Nong, T. H. Dang, Florian Godel, and S. S. Dhillon

Subjects
Materials science, Condensed matter physics, Terahertz radiation, Topological insulator, Spin Hall effect, Physics::Optics, Condensed Matter::Strongly Correlated Electrons, Emission spectrum, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Spin (physics), Spectroscopy, Fermi gas, Surface states
Abstract

Terahertz (THz) emission spectroscopy in spin systems has become a very powerful method to generate THz radiation and to investigate the properties of Rashba or Topological Insulator surface states. Broadband THz emission can be generated in heavy metallic or in more general Rashba systems. In 3d/5d transient metal bilayers THz emission is via the Inverse Spin Hall effect. Beyond heavy metal structures, Rashba states are strong candidates for THz-spintronics owing to their high spin to charge conversion properties. Here we present a 2D Electron Gas with strong Rashba spin-orbit coupling, NiFe/LaAlO 3 /SrTiO 3 , and demonstrate THz emission is via the Inverse Edelstein Effect.

Published
2020
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19. Very Long Term Stabilization of a 2D Magnet down to the Monolayer for Device Integration

Author

Bernard Servet, Sophie Collin, Pierre Seneor, Aymeric Vecchiola, Marta Galbiati, Pomme Hirschauer, Bruno Dlubak, Frédéric Petroff, Florian Godel, Victor Zatko, Andrés Cantarero, Marie-Blandine Martin, Karim Bouzehouane, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Thales Research and Technology [Palaiseau], and THALES

Subjects
010302 applied physics, [PHYS]Physics [physics], Materials science, Spintronics, Nanotechnology, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Electronic, Optical and Magnetic Materials, Term (time), Fragility, Ferromagnetism, Magnet, 0103 physical sciences, Monolayer, Materials Chemistry, Electrochemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

2D materials have recently demonstrated a strong potential for spintronic applications. This has been further reinforced by the discovery of ferromagnetic 2D layers. Nevertheless, the fragility of ...

Published
2020
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20. Anomalous Hall effect in 3d/5d multilayers mediated by interface scattering and nonlocal spin conductivity

Author

Florian Godel, Nicolas Reyren, T. H. Dang, Q. Barbedienne, D. Q. To, Henri Jaffrès, J.-M. George, E. Rongione, and Stéphane Collin

Subjects
Materials science, Condensed matter physics, Scattering, Inverse, 02 engineering and technology, Conductivity, 021001 nanoscience & nanotechnology, 01 natural sciences, Specularity, Hall effect, 0103 physical sciences, Perpendicular, Specular reflection, 010306 general physics, 0210 nano-technology, Electron scattering
Abstract

We have evidenced unconventional anomalous Hall effects (AHEs) in $3d/5d$ (${\mathrm{Co}0.2\mathrm{nm}/\mathrm{Ni}0.6\mathrm{nm})}_{N}$ multilayers grown on a thin Pt layer or thin Au:W alloys with perpendicular magnetic anisotropy (PMA) properties. The inversion of AHEs observed with one Pt series is explained by considering the opposite sign of the effective spin-orbit coupling of Pt compared to Co/Ni combined with peculiar specular electronic reflections. Using advanced simulations methods for the description of the spin-current profiles based on the spin-dependent Boltzmann formalism, we extracted the spin-Hall angle (SHA) of Pt and Co/Ni of opposite sign. The extracted SHA for Pt, $+20%$, is opposite to the one of Co/Ni, giving rise to an effective AHE inversion for thin Co/Ni multilayers (with the number of repetition layers $Nl17$). The spin-Hall angle in Pt is found to be larger than the one previously measured by complementary spin-pumping inverse spin-Hall effect experiments in a geometry of current perpendicular to the plane. Whereas magnetic proximity effects cannot explain the effect, spin-current leakage and spin-orbit assisted electron scattering at Pt/(Co,Ni) interfaces fit the experiments. We also extract the main relevant electronic transport parameters governing the overall effects in current-in-plane (CIP) currents and demonstrate, in particular, that the specularity/nonspecularity in the electronic diffusion processes play an essential role to explain the observed results.

Published
2020
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21. Ultrafast spin-charge interconversion in Rashba states probed by time-domain THz spectroscopy

Author

Manuel Bibes, Albert Fert, Florian Godel, Kirill D. Belashchenko, Diogo C. Vaz, Juliette Mangeney, Sukhdeep Dhillon, Luis Moreno, Juan-Carlos Rojas-Sánchez, Jérôme Tignon, Jean-Philippe Attané, Daniel Dolfi, Jean-Marie George, T. H. Dang, P. Bortolotti, Hanond Nong, Giovanni Baez Flores, Sophie Collin, Henri Jaffrès, J. Hawecker, Romain Lebrun, Laurent Vila, Abdelmadjid Anane, Paul Noël, Enzo Faycal Rongione, and Pierre Seneor

Subjects
Materials science, Condensed matter physics, Terahertz radiation, Topological insulator, Spin Hall effect, Physics::Optics, Condensed Matter::Strongly Correlated Electrons, Emission spectrum, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Spin (physics), Fermi gas, Ultrashort pulse, Surface states
Abstract

Terahertz (THz) emission spectroscopy in spin systems has become a very powerful method to generate THz radiation and to investigate the properties of Rashba or Topological Insulator surface states. The THz emission can be generated in heavy metallic or in more general Rashba systems. In 3d/5d transient metal bilayers THz emission in via the Inverse Spin Hall effect. Beyond heavy metal structures, Rashba states are strong candidates for THz-spintronics owing to their high spin to charge conversion properties. Here we present 2D electron gas with strong Rashba spin-orbit coupling and demonstrate THz emission via the Inverse Edelstein Effect.

Published
2020
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22. Tailored flux pinning in superconductor/ferromagnet multilayers with engineered magnetic domain morphology from stripes to skyrmions

Author

Javier E. Villegas, Xavier Palermo, Florian Godel, Alexandre I. Buzdin, Jacobo Santamaria, Sophie Collin, Nicolas Reyren, Anke Sander, Vincent Cros, Salvatore Mesoraca, A. V. Samokhvalov, Karim Bouzehouane, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institute for Physics of Microstructures of the RAS, Russian Academy of Sciences [Moscow] (RAS), Instituto Universitario de Investigacion de Nanocienca de Aragon, University of Zaragoza - Universidad de Zaragoza [Zaragoza], Manufacturing Department (MGEP), Mondragon Unibertsitatea, Centre de physique moléculaire optique et hertzienne (CPMOH), Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1, THALES [France]-Centre National de la Recherche Scientifique (CNRS), ANR-15-CE24-0008,SUPERTRONICS,Control de courants supraconducteurs via des effets de spin et de champ: fondements pour une électronique non conventionnelle(2015), ANR-17-CE30-0018,Optofluxonics,Manipulation optique de quanta de flux individuels dans les supraconducteurs et applications(2017), ANR-11-IDEX-0003,IPS,Idex Paris-Saclay(2011), European Project: 647100,H2020,ERC-2014-CoG,SUSPINTRONICS(2015), and THALES-Centre National de la Recherche Scientifique (CNRS)

Subjects
Superconductivity, Flux pinning, Materials science, Condensed matter physics, Magnetic domain, Skyrmion, Condensed Matter - Superconductivity, Stacking, General Physics and Astronomy, FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Vortex, Superconductivity (cond-mat.supr-con), [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Ferromagnetism, Condensed Matter::Superconductivity, 0103 physical sciences, Thin film, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; Superconductor/Ferromagnet (S/F) hybrid systems show interesting magneto-transport behaviors that result from the transfer of properties between both constituents. For instance, magnetic memory can be transferred from the F into the S through the pinning of superconducting vortices by the ferromagnetic textures. The ability to tailor this type of induced behavior is important to broaden its range of application. Here we show that engineering the F magnetization reversal allows tuning the strength of the vortex pinning (and memory) effects, as well as the field range in which they appear. This is done by using magnetic multilayers in which Co thin films are combined with different heavy metals (Ru, Ir, Pt). By choosing the materials, thicknesses, and stacking order of the layers, we can design the characteristic domain size and morphology, from out-of-plane magnetized stripe domains to much smaller magnetic skyrmions. These changes strongly affect the magneto-transport properties. The underlying mechanisms are identified by comparing the experimental results to a magnetic pinning model. * javier.villegas@cnrs-thales.fr 2

Published
2020
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23. WS2 2D Semiconductor Down to Monolayers by Pulsed-Laser Deposition for Large-Scale Integration in Electronics and Spintronics Circuits

Author

Victor Zatko, Anke Sander, Florian Godel, Odile Bezencenet, Bernard Servet, C. Carrétéro, Pierre Brus, Marie-Blandine Martin, Marta Galbiati, Bruno Dlubak, Pierre Seneor, Aymeric Vecchiola, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Thales Research and Technology [Palaiseau], and THALES

Subjects
Materials science, Tungsten disulfide, WS2, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Pulsed laser deposition, chemistry.chemical_compound, Monolayer, Deposition (phase transition), General Materials Science, Electronics, 2D semiconductors, Electronic circuit, spintronics, Spintronics, business.industry, Nanotecnologia, 021001 nanoscience & nanotechnology, pulsed-laser deposition, [SPI.TRON]Engineering Sciences [physics]/Electronics, 0104 chemical sciences, Espectroscòpia Raman, Semiconductor, chemistry, Semiconductors, Raman spectroscopy, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, X-ray photoemission spectroscopy, 0210 nano-technology, business
Abstract

International audience; We report on the achievement of a large-scale tungsten disulfide (WS2) 2D semiconducting platform derived by pulsed-laser deposition (PLD) on both insulating substrates (SrTiO3), as required for in-plane semiconductor circuit definition, and ferromagnetic spin sources (Ni), as required for spintronics applications. We show thickness and phase control, with highly homogeneous wafer-scale monolayers observed under certain conditions, as demonstrated by X-ray photoelectron spectroscopy and Raman spectroscopy mappings. Interestingly, growth appears to be dependent on the substrate selection, with a dramatically increased growth rate on Ni substrates. We show that this 2D-semiconductor integration protocol preserves the interface integrity. Illustratively, the WS2/Ni electrode is shown to be resistant to oxidation (even after extended exposure to ambient conditions) and to present tunneling characteristics once integrated into a complete vertical device. Overall, these experiments show that the presented PLD approach used here for WS2 growth is versatile and has a strong potential to accelerate the integration and evaluation of large-scale 2D-semiconductor platforms in electronics and spintronics circuits.

Published
2020
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24. Antiferromagnetic textures in BiFeO3 controlled by strain and electric field

Author

Daniel Sando, Vincent Jacques, Vincent Garcia, Michel Viret, A. Finco, W. Akhtar, Florian Godel, Jean-Yves Chauleau, Stéphane Fusil, Manuel Bibes, A. Haykal, C. Carrétéro, Yorick A. Birkhölzer, Nicolas Jaouen, J. Fischer, Inorganic Materials Science, Laboratoire Charles Coulomb (L2C), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Institute for Nanotechnology (MESA+), University of Twente, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), ANR-17-CE09-0030,PIAF,Imagerie et manipulation des antiferromagnétiques(2017), THALES-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), University of Twente [Netherlands], Centre National de la Recherche Scientifique (CNRS)-THALES, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), and Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique

Subjects
Ferroelectrics and multiferroics, Materials science, Science, General Physics and Astronomy, 02 engineering and technology, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Article, Condensed Matter::Materials Science, Magnetic properties and materials, Electric field, Condensed Matter::Superconductivity, 0103 physical sciences, Antiferromagnetism, Multiferroics, 010306 general physics, lcsh:Science, Spin-½, Magnonics, Multidisciplinary, Spintronics, Condensed matter physics, Condensed Matter::Other, General Chemistry, 021001 nanoscience & nanotechnology, Ferroelectricity, Piezoresponse force microscopy, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], lcsh:Q, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology
Abstract

Antiferromagnetic thin films are currently generating considerable excitement for low dissipation magnonics and spintronics. However, while tuneable antiferromagnetic textures form the backbone of functional devices, they are virtually unknown at the submicron scale. Here we image a wide variety of antiferromagnetic spin textures in multiferroic BiFeO3 thin films that can be tuned by strain and manipulated by electric fields through room-temperature magnetoelectric coupling. Using piezoresponse force microscopy and scanning NV magnetometry in self-organized ferroelectric patterns of BiFeO3, we reveal how strain stabilizes different types of non-collinear antiferromagnetic states (bulk-like and exotic spin cycloids) as well as collinear antiferromagnetic textures. Beyond these local-scale observations, resonant elastic X-ray scattering confirms the existence of both types of spin cycloids. Finally, we show that electric-field control of the ferroelectric landscape induces transitions either between collinear and non-collinear states or between different cycloids, offering perspectives for the design of reconfigurable antiferromagnetic spin textures on demand., Tailoring antiferromagnetic domains is critical for the development of low-dissipative spintronic and magnonic devices. Here the authors demonstrate the control of antiferromagnetic spin textures in multiferroic bismuth ferrite thin films using strain and electric fields.

Published
2020
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25. X-ray magnetic dichroism and tunnel magneto-resistance study of the magnetic phase in epitaxial CrVO x nanoclusters

Author

Loïc Joly, Fabrice Scheurer, Philippe Ohresser, Brice Kengni-Zanguim, Jean-François Dayen, Pierre Seneor, Bruno Dlubak, Florian Godel, and David Halley

Subjects
Condensed Matter::Strongly Correlated Electrons, General Materials Science, Physics::Atomic Physics, Condensed Matter Physics
Abstract

Epitaxial clusters of chromium and chromium–vanadium oxides are studied by tunnel magneto-resistivity measurements, x-ray absorption spectrometry and circular magnetic circular dichroism. They turn out to carry a small magnetic moment that follows a super-paramagnetic behavior. The chromium ion contribution to this magnetization is mainly due to an original magnetic Cr2O3-like phase, whereas usual Cr2O3 is known to be anti-ferromagnetic in the bulk. For mixed clusters, vanadium ions also contribute to the total magnetization and they are coupled to the chromium ion spins. By measuring the dichroic signal at different temperatures, we get insight into the possible spin configurations of vanadium and chromium ions: we propose that the magnetic dipoles observed in the clusters assembly could be related to ionic spins that couple at a very short range, as for instance in short one-dimensional spins chains.

Published
2022
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26. Band-Structure Spin-Filtering in Vertical Spin Valves Based on Chemical Vapor Deposited WS

Author

Victor, Zatko, Marta, Galbiati, Simon Mutien-Marie, Dubois, Mauro, Och, Pawel, Palczynski, Cecilia, Mattevi, Pierre, Brus, Odile, Bezencenet, Marie-Blandine, Martin, Bernard, Servet, Jean-Christophe, Charlier, Florian, Godel, Aymeric, Vecchiola, Karim, Bouzehouane, Sophie, Collin, Frédéric, Petroff, Bruno, Dlubak, and Pierre, Seneor

Abstract

We report on spin transport in WS

Published
2019

27. Band-structure spin-filtering in vertical spin valves based on chemical vapor deposited WS2

Author

Sophie Collin, Jean-Christophe Charlier, Bernard Servet, Pierre Brus, Karim Bouzehouane, Pierre Seneor, Frédéric Petroff, Mauro Och, Marta Galbiati, Aymeric Vecchiola, Florian Godel, Marie-Blandine Martin, Pawel Palczynski, Odile Bezencenet, Simon M-M Dubois, Victor Zatko, Bruno Dlubak, Cecilia Mattevi, The Royal Society, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain = Catholic University of Louvain (UCL), Imperial College London, Thales Research and Technology [Palaiseau], and THALES

Subjects
Materials science, Tungsten disulfide, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, Condensed Matter::Materials Science, Transition metal, tungsten disulfide, Condensed Matter::Superconductivity, spin filtering, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Nanoscience & Nanotechnology, Electronic band structure, 2D, Spin-½, [PHYS]Physics [physics], spintronics, Spin filtering, Condensed matter physics, Spintronics, business.industry, General Engineering, semiconductor, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, magnetic tunnel junction, 0104 chemical sciences, Tunnel magnetoresistance, Semiconductor, chemistry, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, business
Abstract

International audience; We report on spin transport in WS2-based 2D-magnetic tunnel junctions (2D-MTJs), unveiling a band structure spin filtering effect specific to the transition metal dichalcogenides (TMDCs) family. WS2 mono-, bi-, and trilayers are derived by a chemical vapor deposition process and further characterized by Raman spectroscopy, atomic force microscopy (AFM), and photoluminescence spec-troscopy. The WS2 layers are then integrated in complete Co/Al2O3 /WS2/Co MTJ hybrid spin-valve structures. We make use of a tunnel Co/Al2O3 spin analyzer to probe the extracted spin-polarized current from the WS2/Co interface and its evolution as a function of WS2 layer thicknesses. For monolayer WS2, our technological approach enables the extraction of the largest spin signal reported for a TMDC-based spin valve, corresponding to a spin polarization of PCo/WS2 = 12%. Interestingly, for bi-and trilayer WS2, the spin signal is reversed, which indicates a switch in the mechanism of interfacial spin extraction. With the support of ab initio calculations, we propose a model to address the experimentally measured inversion of the spin polarization based on the change in the WS2 band structure while going from monolayer (direct bandgap) to bilayer (indirect bandgap). These experiments illustrate the rich potential of the families of semiconducting 2D materials for the control of spin currents in 2D-MTJs.

Published
2019
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28. Path to Overcome Material and Fundamental Obstacles in Spin Valves Based on MoS2 and Other Transition-Metal Dichalcogenides

Author

Marta Galbiati, Samuel Mañas-Valero, Jean-Christophe Charlier, Pierre Seneor, Florian Godel, Sergio Tatay, Eugenio Coronado, Maëlis Piquemal-Banci, Simon M-M Dubois, Regina Galceran, Alicia Forment-Aliaga, Bruno Dlubak, and Aymeric Vecchiola

Subjects
Spin filtering, Materials science, Fabrication, Spintronics, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Engineering physics, Transition metal, Modulation, 0103 physical sciences, Path (graph theory), Perpendicular anisotropy, 010306 general physics, 0210 nano-technology, Spin-½
Abstract

The recent introduction of two-dimensional materials into magnetic tunnel junctions (2D MTJs) offers very promising properties for spintronics, such as atomically defined interfaces, spin filtering, perpendicular anisotropy, and modulation of spin-orbit torque. Nevertheless, the difficulty of integrating exfoliated 2D materials into spintronic devices has limited exploration. Here the authors find a fabrication process leading to superior performance in MTJs based on transition-metal dichalcogenides, and further suggest a path to alleviate basic issues of technology and physics for 2D MTJs.

Published
2019
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29. A perpendicular graphene/ferromagnet electrode for spintronics

Author

C. Carrétéro, Marta Galbiati, Bruno Dlubak, Odile Bezencenet, Nicolas Reyren, Anke Sander, Pierre Seneor, Florian Godel, Victor Zatko, Hiroshi Naganuma, Marie-Blandine Martin, Center for Innovative Integrated Electronics Systems, Tohoku University, Tohoku University [Sendai], Graduate School of Engineering, Tohoku University, Center for Spintronics Integrated Systems, Tohoku University, Center for Spintronics Research Network, Tohoku University, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Thales Research and Technology [Palaiseau], and THALES

Subjects
Materials science, Physics and Astronomy (miscellaneous), 02 engineering and technology, Chemical vapor deposition, 01 natural sciences, law.invention, Condensed Matter::Materials Science, law, 0103 physical sciences, Perpendicular, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Anisotropy, Materials, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], 010302 applied physics, Spintronics, Condensed matter physics, Graphene, Sputter deposition, 021001 nanoscience & nanotechnology, Innovacions tecnològiques, Ferromagnetism, Magnetic damping, 0210 nano-technology
Abstract

We report on the large-scale integration of graphene layers over a FePd perpendicular magnetic anisotropy (PMA) platform, targeting further downscaling of spin circuits. An L10 FePd ordered alloy showing both high magneto-crystalline anisotropy and a low magnetic damping constant, is deposited by magnetron sputtering. The graphene layer is then grown on top of it by large-scale chemical vapor deposition. A step-by-step study, including structural and magnetic analyses by x-ray diffraction and Kerr microscopy, shows that the measured FePd properties are preserved after the graphene deposition process. This scheme provides a graphene protected perpendicular spin electrode showing resistance to oxidation, atomic flatness, stable crystallinity, and perpendicular magnetic properties. This, in turn, opens the way to the generalization of hybrid 2D-materials on optimized PMA platforms, sustaining the development of spintronics circuits based on perpendicular spin-sources as required, for instance, for perpendicular-magnetic random-access memory schemes.

Published
2020
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30. A Local Study of the Transport Mechanisms in MoS2 Layers for Magnetic Tunnel Junctions

Author

Pierre Seneor, Alicia Forment-Aliaga, Florian Godel, Regina Galceran, Aymeric Vecchiola, Josep Canet-Ferrer, Maëlis Piquemal-Banci, Samuel Mañas-Valero, Marta Galbiati, Eugenio Coronado, Bruno Dlubak, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Instituto de Ciencia Molecular (ICMol), Universitat de València (UV), and Institut de Ciencies Fotoniques [Castelldefels] (ICFO)

Subjects
010302 applied physics, [PHYS]Physics [physics], Thin layers, Materials science, Condensed matter physics, Magnetoresistance, Spintronics, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Local study, Characterization (materials science), 0103 physical sciences, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Electrical conductor, Quantum tunnelling, ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract

MoS2-based vertical spintronic devices have attracted an increasing interest thanks to theoretical predictions of large magnetoresistance signals. However, experimental performances are still far from expectations. Here, we carry out the local electrical characterization of thin MoS2 flakes in a Co/Al2O3/MoS2 structure through conductive tip AFM measurements. We show that thin MoS2 presents a metallic behavior with a strong lateral transport contribution that hinders the direct tunnelling through thin layers. Indeed, no resistance dependence is observed with the flake thickness. These findings reveal a spin depolarization source in the MoS2-based spin valves, thus pointing to possible solutions to improve their spintronic properties.

Published
2018
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31. A Local Study of the Transport Mechanisms in MoS

Author

Marta, Galbiati, Aymeric, Vecchiola, Samuel, Mañas-Valero, Josep, Canet-Ferrer, Regina, Galceran, Maëlis, Piquemal-Banci, Florian, Godel, Alicia, Forment-Aliaga, Bruno, Dlubak, Pierre, Seneor, and Eugenio, Coronado

Abstract

MoS

Published
2018

32. Insulator-to-Metallic Spin-Filtering in 2D-Magnetic Tunnel Junctions Based on Hexagonal Boron Nitride

Author

Robert S. Weatherup, Jean-Christophe Charlier, John Robertson, Stephan Hofmann, Pierre Seneor, Marie-Blandine Martin, Piran R. Kidambi, Maëlis Piquemal-Banci, Stéphane Xavier, Bruno Dlubak, Albert Fert, Abdelmadjid Anane, Sabina Caneva, Karim Bouzehouane, Regina Galceran, Florian Godel, Frédéric Petroff, Simon M-M Dubois, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Laboratory for Photovoltaics Luxembourg, University of Luxembourg [Luxembourg], University of Cambridge [UK] (CAM), Thales Research & Technology France, THALES, Unité de Physique-Chimie et physique des matériaux (LLN), and Université Catholique de Louvain = Catholic University of Louvain (UCL)

Subjects
Materials science, General Physics and Astronomy, Hexagonal boron nitride, Insulator (electricity), 02 engineering and technology, Chemical vapor deposition, 01 natural sciences, chemical vapor deposition, Metal, Ab initio quantum chemistry methods, 0103 physical sciences, General Materials Science, hexagonal boron nitride, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, spintronics, Spin filtering, Spintronics, Condensed matter physics, General Engineering, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, 2D materials, visual_art, visual_art.visual_art_medium, 0210 nano-technology
Abstract

International audience; We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into magnetic tunnel junctions (2D-MTJs) by fabricating two illustrative systems (Co/h-BN/Co and Co/h-BN/Fe) and by discussing h-BN potential for metallic spin filtering. The h-BN is directly grown by chemical vapor deposition on prepatterned Co and Fe stripes. Spin-transport measurements reveal tunnel magneto-resistances in these h-BN-based MTJs as high as 12% for Co/h-BN/h-BN/Co and 50% for Co/h-BN/Fe. We analyze the spin polarizations of h-BN/Co and h-BN/Fe interfaces extracted from experimental spin signals in light of spin filtering at hybrid chemisorbed/ physisorbed h-BN, with support of ab initio calculations. These experiments illustrate the strong potential of h-BN for MTJs and are expected to ignite further investigations of 2D materials for large signal spin devices.

Published
2018
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33. Tuning contact transport mechanisms in bilayer MoSe 2 transistors up to Fowler–Nordheim regime

Author

Bernard Doudin, M. Venkata Kamalakar, Florian Godel, Guillaume Froehlicher, Louis Donald Notemgnou Mouafo, Stéphane Berciaud, Jean-Francois Dayen, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), and Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Schottky barrier, Nanotechnology, Thermionic emission, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, General Materials Science, Quantum tunnelling, business.industry, Mechanical Engineering, General Chemistry, Semiconductor device, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism, Band bending, Semiconductor, chemistry, Mechanics of Materials, Molybdenum diselenide, Optoelectronics, Field-effect transistor, 0210 nano-technology, business
Abstract

Atomically thin molybdenum diselenide (MoSe 2 ) is an emerging two-dimensional (2D) semiconductor with significant potential for electronic, optoelectronic, spintronic applications and a common platform for their possible integration. Tuning interface charge transport between such new 2D materials and metallic electrodes is a key issue in 2D device physics and engineering. Here, we report tunable interface charge transport in bilayer MoSe 2 field effect transistors with Ti/Au contacts showing high on/off ratio up to 10 7 at room temperature. Our experiments reveal a detailed map of transport mechanisms obtained by controlling the interface band bending profile via temperature, gate and source-drain bias voltages. This comprehensive investigation leads to demarcating regimes and tuning in transport mechanisms while controlling the interface barrier profile. The careful analysis allows us to identify thermally activated regime at low carrier density, and Schottky barrier driven mechanisms at higher carrier density demonstrating the transition from low-field direct tunneling/ thermionic emission to high-field Fowler–Nordheim tunneling. Furthermore, we show that the transition voltage V trans to Fowler–Nordheim correlates directly to the difference between the chemical potential of the metal electrode and the conduction band minimum in the 2D semiconductor, which opens up opportunities for new theoretical and experimental investigations. Our approach being generic can be extended to other 2D materials, and the possibility of tuning contact transport regimes is promising for designing MoSe 2 device applications.

Published
2017
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34. M-Plane GaN/InAlN Multiple Quantum Wells in Core–Shell Wire Structure for UV Emission

Author

Christophe Durand, Pierre-Henri Jouneau, Catherine Bougerol, Raphaël Butté, Georg Rossbach, Anna Mukhtarova, Jean-François Carlin, Nicolas Grandjean, Joël Eymery, Florian Godel, Nanophysique et Semiconducteurs (NPSC), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), 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), 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), Ecole Polytechnique Fédérale de Lausanne (EPFL), Nanostructures et Rayonnement Synchrotron (NRS ), Modélisation et Exploration des Matériaux (MEM), 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]), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), Nanophysique et Semiconducteurs (NEEL - NPSC), and 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)

Subjects
Threading dislocations, Materials science, Condensed matter physics, business.industry, Multiple quantum, Quantum-confined Stark effect, Polarization (waves), Epitaxy, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Core shell, Planar, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, Perpendicular, Optoelectronics, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, Electrical and Electronic Engineering, business, ComputingMilieux_MISCELLANEOUS, Biotechnology
Abstract

We report on the epitaxial growth of high-quality core–shell nonpolar m-plane GaN/InAlN multiple quantum wells (MQWs) on the sidewall facets of c-oriented hexagonal GaN wires. Pseudomorphic growth without generation of threading dislocations has been established for planar GaN/InAlN (In = 15%) MQWs grown on m-GaN substrates, although m-plane InAlN epilayers cannot be grown perfectly lattice-matched to GaN along the two in-plane directions. Calculations based on elasticity theory indicate that the significant amount of strain oriented along the c-axis is the likely factor favoring the formation of cracks along this direction. For the core–shell wire geometry, such cracks are not observed, leading to high structural quality MQWs. A significant UV emission centered around 3.7 eV at room temperature with a strong polarization perpendicular to the wire axis is observed for those core–shell wires, which is consistent with k·p method calculations, proving the absence of quantum confined Stark effect on nonpolar ...

Published
2013
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35. Conductance Oscillations in a Graphene/Nanocluster Hybrid Material: Toward Large-Area Single-Electron Devices

Author

Yves Henry, D. Halley, Louis Donald Notemgnou Mouafo, Stéphane Berciaud, Jean-Francois Dayen, Bernard Doudin, Guillaume Froehlicher, Florian Godel, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), and univOAK, Archive ouverte

Subjects
Materials science, Oxide, Nanoparticle, chemistry.chemical_element, FOS: Physical sciences, Nanotechnology, 02 engineering and technology, 01 natural sciences, 7. Clean energy, Nanoclusters, law.invention, chemistry.chemical_compound, Aluminium, law, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Materials Science, 010306 general physics, Condensed Matter - Materials Science, [CHIM.MATE] Chemical Sciences/Material chemistry, Condensed Matter - Mesoscale and Nanoscale Physics, Graphene, Mechanical Engineering, Conductance, Materials Science (cond-mat.mtrl-sci), [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, chemistry, Mechanics of Materials, 0210 nano-technology, Hybrid material, Layer (electronics)
Abstract

Large assemblies of self-organized aluminum nanoclusters embedded in an oxide layer are formed on graphene templates and used to build tunnel-junction devices. Unexpectedly, single-electron-transport behavior with well-defined Coulomb oscillations is observed for a record junction area of up to 100 mu m(2) containing millions of metal islands. Such graphene-metal nanocluster hybrid materials offer new prospects for single-electron electronics.

Published
2016
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36. Anisotropic Magneto-Coulomb Properties of 2D-0D Heterostructure Single Electron Device

Author

L. Simon, Hicham Majjad, Louis Donald Notemgnou Mouafo, Pierre Seneor, Samar Hajjar-Garreau, Florian Godel, Georgian Melinte, Ovidiu Ersen, Jean-Francois Dayen, Bruno Dlubak, Bernard Doudin, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Institut de Science des Matériaux de Mulhouse (IS2M), Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), and Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique

Subjects
Materials science, Magnetoresistance, 02 engineering and technology, 01 natural sciences, Nanoclusters, law.invention, Condensed Matter::Materials Science, law, 0103 physical sciences, Physics::Atomic and Molecular Clusters, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Quantum tunnelling, Spintronics, business.industry, Graphene, Mechanical Engineering, Coulomb blockade, Heterojunction, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Ferromagnetism, Mechanics of Materials, Optoelectronics, 0210 nano-technology, business
Abstract

International audience; Fabrication and spintronics properties of 2D–0D heterostructures are reported. Devices based on graphene (“Gr”)–aluminium nanoclusters heterostructures show robust and reproducible single‐electron transport features, in addition to spin‐dependent functionality when using a top magnetic electrode. The magnetic orientation of this single ferromagnetic electrode enables the modulation of the environmental charge experienced by the aluminium nanoclusters. This anisotropic magneto‐Coulomb effect, originating from spin–orbit coupling within the ferromagnetic electrode, provides tunable spin valve‐like magnetoresistance signatures without the requirement of spin coherent charge tunneling. These results extend the capability of Gr to act both as electrode and as a platform for the growth of 2D–0D mixed‐dimensional van der Waals heterostructures, providing magnetic functionalities in the Coulomb blockade regime on scalable spintronic devices. These heterostructures pave the way towards novel device architectures at the crossroads of 2D material physics and spin electronics.

Published
2018
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37. Epitaxial ferromagnetic single clusters and smooth continuous layers on large area MgO/CVD graphene substrates

Author

Jean-Francois Dayen, Bernard Doudin, Hicham Majjad, Florian Godel, Christian Meny, and D. Halley

Subjects
Materials science, Polymers and Plastics, business.industry, Metals and Alloys, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Biomaterials, Ferromagnetism, Optoelectronics, 0210 nano-technology, business, Cvd graphene
Published
2018
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38. Controlling the magnetic anisotropy in epitaxialCr2O3clusters by an electric field

Author

Mohamad Hamieh, Bernard Doudin, D. Halley, Yves Henry, Nabil Najjari, and Florian Godel

Subjects
Physics, Condensed matter physics, Magnetoelectric effect, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Magnetic field, Condensed Matter::Materials Science, Magnetization, Magnetic anisotropy, Tunnel magnetoresistance, Tunnel junction, Condensed Matter::Superconductivity, Electric field, Anisotropy
Abstract

Magnetic properties of ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ epitaxial clusters inserted in an Fe/MgO/Fe tunnel barrier are revealed by their tunnel magnetoresistance signature. The cluster assembly has been shown in a previous work to behave as a superparamagnet when a magnetic field was applied in the plane of the tunnel junction. We here demonstrate that an external large out-of plane electric field (in the order of 0.5 GV/m) favors in-plane magnetization orientation. This is due to an electric-field-induced magnetic anisotropy along the normal to the plane, corresponding to large anisotropy fields reaching up to 2 T. The assembly of clusters is thus strictly speaking not superparamagnetic and its magnetization cannot be exactly described by a Langevin law. This is attributed either to a strain-induced enhanced magnetoelectric effect or to a voltage-induced change of the magnetic anisotropy at interfaces with MgO.

Published
2015
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39. Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions

Author

Bernard Doudin, M. Venkata Kamalakar, D. Halley, Yves Henry, Florian Godel, and Jean-Francois Dayen

Subjects
Physics, Fabrication, Physics and Astronomy (miscellaneous), Condensed Matter - Mesoscale and Nanoscale Physics, business.industry, Graphene, Aucun, FOS: Physical sciences, Biasing, Epitaxy, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, law.invention, Tunnel magnetoresistance, Condensed Matter::Materials Science, Ferromagnetism, law, Condensed Matter::Superconductivity, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Electrode, Optoelectronics, Condensed Matter::Strongly Correlated Electrons, business, Electronic band structure
Abstract

We report on the fabrication and characterization of vertical spin-valve structures using a thick epitaxial MgO barrier as spacer layer and a graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show robust and scalable tunnel magnetoresistance, with several changes of sign upon varying the applied bias voltage. These findings are explained by a model of phonon-assisted transport mechanisms that relies on the peculiarity of the band structure and spin density of states at the hybrid graphene|Ni interface.

Published
2014

40. Epitaxy of MgO magnetic tunnel barriers on epitaxial graphene

Author

D. Halley, Yves Henry, Florian Godel, Stéphane Berciaud, D. Vignaud, Emmanuelle Pichonat, Hicham Majjad, Jean-Francois Dayen, Dominik Metten, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN), Centrale Lille-Institut supérieur de l'électronique et du numérique (ISEN)-Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, and Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)

Subjects
Materials science, Bioengineering, Nanotechnology, 02 engineering and technology, Epitaxy, 01 natural sciences, law.invention, law, 0103 physical sciences, General Materials Science, Dewetting, Electrical and Electronic Engineering, 010306 general physics, Quantum tunnelling, Spintronics, Graphene, business.industry, Mechanical Engineering, General Chemistry, 021001 nanoscience & nanotechnology, Ferromagnetism, Mechanics of Materials, Optoelectronics, 0210 nano-technology, business, Graphene nanoribbons, Molecular beam epitaxy
Abstract

Epitaxial growth of electrodes and tunnel barriers on graphene is one of the main technological bottlenecks for graphene spintronics. In this paper, we demonstrate that MgO(111) epitaxial tunnel barriers, one of the prime candidates for spintronic application, can be grown by molecular beam epitaxy on epitaxial graphene on SiC(0001). Ferromagnetic metals (Fe, Co, Fe20Ni80) were epitaxially grown on top of the MgO barrier, thus leading to monocrystalline electrodes on graphene. Structural and magnetic characterizations were performed on these ferromagnetic metals after annealing and dewetting: they form clusters with a 100 nm typical lateral width, which are mostly magnetic monodomains in the case of Fe. This epitaxial stack opens the way to graphene spintronic devices taking benefits from a coherent tunnelling current through the epitaxial MgO/graphene stack.

Published
2013
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41. Voltage-dependent magnetic phase transition in magneto-electric epitaxial Cr2O3nanoclusters

Author

Florian Godel, D. Halley, Mohamad Hamieh, Yves Henry, Bernard Doudin, and Nabil Najjari

Subjects
Quantum phase transition, Materials science, Condensed matter physics, Mechanical Engineering, Transition temperature, Bioengineering, Nanotechnology, 02 engineering and technology, General Chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Nanoclusters, Condensed Matter::Materials Science, Ferromagnetism, Mechanics of Materials, Electric field, Phase (matter), 0103 physical sciences, General Materials Science, Electrical and Electronic Engineering, 010306 general physics, 0210 nano-technology, Magnetic dipole, Voltage
Abstract

We observe, as a function of temperature, a second order magnetic phase transition in nanometric Cr2O3 clusters that are epitaxially embedded in an insulating MgO matrix. They are investigated through their tunnel magneto-resistance signature, the MgO layer being used as a tunnel barrier. We infer the small magnetic dipoles carried by the Cr2O3 clusters and provide evidence of a magnetic phase transition at low temperature in those clusters: they evolve from an anti ferromagnetic state, with zero net moment close to 0 K, to a weak ferromagnetic state that saturates above about 10 K. The influence of magneto-electric effects on the weak ferromagnetic phase is also striking: the second order transition temperature turns out to be linearly dependent on the applied electric field.

Published
2016
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42. Band-Gap Landscape Engineering in Large-Scale 2D Semiconductor van der Waals Heterostructures

Author

Simon M-M Dubois, Victor Zatko, Jean-Christophe Charlier, Pierre Seneor, Marie-Blandine Martin, Federico Panciera, Bruno Dlubak, Gilles Patriarche, Bernard Servet, Florian Godel, J. Peiro, C. Carrétéro, Sophie Collin, Marta Galbiati, Pierre Brus, Anke Sander, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain = Catholic University of Louvain (UCL), Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Thales Research and Technologies [Orsay] (TRT), THALES, and UCL - SST/IMCN/MODL - Modelling

Subjects
Van der waals heterostructures, Materials science, Scale (ratio), Band gap, quantum well, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Pulsed laser deposition, chemistry.chemical_compound, tungsten disulfide, tungsten diselenide, Tungsten diselenide, General Materials Science, Physics::Atomic Physics, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], van der Waals heterostructure, pulsed laser deposition, Quantum well, 2D semiconductors, Condensed matter physics, business.industry, General Engineering, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Semiconductor, chemistry, 0210 nano-technology, business
Abstract

International audience; We present a growth process relying on pulsed laser deposition for the elaboration of complex van der Waals heterostructures on large scales, at a 400°C CMOS-compatible temperature. Illustratively, we define a multilayer quantum well geometry through successive in situ growths, leading to WSe2 being encapsulated into WS2 layers. The structural constitution of the quantum well geometry is confirmed by Raman spectroscopy combined with transmission electron microscopy. The large-scale high homogeneity of the resulting 2D van der Waals heterostructure is also validated by macro-and microscale Raman mappings. We illustrate the benefit of this integrative in situ approach by showing the structural preservation of even the most fragile 2D layers once encapsulated in a van der Waals heterostructure. Finally, we fabricate a vertical tunneling device based on these large-scale layers and discuss the clear signature of electronic transport controlled by the quantum well configuration with ab initio calculations in support. The flexibility of this direct growth approach, with multilayer stacks being built in a single run, allows for the definition of complex 2D heterostructures barely accessible with usual exfoliation or transfer techniques of 2D materials. Reminiscent of the III−V semiconductors' successful exploitation, our approach unlocks virtually infinite combinations of large 2D material families in any complex van der Waals heterostructure design.

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43. Nonreciprocal transport in a Rashba ferromagnet, delafossite PdCoO$_2$

Author

Takayuki Harada, Jin Hong Lee, Atsushi Tsukazaki, Florian Godel, Lourdes Marcano, Felix Trier, Sergio Valencia, and Manuel Bibes

Subjects
Rashba-type spin−orbit interaction, Delafossite nanofilms, Materials science, Magnetoresistance, Oxide, FOS: Physical sciences, Bioengineering, 02 engineering and technology, engineering.material, 01 natural sciences, symbols.namesake, chemistry.chemical_compound, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Nonreciprocal transport, General Materials Science, 010306 general physics, Surface and interfacial phenomena, Nernst effect, Perovskite (structure), Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Mechanical Engineering, Surface ferromagnetism, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 3. Good health, Delafossite, Ferromagnetism, chemistry, symbols, engineering, Curie temperature, 0210 nano-technology, Transport phenomena
Abstract

Rashba interfaces yield efficient spin-charge interconversion and give rise to nonreciprocal transport phenomena. Here, we report magnetotransport experiments in few-nanometer-thick films of PdCoO$_2$, a delafossite oxide known to display a large Rashba splitting and surface ferromagnetism. By analyzing the angle dependence of the first- and second-harmonic longitudinal and transverse resistivities, we identify a Rashba-driven unidirectional magnetoresistance that competes with the anomalous Nernst effect below the Curie point. We estimate a Rashba coefficient of 0.75 {\pm} 0.3 eV {\AA} and argue that our results qualify delafossites as a new family of oxides for nano-spintronics and spin-orbitronics, beyond perovskite materials., Comment: Accepted in Nano Lett

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45. Atomic layer deposition of a MgO barrier for a passivated black phosphorus spintronics platform

Author

Pierre Brus, Bernard Servet, Marta Galbiati, Florian Godel, M. Martin, Pierre Seneor, Frédéric Petroff, Etienne Gaufrès, Bruno Dlubak, David Perconte, Odile Bezencenet, Regina Galceran, L.-M. Kern, Annick Loiseau, F. Bouamrane, Victor Zatko, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), Centre National de la Recherche Scientifique (CNRS)-ONERA, DMAS, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Thales Research and Technology [Palaiseau], and THALES

Subjects
010302 applied physics, Materials science, Fabrication, Physics and Astronomy (miscellaneous), Passivation, Spintronics, business.industry, Nucleation, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Espectroscòpia Raman, Atomic layer deposition, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, Thin film, 0210 nano-technology, business, Layer (electronics), Materials, Quantum tunnelling
Abstract

International audience; We demonstrate a stabilized black phosphorus (BP) 2D platform thanks to an ultrathin MgO barrier, as required for spintronic device integration. The in-situ MgO layer deposition is achieved by using a large-scale atomic layer deposition process with high nucleation density. Raman spectroscopy studies show that this layer protects the BP from degradation in ambient conditions, unlocking in particular the possibility to carry out usual lithographic fabrication steps. The resulting MgO/BP stack is then integrated in a device and probed electrically, confirming the tunnel properties of the ultrathin MgO contacts. We believe that this demonstration of a BP material platform passivated with a functional MgO tunnel barrier provides a promising perspective for BP spin transport devices.

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46. 2D-MTJs: introducing 2D materials in magnetic tunnel junctions.

Author

Maëlis Piquemal-Banci, Regina Galceran, Marie-Blandine Martin, Florian Godel, Abdelmadjid Anane, Frederic Petroff, Bruno Dlubak, and Pierre Seneor

Subjects
MAGNETIC tunnel junction devices, TWO-dimensional materials (Nanotechnology), SPINTRONICS
Abstract

This review focuses on the recent experimental integration of 2D materials, mostly graphene but also h-BN and dichalochogenides, such as MoS2 and WS2, in magnetic tunnel junctions. The main remarkable characteristic of 2D materials is the ability to gain high homogeneous atomic control over their thickness, as this is barely achievable with the usual 3D materials deposited through conventional physical vapour deposition (PVD) growth techniques. This could become a critical asset for spintronics with regard to the fabrication of spin valves, where ultra-thin layers with extreme control are targeted, especially for spin-polarized electron tunnelling. A complete overview of the state of the art is presented, and the different integrative pathways of 2D materials with ferromagnets are addressed, including the exfoliation of 2D flakes from crystals, the wet transfer steps of large scale layers, and direct chemical vapour deposition (CVD) growths catalysed on ferromagnetic electrodes. Interestingly, these recent experiments have already highlighted some novel properties that emanate from 2D-based heterostructures, such as passivation against oxidation diffusion and augmented spin filtering at the interface. Many perspectives are thus being opened up in the exploration of the vast amount of 2D material families and their association in heterostructures, targeting specific spin device properties. [ABSTRACT FROM AUTHOR]

Published
2017
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47. Voltage-dependent magnetic phase transition in magneto-electric epitaxial Cr2O3 nanoclusters.

Author

David Halley, Nabil Najjari, Florian Godel, Mohamad Hamieh, Bernard Doudin, and Yves Henry

Subjects
CHROMIUM oxide, MAGNETIC transitions, MAGNETO-electric machines, EPITAXIAL layers, NANOPARTICLES
Abstract

We observe, as a function of temperature, a second order magnetic phase transition in nanometric Cr2O3 clusters that are epitaxially embedded in an insulating MgO matrix. They are investigated through their tunnel magneto-resistance signature, the MgO layer being used as a tunnel barrier. We infer the small magnetic dipoles carried by the Cr2O3 clusters and provide evidence of a magnetic phase transition at low temperature in those clusters: they evolve from an anti ferromagnetic state, with zero net moment close to 0 K, to a weak ferromagnetic state that saturates above about 10 K. The influence of magneto-electric effects on the weak ferromagnetic phase is also striking: the second order transition temperature turns out to be linearly dependent on the applied electric field. [ABSTRACT FROM AUTHOR]

Published
2016
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