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1. Formation of Monolayer Charge Density Waves and Anomalous Edge Doping in Na Doped Bulk VSe2

Author

Ulysse Chazarin, Mahé Lezoualc'h, Jyh‐Ping Chou, Woei Wu Pai, Abhishek Karn, Raman Sankar, Cyril C. Chacon, Yann Girard, Vincent Repain, Amandine Bellec, Sylvie Rousset, Alexander Smogunov, Yannick J. Dappe, and Jérôme Lagoute

Subjects
electrostatic effect, scanning tunneling microscope, transition metal dichalcogenides, VSe 2, Physics, QC1-999, Technology
Abstract

Abstract Alkali atom doping is an efficient way to induce charge transfer and Fermi level tuning in layered materials through intercalation. However, there is a general lack of microscopic understanding of the effect of doping inhomogeneity in geometric and electronic aspects. Here, we report surface doping of a bulk VSe2 crystal by sodium. Na atoms form intercalated subsurface islands that modify the electronic phase of the top layer of VSe2. In addition to n‐doping, the charge density wave of the intercalated VSe2 surface layer changes from the (4 × 4) bulk phase to the (3×7) known in monolayer phase of VSe2. Surprisingly, an electronic state at the edges of Na‐intercalated area shift anomalously upward in energy as detected by scanning tunneling spectroscopy. This is explained by a local gating effect resulting from local dipoles at the edges. The study illustrates a clear example of intercalation effect that should be general in alkali‐intercalated bulk layered materials.

Published
2023
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2. Molecular-scale dynamics of light-induced spin cross-over in a two-dimensional layer

Author

Kaushik Bairagi, Olga Iasco, Amandine Bellec, Alexey Kartsev, Dongzhe Li, Jérôme Lagoute, Cyril Chacon, Yann Girard, Sylvie Rousset, Frédéric Miserque, Yannick J Dappe, Alexander Smogunov, Cyrille Barreteau, Marie-Laure Boillot, Talal Mallah, and Vincent Repain

Subjects
Science
Abstract

Spin crossover molecules may find applications in ultimately small magnetic devices, given the sensitivity of their spin-states to external stimuli. Here, the authors show a light-induced transition between two ordered dynamic phases in two-dimensional spin crossover layers on a metallic surface.

Published
2016
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3. Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

Author

Paolo Campiglio, Romain Breitwieser, Vincent Repain, Solène Guitteny, Cyril Chacon, Amandine Bellec, Jérôme Lagoute, Yann Girard, Sylvie Rousset, Adele Sassella, Mighfar Imam, and Shobhana Narasimhan

Subjects
magnetic anisotropy, self-assembled monolayers, scanning tunneling microscopy, Science, Physics, QC1-999
Abstract

We demonstrate that the deposition of a self-assembled monolayer of alkanethiolates on a 1 nm thick cobalt ultrathin film grown on Au(111) induces a spin reorientation transition from in-plane to out-of-plane magnetization. Using ab initio calculations, we show that a methanethiolate layer changes slightly both the magnetocrystalline and shape anisotropy, both effects almost cancelling each other out for a 1 nm Co film. Finally, the change in hysteresis cycles upon alkanethiolate adsorption could be assigned to a molecular-induced roughening of the Co layer, as shown by STM. In addition, we calculate how a methanethiolate layer modifies the spin density of states of the Co layer and we show that the spin polarization at the Fermi level through the organic layer is reversed as compared to the uncovered Co. These results give new theoretical and experimental insights for the use of thiol-based self-assembled monolayers in spintronic devices.

Published
2015
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4. Growth and local electronic properties of Cobalt nanodots underneath graphene on SiC(0001)

Author

Yann Girard, Sarah Benbouabdellah, Outhmane Chahib, Cyril Chacon, Amandine Bellec, Vincent Repain, Jérôme Lagoute, Yannick J. Dappe, César González, Wei-Bin Su, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France, Departamento de Fisica de Materiales, Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), and Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan

Subjects
Scanning tunneling microscopy / spectroscopy, Density functional theory calculations, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, General Chemistry, Cobalt, Silicon carbide, Graphene, Field effect resonance
Abstract

International audience; The coupling of graphene with a ferromagnetic material opens opportunities for technological innovations in spintronics. To obtain this coupling it is necessary to control the elaboration of interfaces at the atomic scale. Here, we present results on cobalt intercalation between graphene and a buffer layer supported on a SiC(0001) substrate. As a result, we obtain cobalt islands covered by graphene whose local electronic properties are measured by scanning tunneling microscopy and spectroscopy. These islands reveal two very distinct shapes and properties. Small-islands with atomic height and very narrow size distribution and, more interestingly, flat cobalt nanodots lower than one nanometer high, that are encapsulated by graphene. Compared to a graphene monolayer on SiC, those nanodots exhibit very different spectroscopic signatures. Using dI/dV local differential conductance spectra together with an analysis of image potential surface states measured thanks to dz/dV spectra, we show that graphene on the nanodots is neutrally charged. Moreover, its 4.65 eV work function is surprisingly larger than the predicted value of 3.8 eV for graphene on Co. First principle calculations show that those Co nanodots can be seen as cobalt bilayer sandwiched between two carbon planes.

Published
2023

5. Interface versus Bulk Light-Induced Switching in Spin-Crossover Molecular Ultrathin Films Adsorbed on a Metallic Surface

Author

Massine Kelai, Arthur Tauzin, Anastasia Railean, Vincent Repain, Jérôme Lagoute, Yann Girard, Sylvie Rousset, Edwige Otero, Talal Mallah, Marie-Laure Boillot, Cristian Enachescu, Amandine Bellec, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Alexandru Ioan Cuza University of Iași [Romania], Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), UEFISCDI Romania (grant number PN-III-P4-ID-PCE-2020-1946), and European Project: 766726,211587,COSMICS(2017)

Subjects
[PHYS]Physics [physics], General Materials Science, Physical and Theoretical Chemistry
Abstract

International audience

Published
2023

6. Formation of Monolayer Charge Density Waves and Anomalous Edge Doping in Na Doped Bulk VSe 2

Author

Ulysse Chazarin, Mahé Lezoualc'h, Jyh‐Ping Chou, Woei Wu Pai, Abhishek Karn, Raman Sankar, Cyril C. Chacon, Yann Girard, Vincent Repain, Amandine Bellec, Sylvie Rousset, Alexander Smogunov, Yannick J. Dappe, Jérôme Lagoute, CEA- Saclay (CEA), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
[PHYS]Physics [physics], Mechanics of Materials, Mechanical Engineering
Abstract

International audience

Published
2022

7. Voltage-Induced Bistability of Single Spin-Crossover Molecules in a Two-Dimensional Monolayer

Author

Marie-Laure Boillot, Jérôme Lagoute, Kaushik Bairagi, Massine Kelai, Amandine Bellec, Vincent Repain, Yongfeng Tong, Yann Girard, Sylvie Rousset, Talal Mallah, Cristian Enachescu, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Alexandru Ioan Cuza University of Iași [Romania], and European Project: 766726,211587,COSMICS(2017)

Subjects
Materials science, Spintronics, Spin states, Bistability, Relaxation (NMR), [CHIM.MATE]Chemical Sciences/Material chemistry, Molecular physics, law.invention, Spin crossover, law, Monolayer, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, Physical and Theoretical Chemistry, Scanning tunneling microscope, Spin-½
Abstract

International audience; Bistable spin-crossover molecules are particularly interesting for the development of innovative electronic and spintronic devices as they present two spin states that can be controlled by external stimuli. In this paper, we report the voltage-induced switching of the high spin/low spin electronic states of spin-crossover molecules self-assembled in dense 2D networks on Au(111) and Cu(111) by scanning tunneling microscopy at low temperature. On Au(111), voltage pulses lead to the nonlocal switching of the molecules from any─high or low─spin state to the other followed by a spontaneous relaxation toward their initial state within minutes. On the other hand, on Cu(111), single molecules can be addressed at will. They retain their new electronic configuration after a voltage pulse. The memory effect demonstrated on Cu(111) is due to an interplay between long-range intermolecular interaction and molecule/substrate coupling as confirmed by mechanoelastic simulations.

Published
2021

8. Identification and Manipulation of Defects in Black Phosphorus

Author

Rishav Harsh, Sourav Mondal, Devina Sharma, Mehdi Bouatou, Cyril Chacon, Maxim Ilyn, Celia Rogero, Vincent Repain, Amandine Bellec, Yann Girard, Sylvie Rousset, Raman Sankar, Woei Wu Pai, Shobhana Narasimhan, Jérôme Lagoute, Indo-French Centre for the Promotion of Advanced Research, Agence Nationale de la Recherche (France), Sheikh Saqr Laboratory (India), and Board of Research in Nuclear Sciences (India)

Subjects
General Materials Science, Physical and Theoretical Chemistry
Abstract

We identify and manipulate commonly occurring defects in black phosphorus, combining scanning tunneling microscopy experiments with density functional theory calculations. A ubiquitous defect, imaged at negative bias as a bright dumbbell extending over several nanometers, is shown to arise from a substitutional Sn impurity in the second sublayer. Another frequently observed defect type is identified as arising from an interstitial Sn atom; this defect can be switched to a more stable configuration consisting of a Sn substitutional defect + P adatom, by application of an electrical pulse via the STM tip. DFT calculations show that this pulse-induced structural transition switches the system from a non-magnetic configuration to a magnetic one. We introduce States Projected Onto Individual Layers (SPOIL) quantities which provide information about atom-wise and orbital-wise contributions to bias-dependent features observed in STM images., We acknowledge the Indo-French Centre for the Promotion of Advanced Scientific Research (CEFIPRA) for funding our collaboration. We are especially grateful for assistance provided by the Late Ms. A. Sathidevi. We are grateful to the ANR and MOST (DEFINE2D Project No. ANR-20-CE09-0023, MOST 110-2923-M-002-010) for financial support and the TUE-CMS, JNCASR, and the Sheikh Saqr Laboratory, JNCASR, for computational resources. D.S. acknowledges support from the NPDF of the Science and Engineering Research Board (SERB), Government of India.

Published
2022

9. Synthesis and Properties of Nanostructured Tungsten Oxide on Au(111)

Author

Jérôme Lagoute, Vincent Repain, Mahamadou Seydou, Sylvie Rousset, Yann Girard, Philippe Decorse, Cyril Chacon, Mariem Ben Youssef, Rishav Harsh, Philippe Lang, Amandine Bellec, Jean-Yves Piquemal, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS (UMR_7086)), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Paris Diderot - Paris 7 (UPD7)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nanostructure, Materials science, Tungsten oxide, [CHIM.MATE]Chemical Sciences/Material chemistry, 02 engineering and technology, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, General Energy, Chemical engineering, 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Physical and Theoretical Chemistry, 010306 general physics, 0210 nano-technology
Abstract

International audience; WO 3 nanostructures have been synthesized on Au(111) through solution processing. Three types of structures have been obtained, reticulated polymeric structures, two dimensional WO 3 (111) and three-dimensional islands. Their electronic properties have been probed by scanning tunneling spectroscopy. The reticulated structure has a featureless spectrum. WO 3 (111) shows n-type semiconducting properties with resonances corresponding to surface states arising from W 5d states. Those oxyde nanostructures are efficiently decoupling the electronic states of molecular adsorbates from the metal substrate.

Published
2020

10. Effect of bonding and antibonding character of electronic states on their tunneling spectra

Author

Omar Lahrache, Mehdi Bouatou, Cyril Chacon, Yann Girard, Yannick J. Dappe, Jérôme Lagoute, Alexander Smogunov, 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), Groupe Modélisation et Théorie (GMT), 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, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), MOST (No. 110-2923-M-002 -010), and ANR-20-CE09-0023,DEFINE2D,Ingénierie des défauts dans les matériaux 2D: propriétés à l'échelle atomique et interaction avec des molécules(2020)

Subjects
[PHYS]Physics [physics]
Abstract

International audience; We argue that the bonding or antibonding character of electronic states of a substrate can influence significantly the observed scanning tunneling microscopy (STM) spectra. In particular, the antibonding states formed bynonorthogonal orbitals of the substrate present much stronger extension in the vacuum compared to corresponding bonding combinations and are therefore much more visible in STM experiments. A clear example is providedby black phosphorus (BP), which is one of the most interesting two-dimensional layered materials nowadays. The pronounced asymmetry in its conductance spectra, with significant increase at positive voltage, can beattributed to the antibonding nature of the conduction band compared to the bonding valence band, despite the same pz -orbital character. Furthermore, this asymmetry can be at the origin of different broadenings of frontiermolecular orbitals observed experimentally for molecules on BP.

Published
2022

11. Intraconfigurational Transition due to Surface-Induced Symmetry Breaking in Noncovalently Bonded Molecules

Author

Cyrille Barreteau, Robert Sporken, Rishav Harsh, Yann Girard, Vincent Repain, Alexander Smogunov, Jérôme Lagoute, Cyril Chacon, Frédéric Joucken, Mads Brandbyge, Amandine Bellec, Fei Gao, Sylvie Rousset, Mehdi Bouatou, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Center for Nanostructured Graphene, Danmarks Tekniske Universitet (DTU), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), 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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Materials science, Graphene, 02 engineering and technology, Weak interaction, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, Atomic orbital, law, Chemical physics, Molecule, General Materials Science, Redistribution (chemistry), Electron configuration, Symmetry breaking, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Physics::Chemical Physics, Physical and Theoretical Chemistry, 0210 nano-technology, Ground state, ComputingMilieux_MISCELLANEOUS
Abstract

The interaction of molecules with surfaces plays a crucial role in the electronic and chemical properties of supported molecules and needs a comprehensive description of interfacial effects. Here, we unveil the effect of the substrate on the electronic configuration of iron porphyrin molecules on Au(111) and graphene, and we provide a physical picture of the molecule-surface interaction. We show that the frontier orbitals derive from different electronic states depending on the substrate. The origin of this difference comes from molecule-substrate orbital selective coupling caused by reduced symmetry and interaction with the substrate. The weak interaction on graphene keeps a ground state configuration close to the gas phase, while the stronger interaction on gold stabilizes another electronic solution. Our findings reveal the origin of the energy redistribution of molecular states for noncovalently bonded molecules on surfaces.

Published
2020

12. Negative Differential Resistance in Spin-Crossover Molecular Devices

Author

Dongzhe Li, Yongfeng Tong, Kaushik Bairagi, Massine Kelai, Yannick J. Dappe, Jérôme Lagoute, Yann Girard, Sylvie Rousset, Vincent Repain, Cyrille Barreteau, Mads Brandbyge, Alexander Smogunov, Amandine Bellec, Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), 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), and Danmarks Tekniske Universitet = Technical University of Denmark (DTU)

Subjects
Coulomb blockade, Condensed Matter - Mesoscale and Nanoscale Physics, Negative differential resistance, Landauer-Büttiker scattering theory, Spin-crossover molecule, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), scanning tunneling microscopy, FOS: Physical sciences, General Materials Science, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, density functional theory
Abstract

We demonstrate, based on low-temperature scanning tunneling microscopy (STM) and spectroscopy, a pronounced negative differential resistance (NDR) in spin-crossover (SCO) molecular devices, where a Fe$^{\text{II}}$ SCO molecule is deposited on surfaces. The STM measurements reveal that the NDR is robust with respect to substrate materials, temperature, and the number of SCO layers. This indicates that the NDR is intrinsically related to the electronic structure of the SCO molecule. Experimental results are supported by density functional theory (DFT) with non-equilibrium Green's functions (NEGF) calculations and a generic theoretical model. While the DFT+NEGF calculations reproduce NDR for a special atomically-sharp STM tip, the effect is attributed to the energy-dependent tip density of states rather than the molecule itself. We, therefore, propose a Coulomb blockade model involving three molecular orbitals with very different spatial localization as suggested by the molecular electronic structure., Comment: 4 figures

Published
2022
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13. Visualizing In-Plane Junctions in Nitrogen-Doped Graphene

Author

Mehdi Bouatou, Cyril Chacon, Aleksander Bach Lorentzen, Huu Thoai Ngo, Yann Girard, Vincent Repain, Amandine Bellec, Sylvie Rousset, Mads Brandbyge, Yannick J. Dappe, Jérôme Lagoute, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), 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), Groupe Modélisation et Théorie (GMT), 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, and ANR-20-CE09-0023,DEFINE2D,Ingénierie des défauts dans les matériaux 2D: propriétés à l'échelle atomique et interaction avec des molécules(2020)

Subjects
Biomaterials, p-n junction, graphene, Electrochemistry, nitrogen doping, scanning tunneling microscopy, scanning tunneling spectroscopy, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Abstract

International audience; Controlling the spatial distribution of dopants in graphene is the gateway to the realization of graphene-based electronic components. Here, we show that a submonolayer of self-assembled physisorbed molecules can be used as a resist during a post-synthesis nitrogen doping process to realize a nanopatterning of nitrogen dopants in graphene. The resulting formation of domains with different nitrogen concentrations allows obtaining nn' and pn junctions in graphene. We use scanning tunneling microscopy to measure the electronic properties of the junctions at the atomic scale and reveal their intrinsic width that is found to be around 7 nm corresponding to a sharp junction regime.

Published
2022

14. Thermal Bistability of an Ultrathin Film of Iron(II) Spin-Crossover Molecules Directly Adsorbed on a Metal Surface

Author

Cristian Enachescu, Yann Girard, Massine Kelai, Philippe Sainctavit, Marie-Laure Boillot, M.-A. Arrio, Arthur Tauzin, Jérôme Lagoute, Sylvie Rousset, Edwige Otero, Talal Mallah, Weibin Li, Vincent Repain, Amandine Bellec, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Alexandru Ioan Cuza University of Iasi, University of Iasi, Grant of the Romanian ministry of research, Innovation and Digitization, CNCS/CCCDI-UEFISCDI, project N° PN-III-P4-ID-PCE-2020-1946, European Project: 766726,211587,COSMICS(2017), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), and SOLEIL Synchrotron, L'Orme des Merisiers, 91198 Gif-sur-Yvette, France

Subjects
Materials science, Absorption spectroscopy, Bistability, 02 engineering and technology, Substrate (electronics), [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010402 general chemistry, 01 natural sciences, Condensed Matter::Materials Science, symbols.namesake, Thermal Bistability, Spin crossover, Monolayer, General Materials Science, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, ComputingMilieux_MISCELLANEOUS, Arrhenius equation, Substrate Interaction, Spintronics, Mechanoelastic Model, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, X-ray Absorption Spectroscopy, Spin-Crossover, Chemical physics, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

Spin-crossover molecules are very attractive compounds to realize multifunctional spintronic devices. Understanding their properties when deposited on metals is therefore crucial for their future rational implementation as ultrathin films in such devices. Using X-ray absorption spectroscopy, we study the thermal transition of the spin-crossover compound FeII((3,5-(CH3)2Pz)3BH)2 from submonolayer to multilayers on a Cu(111) substrate. We determine how the residual fraction of high spin molecules at low temperature, as well as the bistability range and the temperature of switching, depends on the layer thickness. The most spectacular effect is the clear opening of a 35 ± 9 K thermal hysteresis loop for a 3.0 ± 0.7 monolayers thick film. To better understand the role played by the substrate and the dimensionality on the thermal bistability, we have performed Monte Carlo Arrhenius simulations in the framework of a mechanoelastic model that include a molecule-substrate interaction. This model reproduces well the main features observed experimentally and can predict how the spin-crossover transition is modified by the thickness and the substrate interaction.

Published
2021

15. Herkulesaufgabe: evidenzbasierte Regulierung im Telekommunikationssektor

Author

Yann Girard, Franziska Neumann, and Johannes Farrenkopf

Subjects
L96, Political science, ddc:330, Business, Management and Accounting (miscellaneous), L51, D04, Humanities
Abstract

Die aktuellen wirtschaftspolitischen Debatten um den stockenden Ausbau einer flächendeckenden Glasfaserinfrastruktur und um die Versteigerung der 5G-Mobilfunkfrequenzen zeigen, dass die Regulierung von Telekommunikationsmärkten in Deutschland vor großen Herausforderungen steht. Im Kern entzünden sich die Konflikte an einer Abwägung zwischen dem zügigen Ausbau moderner Telekommunikationsnetze und einer flächendeckenden Verfügbarkeit von Telekommunikationsdienstleistungen zu günstigen Preisen. Evidenzbasierte Ex-ante-Analysen zur Folgenabschätzung wirtschaftspolitischer Maßnahmen stellen eine hilfreiche Entscheidungsgrundlage dar.

Published
2019

16. Addressing single spin crossover molecules in a two-dimensional monolayer

Author

Yongfeng Tong, Massine Kelaï, Kaushik Bairagi, Vincent Repain, Jérôme Lagoute, Yann Girard, Sylvie Rousset, Marie-Laure Boillot, Talal Mallah, Cristian Enachescu, and Amandine Bellec

Abstract

Bistable spin-crossover molecules are particularly interesting to the development of innovative electronic and spintronic devices as they present two spin states that can be controlled by external stimuli. In this purpose, being able to switch at will the spin state of a single molecule in a dense molecular array is a key milestone. However, the elastic interactions between the molecules favour more cooperative behaviour where patches of neighbouring molecules switches simultaneously. We demonstrate here that the interaction of iron II spin-crossover molecules with a metallic substrate can strongly reduce their cooperative behaviour until addressing independently single molecular spin state. Mechanoelastic model is able to reproduce well such findings.

Published
2021

17. Robust magnetic anisotropy of a monolayer of hexacoordinate Fe( ii ) complexes assembled on Cu(111)

Author

Olga Iasco, V. Repain, Cyril Chacon, Massine Kelai, Mihail Atanasov, Régis Guillot, Edwige Otero, Philippe Sainctavit, Marie-Laure Boillot, Luqiong Zhang, Frank Neese, Talal Mallah, Jérôme Lagoute, Eric Rivière, Benjamin Cahier, S. Rousset, Amandine Bellec, Marie-Anne Arrio, Anne-Laure Barra, Yann Girard, Yongfeng Tong, Mathématique et Physique Quantique (MPQ), Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft, Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences (BAS), Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Synchrotron SOLEIL (SSOLEIL), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)

Subjects
Tris, Materials science, chemistry.chemical_element, FOS: Physical sciences, 02 engineering and technology, Substrate (electronics), [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010402 general chemistry, 01 natural sciences, Inorganic Chemistry, chemistry.chemical_compound, spin crossover, monolayer, Monolayer, Molecule, [CHIM.COOR]Chemical Sciences/Coordination chemistry, ZFS, Boron, theoretical calculations, Condensed Matter - Materials Science, magnetic anisotropy, XMCD, Fe(II), Ligand, Hexacoordinate, Materials Science (cond-mat.mtrl-sci), [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, 3. Good health, Magnetic anisotropy, Crystallography, chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; The tris pyrazolyl borate ligand imposes a rigid scaffold around Fe( ii ) ensuring a robust magnetic anisotropy when the molecules assembled as monolayers suffer from the dissymmetric environment of the substrate/vacuum interface.

Published
2021
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18. Black Phosphorus for Directed Molecular Assembly with Weak Electronic Coupling

Author

Alexander Smogunov, Cyril Chacon, Mehdi Bouatou, Sylvie Rousset, Rishav Harsh, Vincent Repain, Jérôme Lagoute, Yann Girard, Amandine Bellec, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Mechanical Engineering, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, black phosphorus, 01 natural sciences, Black phosphorus, 0104 chemical sciences, law.invention, Coupling (electronics), Mechanics of Materials, law, Chemical physics, scanning tunneling microscopy, Density functional theory, molecules, Scanning tunneling microscope, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, density functional theory
Abstract

International audience; The combination of two-dimensional materials with organic molecules offers the possibility to obtain low dimensional hybrid materials with tailored properties. Black phosphorus is a monoelemental semiconducting material with a non-planar puckered atomic structure. Here, we study porphyrin molecules on black phosphorus and show that they self-assemble with an epitaxial relationship indicating that the molecule-surface interaction largely dominates the molecule-molecule interaction. The atomic structure of black phosphorus is found to be at the origin of the substrate driven self-assembly. Despite this strong interaction with molecules, the electronic coupling is found to be weak allowing the molecules to maintain the properties of their gas phase, which is the usual behaviour for van der Waals materials. Therefore, the combination of the peculiar puckered structure with the van der Waals nature of black phosphorus provides this material with the ability to interact strongly enough with adsorbed molecules to drive their assembly but weakly enough to keep their electronic properties intact.

Published
2021
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19. High density synthesis of topological point defects in graphene on 6H–SiC(000 1 ¯ )

Author

Amandine Bellec, Vincent Repain, Hakim Amara, Sylvain Latil, Quentin Berrahal, Sylvie Rousset, Cyril Chacon, Jérôme Lagoute, Yann Girard, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), Centre National de la Recherche Scientifique (CNRS)-ONERA, 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), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ONERA-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Grain Boundaries, Scanning tunneling spectroscopy, 02 engineering and technology, Growth, Silicon carbide, 010402 general chemistry, 01 natural sciences, Defect engineering, Topological defect, law.invention, chemistry.chemical_compound, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Monolayer, General Materials Science, business.industry, Graphene, Fermi energy, General Chemistry, 021001 nanoscience & nanotechnology, Crystallographic defect, Scanning tunelling microscopy/ spectroscopy, 0104 chemical sciences, chemistry, Density functional theory, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, 0210 nano-technology, business, Flower formation
Abstract

The control of the physical properties of graphene is a forefront challenge for the development of applications based on this material. Defect engineering is a promising strategy to attain new properties by the insertion of well-defined defects in the carbon lattice. Among the many topological defects of graphene, the one that has the lowest energy per dislocation is a quasi-point-like defect, the so-called Flower Defect (FD). It is generally produced randomly during the graphene synthesis. The deliberate insertion of this defect is promising for the tuning of graphene electronic properties but necessitate to establish a synthesis route allowing to control the formation of flower defects. Here we report a controlled synthesis of graphene with FD using gold as an activator during the graphene synthesis from a 6H–SiC(000 1 ¯ ) silicon carbide wafer. The synthesis consists of a two-step procedure. Creation of a proto-graphene template where one monolayer of gold is evaporated followed by synthesis close to 1200 °C. This leads to a high density of FD, around 10 12 cm - 2 . These results are supported by first-principles calculations showing that gold decreases the flower formation energy by a factor of 2. Scanning tunneling spectroscopy measurements reveal unexpected resonances close to the Fermi energy.

Published
2020

20. Direct Observation of the Reduction of a Molecule on Nitrogen Pairs in Doped Graphene

Author

Jérôme Lagoute, Mehdi Bouatou, Sourav Mondal, Yann Girard, Vincent Repain, Amandine Bellec, Shobhana Narasimhan, Frédéric Joucken, Robert Sporken, Cyril Chacon, Sylvie Rousset, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Groupe Modélisation et Théorie (GMT), 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, Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Bioengineering, 02 engineering and technology, 01 natural sciences, Redox, Atomic units, law.invention, Doped graphene, Charge transfer, law, 0103 physical sciences, Molecule, General Materials Science, Redistribution (chemistry), [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Scanning tunneling microscopy, ComputingMilieux_MISCELLANEOUS, Dopant, Graphene, Mechanical Engineering, Doping, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Chemical physics, Scanning tunneling microscope, 0210 nano-technology
Abstract

Incorporating functional atomic sites in graphene is essential for realizing advanced two-dimensional materials. Doping graphene with nitrogen offers the opportunity to tune its chemical activity with significant charge redistribution occurring between molecules and substrate. The necessary atomic scale understanding of how this depends on the spatial distribution of dopants, as well as their positions relative to the molecule, can be provided by scanning tunneling microscopy. Here we show that a noncovalently bonded molecule such as CoPc undergoes a variable charge transfer when placed on N-doped graphene; on a nitrogen pair, it undergoes a redox reaction with an integral charge transfer whereas a lower fractional charge transfer occurs over a single nitrogen. Thus, the charge state of molecules can be tuned by suitably tailoring the conformation of dopant atoms.

Published
2020

21. Control of Dipolar Switches on Graphene by a Local Electric Field

Author

Yannick J. Dappe, Jérôme Lagoute, Yann Girard, Cyril Chacon, Sylvie Rousset, Robert Sporken, César González, Mehdi Bouatou, Amandine Bellec, Vincent Repain, Frédéric Joucken, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Universidad Autónoma de Madrid (UAM), Groupe Modélisation et Théorie (GMT), 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, Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Universidad Autonoma de Madrid (UAM), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, law.invention, law, Electric field, Molecule, Electronics, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, Molecular switch, business.industry, Graphene, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Dipole, General Energy, Optoelectronics, Scanning tunneling microscope, 0210 nano-technology, business, Realization (systems)
Abstract

The realization of molecular electronic devices relies on the ability to perform elementary operations with functional molecules. Molecular switches are established candidates to realize basic electronic functions and data storage. Macrocyclic molecules such as phthalocyanines and their derivatives provide a family of compounds that can be switched by external stimuli between two stable states. Using scanning tunneling microscopy, we investigated tin phthalocyanine on graphene. We show that these molecules can be reversibly switched between two states and that the interaction of their electric dipole with a local electric field drives the switching yield and direction. The control at the single-molecule level of the molecular conformation in a bidimensional lattice is then used to achieve high-density data storage.

Published
2020

22. Comparing Regulatory Designs for the Transmission of Offshore Wind Energy

Author

Yann Girard, Claudia Kemfert, and Julius Stoll

Subjects
Economics and Econometrics, business.industry, Economics, media_common.quotation_subject, transmission, regulation, Management, Monitoring, Policy and Law, Environmental economics, Renewable energy, Cost efficiency, Offshore wind power, Transmission (telecommunications), Economic cost, Submarine pipeline, Quality (business), Asset (economics), Business, Electricity, offshore wind, Energy (miscellaneous), media_common
Abstract

Offshore wind plays an ever-increasing role for the global transition to renewable energy. For offshore wind energy to be successful, cost-effective transport of the produced electricity to shore is necessary. The development and operation of the offshore transmission asset is costly and regulated differently across the globe. In most countries, the TSO is responsible for the transmission and develops and operates the asset separately from the offshore wind farm. Other countries have established a competitive tender with integrated development of the offshore wind farm and the transmission asset. However, there is so far no empirical analysis of the economic benefits of different regulatory designs regarding the offshore transmission assets. In this paper, we collect a unique data set on offshore transmission assets that compares empirical cost and quality of offshore transmission assets in two countries with different regulatory regimes for the first time. With project level data we can control for geographical as well as technical difference to assess which regulatory design might lead to lower economic costs for the offshore transmission asset. Comparing the cost in the two leading countries for offshore wind energy, we find that a competitive regime leads to lower transmission cost and similar transmission availability.

Published
2020

23. Selective control of molecule charge state on graphene using tip-induced electric field and nitrogen doping

Author

Sylvie Rousset, Van Dong Pham, Shobhana Narasimhan, Yann Girard, Amandine Bellec, Yannick J. Dappe, Mario Pelaez-Fernandez, Cyril Chacon, Vincent Repain, Sukanya Ghosh, Robert Sporken, Jérôme Lagoute, Frédéric Joucken, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Paul-Drude-Institut für Festkörperelektronik (PDI), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Abdus Salam International Centre for Theoretical Physics [Trieste] (ICTP), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), Paul-Drude-Institut für Festkörperelektronik, Université de Namur [Namur], 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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Materials science, Ab initio, 02 engineering and technology, 01 natural sciences, law.invention, lcsh:Chemistry, law, Ab initio quantum chemistry methods, Electric field, 0103 physical sciences, Physics::Atomic and Molecular Clusters, lcsh:TA401-492, [CHIM]Chemical Sciences, General Materials Science, Physics::Chemical Physics, 010306 general physics, Graphene, Mechanical Engineering, Charge (physics), General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Dipole, lcsh:QD1-999, Mechanics of Materials, Chemical physics, Density functional theory, lcsh:Materials of engineering and construction. Mechanics of materials, 0210 nano-technology, Voltage
Abstract

The combination of graphene with molecules offers promising opportunities to achieve new functionalities. In these hybrid structures, interfacial charge transfer plays a key role in the electronic properties and thus has to be understood and mastered. Using scanning tunneling microscopy and ab initio density functional theory calculations, we show that combining nitrogen doping of graphene with an electric field allows for a selective control of the charge state in a molecular layer on graphene. On pristine graphene, the local gating applied by the tip induces a shift of the molecular levels of adsorbed molecules and can be used to control their charge state. Ab initio calculations show that under the application of an electric field, the hybrid molecule/graphene system behaves like an electrostatic dipole with opposite charges in the molecule and graphene sub-units that are found to be proportional to the electric field amplitude, which thereby controls the charge transfer. When local gating is combined with nitrogen doping of graphene, the charging voltage of molecules on nitrogen is greatly lowered. Consequently, applying the proper electric field allows one to obtain a molecular layer with a mixed charge state, where a selective reduction is performed on single molecules at nitrogen sites.

Published
2019

24. Properties of Functionalized Carbon Nanotubes and Their Interaction with a Metallic Substrate Investigated by Scanning Tunneling Microscopy

Author

Maria Cristina dos Santos, Jérôme Lagoute, Van Dong Pham, Cyril Chacon, Jean-Sébastien Lauret, Mauricio Terrones, Stéphane Campidelli, Amandine Bellec, Yann Girard, Vincent Repain, Sylvie Rousset, Christophe Voisin, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN), Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Energie (ex SIS2M) (NIMBE UMR 3685), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Aimé Cotton (LAC), École normale supérieure - Cachan (ENS Cachan)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Pierre Aigrain (LPA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Center for 2-Dimensional and Layered Materials, Pennsylvania State University (Penn State), Penn State System-Penn State System, Institute of Carbon Science and Technology, Shinshu University [Nagano], Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen [Groningen], Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École normale supérieure - Cachan (ENS Cachan), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-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)-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), Zernike Institute for Advanced Materials, Brazilian Agency FAPESP, ANR-10-LABX-0096,SEAM,Science and Engineering for Advanced Materials and devices(2010), Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN UMR 3685), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-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-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), ANR-11-LABX-086 - ANR-11-IDEX-05-02,LabEx SEAM,Science and Engineering for Advanced Materials and devices, Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Photophysics and OptoElectronics

Subjects
Nanotube, Materials science, GRAPHITE, PHASE, Selective chemistry of single-walled nanotubes, Mechanical properties of carbon nanotubes, Nanotechnology, 02 engineering and technology, Carbon nanotube, 010402 general chemistry, 01 natural sciences, law.invention, Condensed Matter::Materials Science, MOLECULES, NONCOVALENT FUNCTIONALIZATION, law, ALKANE, Physical and Theoretical Chemistry, [PHYS]Physics [physics], Local density of states, ATOMIC-STRUCTURE, RECOGNITION, [CHIM.MATE]Chemical Sciences/Material chemistry, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Optical properties of carbon nanotubes, General Energy, Carbon nanobud, PORPHYRIN, TRANSISTORS, BIOSENSORS, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; Non-covalent functionalization of carbon nanotubes (CNTs) allows the combination of the remarkable physical properties of these one-dimensional systems with the properties of the functional molecules and, at the same time, modifies the physico-chemical properties of nanotubes for specific applications. The use of functionalized carbon nanotubes in electronics often requires the deposition of the nanotubes on a substrate, and eventually an annealing step, which can modify their properties due to molecule-surface interactions. Using scanning tunneling microscopy/spectroscopy (STM/STS) and classical molecular dynamics (MD) simulations we studied the physical properties of carbon nanotubes functionalized with porphyrin derivatives and discuss the effect of physisorption and sample annealing on the nanotube surface. The results reveal that the functionalized parts exhibit non periodic structure with a significant modification of the local density of states. The coverage degree, can be estimated from STM images. When the sample is annealed, STM data clearly show an unwrapping of the functionalizing species leading to a lowering of the coverage degree. In addition, periodic structures were observed that correspond to the surfactants originally present in the CNT sample, revealing that the surfactants are still present in such functionalized nanotubes. These results provide information on the structure and properties of polymer functionalized nanotubes and the effect of substrate interaction and sample annealing that can markedly modify the structure and properties of the functionalized nanotubes.

Published
2017
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25. Controlling Hydrogen-Transfer Rate in Molecules on Graphene by Tunable Molecular Orbital Levels

Author

Jérôme Lagoute, Amandine Bellec, Sylvie Rousset, Yann Girard, Alexander Smogunov, Rishav Harsh, Vincent Repain, Robert Sporken, Frédéric Joucken, Cyril Chacon, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-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), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-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)-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, and Université de Namur [Namur]

Subjects
Molecular switch, Materials science, Dopant, Graphene, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, law, Chemical physics, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Molecule, General Materials Science, Molecular orbital, Physical and Theoretical Chemistry, Scanning tunneling microscope, 0210 nano-technology, Excitation, Quantum tunnelling
Abstract

International audience; Molecular switches are building blocks of potential interest to store binary information, especially when they can be organized in periodic lattices. Among the variety of possible systems, switches based on hydrogen transfer are of special importance because they allow the switching operation to occur without severe conformational change that may interfere with neighboring molecular units. We have studied the excitation process of hydrogen transfer inside porphyrin molecules assembled on a graphene surface, using a low-temperature scanning tunneling microscope. We show that this hydrogen transfer is induced by an electronic resonant tunneling process through the molecular orbitals. Using nitrogen doping of graphene, we tune the rate of hydrogen transfer by shifting the molecular orbital energies owing to the charge transfer at nitrogen dopant sites in the graphene lattice. The control of the switching process allows the storage of information inside a molecular lattice, which is demonstrated by writing an artificial pattern inside a molecular island.

Published
2019

26. Importance of Epitaxial Strain at a Spin-Crossover Molecule–Metal Interface

Author

Yannick J. Dappe, Talal Mallah, Cynthia Fourmental, Jérôme Lagoute, Cristian Enachescu, Cyrille Barreteau, Sourav Mondal, Shobhana Narasimhan, Marie-Laure Boillot, Rajdeep Banerjee, Sylvie Rousset, Alessandro Coati, Amandine Bellec, Yann Girard, Vincent Repain, Cyril Chacon, Alexander Smogunov, Yves Garreau, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de chimie inorganique (LCI), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Department of Solid State and Theoretical Physics, Alexandru Ioan Cuza University of Iași [Romania], Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), Theoretical Sciences Unit, European Project: 766726,211587,COSMICS(2017), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-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)-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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Diffraction, Materials science, Spin states, Spintronics, 02 engineering and technology, Substrate (electronics), 010402 general chemistry, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, 0104 chemical sciences, Chemical physics, Spin crossover, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Molecule, General Materials Science, Physical and Theoretical Chemistry, 0210 nano-technology, Spin-½
Abstract

International audience; Spin-crossover molecules are very appealing for use in multifunctional spintronic devices because of their ability to switch between high-spin and low-spin states with external stimuli such as voltage and light. In actual devices, the molecules are deposited on a substrate, which can modify their properties. However, surprisingly little is known about such molecule–substrate effects. Here we show for the first time, by grazing incidence X-ray diffraction, that an FeII spin-crossover molecular layer displays a well-defined epitaxial relationship with a metal substrate. Then we show, by both density functional calculations and a mechanoelastic model, that the resulting epitaxial strain and the related internal pressure can induce a partial spin conversion at low temperatures, which has indeed been observed experimentally. Our results emphasize the importance of substrate-induced spin state transitions and raise the possibility of exploiting them.

Published
2019

27. Experimental and theoretical investigations of magnetic anisotropy and magnetic hardening at molecule/ferromagnet interfaces

Author

C. Fourmental, Cyrille Barreteau, Yann Girard, L. Le Laurent, Jérôme Lagoute, Sylvie Rousset, Kaushik Bairagi, Cyril Chacon, Alexander Smogunov, Vincent Repain, Amandine Bellec, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-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)-Centre National de la Recherche Scientifique (CNRS), European Project: 766726,211587,COSMICS(2017), 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, LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), and Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Kerr effect, Materials science, Condensed matter physics, Magnetism, 02 engineering and technology, Coercivity, 021001 nanoscience & nanotechnology, 01 natural sciences, Condensed Matter::Materials Science, Magnetization, Magnetic anisotropy, Ferromagnetism, Ab initio quantum chemistry methods, Magnet, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 010306 general physics, 0210 nano-technology
Abstract

We measure by means of in situ magneto-optical Kerr effect the magnetism of ultrathin magnetic films supported on gold and platinum during the capping with molecular layers. We observe both for ${\mathrm{C}}_{60}$ and ${\mathrm{Alq}}_{3}$ molecules deposited on Co films an enhancement of the out-of-plane magnetic anisotropy, leading to a magnetic hardening for out-of-plane magnetization. Surprisingly, the amplitude of this hardening depends strongly on the underlying substrate. While we find an increase of the coercive field around 100% for Co/Au(111), it can reach almost 600% on Co/Pt(111). Those results are discussed by using both tight-binding and ab initio calculations. It is shown on the case of ${\mathrm{C}}_{60}$ that both the adsorption geometry and the strain in the magnetic layer can be key ingredients to predict the quantitative change of magnetic anisotropy induced by the interface between a magnetic material and a molecular layer. On the contrary, the crystalline stacking of the Co has a minor influence.

Published
2018

28. Temperature-, Light-, and Soft X-ray-Induced Spin Crossover in a Single Layer of Fe II -Pyrazolylborate Molecules in Direct Contact with Gold

Author

Cynthia Fourmental, Talal Mallah, Olga Iasco, Marie-Laure Boillot, Jérôme Lagoute, Fadi Choueikani, Vincent Repain, Edwige Otero, Philippe Sainctavit, Kaushik Bairagi, Amandine Bellec, Philippe Ohresser, Yann Girard, Cyril Chacon, Sylvie Rousset, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Multimatériaux et Interfaces (LMI), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Groupe de Physique des Solides (GPS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Unité de Nutrition Humaine - Clermont Auvergne (UNH), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne (UCA), Dispositifs et Instrumentation en Optoélectronique et micro-ondes (DIOM), Université Jean Monnet [Saint-Étienne] (UJM), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Unité de Nutrition Humaine (UNH), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020]), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Jean Monnet - Saint-Étienne (UJM)

Subjects
Materials science, Spin states, Absorption spectroscopy, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, law.invention, law, Spin crossover, Phase (matter), Monolayer, Molecule, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Spintronics, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, General Energy, Chemical physics, Condensed Matter::Strongly Correlated Electrons, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; Understanding the properties of spin-crossover molecules in direct contact with metals is crucial for their future integration in electronic and spintronic devices. By X-ray absorption spectroscopy, we investigate the properties of Fe-II((3,5-(CH3)(2)Pz)(3)BH)(2) molecules in the form of monolayer islands on a metallic substrate, namely, Au(111). We demonstrate that the spin crossover transition can be thermally induced from the high spin state to a mixed spin state phase containing one-third of high-spin state and two-thirds of low-spin-state molecules in agreement with previous work by scanning tunneling microscopy. In addition, at 4.4 K, the spin crossover from the low spin state to the high spin state can also be induced by X-ray and by light excitations.

Published
2017

29. STM study of C60F18 high dipole moment molecules on Au(111)

Author

V.G. Stankevich, Sylvie Rousset, Amandine Bellec, Ratibor G. Chumakov, K. A. Menshikov, A. M. Lebedev, L. P. Sukhanov, Cyril Chacon, Yann Girard, Vincent Repain, N. Yu. Svechnikov, Jérôme Lagoute, Kaushik Bairagi, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Département Mécanismes d'Accidents (INRETS/MA), and Institut National de Recherche sur les Transports et leur Sécurité (INRETS)

Subjects
Self assembled monolayer, 7. Clean energy, law.invention, Fullerene, law, Scanning tunneling microscopy and spectroscopy, Materials Chemistry, High dipole moment molecules, Molecule, Hexagonal lattice, Spectroscopy, [PHYS]Physics [physics], Chemistry, Self-assembled monolayer, Surfaces and Interfaces, Condensed Matter Physics, Fluorofullerene, Surfaces, Coatings and Films, Amorphous solid, Electric dipole moment, Crystallography, Dipole, 13. Climate action, Scanning tunneling microscope, Atomic physics, Molecules self assembling
Abstract

European Conference on Surface Science (ECOSS), Antalya, TURKEY, AUG 31-SEP 05, 2014; Scanning tunneling microscopy and spectroscopy studies of C60F18 molecules deposited on Au(111) are reported and compared to C-60 molecules both at liquid helium temperature and room temperature (RT). Whereas adsorption and electronic properties of C60F18 single molecules were studied at low temperature (LT), self-assemblies were investigated at RT. In both cases, the fluorine atoms of the C60F18 molecules are pointed towards the surface. Individual C60F18 molecules on Au(111) have a HOMO-LUMO gap of 2.9 eV. The self-assembled islands exhibit a close-packed hexagonal lattice with amorphous borders. The comparison with C-60 molecules clearly demonstrates the influence of the C60F15 electric dipole moment (EDM) on the electronic properties of single molecules and on the thermodynamics of self-assembled islands. Besides, the apparent height value of a separate molecule increases in a self-assembly environment as a result of a depolarization phenomenon. (C) 2015 Elsevier B.V. All rights reserved.

Published
2015

30. Tuning the Electronic and Dynamical Properties of a Molecule by Atom Trapping Chemistry

Author

Jérôme Lagoute, Enrique Abad, Van Dong Pham, Sylvie Rousset, Amandine Bellec, Alexander Smogunov, Yannick J. Dappe, Cyril Chacon, Yann Girard, Vincent Repain, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Departamento de Física Teórica de la Materia Condensada [Madrid] (DFTMC), Facultad de Ciencas [Madrid], Universidad Autonoma de Madrid (UAM)-Universidad Autonoma de Madrid (UAM), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0096,SEAM,Science and Engineering for Advanced Materials and devices(2010), Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid (UAM), 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), Universidad Autónoma de Madrid (UAM)-Universidad Autónoma de Madrid (UAM), 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, and ANR-11-LABX-086 - ANR-11-IDEX-05-02,LabEx SEAM,Science and Engineering for Advanced Materials and devices

Subjects
General Physics and Astronomy, 02 engineering and technology, Trapping, 010402 general chemistry, 01 natural sciences, law.invention, Metal, chemistry.chemical_compound, single-molecule manipulation, Deprotonation, molecular rotor, law, Computational chemistry, Tetraphenylporphyrin, Molecule, General Materials Science, density functional theory, Pyrrole, [PHYS]Physics [physics], General Engineering, 021001 nanoscience & nanotechnology, 0104 chemical sciences, chemistry, Chemical physics, visual_art, visual_art.visual_art_medium, scanning tunneling microscopy, Density functional theory, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; The ability to trap adatoms with an organic molecule on a surface has been used to obtain a range of molecular functionalities controlled by the choice of the molecular trapping site and local deprotonation. The tetraphenylporphyrin molecule used in this study contains three types of trapping sites: two carbon rings (phenyl and pyrrole) and the center of a macrocycle. Catching a gold adatom on the carbon rings leads to an electronic doping of the molecule, whereas trapping the adatom at the macrocycle center with single deprotonation leads to a molecular rotor and a second deprotonation leads to a molecular jumper. We call " atom trapping chemistry " the control of the structure, electronic, and dynamical properties of a molecule achieved by trapping metallic atoms with a molecule on a surface. In addition to the examples previously described, we show that more complex structures can be envisaged.

Published
2017

31. Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CNx-nanotubes

Author

Annick Loiseau, Cyril Chacon, V. Repain, Raul Arenal, Yann Girard, Hong Lin, Jean-Sébastien Lauret, Jérôme Lagoute, S. Rousset, François Ducastelle, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), Centre National de la Recherche Scientifique (CNRS)-ONERA, Laboratoire de Photonique Quantique et Moléculaire (LPQM), École normale supérieure - Cachan (ENS Cachan)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Laboratorio de microscopias avanzadas (LMA), University of Zaragoza - Universidad de Zaragoza [Zaragoza], Grant of CNano IdF 'SAMBA', ONERA-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-CentraleSupélec-École normale supérieure - Cachan (ENS Cachan)

Subjects
Materials science, Scanning tunneling spectroscopy, Selective chemistry of single-walled nanotubes, Carbon nanotubes, Energy Engineering and Power Technology, FOS: Physical sciences, Nanotechnology, 02 engineering and technology, Carbon nanotube, 01 natural sciences, law.invention, Condensed Matter::Materials Science, law, 0103 physical sciences, Molecular orbital, 010306 general physics, Scanning Tunneling Spectroscopy, Condensed Matter - Materials Science, Electron energy loss spectroscopy, General Engineering, Molecular electronics, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Optical properties of carbon nanotubes, 73.22.Dj, 68.37.Ef, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Scanning tunneling microscope, 0210 nano-technology
Abstract

Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one-dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviour, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on the experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy.

Published
2017

32. Electronic Interaction between Nitrogen-Doped Graphene and Porphyrin Molecules

Author

Cyril Chacon, S. Rousset, Yann Girard, Van Dong Pham, Amandine Bellec, Ouafi Mouhoub, Frédéric Joucken, V. Repain, Jérôme Lagoute, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), ONERA-Centre National de la Recherche Scientifique (CNRS), Mathématique et Physique Quantique (MPQ), Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Knoop, Martina, and Université de Namur [Namur]

Subjects
Materials science, Scanning tunneling spectroscopy, General Physics and Astronomy, tetraphenylporphyrins, Nanotechnology, 02 engineering and technology, Electronic structure, 010402 general chemistry, 01 natural sciences, [PHYS] Physics [physics], law.invention, chemistry.chemical_compound, law, Tetraphenylporphyrin, Molecule, General Materials Science, [PHYS]Physics [physics], Graphene, graphene, charge transfer, nitrogen doping, General Engineering, self-assembly, 021001 nanoscience & nanotechnology, Porphyrin, 0104 chemical sciences, chemistry, scanning tunneling microscopy, scanning tunneling spectroscopy, 0210 nano-technology, Bilayer graphene, Graphene nanoribbons
Abstract

The chemical doping of graphene is a promising route to improve the performances of graphene-based devices through enhanced chemical reactivity, catalytic activity, or transport characteristics. Understanding the interaction of molecules with doped graphene at the atomic scale is therefore a leading challenge to be overcome for the development of graphene-based electronics and sensors. Here, we use scanning tunneling microscopy and spectroscopy to study the electronic interaction of pristine and nitrogen-doped graphene with self-assembled tetraphenylporphyrin molecules. We provide an extensive measurement of the electronic structure of single porphyrins on Au(111), thus revealing an electronic decoupling effect of the porphyrins adsorbed on graphene. A tip-induced switching of the inner hydrogen atoms of porphyrins, first identified on Au(111), is observed on graphene, allowing the identification of the molecular conformation of porphyrins in the self-assembled molecular layer. On nitrogen-doped graphene, a local modification of the charge transfer around the nitrogen sites is evidenced via a downshift of the energies of the molecular elecronic states. These data show how the presence of nitrogen atoms in the graphene network modifies the electronic interaction of organic molecules with graphene. These results provide a basic understanding for the exploitation of doped graphene in molecular sensors or nanoelectronics.

Published
2014

33. Order-disorder phase transition inAu2Feon Ru(0001)

Author

Alessandro Coati, Yann Girard, Jérôme Lagoute, Amandine Bellec, Sylvie Rousset, Yves Garreau, Vincent Repain, J.-B. Marie, and Cyril Chacon

Subjects
Diffraction, Phase transition, Materials science, Condensed matter physics, Alloy, Order (ring theory), 02 engineering and technology, engineering.material, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, law.invention, law, 0103 physical sciences, engineering, Scanning tunneling microscope, 010306 general physics, 0210 nano-technology, Bimetallic strip, Solid solution
Abstract

Order-disorder transition of the epitaxial surface alloy of bulk immiscible elements ${\mathrm{Au}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$ on Ru(0001) is studied using complementary experiments of scanning tunneling microscopy and grazing incidence x-ray diffraction. For $x\ensuremath{\simeq}1/3$, we evidence an apparent continuous transition towards disorder with increasing temperature from 550 to 700 K. An ordered ${\mathrm{Au}}_{2}\mathrm{Fe}$ two-dimensional alloy is found to be composed of nanometer size domains of the three variants that switch to a two-dimensional solid solution with temperature. A two-levels model is developed to analyze those results which conducts to interpret this phase transition as the result of an order-disorder transition within two dimensional uncorrelated grains, or domains, with nearly fixed size. This system is a good candidate in order to study two-dimensional phase transitions of surface alloy, a largely unexplored domain but crucial to understanding thermal stability of bimetallic nanoparticles.

Published
2016

34. Correction to Temperature-, Light-, and Soft X-ray-Induced Spin Crossover in a Single Layer of FeII-Pyrazolylborate Molecules in Direct Contact with Gold

Author

Kaushik Bairagi, Amandine Bellec, Cynthia Fourmental, Yongfeng Tong, Olga Iasco, Jérôme Lagoute, Cyril Chacon, Yann Girard, Sylvie Rousset, Fadi Choueikani, Edwige Otero, Philippe Ohresser, Philippe Sainctavit, Marie-Laure Boillot, Talal Mallah, and Vincent Repain

Subjects
General Energy, 010405 organic chemistry, Physical and Theoretical Chemistry, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
Published
2018

35. Growth of Bi on Cu(111): Alloying and dealloying transitions

Author

S. Rousset, Yann Girard, Jérôme Lagoute, V. Repain, G. de Abreu, Cyril Chacon, Département Mécanismes d'Accidents (INRETS/MA), Institut National de Recherche sur les Transports et leur Sécurité (INRETS), Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), and Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Alloy, chemistry.chemical_element, 02 engineering and technology, engineering.material, 01 natural sciences, Surface alloy, Overlayer, law.invention, Bismuth, Adsorption, Transition metal, law, 0103 physical sciences, Monolayer, Materials Chemistry, Scanning tunneling microscopy, 010306 general physics, [PHYS]Physics [physics], Condensed matter physics, Surfaces and Interfaces, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Copper, Surfaces, Coatings and Films, Dealloying, Crystallography, chemistry, engineering, Scanning tunneling microscope, 0210 nano-technology
Abstract

We report on the observation of surface alloying and dealloying transitions during the submonolayer growth of Bi on the Cu(111) surface. In-situ scanning tunneling microscopy (STM) analysis reveals that at low coverage, and for quasi thermodynamical equilibrium, embedded Bi atoms are randomly distributed within the first Cu layer. Near the ideal coverage of 1/3, we observe an ordered BiCu2 substitutional surface alloy. Between 1/3 and 1/2 monolayer a dealloying process takes place where the surface alloy coexists with two different domains of dense Bi overlayer. In order to understand the mechanisms behind this process, the ordered alloy has been used as a template for subsequent Bi adsorption. An apparently etched surface develops during deposition and using STM image analysis, we propose that this growth mode is accompanied by a large Bi and Cu atoms redistribution inside the surface alloy. (C) 2013 Elsevier B.V. All rights reserved.

Published
2013

36. Symmetry-selected spin-split hybrid states inC60/ferromagneticinterfaces

Author

C. Chacon, Cyrille Barreteau, Sylvie Rousset, Jérôme Lagoute, Seiji Leo Kawahara, Alexander Smogunov, V. Repain, Dongzhe Li, and Yann Girard

Subjects
Materials science, Condensed matter physics, Spin polarization, Spintronics, Condensed Matter::Other, Orbital hybridisation, Scanning tunneling spectroscopy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Orientation (vector space), Condensed Matter::Materials Science, Ferromagnetism, 0103 physical sciences, Molecular orbital, 010306 general physics, 0210 nano-technology, Spin (physics)
Abstract

The understanding of orbital hybridization and spin polarization at the organic-ferromagnetic interface is essential in the search for efficient hybrid spintronic devices. Here, using first-principles calculations, we report a systematic study of spin-split hybrid states of ${\mathrm{C}}_{60}$ deposited on various ferromagnetic surfaces: bcc-Cr(001), bcc-Fe(001), bcc-Co(001), fcc-Co(001), and hcp-Co(0001). We show that the adsorption geometry of the molecule with respect to the surface crystallographic orientation of the magnetic substrate as well as the strength of the interaction play a crucial role in the spin polarization of the hybrid orbitals. We find that a large spin polarization in vacuum above the buckyball can only be achieved if the molecule is adsorbed upon a bcc-(001) surface by its pentagonal ring. Therefore, bcc-Cr(001), bcc-Fe(001), and bcc-Co(001) are the optimal candidates. Spin-polarized scanning tunneling spectroscopy measurements on single ${\mathrm{C}}_{60}$ adsorbed on Cr(001) and Co/Pt(111) also confirm that the symmetry both of the substrate and of the molecular conformation has a strong influence on the induced spin polarization. Our finding may give valuable insights for further engineering of spin filtering devices through single molecular orbitals.

Published
2016

37. Control of Molecule-Metal Interaction by Hydrogen Manipulation in an Organic Molecule

Author

Yann Girard, Yannick J. Dappe, Vincent Repain, Van Dong Pham, Amandine Bellec, Jérôme Lagoute, Alexander Smogunov, Sylvie Rousset, Cyril Chacon, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), V.R. thanks the Institut Universitaire de France for support.The calculations have been performed using HPC computation resources from GENCI-[TGCC] (Grant 2016097416)., ANR-11-LABX-086 - ANR-11-IDEX-05-02,LabEx SEAM,Science and Engineering for Advanced Materials and devices, The calculations have been performed using HPC computation resources from GENCI-[TGCC] (Grant 2016097416)., ANR-10-LABX-0096,SEAM,Science and Engineering for Advanced Materials and devices(2010), 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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Hydrogen, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Molecular conformation, law.invention, Metal, ATOMS, chemistry.chemical_compound, Computational chemistry, Ab initio quantum chemistry methods, law, Molecule, General Materials Science, Physical and Theoretical Chemistry, Wave function, PORPHYRIN MOLECULES, AU(111), [PHYS]Physics [physics], Chemistry, SCANNING-TUNNELING-MICROSCOPY, 021001 nanoscience & nanotechnology, Porphyrin, 0104 chemical sciences, ROOM-TEMPERATURE, SINGLE, visual_art, visual_art.visual_art_medium, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; Free-base porphyrin molecules offer appealing options to tune the interaction with their environment via the manipulation of their inner hydrogen atoms and molecular conformation. Using scanning tunneling microscopy we show, through a systematic study, that the molecular conformation, electronic gap, wave function, and molecule-substrate interaction are modified by hydrogen switch or removal. Experimental results in combination with ab initio calculations provide an understanding of the underlying physical process.

Published
2016

38. Molecular-scale dynamics of light-induced spin cross-over in a two-dimensional layer

Author

Jérôme Lagoute, Cyril Chacon, Kaushik Bairagi, Cyrille Barreteau, Alexey Kartsev, Olga Iasco, Talal Mallah, Frédéric Miserque, Alexander Smogunov, Dongzhe Li, Yannick J. Dappe, Amandine Bellec, Yann Girard, Vincent Repain, Marie-Laure Boillot, Sylvie Rousset, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude de la Corrosion Aqueuse (LECA), Service de la Corrosion et du Comportement des Matériaux dans leur Environnement (SCCME), Département de Physico-Chimie (DPC), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Département de Physico-Chimie (DPC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction de l'Energie Nucléaire (CEA-DEN), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-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)-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, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Spin states, Science, General Physics and Astronomy, Nanotechnology, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Article, Ab initio quantum chemistry methods, Quantum tunnelling, Spin-½, спиновые состояния, [PHYS]Physics [physics], Multidisciplinary, Spintronics, Spin engineering, General Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Chemical physics, Spinplasmonics, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, спин, Nanomechanics
Abstract

Spin cross-over molecules show the unique ability to switch between two spin states when submitted to external stimuli such as temperature, light or voltage. If controlled at the molecular scale, such switches would be of great interest for the development of genuine molecular devices in spintronics, sensing and for nanomechanics. Unfortunately, up to now, little is known on the behaviour of spin cross-over molecules organized in two dimensions and their ability to show cooperative transformation. Here we demonstrate that a combination of scanning tunnelling microscopy measurements and ab initio calculations allows discriminating unambiguously between both states by local vibrational spectroscopy. We also show that a single layer of spin cross-over molecules in contact with a metallic surface displays light-induced collective processes between two ordered mixed spin-state phases with two distinct timescale dynamics. These results open a way to molecular scale control of two-dimensional spin cross-over layers., Spin crossover molecules may find applications in ultimately small magnetic devices, given the sensitivity of their spin-states to external stimuli. Here, the authors show a light-induced transition between two ordered dynamic phases in two-dimensional spin crossover layers on a metallic surface.

Published
2016

39. Quasi unidimensional growth of Co nanostructures on a strained Au(111) surface

Author

Yann Girard, S. Rousset, Paolo Campiglio, Olivier Fruchart, Jérôme Lagoute, V. Repain, Cyril Chacon, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Micro et NanoMagnétisme (MNM), 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), ANR-05-NANO-0073,VERNANOMAG,Versatilité de réseaux auto-organisés de nanostructures et matériaux magnétiques : fabrication et fonctionnalités(2005), MNM - Micro et NanoMagnétisme, Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), ANR-NANO-018-04, ANR-05-NANO-073,ANR-NANO-018-04, and ANR-05-NANO-073

Subjects
Surface diusion, Materials science, Nanostructure, Diffusion, Nucleation, chemistry.chemical_element, 02 engineering and technology, 01 natural sciences, law.invention, Low index single crystal surfaces, Metal-metal magnetic thin lm structures, law, 0103 physical sciences, Materials Chemistry, Deposition (phase transition), Scanning tunneling microscopy, 010306 general physics, Surface diffusion, Self-assembly, Cobalt, Surfaces and Interfaces, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 68.55.-a, Surfaces, Coatings and Films, Crystallography, chemistry, Chemical engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Scanning tunneling microscope, 0210 nano-technology, Platinum
Abstract

International audience; We investigated to which extent a uniaxially-strained Au(111) surface, thereby displaying linear reconstructions, may be used as a template for the growth of elongated nanostructures. Cobalt has been used as a deposition material, and two routes have been followed satisfactorily. The rst one consists in the control of diusion through the temperature of deposition. The second one consists in a rst step of platinum seeding in the reconstruction, followed by cobalt deposition with nucleation on the platinum seeds.

Published
2011

40. Many-body effects in electronic bandgaps of carbon nanotubes measured by scanning tunnelling spectroscopy

Author

Cyril Chacon, Jérôme Lagoute, Sylvie Rousset, Jean-Sébastien Lauret, Hong Lin, Vincent Repain, Yann Girard, François Ducastelle, and A. Loiseau

Subjects
Materials science, Band gap, Mechanical Engineering, Optical measurements, Selective chemistry of single-walled nanotubes, Tunnelling spectroscopy, Nanotechnology, General Chemistry, Carbon nanotube, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Condensed Matter Physics, Many body, law.invention, Optical properties of carbon nanotubes, Condensed Matter::Materials Science, Mechanics of Materials, law, General Materials Science, Electronic properties
Abstract

Single-walled carbon nanotubes provide an ideal system for studying the properties of one-dimensional (1D) materials, where strong electron-electron interactions are expected. Optical measurements have recently reported the existence of excitons in semiconducting nanotubes, revealing the importance of many-body effects. Surprisingly, pioneering electronic structure calculations and scanning tunnelling spectroscopy (STS) experiments report the same gap values as optical experiments. Here, an experimental STS study of the bandgap of single-walled semiconducting nanotubes, demonstrates a continuous transition from the gap reduced by the screening resulting from the metal substrate to the intrinsic gap dominated by many-body interactions. These results provide a deeper knowledge of many-body interactions in these 1D systems and a better understanding of their electronic properties, which is a prerequisite for any application of nanotubes in the ultimate device miniaturization for molecular electronics, or spintronics.

Published
2010

41. Effect of a Gold Overlayer Contamination on the Growth and Magnetic Properties of Au/Co/Au(111)

Author

Jérôme Lagoute, Y. Nahas, Yann Girard, Vincent Repain, Cyril Chacon, and Sylvie Rousset

Subjects
Materials science, Layer by layer, Analytical chemistry, chemistry.chemical_element, Bioengineering, Surfaces and Interfaces, Substrate (electronics), Condensed Matter Physics, Surfaces, Coatings and Films, law.invention, Overlayer, Crystallography, Magnetization, Magneto-optic Kerr effect, chemistry, Mechanics of Materials, law, Vacancy defect, Scanning tunneling microscope, Cobalt, Biotechnology
Abstract

The presence of chlorine in gold is found to modified drastically the growth mode of Au on a Au(111) substrate. Whereas pure gold can grow layer by layer by step flow, contaminated gold is found to make random and/or vacancy islands and to modify the Au(111) herringbone reconstruction structure. The influence of a contaminated gold capping on the magnetic properties of cobalt ultrathin films has been investigated by in situ Magneto Optical Kerr Effect measurements. Surprisingly, the interface anisotropy is found to be of opposite sign as compared to the one of pure gold and thus favoring an in-plane magnetization. [DOI: 10.1380/ejssnt.2010.21]

Published
2010

42. Combined STM/STS, TEM/EELS investigation of CNx-SWNTs

Author

S. Enouz, Sylvie Rousset, Yann Girard, Cyril Chacon, Odile Stéphan, Hong Lin, Vincent Repain, Raul Arenal, Jérôme Lagoute, A. Loiseau, and L. Bresson

Subjects
Chemistry, Doping, Analytical chemistry, chemistry.chemical_element, Carbon nanotube, Condensed Matter Physics, Nitrogen, Electronic, Optical and Magnetic Materials, law.invention, Characterization (materials science), law, Transmission electron microscopy, Impurity, Scanning tunneling microscope, Carbon
Abstract

Nitrogen doped single-walled carbon nanotubes (CN x -SWNTs) were successfully synthesized by vaporizing a C:Ni/Y target by a CO2 continuous laser under a nitrogen atmosphere. The as-grown nanotubes were investigated by combining TEM/EELS and STM/STS techniques. According to TEM observations, the tubes are mostly single-walled and few defects are found. Local chemical characterization was performed by EELS analysis, which proves the presence of nitrogen in both individual tubes and SWNTs bundles and indicates a nitrogen concentration around 1 at.%. STM observations of CN x -SWNTS have been then undertaken and atomic resolution images were obtained. First STM analyses of these nanotubes show some defects which have never been observed in pure carbon nanptubes before.

Published
2008

43. Charge transfer and electronic doping in nitrogen-doped graphene

Author

A. Taleb-Ibrahimi, Sylvie Rousset, Antonio Tejeda, Frédéric Joucken, Patrick Le Fèvre, Amandine Bellec, Cyril Chacon, François Ducastelle, Edward H. Conrad, Hakim Amara, Jacques Ghijsen, Jérôme Lagoute, Robert Sporken, Yann Girard, Vincent Repain, Yann Tison, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), CASSIOPEE, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS)-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), Centre National de la Recherche Scientifique (CNRS), Groupe de Physique des Solides (GPS), Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Centre National de la Recherche Scientifique (CNRS)-THALES, Unité Mixte de Physique (UNIVERSITE PARIS SUD), Université Paris-Sud - Paris 11 (UP11), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), and ONERA

Subjects
Multidisciplinary, Materials science, Dopant, Graphene, Binding energy, Doping, 02 engineering and technology, Electronic structure, 021001 nanoscience & nanotechnology, Bioinformatics, 01 natural sciences, Article, law.invention, Condensed Matter::Materials Science, X-ray photoelectron spectroscopy, law, Chemical physics, Condensed Matter::Superconductivity, 0103 physical sciences, Physics::Atomic and Molecular Clusters, [CHIM]Chemical Sciences, Scanning tunneling microscope, 010306 general physics, 0210 nano-technology, Spectroscopy
Abstract

Understanding the modification of the graphene’s electronic structure upon doping is crucial for enlarging its potential applications. We present a study of nitrogen-doped graphene samples on SiC(000"Equation missing") combining angle-resolved photoelectron spectroscopy, scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy (XPS). The comparison between tunneling and angle-resolved photoelectron spectra reveals the spatial inhomogeneity of the Dirac energy shift and that a phonon correction has to be applied to the tunneling measurements. XPS data demonstrate the dependence of the N 1s binding energy of graphitic nitrogen on the nitrogen concentration. The measure of the Dirac energy for different nitrogen concentrations reveals that the ratio usually computed between the excess charge brought by the dopants and the dopants’ concentration depends on the latter. This is supported by a tight-binding model considering different values for the potentials on the nitrogen site and on its first neighbors.

Published
2015

44. Giant tunnel-electron injection in nitrogen-doped graphene

Author

Mattias Lau Nøhr Palsgaard, Yann Tison, Mads Brandbyge, Jérôme Lagoute, Sylvie Rousset, Amandine Bellec, Yann Girard, Vincent Repain, François Ducastelle, Edward H. Conrad, Nick Papior Andersen, Cyril Chacon, Frédéric Joucken, Robert Sporken, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur], Georgia Institute of Technology [Atlanta], Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), ONERA-Centre National de la Recherche Scientifique (CNRS), Center for Nanostructured Graphene, Université de Namur [Namur] (UNamur), and Centre National de la Recherche Scientifique (CNRS)-ONERA

Subjects
GRAPHENE, Materials science, 02 engineering and technology, Electron, PHYSICS, 01 natural sciences, Molecular physics, law.invention, [SPI.MAT]Engineering Sciences [physics]/Materials, symbols.namesake, Condensed Matter::Materials Science, AZOTE, law, Ab initio quantum chemistry methods, Condensed Matter::Superconductivity, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Physics::Chemical Physics, 010306 general physics, Spectroscopy, Quantum tunnelling, Graphene, Fermi level, Conductance, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, symbols, ELECTRON, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; Scanning tunneling microscopy experiments have been performed to measure the local electron injection in nitrogen-doped graphene on SiC(000¯1) and were successfully compared to ab initio calculations. In graphene, a gaplike feature is measured around the Fermi level due to a phonon-mediated tunneling channel. At nitrogen sites, this feature vanishes due to an increase of the elastic channel that is allowed because of symmetry breaking induced by the nitrogen atoms. A large conductance enhancement by a factor of up to 500 was measured at the Fermi level by comparing local spectroscopy at nitrogen sites and at carbon sites. Nitrogen doping can therefore be proposed as a way to improve tunnel-electron injection in graphene.

Published
2015

45. C$_{60}$ as an Atom Trap to Capture Co Adatoms

Author

Sylvie Rousset, Peng Yang, Dongzhe Li, Yannick J. Dappe, Cyril Chacon, Cyrille Barreteau, Alexander Smogunov, Yann Girard, Vincent Repain, Jérôme Lagoute, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Xidian University, 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), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), DTU Nanotech, Technical University of Denmark [Lyngby] (DTU), The calculations in this work was performed using HPC resources from GENCI-CINES (Grant Nos. x2013096813), 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, and Danmarks Tekniske Universitet = Technical University of Denmark (DTU)

Subjects
[PHYS]Physics [physics], Chemistry, Scanning tunneling spectroscopy, Trapping, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, law.invention, Metal, Condensed Matter::Materials Science, General Energy, Chemical physics, law, visual_art, Atom, Physics::Atomic and Molecular Clusters, visual_art.visual_art_medium, Cluster (physics), Molecule, Density functional theory, Physical and Theoretical Chemistry, Atomic physics, Scanning tunneling microscope, Physics::Chemical Physics, [MATH]Mathematics [math]
Abstract

International audience; C$_{60}$ molecules were used to trap Co adatoms and clusters on a Au(111) surface using atomic/molecular manipulation with a scanning tunneling microscope. Two manipulation pathways (successive integration of single Co atoms in one molecule or direct integration of a Co cluster) were found to efficiently allow the formation of complexes mixing a C$_{60}$ molecule with Co atoms. Scanning tunneling spectroscopy reveals the robustness of the π states of C$_{60}$ that are preserved after Co trapping. Scanning tunneling microscopy images and density functional theory calculations reveal that dissociated Co clusters of up to nine atoms can be formed at the molecule−substrate interface. These results open new perspectives in the interactions between metal adatoms and molecules, for applications in metal−organic devices.

Published
2015

46. Electronic interaction between nitrogen atoms in doped graphene

Author

Luc Henrard, Dimpy Sharma, Yann Tison, Ahmed Ghedjatti, Cyril Chacon, Frédéric Joucken, Hakim Amara, Sylvie Rousset, Yann Girard, Vincent Repain, Jérôme Lagoute, François Ducastelle, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Groupe de Physique des Solides (GPS), Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), and ONERA

Subjects
Atoms, Electronic structure, Materials science, Nitrogen, Binding sites, Nitrogen-doping, Potential applications of graphene, STM, General Physics and Astronomy, Nanotechnology, 02 engineering and technology, Binding energy, 010402 general chemistry, 01 natural sciences, DFT, STS, law.invention, Tight binding, law, tight-binding, Physics::Atomic and Molecular Clusters, [CHIM]Chemical Sciences, General Materials Science, Point defects, Doping (additives), Scanning tunneling microscopy, Dopant, Graphene, General Engineering, nitrogen doping, Chemical bonds, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Chemical physics, Electronic properties, Density functional theory, Scanning tunneling microscope, 0210 nano-technology, Graphene nanoribbons
Abstract

cited By 20; International audience; Many potential applications of graphene require either the possibility of tuning its electronic structure or the addition of reactive sites on its chemically inert basal plane. Among the various strategies proposed to reach these objectives, nitrogen doping, i.e., the incorporation of nitrogen atoms in the carbon lattice, leads in most cases to a globally n-doped material and to the presence of various types of point defects. In this context, the interactions between chemical dopants in graphene have important consequences on the electronic properties of the systems and cannot be neglected when interpreting spectroscopic data or setting up devices. In this report, the structural and electronic properties of complex doping sites in nitrogen-doped graphene have been investigated by means of scanning tunneling microscopy and spectroscopy, supported by density functional theory and tight-binding calculations. In particular, based on combined experimental and simulation works, we have systematically studied the electronic fingerprints of complex doping configurations made of pairs of substitutional nitrogen atoms. Localized bonding states are observed between the Dirac point and the Fermi level in contrast with the unoccupied state associated with single substitutional N atoms. For pyridinic nitrogen sites (i.e., the combination of N atoms with vacancies), a resonant state is observed close to the Dirac energy. This insight into the modifications of electronic structure induced by nitrogen doping in graphene provides us with a fair understanding of complex doping configurations in graphene, as it appears in real samples. © 2015 American Chemical Society.

Published
2015

47. Copyright and innovation: Fit for digitization?

Author

Christian Handke, Yann Girard, and Anselm Mattes

Subjects
O31, creative industries, jel:Z11, O34, copyright, jel:D23, innovation, jel:O31, Z11, jel:O34, digitization, ddc:330, D23, innovation, copyright, digitization, user-generated content, creative industries, user-generated content
Abstract

It is contentious to what extent the existing copyright system contributes to the positive development of the regulated sectors of society. The present report shows that substantially more musical works and movies have been released in recent years than before the diffusion of digital copying technology. At the same time, the average quality of these works has been stable according to user assessments. Countries with stronger copyright protection do not exhibit greater supply of new works. Accordingly, the relatively strict copyright protection in some countries does not seem to promote the supply of new creative works. The present report also considers whether user-generated content (UGC) complements or substitutes professional content. An increasing supply of valuable UGC is not reflected in official economic statistics. In all probability, copyright protection promotes user-generated content less than professional content. As a result, substituting professional content with “amateur material” could reduce the socially desirable strength of copyright protection. However, we find that almost half of all works available on YouTube are professional content. Professional works are watched and recommended more frequently than the average. In addition, a large proportion of UGC on YouTube draws on professional works. There is little evidence that professional content would be widely replaced. It follows that UGC could also be supported by an efficient copyright system, which strengthens the supply of professional content without excessively limiting its further use as input for UGC.

Published
2015

48. Urheberrechtsschutz und Innovation: Fit für die Digitalisierung?

Author

Christian Handke, Yann Girard, and Anselm Mattes

Subjects
O31, creative industries, jel:Z11, O34, copyright, jel:D23, innovation, jel:O31, Z11, jel:O34, digitization, ddc:330, D23, innovation, copyright, digitization, user-generated content, creative industries, user-generated content
Abstract

It is contentious to what extent the existing copyright system contributes to the positive development of the regulated sectors of society. The present report shows that substantially more musical works and movies have been released in recent years than before the diffusion of digital copying technology At the same time, the average quality of these works has been stable according to user assessments. Countries with stronger copyright protection do not exhibit greater supply of new works. Accordingly, the relatively strict copyright protection in some countries does not seem to promote the supply of new creative works. The present report also considers whether user-generated content (UGC) complements or substitutes professional content. An increasing supply of valuable UGC is not reflected in official economic statistics. In all probability, copyright protection promotes user-generated content less than professional content. As a result, substituting professional content with “amateur material” could reduce the socially desirable strength of copyright protection. However, we find that almost half of all works available on YouTube are professional content. Professional works are watched and recommended more frequently than the average. In addition, a large proportion of UGC on YouTube draws on professional works. There is little evidence that professional content would be widely replaced. It follows that UGC could also be supported by an efficient copyright system, which strengthens the supply of professional content without excessively limiting its further use as input for UGC. Im Zusammenhang mit der Digitalisierung ist es seit Jahren strittig, inwieweit das bestehende Urheberrecht zu einer nachhaltig positiven Entwicklung der geregelten Gesellschaftsbereiche beiträgt. Dieser Bericht belegt, dass in den letzten Jahren deutlich mehr Musik und Filme veröffentlicht worden sind als vor der Verbreitung digitaler Kopiertechnologie. Nutzerbewertungen zufolge ist dabei die durchschnittliche Qualität der Veröffentlichungen in etwa gleich geblieben. Zudem werden in Ländern mit stärkerem Urheberrechtsschutz nicht signifikant mehr neue Werke veröffentlicht. Relativ starke Urheberrechtsschutzmaßnahmen in einigen Ländern fördern demnach das Angebot neuer kreativer Werk nicht. Dieser Bericht betrachtet ebenfalls, ob professionelle Inhalte durch nutzergenerierte Inhalte (User Generated Content) ergänzt oder ersetzt werden. Diese Art von Veröffentlichungen ohne direktes Erwerbsinteresse wird in den üblichen Statistiken nicht erfasst und erhöht die Vielfalt des Angebots zusätzlich. Nutzergenerierte Inhalte werden durch einen starken Urheberrechtsschutz wahrscheinlich weniger gefördert als professionelle Inhalte. Ein Ersatz professioneller Inhalte durch „Amateur-Veröffentlichungen“ könnte also den gesamtgesellschaftlich erstrebenswerten Urheberrechtsschutz verringern. Wir finden allerdings, dass professionelle Inhalte auch auf YouTube fast die Hälfte des Angebots ausmachen, überdurchschnittlich häufig aufgerufen und positiv bewertet werden. Ein weitgehender Ersatz professioneller Inhalte ist nicht zu erkennen. Außerdem beinhaltet ein großer Teil der auf YouTube befindlichen nutzergenerierten Inhalte Teile professioneller Veröffentlichungen. Demzufolge könnte auch das Angebot nutzergenerierter Inhalte von einem effizienteren Urheberrechtsschutz gefördert werden, der das professionelle Angebot kreativer Werke stärkt, ohne dessen weitere Nutzung als Input für nutzergenerierte Inhalte übermäßig einzuschränken.

Published
2015

49. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

Author

Cyrille Barreteau, R. Breitwieser, Cyril Chacon, Y. Chao, Yu-Cheng Hu, Amandine Bellec, Vincent Repain, Yves Garreau, Sylvie Rousset, Dongzhe Li, Woei Wu Pai, Yann Girard, Jérôme Lagoute, Alexander Smogunov, Kaushik Bairagi, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), National Taiwan University [Taiwan] (NTU), 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), Groupe Modélisation et Théorie (GMT), 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, DTU Nanotech, Danmarks Tekniske Universitet = Technical University of Denmark (DTU), The ab initio calculations were performed using HPC resources from GENCI- [TGCC/IDRIS] (Grants No. 2014096813 and No. 2015097416), ANR-12-BS10-0006,SPIROU,Magnéto-résistance de nano-objets moléculaires(2012), European Project: 259297,EC:FP7:ERC,ERC-2010-StG_20091028,MAGNETALS(2010), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-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)-Centre National de la Recherche Scientifique (CNRS), and Technical University of Denmark [Lyngby] (DTU)

Subjects
7530Gw, [PHYS]Physics [physics], Materials science, Condensed matter physics, General Physics and Astronomy, 7320Hb, Overlayer, Magnetic anisotropy, 7820Ls, Atomic orbital, Ab initio quantum chemistry methods, Molecule, Thin film, Anisotropy, Spin (physics), 7570Cn
Abstract

We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the C60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C60 pz and Co dz2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C60 with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

Published
2015

50. Building uniform and long-range ordered nanostructures on a surface by nucleation on a point defect array

Author

Yann Girard, Stanislas Rohart, Antonio Tejeda, V. Repain, Sylvie Rousset, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), and Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Materials science, Nanostructure, business.industry, Nucleation, chemistry.chemical_element, 02 engineering and technology, Rate equation, Atmospheric temperature range, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Condensed Matter::Materials Science, Optics, chemistry, Chemical physics, 0103 physical sciences, General Materials Science, Kinetic Monte Carlo, 010306 general physics, 0210 nano-technology, business, Cobalt, Vicinal, Quantum tunnelling
Abstract

International Workshop on Self-Organized Nanostructures, Cargese, FRANCE, JUL 17-23, 2005; International audience; We present both experimental and simulated results of ordered growth of cobalt nano-islands on a Au(111) vicinal template. Firstly, the temperature range for ordered growth and the islands size distributions are investigated by a rate equation model and kinetic Monte Carlo (KMC) simulations. Secondly, the incidence of the surface structure on the growth of cobalt is studied in detail by means of variable temperature scanning tunnelling microscopy experiments and KMC simulations. The underlying atomic processes responsible for the ordered growth are discussed.

Published
2006

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