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1. Using Light to Polarize and Detect Electron Spins in Silicon

Author

Marie, Xavier, Lagarde, Delphine, Balocchi, Andrea, Robert, Cedric, Lombez, Laurent, Renucci, Pierre, Amand, Thierry, and Cadiz, Fabian

Subjects
Condensed Matter - Materials Science
Abstract

Despite decades of research, demonstration of all-optical detection and control of free electron spins in silicon remains elusive. Here, we directly probe the electron spin properties in bulk silicon by measuring the polarization of luminescence following circularly polarized light excitation. The experiments performed for both direct and indirect gap excitation allow not only an experimental determination of the optical selection rules in silicon for the different phononassisted transitions but they also lead to the measurement of the spin relaxation of electrons in conditions which are not accessible using transport techniques. We also measure the spin properties of free excitons in bulk silicon, a very little explored field.

Published
2024

2. Optimal Linear Signal: An Unsupervised Machine Learning Framework to Optimize PnL with Linear Signals

Author

Renucci, Pierre

Subjects
Quantitative Finance - Statistical Finance, Computer Science - Machine Learning
Abstract

This study presents an unsupervised machine learning approach for optimizing Profit and Loss (PnL) in quantitative finance. Our algorithm, akin to an unsupervised variant of linear regression, maximizes the Sharpe Ratio of PnL generated from signals constructed linearly from exogenous variables. The methodology employs a linear relationship between exogenous variables and the trading signal, with the objective of maximizing the Sharpe Ratio through parameter optimization. Empirical application on an ETF representing U.S. Treasury bonds demonstrates the model's effectiveness, supported by regularization techniques to mitigate overfitting. The study concludes with potential avenues for further development, including generalized time steps and enhanced corrective terms., Comment: The code of the model and the empiric strategy are available on my GitHub: Cnernc/OptimalLinearSignal

Published
2023

3. Kapitza-resistance-like exciton dynamics in atomically flat MoSe$_{2}$-WSe$_{2}$ lateral heterojunction

Author

Lamsaadi, Hassan, Beret, Dorian, Paradisanos, Ioannis, Renucci, Pierre, Lagarde, Delphine, Marie, Xavier, Urbaszek, Bernhard, Gan, Ziyang, George, Antony, Watanabe, Kenji, Taniguchi, Takashi, Turchanin, Andrey, Lombez, Laurent, Combe, Nicolas, Paillard, Vincent, and Poumirol, Jean-Marie

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

Being able to control the neutral excitonic flux is a mandatory step for the development of future room-temperature two-dimensional excitonic devices. Semiconducting Monolayer Transition Metal Dichalcogenides (TMD-ML) with extremely robust and mobile excitons are highly attractive in this regard. However, generating an efficient and controlled exciton transport over long distances is a very challenging task. Here we demonstrate that an atomically sharp TMD-ML lateral heterostructure (MoSe$_{2}$-WSe$_{2}$) transforms the isotropic exciton diffusion into a unidirectional excitonic flow through the junction. Using tip-enhanced photoluminescence spectroscopy (TEPL) and a modified exciton transfer model, we show a discontinuity of the exciton density distribution on each side of the interface. We introduce the concept of exciton Kapitza resistance, by analogy with the interfacial thermal resistance referred to as Kapitza resistance. By comparing different heterostructures with or without top hexagonal boron nitride (hBN) layer, we deduce that the transport properties can be controlled, over distances far greater than the junction width, by the exciton density through near-field engineering and/or laser power density. This work provides a new approach for controlling the neutral exciton flow, which is key toward the conception of excitonic devices.

Published
2023
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4. Interface engineering of charge-transfer excitons in 2D lateral heterostructures

Author

Rosati, Roberto, Paradisanos, Ioannis, Huang, Libai, Gan, Ziyang, George, Antony, Watanabe, Kenji, Taniguchi, Takashi, Lombez, Laurent, Renucci, Pierre, Turchanin, Andrey, Urbaszek, Bernhard, and Malic, Ermin

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe$_2$-WSe$_2$ heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures., Comment: 10 pagers, 4 figures

Published
2023
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5. Controlling the helicity of light by electrical magnetization switching

Author

Dainone, Pambiang Abel, Prestes, Nicholas Figueiredo, Renucci, Pierre, Bouché, Alexandre, Morassi, Martina, Devaux, Xavier, Lindemann, Markus, George, Jean-Marie, Jaffrès, Henri, Lemaitre, Aristide, Xu, Bo, Stoffel, Mathieu, Chen, Tongxin, Lombez, Laurent, Lagarde, Delphine, Cong, Guangwei, Ma, Tianyi, Pigeat, Philippe, Vergnat, Michel, Rinnert, Hervé, Marie, Xavier, Han, Xiufeng, Mangin, Stephane, Rojas-Sánchez, Juan-Carlos, Wang, Jian-Ping, Beard, Matthew C., Gerhardt, Nils C., Žutić, Igor, and Lu, Yuan

Published
2024
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6. Exciton spectroscopy and diffusion in MoSe2-WSe2 lateral heterostructures encapsulated in hexagonal boron nitride

Author

Beret, Dorian, Paradisanos, Ioannis, Gan, Ziyang, dehaghani, Emad Naja, George, Antony, Lehnert, Tibor, Biskupek, Johannes, Shree, Shivangi, Estrada-Real, Ana, Lagarde, Delphine, Poumirol, Jean-Marie, Paillard, Vincent, Watanabe, Kenji, Taniguchi, Takashi, Marie, Xavier, Kaiser, Ute, Renucci, Pierre, Lombez, Laurent, Turchanin, Andrey, and Urbaszek, Bernhard

Subjects
Condensed Matter - Materials Science
Abstract

Chemical vapor deposition (CVD) allows lateral edge epitaxy of transition metal dichalcogenide heterostructures with potential applications in optoelectronics. Critical for carrier and exciton transport is the quality of the two materials that constitute the monolayer and the nature of the lateral heterojunction. Important details of the optical properties were inaccessible in as-grown heterostructure samples due to large inhomogeneous broadening of the optical transitions. Here we perform optical spectroscopy at T = 4 K and also at 300 K to access the optical transitions in CVD grown MoSe2-WSe2 lateral heterostructures that are transferred from the growth-substrate and are encapsulated in hBN. Photoluminescence (PL), reflectance contrast and Raman spectroscopy reveal considerably narrowed optical transition linewidth similar to high quality exfoliated monolayers. In high-resolution transmission electron microscopy (HRTEM) we find near-atomically sharp junctions with a typical extent of 3nm for the covalently bonded MoSe2-WSe2. In PL imaging experiments we find effective excitonic diffusion length that are longer for WSe2 than for MoSe2 at low T=4 K, whereas at 300 K this trend is reversed., Comment: Main and supplement

Published
2022
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7. Optical detection of long electron spin transport lengths in a monolayer semiconductor

Author

Ren, Lei, Lombez, Laurent, Robert, Cedric, Beret, Dorian, Lagarde, Delphine, Urbaszek, Bernhard, Renucci, Pierre, Taniguchi, Takashi, Watanabe, Kenji, Crooker, Scott A., and Marie, Xavier

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Using a spatially-resolved optical pump-probe experiment, we measure the lateral transport of spin/valley polarized electrons over very long distances (tens of micrometers) in a single WSe2 monolayer. By locally pumping the Fermi sea of 2D electrons to a high degree of spin/valley polarization (up to 75%) using circularly-polarized light, the lateral diffusion of the electron polarization can be mapped out via the photoluminescence induced by a spatially-separated and linearly-polarized probe laser. Up to 25% spin-valley polarization is observed at pump-probe separations up to 20 microns. Characteristic spin/valley diffusion lengths of 18 +/- 3 um are revealed at low temperatures. The dependence on temperature, pump helicity, pump intensity, and electron density highlight the key roles played by spin relaxation time and pumping efficiency on polarized electron transport in monolayer semiconductors possessing spin-valley locking.

Published
2022
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8. Second harmonic generation control in twisted bilayers of transition metal dichalcogenides

Author

Paradisanos, Ioannis, Raven, Andres Manuel Saiz, Amand, Thierry, Robert, Cedric, Renucci, Pierre, Watanabe, Kenji, Taniguchi, Takashi, Gerber, Iann C., Marie, Xavier, and Urbaszek, Bernhard

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The twist angle in transition metal dichalcogenide (TMD) heterobilayers is a compelling degree of freedom that determines electron correlations and the period of lateral confinement of moir\'e excitons. Here we perform polarization-resolved second harmonic generation (SHG) spectroscopy of MoS2/WSe2 heterostructures. We demonstrate that by choosing suitable laser energies the twist angle between two monolayers can be measured directly on the assembled heterostructure. We show that the amplitude and polarization of the SHG signal from the heterostructure are determined by the twist angle between the layers and exciton resonances at the SH energy. For heterostructures with close to zero twist angle, we observe changes of exciton resonance energies and the appearance of new resonances in the linear and non-linear susceptibilities., Comment: main text and supplement

Published
2021
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9. Large perpendicular magnetic anisotropy in Ta/CoFeB/MgO on full coverage monolayer MoS2 and first principle study of its electronic structure

Author

Zhou, Ziqi, Marcon, Paul, Devaux, Xavier, Pigeat, Philippe, Bouché, Alexandre, Migot, Sylvie, Jaafar, Abdallah, Arras, Remi, Vergnat, Michel, Ren, Lei, Tornatzky, Hans, Robert, Cedric, Marie, Xavier, George, Jean-Marie, Jaffrès, Henri-Yves, Stoffel, Mathieu, Rinnert, Hervé, Wei, Zhongming, Renucci, Pierre, Calmels, Lionel, and Lu, Yuan

Subjects
Condensed Matter - Materials Science
Abstract

Perpendicularly magnetized spin injector with high Curie temperature is a prerequisite for developing spin optoelectronic devices on 2D materials working at room temperature (RT) with zero applied magnetic field. Here, we report the growth of Ta/CoFeB/MgO structures with a large perpendicular magnetic anisotropy (PMA) on full coverage monolayer (ML) MoS2. A large perpendicular interface anisotropy energy of 0.975mJ/m2 has been obtained at the CoFeB/MgO interface, comparable to that observed in magnetic tunnel junction systems. It is found that the insertion of MgO between the ferromagnetic metal (FM) and the 2D material can effectively prevent the diffusion of the FM atoms into the 2D material. Moreover, the MoS2 ML favors a MgO(001) texture and plays a critical role to establish the large PMA. First principle calculations on a similar Fe/MgO/MoS2 structure reveal that the MgO thickness can modify the MoS2 band structure, from an indirect bandgap with 7ML-MgO to a direct bandgap with 3ML-MgO. Proximity effect induced by Fe results in a splitting of 10meV in the valence band at the {\Gamma} point for the 3ML-MgO structure while it is negligible for the 7ML-MgO structure. These results pave the way to develop RT spin optoelectronic devices on 2D transition-metal dichalcogenide materials.

Published
2021

10. Author Correction: Controlling the helicity of light by electrical magnetization switching

Author

Dainone, Pambiang Abel, Prestes, Nicholas Figueiredo, Renucci, Pierre, Bouché, Alexandre, Morassi, Martina, Devaux, Xavier, Lindemann, Markus, George, Jean-Marie, Jaffrès, Henri, Lemaitre, Aristide, Xu, Bo, Stoffel, Mathieu, Chen, Tongxin, Lombez, Laurent, Lagarde, Delphine, Cong, Guangwei, Ma, Tianyi, Pigeat, Philippe, Vergnat, Michel, Rinnert, Hervé, Marie, Xavier, Han, Xiufeng, Mangin, Stephane, Rojas-Sánchez, Juan-Carlos, Wang, Jian-Ping, Beard, Matthew C., Gerhardt, Nils C., Žutić, Igor, and Lu, Yuan

Published
2024
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11. Spin-injection and spin-relaxation in p-doped InGaAs/GaAs quantum-dot spin light emitting diode at zero magnetic field

Author

Giba, Alaa E., Gao, Xue, Stoffel, Mathieu, Devaux, Xavier, Xu, Bo, Marie, Xavier, Renucci, Pierre, Jaffrès, Henri, George, Jean-Marie, Cong, Guangwei, Wang, Zhanguo, Rinnert, Hervé, and Lu, Yuan

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We report on efficient spin injection in p-doped InGaAs/GaAs quantum-dot (QD) spin light emitting diode (spin-LED) under zero applied magnetic field. A high degree of electroluminescence circular polarization (Pc) ~19% is measured in remanence up to 100K. This result is obtained thanks to the combination of a perpendicularly magnetized CoFeB/MgO spin injector allowing efficient spin injection and an appropriate p-doped InGaAs/GaAs QD layer in the active region. By analyzing the bias and temperature dependence of the electroluminescence circular polarization, we have evidenced a two-step spin relaxation process. The first step occurs when electrons tunnel through the MgO barrier and travel across the GaAs depletion layer. The spin relaxation is dominated by the Dyakonov-Perel mechanism related to the kinetic energy of electrons, which is characterized by a bias dependent Pc. The second step occurs when electrons are captured into QDs prior to their radiative recombination with holes. The temperature dependence of Pc reflects the temperature induced modification of the QDs doping, together with the variation of the ratio between the charge carrier lifetime and the spin relaxation time inside the QDs. The understanding of these spin relaxation mechanisms is essential to improve the performance of spin LED for future spin optoelectronic applications at room temperature under zero applied magnetic field., Comment: 24 pages, 5 figures

Published
2020

12. Electrical Detection of Light Helicity using a Quantum Dots based Hybrid Device at Zero Magnetic Field

Author

Cadiz, Fabian, Lagarde, Delphine, Tao, Bingshan, Frougier, Julien, Xu, Bo, Jaffrès, Henri, Wang, Zhanguo, Han, Xiufeng, George, Jean Marie, Carrere, Hélène, Balocchi, Andrea, Amand, Thierry, Marie, Xavier, Urbaszek, Bernhard, Lu, Yuan, and Renucci, Pierre

Subjects
Physics - Applied Physics
Abstract

Photon helicity-dependent photocurrent is measured at zero magnetic field on a device based on an ensemble of InGaAs/GaAs quantum dots that are embedded into a GaAs-based p-i-n diode. Our main goal is to take advantage of the long electron spin relaxation time expected in these nano-objects. In these experiments, no external magnetic field is required thanks to the use of an ultrathin magnetic CoFeB/MgO electrode, presenting perpendicular magnetic anisotropy (PMA). We observe a clear asymmetry of the photocurrent measured under respective right and left polarized light that follows the hysteresis of the magnetic layer. The amplitude of this asymmetry at zero magnetic field decreases with increasing temperatures and can be controlled with the bias. Polarization-resolved photoluminescence is detected in parallel while the device is operated as a photodetector. This demonstrates the multifunctional capabilities of the device and gives valuable insights into the spin relaxation of the electrons in the quantum dots.

Published
2020
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13. Interlayer excitons in bilayer MoS2 with strong oscillator strength up to room temperature

Author

Gerber, Iann C., Courtade, Emmanuel, Shree, Shivangi, Robert, Cedric, Taniguchi, Takashi, Watanabe, Kenji, Balocchi, Andrea, Renucci, Pierre, Lagarde, Delphine, Marie, Xavier, and Urbaszek, Bernhard

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Coulomb bound electron-hole pairs, excitons, govern the optical properties of semi-conducting transition metal dichalcogenides like MoS$_2$ and WSe$_2$. We study optical transitions at the K-point for 2H homobilayer MoS$_2$ in Density Functional Theory (DFT) including excitonic effects and compare with reflectivity measurements in high quality samples encapsulated in hexagonal BN. In both calculated and measured spectra we find a strong interlayer exciton transition in energy between A and B intralayer excitons, observable for T$=4 -300$ K, whereas no such transition is observed for the monolayer in the same structure in this energy range. The interlayer excitons consist of an electron localized in one layer and a hole state delocalized over the bilayer, which results in the unusual combination of high oscillator strength and a static dipole moment. We also find signatures of interlayer excitons involving the second highest valence band (B) and compare absorption calculations for different bilayer stackings. For homotrilayer MoS$_2$ we also observe interlayer excitons and an energy splitting between different intralayer A-excitons originating from the middle and outer layers, respectively., Comment: 9 pages, 6 figures

Published
2018
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14. Electronic structure of the Co(0001)/MoS2 interface, and its possible use for electrical spin injection in a single MoS2 layer

Author

Garandel, Thomas, Arras, Rémi, Marie, Xavier, Renucci, Pierre, and Calmels, Lionel

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Applied Physics
Abstract

The ability to perform efficient electrical spin injection from ferromagnetic metals into two-dimensional semiconductor crystals based on transition metal dichalcogenide monolayers is a prerequisite for spintronic and valleytronic devices using these materials. Here, the hcp Co(0001)/MoS2 interface electronic structure is investigated by first-principles calculations based on the density functional theory. In the lowest energy configuration of the hybrid system after optimization of the atomic coordinates, we show that interface sulfur atoms are covalently bound to one, two or three cobalt atoms. A decrease of the Co atom spin magnetic moment is observed at the interface, together with a small magnetization of S atoms. Mo atoms also hold small magnetic moments which can take positive as well as negative values. The charge transfers due to covalent bonding between S and Co atoms at the interface have been calculated for majority and minority spin electrons and the connections between these interface charge transfers and the induced magnetic properties of the MoS2 layer are discussed. Band structure and density of states of the hybrid system are calculated for minority and majority spin electrons, taking into account spin-orbit coupling. We demonstrate that MoS2 bound to the Co contact becomes metallic due to hybridization between Co d and S p orbitals. For this metallic phase of MoS2, a spin polarization at the Fermi level of 16 % in absolute value is calculated, that could allow spin injection into the semiconducting MoS2 monolayer channel. Finally, the symmetry of the majority and minority spin electron wave functions at the Fermi level in the Co-bound metallic phase of MoS2 and the orientation of the border between the metallic and semiconducting phases of MoS2 are investigated, and their impact on spin injection into the MoS2 channel is discussed.

Published
2018

15. Ultra-low power threshold for laser induced changes in optical properties of 2D Molybdenum dichalcogenides

Author

Cadiz, Fabian, Robert, Cedric, Wang, Gang, Kong, Wilson, Fan, Xi, Blei, Mark, Lagarde, Delphine, Gay, Maxime, Manca, Marco, Taniguchi, Takashi, Watanabe, Kenji, Amand, Thierry, Marie, Xavier, Renucci, Pierre, Tongay, Sefaattin, and Urbaszek, Bernhard

Subjects
Condensed Matter - Materials Science, Physics - Optics
Abstract

The optical response of traditional semiconductors depends on the laser excitation power used in experiments. For two-dimensional (2D) semiconductors, laser excitation effects are anticipated to be vastly different due to complexity added by their ultimate thinness, high surface to volume ratio, and laser-membrane interaction effects. We show in this article that under laser excitation the optical properties of 2D materials undergo irreversible changes. Most surprisingly these effects take place even at low steady state excitation, which is commonly thought to be non-intrusive. In low temperature photoluminescence (PL) we show for monolayer (ML) MoSe2 samples grown by different techniques that laser treatment increases significantly the trion (i.e. charged exciton) contribution to the emission compared to the neutral exciton emission. Comparison between samples exfoliated onto different substrates shows that laser induced doping is more efficient for ML MoSe2 on SiO2/Si compared to h-BN and gold. For ML MoS2 we show that exposure to laser radiation with an average power in the $\mu$W/$\mu$m$^2$ range does not just increase the trion-to-exciton PL emission ratio, but may result in the irreversible disappearance of the neutral exciton PL emission and a shift of the main PL peak to lower energy., Comment: 16 pages, 5 figures

Published
2016
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16. Well separated trion and neutral excitons on superacid treated MoS2 monolayers

Author

Cadiz, Fabian, Tricard, Simon, Gay, Maxime, Lagarde, Delphine, Wang, Gang, Robert, Cedric, Renucci, Pierre, Urbaszek, Bernhard, and Marie, Xavier

Subjects
Condensed Matter - Materials Science
Abstract

Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS2 MLs the photoluminescence (PL) spectra even at low temperature consists typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here we show that in superacid treated MoS2 MLs the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T=4 K, with linewidth for the neutral exciton of 15 meV, but with similar intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emission. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.

Published
2016
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18. Controlling the polarization eigenstate of a quantum dot exciton with light

Author

Belhadj, Thomas, Simon, Claire-Marie, Amand, Thierry, Renucci, Pierre, Krebs, Olivier, Lemaitre, Aristide, Voisin, Paul, Marie, Xavier, and Urbaszek, Bernhard

Subjects
Physics - Optics
Abstract

We demonstrate optical control of the polarization eigenstates of a neutral quantum dot exciton without any external fields. By varying the excitation power of a circularly polarized laser in micro-photoluminescence experiments on individual InGaAs quantum dots we control the magnitude and direction of an effective internal magnetic field created via optical pumping of nuclear spins. The adjustable nuclear magnetic field allows us to tune the linear and circular polarization degree of the neutral exciton emission. The quantum dot can thus act as a tunable light polarization converter., Comment: 5 pages, 3 figures

Published
2009
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19. Kapitza-resistance-like exciton dynamics in atomically flat MoSe2-WSe2 lateral heterojunction

Author

Lamsaadi, Hassan, primary, Beret, Dorian, additional, Paradisanos, Ioannis, additional, Renucci, Pierre, additional, Lagarde, Delphine, additional, Marie, Xavier, additional, Urbaszek, Bernhard, additional, Gan, Ziyang, additional, George, Antony, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Turchanin, Andrey, additional, Lombez, Laurent, additional, Combe, Nicolas, additional, Paillard, Vincent, additional, and Poumirol, Jean-Marie, additional

Published
2023
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22. Interface engineering of charge-transfer excitons in 2D lateral heterostructures

Author

Rosati, Roberto, primary, Paradisanos, Ioannis, additional, Huang, Libai, additional, Gan, Ziyang, additional, George, Antony, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Lombez, Laurent, additional, Renucci, Pierre, additional, Turchanin, Andrey, additional, Urbaszek, Bernhard, additional, and Malic, Ermin, additional

Published
2023
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23. LA SCIENCE OUVERTE : STRATÉGIE DE L’INSA TOULOUSE 2021-2026

Author

Dietrich, Nicolas, Moulis, Anais, Cadiou, Maelle, Buffière, Aubin, Guillard, Laetitia, Carla, Ana, Ohms, Claire, Renucci, Pierre, Monteil, Thierry, Liné, Alain, Chassot, Christophe, Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT), Toulouse Biotechnology Institute (TBI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and INSA TOULOUSE

Subjects
Science Ouverte, [SDE.ES]Environmental Sciences/Environmental and Society
Abstract

Ce texte a été préparé par la commission pour la science ouverte, composée de membres des conseils d’administration et scientifique de l’INSA Toulouse, des équipes du Service Commun de Documentation (BIB’INSA) et de la direction de la recherche, entre janvier et mai 2022. Il fait suite à la promulgation de la loi pour une république numérique (2016), la publication de la recommandation de l’UNESCO sur la Science ouverte et au second Plan national pour la Science Ouverte lancé en 2021 par le Ministère de l’Enseignement Supérieur, de la Recherche et de l’Innovation (MESRI).Résultat d’un travail collaboratif, ce document stratégique a pour ambition de préciser la politique de l’INSA Toulouse en matière de Science Ouverte à travers 7 piliers et d’affirmer, pour chacun de ceux-ci, les objectifs et les engagements de l’établissement à court, moyen et long termes. Il accompagne le plan pluriannuel d’actions qui permettra très concrètement d’appuyer les avancées en faveur de la science ouverte et d’en suivre et mesurer les effets.

Published
2022

24. Exciton spectroscopy and unidirectional transport in MoSe2-WSe2 lateral heterostructures encapsulated in hexagonal boron nitride

Author

Beret, Dorian, primary, Paradisanos, Ioannis, additional, Lamsaadi, Hassan, additional, Gan, Ziyang, additional, Najafidehaghani, Emad, additional, George, Antony, additional, Lehnert, Tibor, additional, Biskupek, Johannes, additional, Kaiser, Ute, additional, Shree, Shivangi, additional, Estrada-Real, Ana, additional, Lagarde, Delphine, additional, Marie, Xavier, additional, Renucci, Pierre, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Weber, Sébastien, additional, Paillard, Vincent, additional, Lombez, Laurent, additional, Poumirol, Jean-Marie, additional, Turchanin, Andrey, additional, and Urbaszek, Bernhard, additional

Published
2022
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25. Kapitza-resistance-like exciton dynamics in atomically flat MoSe2-WSe2 lateral heterojunction.

Author

Lamsaadi, Hassan, Beret, Dorian, Paradisanos, Ioannis, Renucci, Pierre, Lagarde, Delphine, Marie, Xavier, Urbaszek, Bernhard, Gan, Ziyang, George, Antony, Watanabe, Kenji, Taniguchi, Takashi, Turchanin, Andrey, Lombez, Laurent, Combe, Nicolas, Paillard, Vincent, and Poumirol, Jean-Marie

Subjects
INTERFACIAL resistance, HETEROJUNCTIONS, EXCITON theory, BORON nitride, TRANSITION metals, POWER density
Abstract

Being able to control the neutral excitonic flux is a mandatory step for the development of future room-temperature two-dimensional excitonic devices. Semiconducting Monolayer Transition Metal Dichalcogenides (TMD-ML) with extremely robust and mobile excitons are highly attractive in this regard. However, generating an efficient and controlled exciton transport over long distances is a very challenging task. Here we demonstrate that an atomically sharp TMD-ML lateral heterostructure (MoSe2-WSe2) transforms the isotropic exciton diffusion into a unidirectional excitonic flow through the junction. Using tip-enhanced photoluminescence spectroscopy (TEPL) and a modified exciton transfer model, we show a discontinuity of the exciton density distribution on each side of the interface. We introduce the concept of exciton Kapitza resistance, by analogy with the interfacial thermal resistance referred to as Kapitza resistance. By comparing different heterostructures with or without top hexagonal boron nitride (hBN) layer, we deduce that the transport properties can be controlled, over distances far greater than the junction width, by the exciton density through near-field engineering and/or laser power density. This work provides a new approach for controlling the neutral exciton flow, which is key toward the conception of excitonic devices. Here, the authors use tip-enhanced photoluminescence spectroscopy to show a discontinuity of the exciton density distribution on each side of the interface of a MoSe2/WSe2 lateral heterostructure. They introduce the concept of 'exciton Kapitza resistance' by analogy with the interfacial thermal resistance known as 'Kapitza resistance'. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Exciton spectroscopy and unidirectional transport in MoSe2-WSe2 lateral heterostructures encapsulated in hexagonal boron nitride.

Author

Beret, Dorian, Paradisanos, Ioannis, Lamsaadi, Hassan, Gan, Ziyang, Najafidehaghani, Emad, George, Antony, Lehnert, Tibor, Biskupek, Johannes, Kaiser, Ute, Shree, Shivangi, Estrada-Real, Ana, Lagarde, Delphine, Marie, Xavier, Renucci, Pierre, Watanabe, Kenji, Taniguchi, Takashi, Weber, Sébastien, Paillard, Vincent, Lombez, Laurent, and Poumirol, Jean-Marie

Subjects
BORON nitride, HETEROSTRUCTURES, SCANNING transmission electron microscopy, OPTICAL spectroscopy, CHEMICAL vapor deposition, RAMAN spectroscopy, SPECTRAL line broadening, NONLINEAR optical spectroscopy
Abstract

Chemical vapor deposition (CVD) allows lateral edge epitaxy of transition metal dichalcogenide heterostructures. Critical for carrier and exciton transport is the material quality and the nature of the lateral heterojunction. Important details of the optical properties were inaccessible in as-grown heterostructure samples due to large inhomogeneous broadening of the optical transitions. Here we perform optical spectroscopy of CVD grown MoSe2-WSe2 lateral heterostructures, encapsulated in hBN. Photoluminescence (PL), reflectance contrast and Raman spectroscopy reveal optical transition linewidths similar to high quality exfoliated monolayers, while PL imaging experiments uncover the effective excitonic diffusion length of both materials. The typical extent of the covalently bonded MoSe2-WSe2 heterojunctions is 3 nm measured by scanning transmission electron microscopy (STEM). Tip-enhanced, sub-wavelength optical spectroscopy mapping shows the high quality of the heterojunction which acts as an excitonic diode resulting in unidirectional exciton transfer from WSe2 to MoSe2. [ABSTRACT FROM AUTHOR]

Published
2022
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28. Large Perpendicular Magnetic Anisotropy in Ta/CoFeB/MgO on Full-Coverage Monolayer MoS2 and First-Principles Study of Its Electronic Structure

Author

Zhou, Ziqi, primary, Marcon, Paul, additional, Devaux, Xavier, additional, Pigeat, Philippe, additional, Bouché, Alexandre, additional, Migot, Sylvie, additional, Jaafar, Abdallah, additional, Arras, Rémi, additional, Vergnat, Michel, additional, Ren, Lei, additional, Tornatzky, Hans, additional, Robert, Cedric, additional, Marie, Xavier, additional, George, Jean-Marie, additional, Jaffrès, Henri-Yves, additional, Stoffel, Mathieu, additional, Rinnert, Hervé, additional, Wei, Zhongming, additional, Renucci, Pierre, additional, Calmels, Lionel, additional, and Lu, Yuan, additional

Published
2021
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29. Spin Injection and Relaxation in p -Doped ( In , Ga ) As / Ga As Quantum-Dot Spin Light-Emitting Diodes at Zero Magnetic Field

Author

Giba, Alaa, Gao, Xue, Stoffel, Mathieu, Devaux, Xavier, Xu, Bo, Marie, Xavier, Renucci, Pierre, Jaffrès, Henri, George, Jean-Marie, Cong, Guangwei, Wang, Zhanguo, Rinnert, Hervé, Lu, Yuan, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences (KLSMS), Institute of semiconductors [Chinese Academy of Sciences - Beijing] (IOS), Chinese Academy of Science (CAS)-Chinese Academy of Science (CAS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), 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)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), National Institute of Advanced Industrial Science and Technology (AIST), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Key Laboratory of Semiconductor Materials Science (LSMS), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), THALES [France]-Centre National de la Recherche Scientifique (CNRS), ANR-18-CE24-0017,FEOrgSpin,Contrôle ferroélectrique de la spinterface organique/ferromagnétique(2018), ANR-19-CE24-0005,SIZMO2D,Injection/detection de spin à champ magnétique nul dans des dispositifs SpinOptroniques à base de Semiconducteurs 2D(2019), Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Condensed Matter::Materials Science, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Condensed Matter::Strongly Correlated Electrons, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; We report on efficient spin injection in p-doped (In, Ga)As/GaAs quantum-dot (QD) spin light-emitting diodes (spin LEDs) under zero applied magnetic field. A high degree of electroluminescence circular polarization (P c) ∼19% is measured in remanence up to 100 K. This result is obtained thanks to the combination of a perpendicularly magnetized Co-Fe-B/MgO spin injector allowing efficient spin injection and an appropriate p-doped (In, Ga)As/GaAs QD layer in the active region. By analyzing the bias and temperature dependence of the electroluminescence circular polarization, we evidence a two-step spin-relaxation process. The first step occurs when electrons tunnel through the MgO barrier and travel across the GaAs depletion layer. The spin relaxation is dominated by the Dyakonov-Perel mechanism related to the kinetic energy of electrons, which is characterized by a bias-dependent P c. The second step occurs when electrons are captured into QDs prior to their radiative recombination with holes. The temperature dependence of P c reflects the temperature-induced modification of the QD doping, together with the variation of the ratio between the charge-carrier lifetime and the spin-relaxation time inside the QDs. The understanding of these spin-relaxation mechanisms is essential to improve the performance of spin LEDs for future spin optoelectronic applications at room temperature under zero applied magnetic field.

Published
2020
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31. Spin Injection and Relaxation in p -Doped (In,Ga)As/GaAs Quantum-Dot Spin Light-Emitting Diodes at Zero Magnetic Field

Author

Giba, Alaa E., primary, Gao, Xue, additional, Stoffel, Mathieu, additional, Devaux, Xavier, additional, Xu, Bo, additional, Marie, Xavier, additional, Renucci, Pierre, additional, Jaffrès, Henri, additional, George, Jean-Marie, additional, Cong, Guangwei, additional, Wang, Zhanguo, additional, Rinnert, Hervé, additional, and Lu, Yuan, additional

Published
2020
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32. Comparison of spin photocurrent in devices based on in-plane or out-of-plane magnetized CoFeB spin detectors

Author

Renucci, Pierre, primary, Xue, Xiaodie, additional, Zhu, Laipan, additional, Huang, Wei, additional, Liu, Yu, additional, Zhang, Yang, additional, Zeng, Xiaolin, additional, Wu, Jing, additional, Xu, Bo, additional, Wang, Zhanguo, additional, Chen, Yonghai, additional, Zhang, Weifeng, additional, Marie, Xavier, additional, and Lu, Yuan, additional

Published
2020
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35. Co - Fe - B / Mg O / Ge Spin Photodiode Operating at Telecommunication Wavelength with Zero Applied Magnetic Field

Author

Djeffal, Abdelhak, Cadiz, Fabian, Stoffel, Mathieu, Lagarde, Delphine, Gao, Xue, Jaffrès, Henri, Devaux, Xavier, Migot, Sylvie, Marie, Xavier, Rinnert, Hervé, Mangin, Stéphane, George, Jean-Marie, Renucci, Pierre, Lu, Yuan, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), 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)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), IMPACT N4S, ANR-15-IDEX-0004,LUE,Isite LUE(2015), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UPS), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), 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 (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thalès (UMP CNRS/THALES), Institut National des Sciences Appliquées (INSA), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and THALES [France]-Centre National de la Recherche Scientifique (CNRS)

Subjects
Spin polarization, [PHYS]Physics [physics], [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Spin filtering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM]Chemical Sciences, Optical generation of spin carriers, Polarization of light, Spintronics, [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, Optoelectronics, Magnetic anisotropy, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; We report on the growth and study of Co-Fe-B/MgO/Ge(001) spin photodiode by using a combination of both molecular beam epitaxy (MBE) and sputtering methods. An epitaxial growth of MgO on Ge in MBE is achieved by the deposition of MgO at room temperature (RT) followed by a post-growth anneal-ing at 300 °C. The spin detector, which consists of 1.1-nm ultrathin Co-Fe-B layer capped with 5-nm Ta is subsequently grown by sputtering at RT. After a post-growth annealing of the whole structure at 250 °C, we obtain clear evidence of a strong perpendicular magnetic anisotropy in the temperature range 10-300 K. Co-Fe-B/MgO/Ge(001) heterojunctions are then processed into spin photodiodes demonstrating at zero magnetic field a photocurrent helicity asymmetry of about 0.9% at 9 K and 0.1% at RT at the telecommunication wavelength of 1310 nm. The demonstration of a spin photodiode working at a telecommunication wavelength with zero applied magnetic field is of great interest for future applications of the optical transport of spin information.

Published
2018
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36. Spectrally narrow exciton luminescence from monolayer MoS 2 and MoSe 2 exfoliated onto epitaxially grown hexagonal BN

Author

Courtade, Emmanuel, Han, B., Nakhaie, S., Robert, Cédric, Marie, Xavier, Renucci, Pierre, Taniguchi, T., Watanabe, K., Geelhaar, L., Lopes, J., Urbaszek, B., Laboratoire de physique et chimie des nano-objets ( LPCNO ), 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 ( UPS ), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique ( CNRS ), Paul-Drude-Institut für Festkörperelektronik, National Institute for Materials Science ( NIMS ), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), 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)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Paul-Drude-Institut für Festkörperelektronik (PDI), National Institute for Materials Science (NIMS), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Microscopy, [ PHYS.PHYS.PHYS-OPTICS ] Physics [physics]/Physics [physics]/Optics [physics.optics], Semiconductors, Photoluminescence spectroscopy, Dielectric properties, Transition metal chalcogenides, [CHIM]Chemical Sciences, Heterostructures, Excitons, [ CHIM ] Chemical Sciences, Epitaxy
Abstract

International audience; The strong light-matter interaction in transition metal dichalcogenide (TMD) monolayers (MLs) is governed by robust excitons. Important progress has been made to control the dielectric environment surrounding the MLs, especially through hexagonal boron nitride (hBN) encapsulation which drastically reduces the inhomogeneous contribution to the exciton linewidth. Most studies use exfoliated hBN from high quality flakes grown under high pressure. In this work, we show that hBN grown by molecular beam epitaxy (MBE) over a large surface area substrate has a similarly positive impact on the optical emission from TMD MLs. We deposit MoS2 and MoSe2 MLs on ultrathin hBN films (few MLs thick) grown on Ni/MgO(111) by MBE. Then, we cover them with exfoliated hBN to finally obtain an encapsulated sample: exfoliated hBN/TMD ML/MBE hBN. We observe improved optical quality of our samples compared to TMD MLs exfoliated directly on SiO2 substrates. Our results suggest that hBN grown by MBE could be used as a flat and charge-free substrate for fabricating TMD-based heterostructures on a larger scale.

Published
2018

37. Comparison of spin photocurrent in devices based on in-plane or out-of-plane magnetized CoFeB spin detectors

Author

Xue, Xiaodi, primary, Zhu, Laipan, additional, Huang, Wei, additional, Marie, Xavier, additional, Renucci, Pierre, additional, Liu, Yu, additional, Zhang, Yang, additional, Zeng, Xiaolin, additional, Wu, Jing, additional, Xu, Bo, additional, Wang, Zhanguo, additional, Chen, Yonghai, additional, Zhang, Weifeng, additional, and Lu, Yuan, additional

Published
2019
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38. Large Perpendicular Magnetic Anisotropy in Ta/CoFeB/MgO on Full-Coverage Monolayer MoS2 and First-Principles Study of Its Electronic Structure.

Author

Zhou, Ziqi, Marcon, Paul, Devaux, Xavier, Pigeat, Philippe, Bouché, Alexandre, Migot, Sylvie, Jaafar, Abdallah, Arras, Rémi, Vergnat, Michel, Ren, Lei, Tornatzky, Hans, Robert, Cedric, Marie, Xavier, George, Jean-Marie, Jaffrès, Henri-Yves, Stoffel, Mathieu, Rinnert, Hervé, Wei, Zhongming, Renucci, Pierre, and Calmels, Lionel

Published
2021
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39. Angular Dependence of the Spin Photocurrent in a Co − Fe − B / MgO / n − i − p GaAs Quantum-Well Structure

Author

Zhu, Laipan, Huang, Wei, Renucci, Pierre, Marie, Xavier, Liu, Yu, Li, Yu, Wu, Qing, Zhang, Yang, Xu, Bo, Lu, Yu, Chen, Yonghai, Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences (KLSMS), Institute of semiconductors [Chinese Academy of Sciences - Beijing] (IOS), Chinese Academy of Science (CAS)-Chinese Academy of Science (CAS), Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences [Beijing] (CAS), College of Materials Science and Optoelectronic Technology, University of Chinese Academy Sciences, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), IMPACT N4S, ANR-15-IDEX-0004,LUE,Isite LUE(2015), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Key Laboratory of Semiconductor Materials Science (LSMS), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), 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), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Spin polarization, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], III-V semiconductors, Quantum wells, Photoconductivity, Spin current, [CHIM]Chemical Sciences, Spintronics, Optoelectronics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Diodes
Abstract

International audience; We evidence at room temperature the detection of photogenerated spin currents by using a magnetic electrode without the need of an external magnetic field. The device is based on a semiconductor (Al,Ga)As/GaAs quantum well embedded in a p−i−n junction. The spin filtering is performed owing to a Co−Fe−B/MgO electrode with in-plane magnetization. We observe a helicity-dependent photocurrent when the device is excited under oblique incidence with circularly polarized light. The helicity-dependent photocurrent is explored as a function of the incident and azimuth angles of the incoming light wave vector with respect to the magnetization direction of the magnetic electrode. The results are interpreted as a consequence of the photogenerated average electron spin under oblique incidence in a quantum well governed by optical selection rules involving electron-heavy-hole and electron-light-hole transitions. A systematic study of the helicity asymmetry as a function of the photon energy and applied bias is performed. It demonstrates that this asymmetry is at its maximum close to the GaAs quantum well and (Al,Ga)As bulk optical transitions. The asymmetry can be controlled by an external bias on the structure. Finally, we show that this asymmetry decreases when the temperature increases.

Published
2017
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40. Electronic structure of the Co(0001)/MoS2 interface, and its possible use for electrical spin injection in a single MoS2 layer

Author

Garandel, Thomas, Arras, Rémi, Marie, Xavier, Renucci, Pierre, Calmels, Lionel, Institut National des Sciences Appliquées (INSA), Matériaux et dispositifs pour l'Electronique et le Magnétisme (CEMES-MEM), Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), ANR-11-IDEX-0002-02/10-LABX-0037,NEXT,Nano, EXtreme Measurements & Theory(2011), 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)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-11-IDEX-0002,UNITI,Université Fédérale de Toulouse(2011), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-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), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Mesoscale and Nanoscale Physics (cond-mat.mes-hall), [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons, Physics - Applied Physics, Applied Physics (physics.app-ph)
Abstract

International audience; The ability to perform efficient electrical spin injection from ferromagnetic metals into two-dimensional semiconductor crystals based on transition metal dichalcogenide monolayers is a prerequisite for spintronic and valleytronic devices using these materials. Here, the hcp Co(0001)/MoS2 interface electronic structure is investigated by first-principles calculations based on the density functional theory. In the lowest energy configuration of the hybrid system after optimization of the atomic coordinates, we show that interface sulfur atoms are covalently bound to one, two or three cobalt atoms. A decrease of the Co atom spin magnetic moment is observed at the interface, together with a small magnetization of S atoms. Mo atoms also hold small magnetic moments which can take positive as well as negative values. The charge transfers due to covalent bonding between S and Co atoms at the interface have been calculated for majority and minority spin electrons and the connections between these interface charge transfers and the induced magnetic properties of the MoS2 layer are discussed. Band structure and density of states of the hybrid system are calculated for minority and majority spin electrons, taking into account spin-orbit coupling. We demonstrate that MoS2 bound to the Co contact becomes metallic due to hybridization between Co d and S p orbitals. For this metallic phase of MoS2, a spin polarization at the Fermi level of 16 % in absolute value is calculated, that could allow spin injection into the semiconducting MoS2 monolayer channel. Finally, the symmetry of the majority and minority spin electron wave functions at the Fermi level in the Co-bound metallic phase of MoS2 and the orientation of the border between the metallic and semiconducting phases of MoS2 are investigated, and their impact on spin injection into the MoS2 channel is discussed.

Published
2017
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41. Electronic structure of the Co ( 0001 ) / Mo S 2 interface and its possible use for electrical spin injection in a single Mo S 2 layer

Author

Garandel, T., Arras, Rémi, Marie, Xavier, Renucci, Pierre, Calmels, Lionel, Centre d'élaboration de matériaux et d'études structurales ( CEMES ), 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 ( UPS ), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de physique et chimie des nano-objets ( LPCNO ), Laboratoire de physique et chimie des nano-objets (LPCNO), 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 (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Matériaux et dispositifs pour l'Electronique et le Magnétisme (CEMES-MEM), Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées

Subjects
Spin polarization, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Electronic structure, Ferromagnetism, [CHIM]Chemical Sciences, Condensed Matter::Strongly Correlated Electrons, Density of states, Spintronics, Spin-orbit coupling, [ CHIM ] Chemical Sciences
Abstract

International audience; The ability to perform efficient electrical spin injection from ferromagnetic metals into two-dimensional semiconductor crystals based on transition metal dichalcogenide monolayers is a prerequisite for spintronic and valleytronic devices using these materials. Here, the hexagonal close-packed (hcp) Co(0001)/MoS2 interface electronic structure is investigated by first-principles calculations based on the density functional theory. In the lowest energy configuration of the hybrid system after optimization of the atomic coordinates, we show that interface sulfur atoms are covalently bound to one, two, or three cobalt atoms. A decrease of the Co atom spin magnetic moment is observed at the interface, together with a small magnetization of S atoms. Mo atoms also hold small magnetic moments, which can take positive as well as negative values. The charge transfers due to covalent bonding between S and Co atoms at the interface have been calculated for majority and minority spin electrons, and the connections between these interface charge transfers and the induced magnetic properties of the MoS2 layer are discussed. Band structure and density of states of the hybrid system are calculated for minority and majority spin electrons, taking into account spin-orbit coupling. We demonstrate that MoS2 bound to the Co contact becomes metallic due to hybridization between Co d and S p orbitals. For this metallic phase of MoS2, a spin polarization at the Fermi level of 16% in absolute value is calculated, which could allow spin injection into the semiconducting MoS2 monolayer channel. Finally, the symmetry of the majority and minority spin electron wave functions at the Fermi level in the Co-bound metallic phase of MoS2 and the orientation of the border between the metallic and semiconducting phases of MoS2 are investigated, and their impact on spin injection into the MoS2 channel is discussed.

Published
2017

43. Co - Fe - B/MgO/Ge Spin Photodiode Operating at Telecommunication Wavelength with Zero Applied Magnetic Field

Author

Djeffal, Abdelhak, primary, Cadiz, Fabian, additional, Stoffel, Mathieu, additional, Lagarde, Delphine, additional, Gao, Xue, additional, Jaffrès, Henri, additional, Devaux, Xavier, additional, Migot, Sylvie, additional, Marie, Xavier, additional, Rinnert, Hervé, additional, Mangin, Stéphane, additional, George, Jean-Marie, additional, Renucci, Pierre, additional, and Lu, Yuan, additional

Published
2018
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45. Electrical Initialization of Electron and Nuclear Spins in a Single Quantum Dot at Zero Magnetic Field

Author

Cadiz, Fabian, primary, Djeffal, Abdelhak, additional, Lagarde, Delphine, additional, Balocchi, Andrea, additional, Tao, Bingshan, additional, Xu, Bo, additional, Liang, Shiheng, additional, Stoffel, Mathieu, additional, Devaux, Xavier, additional, Jaffres, Henri, additional, George, Jean-Marie, additional, Hehn, Michel, additional, Mangin, Stephane, additional, Carrere, Helene, additional, Marie, Xavier, additional, Amand, Thierry, additional, Han, Xiufeng, additional, Wang, Zhanguo, additional, Urbaszek, Bernhard, additional, Lu, Yuan, additional, and Renucci, Pierre, additional

Published
2018
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47. Bias Dependence of the Electrical Spin Injection into GaAs from Co-Fe-B/MgO Injectors with Different MgO Growth Processes

Author

Barate, Philippe, Liang, S. H., Zhang, Tiantian, Frougier, J., Xu, B., Schieffer, Philippe, Vidal, M., Jaffres, H., Lépine, B., Tricot, Sylvain, Cadiz, Fabian, Garandel, Thomas, George, J., Amand, Thierry, Devaux, X., Hehn, M., Mangin, S., Tao, B., Han, X, Wang, Z. G., Marie, Xavier, Lu, Y., Renucci, Pierre, Laboratoire de physique et chimie des nano-objets (LPCNO), 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 (UPS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut Jean Lamour (IJL), Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL), Unité mixte de physique CNRS/Thalès (UMP CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11), Chinese Academy of Sciences [Beijing] (CAS), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), THALES, Institut National des Sciences Appliquées (INSA), Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences (KLSMS), Institute of Semiconductors, Chinese Academy of Sciences (IOS), French National Research Agency (ANR)-National Natural Science Foundation of China (NSFC) SISTER project [ANR-11-IS10-0001, NNSFC 61161130527], ENSEMBLE [ANR-14-0028-01, NNSFC 61411136001], French ANR research project INSPIRE [ANR-10-BLAN-1014], NEXT [ANR-10-LABX-0037], FEDER (EU), ANR, Region Lorraine, Grand Nancy, IMPACT N4S, ANR-15-IDEX-04-LUE,LUE,Lorraine Université d'Excellence(2016), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Chinese Academy of Sciences [Changchun Branch] (CAS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Key Laboratory of Semiconductor Materials Science (LSMS), Institute of semiconductors [Chinese Academy of Sciences - Beijing] (IOS), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), ANR-15-IDEX-0004,LUE,Isite LUE(2015), ANR-10-BLAN-1014,INSPIRE,Injection de Spin pour l'émission de lumière polarisée(2010), ANR-11-LABX-0037,CALSIMLAB,LABEX pour la modélisation et la simulation scientifiques en recherche(2011), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Bejing national laboratory of condensed matter Physics, Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-THALES, Chinese Academy of Science (CAS)-Chinese Academy of Science (CAS), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Junctions, [PHYS]Physics [physics], VCSELs, Spin filtering, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], III-V semiconductors, LEDs, Electrical spin injection Electroluminescence, Applications of soft matter, Spintronics, [SPI.TRON]Engineering Sciences [physics]/Electronics, Magnetic tunnel junctions, Condensed Matter::Materials Science, Tunnel junctions, [CHIM]Chemical Sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS
Abstract

International audience; We investigate the influence of the MgO growth process on the bias dependence of the electrical spin injection from a Co−Fe−B/MgO spin injector into a GaAs-based light-emitting diode (spin LED). With this aim, textured MgO tunnel barriers are fabricated either by sputtering or molecular-beam-epitaxy (MBE) methods. For the given growth parameters used for the two techniques, we observe that the circular polarization of the electroluminescence emitted by spin LEDs is rather stable as a function of the injected current or applied bias for the samples with sputtered tunnel barriers, whereas the corresponding circular polarization decreases abruptly for tunnel barriers grown by MBE. We attribute these different behaviors to the different kinetic energies of the injected carriers linked to differing amplitudes of the parasitic hole current flowing from GaAs to Co-Fe-B in both cases.

Published
2017
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48. Excitonic Linewidth Approaching the Homogeneous Limit in MoS 2 -Based van der Waals Heterostructures

Author

Cadiz, Fabian, Courtade, Emmanuel, Robert, Cédric, Wang, Gang, Shen, Y., Cai, H., Taniguchi, T., Watanabe, K., Lagarde, David, Carrère, Hélène, Manca, Marco, Amand, Thierry, Renucci, Pierre, Tongay, S., Marie, Xavier, Urbaszek, B., Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), ASU - School for Engineering of Matter, Transport and Energy, Arizona State University [Tempe] (ASU), National Institute for Materials Science (NIMS), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Luminescence, Semiconductors, Valleytronics, Van der Waals heterostructures, Transition-metal dichalcogenide, Optoelectronics
Abstract

International audience; The strong light-matter interaction and the valley selective optical selection rules make monolayer (ML) MoS2 an exciting 2D material for fundamental physics and optoelectronics applications. But, so far, optical transition linewidths even at low temperature are typically as large as a few tens of meV and contain homogeneous and inhomogeneous contributions. This prevented in-depth studies, in contrast to the better-characterized ML materials MoSe2 and WSe2. In this work, we show that encapsulation of ML MoS2 in hexagonal boron nitride can efficiently suppress the inhomogeneous contribution to the exciton linewidth, as we measure in photoluminescence and reflectivity a FWHM down to 2 meV at T=4 K. Narrow optical transition linewidths are also observed in encapsulated WS2, WSe2, and MoSe2 MLs. This indicates that surface protection and substrate flatness are key ingredients for obtaining stable, high-quality samples. Among the new possibilities offered by the well-defined optical transitions, we measure the homogeneous broadening induced by the interaction with phonons in temperature-dependent experiments. We uncover new information on spin and valley physics and present the rotation of valley coherence in applied magnetic fields perpendicular to the ML.

Published
2017
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49. Well separated trion and neutral excitons on superacid treated MoS 2 monolayers

Author

Cadiz, Fabian, Tricard, Simon, Gay, Maxime, Lagarde, Delphine, Wang, Gang, Robert, Cédric, Renucci, Pierre, Urbaszek, Bernhard, Marie, Xavier, Laboratoire de physique de la matière condensée (LPMC), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Tyndall National Institute [Cork], Institut National des Sciences Appliquées (INSA), 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)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)

Subjects
Condensed Matter::Materials Science, Optical electronics, Semiconductors, Photoluminescence spectroscopy, Condensed Matter::Other, Lasers Excitons, Transition metal chalcogenides, Selection rule, Quasiparticle, [CHIM]Chemical Sciences, Localized states, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Time-resolved photoluminescence
Abstract

International audience; Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS2 MLs, the photoluminescence (PL) spectra even at low temperature consist typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here, we show that in superacid treated MoS2 MLs, the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T = 4 K, with linewidth for the neutral exciton of 15 meV, but both transitions have similar intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emissions. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.

Published
2016

50. Atomic-scale understanding of high thermal stability of the Mo/CoFeB/MgO spin injector for spin-injection in remanence

Author

Tao, Bingshan, primary, Barate, Philippe, additional, Devaux, Xavier, additional, Renucci, Pierre, additional, Frougier, Julien, additional, Djeffal, Abdelhak, additional, Liang, Shiheng, additional, Xu, Bo, additional, Hehn, Michel, additional, Jaffrès, Henri, additional, George, Jean-Marie, additional, Marie, Xavier, additional, Mangin, Stéphane, additional, Han, Xiufeng, additional, Wang, Zhanguo, additional, and Lu, Yuan, additional

Published
2018
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