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18 results on '"Minh-Tuan Dau"'

1. An unusual phenomenon of surface reaction observed during Ge overgrowth on Mn5Ge3/Ge(111) heterostructures

Author

Minh-Tuan Dau, Vinh Le Thanh, Lisa A Michez, Matthieu Petit, Thi-Giang Le, Omar Abbes, Aurélie Spiesser, and Alain Ranguis

Subjects
Science, Physics, QC1-999
Abstract

The Mn _5 Ge _3 compound, thanks to its room-temperature ferromagnetism, metallic character and ability to epitaxially grow on germanium, acts as a potential candidate for spin injection into group-IV semiconductors. Understanding and controlling Ge overgrowth behaviour on Mn _5 Ge _3 /Ge heterostructures represents a crucial step to realize Ge/Mn _5 Ge _3 /Ge multilayers for numerous spintronic applications. Here, we have combined structural and morphological characterizations with magnetic analyses to study the mechanisms of Ge overgrowth on epitaxial Mn _5 Ge _3 layers in the temperature range of 450–550 °C. It is found that deposited Ge instantly reacts with Mn to form a Mn _5 Ge _3 surface layer, which, acting as a surfactant, continuously floats upwards from the growing surface to a distance larger than 70 nm. New Ge layers are successively formed underneath, allowing such a floating Mn _5 Ge _3 surface layer to be stabilized by epitaxy. These observations can be considered as a typical example in which the stabilization of metastable thin films by epitaxy can overcome thermodynamic equilibrium. We have also investigated the effect of carbon adsorption on the top of the Mn _5 Ge _3 layer prior to Ge deposition to control the Mn:Ge reaction. It is shown that adsorbed carbon effectively reduces the out-diffusion of Mn from Mn _5 Ge _3 , allowing Ge layers to stack up on top of Mn _5 Ge _3 . However, at temperatures of 450–550 °C, carbon may react with Mn to form manganese carbides and the resulting Ge overlayers are found to change their orientation from the (111) plane to the (001) plane, which has a higher surface energy. Finally, a strategy to realize Ge/Mn _5 Ge _3 /Ge multilayers will be addressed.

Published
2012
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2. The valley Nernst effect in WSe2

Author

Minh Tuan Dau, Céline Vergnaud, Alain Marty, Cyrille Beigné, Serge Gambarelli, Vincent Maurel, Timotée Journot, Bérangère Hyot, Thomas Guillet, Benjamin Grévin, Hanako Okuno, and Matthieu Jamet

Subjects
Science
Abstract

Atomically thin transition metal dichalcogenides possess a valley degree of freedom, which could enrich the physics underpinning the conventional Nernst effect observed in traditional solids. Here, the authors report experimental evidence of the valley Nernst effect in WSe2 at room temperature.

Published
2019
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3. Descriptor engineering in machine learning regression of electronic structure properties for 2D materials

Author

Minh Tuan Dau, Mohamed Al Khalfioui, Adrien Michon, Antoine Reserbat-Plantey, Stéphane Vézian, and Philippe Boucaud

Subjects
Multidisciplinary
Abstract

We build new material descriptors to predict the band gap and the work function of 2D materials by tree-based machine-learning models. The descriptor’s construction is based on vectorizing property matrices and on empirical property function, leading to mixing features that require low-resource computations. Combined with database-based features, the mixing features significantly improve the training and prediction of the models. We find R$$^{2}$$ 2 greater than 0.9 and mean absolute errors (MAE) smaller than 0.23 eV both for the training and prediction. The highest R$$^{2}$$ 2 of 0.95, 0.98 and the smallest MAE of 0.16 eV and 0.10 eV were obtained by using extreme gradient boosting for the bandgap and work-function predictions, respectively. These metrics were greatly improved as compared to those of database features-based predictions. We also find that the hybrid features slightly reduce the overfitting despite a small scale of the dataset. The relevance of the descriptor-based method was assessed by predicting and comparing the electronic properties of several 2D materials belonging to new classes (oxides, nitrides, carbides) with those of conventional computations. Our work provides a guideline to efficiently engineer descriptors by using vectorized property matrices and hybrid features for predicting 2D materials properties via ensemble models.

Published
2023
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4. The search for manganese incorporation in MoSe 2 monolayer epitaxially grown on graphene

Author

Maxime Gay, Minh-Tuan Dau, Céline Vergnaud, Alain Marty, Frédéric Bonell, Hervé Boukari, Colin Paillet, Bérangère Hyot, Hanako Okuno, Pierre Mallet, Jean-Yves Veuillen, Olivier Renault, Matthieu Jamet, 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), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Nanophysique et Semiconducteurs (NPSC), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Nano-Electronique Quantique et Spectroscopie (QuNES), ANR-18-CE24-0007,MAGICVALLEY,Polarisation de vallée induite par couplage d'échange magnétique dans les matériaux 2D à grande échelle(2018), ANR-10-LABX-0051,LANEF,Laboratory of Alliances on Nanosciences - Energy for the Future(2010), Nanophysique et Semiconducteurs (NEEL - NPSC), and Nano-Electronique Quantique et Spectroscopie (NEEL - QuNES)

Subjects
Materials science, Graphene, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, Manganese, 2D materials, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, law.invention, Crystallography, chemistry, law, 0103 physical sciences, Monolayer, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Magnetic doping, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Scanning tunneling microscopy, 010306 general physics, 0210 nano-technology, Molecular beam epitaxy, Transmission electron microscopy, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2022
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5. Preliminary Study on the Magnetic Properties of GeMn Nanocolumn/Ge Multilayers

Author

Thi Giang Le and Minh Tuan Dau

Subjects
SQUID, Magnetic anisotropy, Materials science, Spintronics, Condensed matter physics, law, Spin valve, Curie temperature, Magnetic semiconductor, Thin film, Molecular beam epitaxy, law.invention
Abstract

Ge0.94Mn0.06 nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge0.94Mn0.06 nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge0.94Mn0.06(40 nm)/Ge(d nm)]9/Ge0.94Mn0.06(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.

Published
2020
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6. New approach for the molecular beam epitaxy growth of scalable WSe

Author

Céline, Vergnaud, Minh-Tuan, Dau, Benjamin, Grévin, Christophe, Licitra, Alain, Marty, Hanako, Okuno, and Matthieu, Jamet

Abstract

The search for high-quality transition metal dichalcogenides mono- and multi-layers grown on large areas is still a very active field of investigation. Here, we use molecular beam epitaxy to grow WSe

Published
2020

7. Van der Waals solid phase epitaxy to grow large-area manganese-doped MoSe$_2$ few-layers on SiO$_2$/Si

Author

Céline Vergnaud, Maxime Gay, Carlos Alvarez, Minh-Tuan Dau, François Pierre, Denis Jalabert, Christophe Licitra, Alain Marty, Cyrille Beigné, Benjamin Grévin, Olivier Renault, Hanako Okuno, Matthieu Jamet, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), 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)), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), SYstèmes Moléculaires et nanoMatériaux pour l’Energie et la Santé (SYMMES), Institut de Chimie du CNRS (INC)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Synthèse, Structure et Propriétés de Matériaux Fonctionnels (STEP), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), CEA-project 2D FACTORY, Agence Nationale de la Recherche within the ANR MoS2ValleyControl project [ANR-14-CE26-0017], CEA-project 2D FACTORY, Agence Nationale de la Recherche within the ANR MAGICVALLEY project, French state funds LANEF [ANR-10-LABX-51-01], 'Recherches Technologiques de Base' Program of the French Ministry of Research, CEA-Enhanced Eurotalents program, ANR-14-CE26-0017,MoS2ValleyControl,Propriétés optiques et de transport dans des mono-couches de MoS2 et discpositifs associés(2014), ANR-18-CE24-0007,MAGICVALLEY,Polarisation de vallée induite par couplage d'échange magnétique dans les matériaux 2D à grande échelle(2018), ANR-10-LABX-0051,LANEF,Laboratory of Alliances on Nanosciences - Energy for the Future(2010), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Materials science, FOS: Physical sciences, 02 engineering and technology, 010402 general chemistry, Epitaxy, 01 natural sciences, large-scale growth, symbols.namesake, [SPI]Engineering Sciences [physics], Monolayer, General Materials Science, Thin film, solid phase epitaxy, structural properties, Condensed Matter - Materials Science, van der Waals epitaxy, Mechanical Engineering, Doping, transition metal dichalcogenides, Materials Science (cond-mat.mtrl-sci), General Chemistry, Magnetic semiconductor, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Amorphous solid, manganese doping, Mechanics of Materials, Chemical physics, symbols, electronic properties, van der Waals force, 0210 nano-technology, Molecular beam epitaxy
Abstract

Large-area growth of continuous transition metal dichalcogenides (TMDCs) layers is a prerequisite to transfer their exceptional electronic and optical properties into practical devices. It still represents an open issue nowadays. Electric and magnetic doping of TMDC layers to develop basic devices such as p-n junctions or diluted magnetic semiconductors for spintronic applications are also an important field of investigation. Here, we have developed two different techniques to grow MoSe$_2$ mono- and multi-layers on SiO$_2$/Si substrates over large areas. First, we co-deposited Mo and Se atoms on SiO$_2$/Si by molecular beam epitaxy in the van der Waals regime to obtain continuous MoSe$_2$ monolayers over 1 cm$^2$. To grow MoSe$_2$ multilayers, we then used the van der Waals solid phase epitaxy which consists in depositing an amorphous Se/Mo bilayer on top of a co-deposited MoSe$_2$ monolayer which serves as a van der Waals growth template. By annealing, we obtained continuous MoSe$_2$ multilayers over 1 cm$^2$. Moreover, by inserting a thin layer of Mn in the stack, we could demonstrate the incorporation of up to 10 \% of Mn in MoSe$_2$ bilayers., 32 pages, 13 figures

Published
2019
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8. Impact of a van der Waals interface on intrinsic and extrinsic defects in an MoSe 2 monolayer

Author

Alain Marty, Hélène Le Poche, Matthieu Jamet, Minh Tuan Dau, Hanako Okuno, Carlos Alvarez, Pascal Pochet, C. Vergnaud, Laboratory of Atomistic Simulation (LSIM ), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux (LITEN), Institut National de L'Energie Solaire (INES), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), CEA-project 2D FACTORY, Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Bioengineering, 02 engineering and technology, MoSe2, 01 natural sciences, law.invention, symbols.namesake, law, molecular beam epitaxy, 0103 physical sciences, Monolayer, transmission electron microscopy, Electron beam processing, General Materials Science, Electrical and Electronic Engineering, van der waals heterostructure, 010306 general physics, Graphene, Mechanical Engineering, transition metal dichalcogenides, General Chemistry, 021001 nanoscience & nanotechnology, Crystallographic defect, Electron diffraction, Mechanics of Materials, Chemical physics, Transmission electron microscopy, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Grain boundary, van der Waals force, 0210 nano-technology
Abstract

International audience; In this work, we study growth and migration of atomic defects in MoSe 2 on graphene using multiple advanced transmission electron microscopy techniques to explore defect behavior in vdW heterostructures. A MoSe 2 /graphene vdW heterostructure is prepared by a direct growth of both monolayers, thereby attaining an ideal vdW interface between the monolayers. We investigate the intrinsic defects (inversion domains and grain boundaries) in synthesized MoSe 2 , their evolution amid growth processing steps, and their influence on the formation and movement of extrinsic defects. Electron diffraction identifies a preferential interlayer orientation of 2° between MoSe 2 and graphene, which is caused by the presence of intrinsic IBD defects. Extrinsic defects (point and line defects) are generated by in situ electron irradiation in the MoSe 2 layer. Our results shed light on how to independently modify the MoSe 2 atomic structure in vdW heterostructures for potential utilization in device processing.

Published
2018
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10. Band-bending induced by charged defects and edges of atomically thin transition metal dichalcogenide films

Author

Pierre Mallet, Minh Tuan Dau, Jean-Yves Veuillen, K. Nogajewski, Matthieu Jamet, T. Le Quang, Marek Potemski, QNES - Nano-Electronique Quantique et Spectroscopie, Institut Néel ( NEEL ), Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes [Saint Martin d'Hères]-Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes [Saint Martin d'Hères], Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes [Saint Martin d'Hères], Laboratoire national des champs magnétiques intenses - Grenoble ( LNCMI ), Centre National de la Recherche Scientifique ( CNRS ), SPINtronique et technologie des composants ( SPINTEC - UMR 8191 ), Institut Nanosciences et Cryogénie ( INAC ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Grenoble Alpes ( UGA ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), ANR-14-CE26-0017,MoS2ValleyControl,Propriétés optiques et de transport dans des mono-couches de MoS2 et discpositifs associés ( 2014 ), European Project : 604391,EC:FP7:ICT,FP7-ICT-2013-FET-F,GRAPHENE ( 2013 ), European Project : 320590,EC:FP7:ERC,ERC-2012-ADG_20120216,MOMB ( 2013 ), Nano-Electronique Quantique et Spectroscopie (QuNES), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), 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 Grenoble Alpes [2016-2019] (UGA [2016-2019]), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANR-14-CE26-0017,MoS2ValleyControl,Propriétés optiques et de transport dans des mono-couches de MoS2 et discpositifs associés(2014), European Project: 604391,EC:FP7:ICT,FP7-ICT-2013-FET-F,GRAPHENE(2013), European Project: 320590,EC:FP7:ERC,ERC-2012-ADG_20120216,MOMB(2013), Nano-Electronique Quantique et Spectroscopie (NEEL - QuNES), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
Materials science, [ PHYS.COND.CM-MS ] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], charge screening, 02 engineering and technology, Dielectric, 01 natural sciences, law.invention, charged defect, law, Electric field, 0103 physical sciences, Monolayer, General Materials Science, 010306 general physics, Condensed matter physics, Graphene, Mechanical Engineering, scanning tunneling microscopy/spectroscopy, graphene, General Chemistry, transition metal dichalcogenide, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electrostatics, film edges, Crystallographic defect, Band bending, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], van der Waals heterostructures, Scanning tunneling microscope, 0210 nano-technology
Abstract

International audience; We report scanning tunneling microscopy/spectroscopy (STM/STS) investigations of the bandbendingin the vicinity of charged point defects and edges of monolayer MoSe$_2$ and mono- andtrilayer WSe$_2$ films deposited on graphitized silicon carbide substrates. By tracing the spatialevolution of the structures of the STS spectra, we evaluate the magnitude and the extent of theband-bending to be equal to few hundreds milielectronvolts and several nanometres, respectively.With the aid of a simple electrostatic model, we show that the spatial variation of the Coulombpotential close to the film edges can be well reproduced by taking into account the metallic screeningby graphene. Additionally, the analysis of our data for trilayer WSe$_2$ provides reasonable estimationsof its dielectric constant ($\epsilon_{WSe}$$_2$ = 20) and of the magnitude of the charge trapped at the defect site(Q = $+e$).

Published
2018
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11. Beyond van der Waals Interaction: The Case of MoSe$_2$ Epitaxially Grown on Few-Layer Graphene

Author

Minh Tuan Dau, Maxime Gay, Daniela Di Felice, Céline Vergnaud, Alain Marty, Cyrille Beigné, Gilles Renaud, Olivier Renault, Pierre Mallet, Toai Le Quang, Jean-Yves Veuillen, Loïc Huder, Vincent T. Renard, Claude Chapelier, Giovanni Zamborlini, Matteo Jugovac, Vitaliy Feyer, Yannick J. Dappe, Pascal Pochet, Matthieu Jamet, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), 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)), 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), Nanostructures et Rayonnement Synchrotron (NRS ), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Nano-Electronique Quantique et Spectroscopie (QuNES), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire de Transport Electronique Quantique et Supraconductivité (LaTEQS), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, Laboratory of Atomistic Simulation (LSIM ), ANR-14-CE26-0017,MoS2ValleyControl,Propriétés optiques et de transport dans des mono-couches de MoS2 et discpositifs associés(2014), ANR-11-EQPX-0010,CRGF,Lignes synchrotron françaises à l'ESRF(2011), ANR-10-LABX-0051,LANEF,Laboratory of Alliances on Nanosciences - Energy for the Future(2010), European Project: 604391,EC:FP7:ICT,FP7-ICT-2013-FET-F,GRAPHENE(2013), 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, and Nano-Electronique Quantique et Spectroscopie (NEEL - QuNES)

Subjects
Materials science, heterojunction, Band gap, General Physics and Astronomy, 02 engineering and technology, MoSe2, Epitaxy, 01 natural sciences, Electron spectroscopy, law.invention, symbols.namesake, law, 0103 physical sciences, Physics::Atomic and Molecular Clusters, band-gap opening, General Materials Science, 010306 general physics, Electronic band structure, [PHYS]Physics [physics], Condensed matter physics, Graphene, General Engineering, charge transfer, Heterojunction, commensurability, 021001 nanoscience & nanotechnology, few-layer graphene, van der Waals interaction, symbols, Density functional theory, van der Waals force, 0210 nano-technology
Abstract

International audience; Van der Waals heterojunctions composed of graphene and transition metal dichalcogenides have gain much attention because of the possibility to control and tailor band structure, promising applications in two-dimensional optoelectronics and electronics. In this report, we characterized the van der Waals heterojunction MoSe$_2$/few-layer graphene with a high-quality interface using cutting-edge surface techniques scaling from atomic to microscopic range. These surface analyses gave us a complete picture of the atomic structure and electronic properties of the heterojunction. In particular, we found two important results: the commensurability between the MoSe$_2$ and few-layer graphene lattices and a band-gap opening in the few-layer graphene. The band gap is as large as 250 meV, and we ascribed it to an interface charge transfer that results in an electronic depletion in the few-layer graphene. This conclusion is well supported by electron spectroscopy data and density functional theory calculations. The commensurability between the MoSe$_2$ and graphene lattices as well as the band-gap opening clearly show that the interlayer interaction goes beyond the simple van der Waals interaction. Hence, stacking two-dimensional materials in van der Waals heterojunctions enables us to tailor the atomic and electronic properties of individual layers. It also permits the introduction of a band gap in few-layer graphene by interface charge transfer.

Published
2018
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12. Beyond van der Waals Interaction: The Case of MoSe

Author

Minh Tuan, Dau, Maxime, Gay, Daniela, Di Felice, Céline, Vergnaud, Alain, Marty, Cyrille, Beigné, Gilles, Renaud, Olivier, Renault, Pierre, Mallet, Toai, Le Quang, Jean-Yves, Veuillen, Loïc, Huder, Vincent T, Renard, Claude, Chapelier, Giovanni, Zamborlini, Matteo, Jugovac, Vitaliy, Feyer, Yannick J, Dappe, Pascal, Pochet, and Matthieu, Jamet

Abstract

Van der Waals heterojunctions composed of graphene and transition metal dichalcogenides have gain much attention because of the possibility to control and tailor band structure, promising applications in two-dimensional optoelectronics and electronics. In this report, we characterized the van der Waals heterojunction MoSe

Published
2018

13. (Invited) The Effect of Carbon Doping on Structural and Magnetic Properties of Mn5Ge3/Ge Heterosctructures

Author

Matthieu Petit, Vinh Le Thanh, Aurelie Spiesser, Minh-Tuan Dau, and Lisa A Michez

Subjects
Spintronics, business.industry, Chemistry, chemistry.chemical_element, Nanotechnology, Heterojunction, Germanium, Epitaxy, Semiconductor, Ferromagnetism, Interstitial defect, Optoelectronics, business, Carbon
Abstract

The Mn5Ge3 compound, thanks to its room-temperature ferromagnetism, metallic character and ability to epitaxially grow on germanium, has emerged as a potential candidate for spin injection into group-IV semiconductors. We investigate the effect of carbon doping in epitaxial Mn5Ge3 films and show that incorporation of carbon into interstitial sites of Mn5Ge3 can allow not only to enhance the magnetic properties but also increase the thermal stability of Mn5Ge3 up to a temperature as high as 850 °C. These results open perspectives to realize spintronic devices based on Mn5Ge3Cx/Ge heterostructures that are compatible with the Si-based complementary metal-oxide-semiconductor (CMOS) technology.

Published
2013
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14. Vertical self-organization of Ge1-xMnx nanocolumn multilayers grown on Ge(001) substrates

Author

Thi Giang Le, Minh Tuan Dau, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), and Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Range (particle radiation), Materials science, business.industry, Statistical and Nonlinear Physics, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Optics, Transmission electron microscopy, 0103 physical sciences, Optoelectronics, 010306 general physics, 0210 nano-technology, business, Molecular beam epitaxy
Abstract

High-resolution transmission electron microscopy (HR-TEM) has been used to investigate the structural properties of GeMn/Ge nanocolumns multilayer samples grown on Ge(001) substrates by means of molecular beam epitaxy (MBE) system. Four bilayers with the spacer thickness in the range between 6 nm and 15 nm and 10 periods of bilayers of Ge[Formula: see text]Mn[Formula: see text]/Ge nanocolumn are presented. A simplified 2D model based on the theory of elastic constant interactions has been used to provide reasonable explanations to the vertical self-organization of GeMn nanocolumns in multilayers.

Published
2016
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16. Carbon diffusion and reactivity in Mn5Ge3 thin films

Author

Luc Bideux, Christine Robert-Goumet, Aurelie Spiesser, Minh Tuan Dau, Lisa Michez, Vinh Le Thanh, Guillaume Monier, Matthieu Petit, Alain Glachant, C. Coudreau, Xavier Barre, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), and Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Diffusion, Doping, Analytical chemistry, chemistry.chemical_element, Context (language use), 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, chemistry, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Curie temperature, Reactivity (chemistry), Thin film, 0210 nano-technology, Ternary operation, Carbon
Abstract

The Curie temperature of Mn5Ge3 has been successfully enhanced by carbon doping. In this context the diffusion of a carbon thin film in Mn5Ge3 has been studied at room temperature. A value of the diffusivity of about D = 2.4 × 10-23 ± 0.5 × 10-23 m2 s-1 is reported. This value is in the typical range of interstitial diffusion coefficients. Moreover Auger Ge and Mn peaks shifts and Ge3d core level have been investigated to get some details on the reactivity of carbon atoms in Mn5Ge3. Mn Auger transitions display a shift of 4 eV whereas Ge transitions do not. Similarly Ge3d core level does not contain C related contribution but presents a Mn one. These observations confirmed the fact that carbon atoms are not inert species for Mn. It suggests that a ternary Ge-Mn-C alloy could occur and should be taken into account when doping the Mn5Ge3 with carbon. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Published
2012
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17. Growth of Germanium Nanowires on Silicon(111) Substrates by Molecular Beam Epitaxy

Author

Vinh Le Thanh, Minh Tuan Dau, R. Baghdad, Matthieu Petit, C. Coudreau, Lisa Michez, Akihiro Watanabe, Sion F. Olive Méndez, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Université Ibn Khaldoun de Tiaret = University of Tiaret, Faculty of Agriculture, Kyushu University, and Ibn Khaldoun University, BP n°78, Route de Zaaroura, 14000 Tiaret, Algeria

Subjects
Ostwald ripening, Materials science, Reflection high-energy electron diffraction, MBE, Biomedical Engineering, Nanowire, Nucleation, chemistry.chemical_element, Bioengineering, Germanium, Nanotechnology, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, VLS, symbols.namesake, General Materials Science, Vapor–liquid–solid method, Wetting layer, Nanowires, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, chemistry, Chemical engineering, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Molecular beam epitaxy
Abstract

International audience; Heteroepitaxial growth of Ge nanowires was carried out on Si(111) substrates by MBE. Au seeds were used as precursor for the VLS growth of the nanowires. Even if the Au droplets do not act as catalyst for the dissociation of gas, they are local preferential areas where the energetic barrier of Ge nucleation is lowered compare to the remaining non activated surface. Two sets of Au seeds were used as precursors for the VLS process. The first set have an average diameter of 125 nm and the second of 25 nm. In-situ RHEED monitoring showed a Au wetting layer between these seeds before the nanowires growth as well as at the end of the Ge nanowires growth. It means that the wetting layer acted as a surfactant from the Si(111) surface to the Ge grown layer between the nanowires. Analysis of SEM images brought the fact that the diffusion of gold from the droplets on the surface and the sidewalls of the nanowires via the Ostwald ripening is a key parameter of the growth of the nanowires.

Published
2011
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