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PhD subjects

19 sujets IRAMIS

Dernière mise à jour : 05-06-2020


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• Solid state physics, surfaces and interfaces

 

Synthesis and study of the optoelectronic properties of heterostructures of two-dimensional semiconductor materials

SL-DRF-20-0521

Research field : Solid state physics, surfaces and interfaces
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie

Laboratoire Innovation, Chimie des Surfaces Et Nanosciences

Saclay

Contact :

Vincent DERYCKE

Starting date : 01-10-2020

Contact :

Vincent DERYCKE
CEA - DRF/IRAMIS/NIMBE/LICSEN

0169085565

Thesis supervisor :

Vincent DERYCKE
CEA - DRF/IRAMIS/NIMBE/LICSEN

0169085565

Personal web page : http://iramis.cea.fr/Pisp/vincent.derycke/

Laboratory link : http://iramis.cea.fr/nimbe/licsen/index.php

Two-dimensional (2D) materials, whose thickness is of atomic dimension (such as graphene for example), have constituted a distinct field of research since 2004. This field is exceptionally dynamic, both fundamentally and in terms of application prospects. Among the 2D materials, monolayers of transition metal dichalcogenides (TMDCs) such as MoS2, MoTe2, WSe2, SnS2, HfS2 ... are ultra-thin semiconductors with particularly interesting properties for electronics, optics or in the field of new energies. Even more remarkably, these 2D materials can be combined with each other to form van der Waals heterostuctures (HS-vdW) and thus lead to the formation of a palette of completely new materials with adjustable properties. Specifically, in the broad family of two-dimensional TMDCs, the project will focus on the combination of direct-gap semiconductor materials with respectively low and high electron affinity to form ultrathin type-II heterostructures. Under illumination, these heterostructures will lead to efficient separation of photo-generated charges, a key phenomenon for photodetectors and photovoltaic devices and for photo-catalysis for example. In this context, this thesis project includes: (1) the synthesis of different 2D semiconductors (MoS2, WS2, SnS2) by CVD (chemical vapor deposition) and their association in vertical or lateral heterostructures, (2) the detailed characterization of the physical and chemical properties of individual materials and heterostructures, (3) the evaluation of the potential of these heterostructures for optoelectronic and catalysis applications. This last aspect will involve the realization and the study of devices such as transistors and phototransistors based on 2D heterostructures, whose operating modes and performances will be studied in detail.
Surface states and charge transfer impact on the kinetics of the oxidation evolution reaction (OER) at the hematite / electrolyte interface in a solar water splitting reaction

SL-DRF-20-0658

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Dana STANESCU

Gheorghe Sorin Chiuzbaian

Starting date : 01-10-2020

Contact :

Dana STANESCU
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 75 48

Thesis supervisor :

Gheorghe Sorin Chiuzbaian
Université Sorbonne, Université Pierre et Marie Curie - Laboratoire de Chimie Physique Matière et Rayonnement

+33 1 44 27 66 15

Personal web page : http://iramis.cea.fr/Pisp/dana.stanescu/

Hydrogen production by water splitting is a clean and viable approach, but it is very greedy in electrical energy. To reduce the energy input we study the possibility of using solar radiation. Absorbed by identified and optimized semiconducting oxides, solar radiation generates electron-hole pairs that will participate in the redox reactions in a solar water splitting process1,2.

Hematite is the prototypical semiconductor material used as a photoanode. Hematite is very abundant, not expensive and with low environmental impact, assets that should be considered with particular attention nowadays. Significant progress has been made to improve the properties of hematite for a more efficient photoelectrolysis reaction2–5. Nevertheless, compared with materials with higher efficiencies6, hematite appears to be less effective due to the reduced holes mean free path2 and to the poor kinetics at the hematite / electrolyte interface during the oxidation7,8. The existence of surface states prevents a direct transfer of the holes in the electrolyte during the water oxidation9. Optimizing surface kinetics by controlling these surface states is therefore the key for hematite efficiency increasing when it is used as photoanode10.

We propose a study aiming at understanding and optimizing the surface kinetics and the time stability of hematite-based photoanodes, at both macro and nano-meter scales and under real working conditions, i.e. during the photoelectrochemical reaction. The hematite nanowires will be deposited by aqueous chemical growth (ACG11). Different surface treatments (ionic abrasion, chemical etching, annealing, surface functionalization, etc.) will be tested and analyzed to improve surface kinetics. Combining scanning transmission X-ray microscopy (STXM) and electron microscopy (TEM12 and ESEM13,14), in operando, using a dedicated electrochemical cell containing hematite nanowires as working electrode, will allow us to determine the chemical composition and the electronic structure at the nanoscale, during the oxidation. This approach will highlight and quantify the surface states responsible for the low OER kinetics of the hematite. Microscopy results will be correlated with the photoelectrochemical activity of photoanodes measured on dedicated photocurrent setup, the surface morphology will be measured by atomic force microscopy (AFM) and SEM and the surface potential measured by Kelvin Probe Force Microscopy (KPFM). In the end, this study should provide specific solutions to improve the efficiency of hematite-based photoanodes for solar water splitting.

1. Fujishima, A. & Honda, K. Nature 238, 37–38 (1972).

2. Krol, R. va de & Grätzel, M. (Springer, 2012).

3. Rioult, M., Magnan, H., Stanescu, D. & Barbier, A. J. Phys. Chem. C 118, (2014).

4. Rioult, M., Stanescu, D., Fonda, E., Barbier, A. & Magnan, H. J. Phys. Chem. C 120, 7482–7490 (2016).

5. Rioult, M., Belkhou, R., Magnan, H., Stanescu, D., Stanescu, S., Maccherozzi, F., Rountree, C. & Barbier, A. Surf. Sci. 641, 310–313 (2015).

6. Kalanoor, B. S., Seo, H. & Kalanur, S. S. Mater. Sci. Energy Technol. 1, 49–62 (2018).

7. Tamirat, A. G., Rick, J., Dubale, A. A., Su, W. N. & Hwang, B. J. Nanoscale Horizons vol. 1 243–267 (2016).

8. Glasscock, J. A., Barnes, P. R. F., Plumb, I. C. & Savvides, N. J. Phys. Chem. C 111, 16477–16488 (2007).

9. Iandolo, B., Wickman, B., Zoric, I. & Hellman, A. J. Mater. Chem. A 3, 16896–16912 (2015).

10. Zhang, J. & Eslava, S. Sustainable Energy and Fuels vol. 3 1351–1364 (2019).

11. Vayssieres, L. International Journal of Nanotechnology vol. 1 1–41 (2004).

12. Ortiz Peña, N., Ihiawakrim, D., Han, M., Lassalle-Kaiser, B., Carenco, S., Sanchez, C., Laberty-Robert, C., Portehault, D. & Ersen, O. ACS Nano 13, 11372–11381 (2019).

13. https://axlr.com/offres-technologies/celdi/.

14. http://www.newtec.fr/fr/celdi/.
Local mapping of the magnetic response of materials

SL-DRF-20-0289

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Aurélie Solignac

Myriam PANNETIER-LECOEUR

Starting date : 01-09-2020

Contact :

Aurélie Solignac
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 95 40

Thesis supervisor :

Myriam PANNETIER-LECOEUR
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 74 10

Personal web page : http://iramis.cea.fr/spec/Phocea/Pisp/index.php?nom=aurelie.solignac

Laboratory link : http://iramis.cea.fr/spec/lno/

More : https://www.speclno.org/

For some materials that have a magnetic response and in particular steels, mechanical and magnetic properties are correlated via the microstructure. The measurement of magnetic properties at the local scale could therefore provide non-destructive access to the mechanical properties of materials and a better understanding of their microstructure. In order to obtain additional contrasts, it is possible to use frequency response mapping when applying an alternating magnetic field (magnetic susceptibility).

A local scale magnetic mapping tool has been developed by combining magnetoresistive magnetic sensors and a scanner. The use of the giant magnetoresistance effect (GMR) allows the development of very sensitive magnetic sensors, detecting magnetic fields of the order of nT/vHz and whose size can be submicronic. The specificity of the system is that three or four sensors positioned on a pyramidal support scan the surface in order to measure the three components of the stray field emitted by the surface of the materials and thus to carry out a 3D mapping with a lateral resolution of the order of ten micrometers.

The thesis will consist in the adaptation of this imager in order to allow the mapping of the magnetic susceptibility of material surfaces over a very wide spectral dynamic range (from DC to 100MHz). In addition to the emission of the AC field and the appropriate detection electronics, Tunnel MagnetoResistance (TMR) sensors will be developed and integrated on the imager. Indeed, TMRs sensors have a better sensitivity than GMRs by a factor of about 20 at high frequency. The problems of surface-to-sensor distance control and temperature drift will also be addressed.

In a second step, calibration samples will be imaged in order to obtain the input data for the theoretical model already developed and thus allow the evaluation by simulations of the magnetic field distributions in ferromagnetic materials, in order to interpret the experimental results.

The study will then focus on systems of particular interest. Two applications are potentially targeted: ferromagnetic steels to correlate magnetic properties with mechanical properties and with other characterization techniques such as Barkhausen noise measurements. The second system concerns the performance evaluation of the imager and sensors developed for the detection of defects at the edges of metal parts under construction by additive manufacturing and in particular the differentiation of fused and non-fused areas.

Multifunctional material for the energy transition and opto-spintronics, based on N-doped BaTiO3

SL-DRF-20-0269

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Antoine BARBIER

Starting date : 01-10-2019

Contact :

Antoine BARBIER
CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Thesis supervisor :

Antoine BARBIER
CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Personal web page : http://iramis.cea.fr/Pisp/antoine.barbier/

Laboratory link : http://iramis.cea.fr/spec/LNO/

N-doped oxides and/or oxinitrides constitute a booming class of compounds with a broad spectrum of useable properties and in particular for novel technologies of carbon-free energy production and optoelectronics. The insertion of nitrogen in the crystal lattice of an oxide semiconductor allows modulating the value of the optical band gap, enabling new functionalities. The production of corresponding single crystalline thin films is highly challenging. In this thesis work, single crystalline N-doped oxides heterostructures will be grown by atomic plasma-assisted molecular beam epitaxy. BaTiO3 will provide ferroelectricity and a favorable absorption spectrum while an additional ferrimagnetic ferrite will give an artificial (opto)multiferroic character. The resulting structures will be investigated with respect to their ferroelectric characteristics, their magneto-electric and optoelectronic couplings and their performances in solar water splitting photo-electrolysis, as a function of the N doping. These observations will be correlated with a detailed understanding of crystalline and electronic structures.



The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, magnetometry and photo-electrolysis as well as in state of the art synchrotron radiation techniques.
Nuclear Magnetic Resonance of tritium: a new tool for understanding tritium speciation in materials of nuclear interest

SL-DRF-20-0567

Research field : Solid state physics, surfaces and interfaces
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie

Laboratoire Structure et Dynamique par Résonance Magnétique (LCF)

Saclay

Contact :

Thibault CHARPENTIER

Starting date : 01-10-2020

Contact :

Thibault CHARPENTIER
CEA - DRF/IRAMIS/NIMBE/LSDRM

33 1 69 08 23 56

Thesis supervisor :

Thibault CHARPENTIER
CEA - DRF/IRAMIS/NIMBE/LSDRM

33 1 69 08 23 56

Personal web page : http://iramis.cea.fr/Pisp/112/thibault.charpentier.html

Laboratory link : http://iramis.cea.fr/nimbe/lsdrm/

Tritium that is a radioactive isotope of hydrogen is an ubiquitous chemical element in the nuclear industry, both in fission and fusion reactors (ITER) where it is the main fuel. However, tritium, as a a light element, is easily trapped in many materials, resulting in significant quantities of tritiated waste.



The CEA has facilities that are unique in the world for handling tritiated materials and for developing tritium chemistry, for whose it would be interesting to combine with tritium nuclear magnetic resonance (NMR) spectroscopy under high-resolution conditions (rotation of the sample at the magic angle - MAS). The level of sophistication reached by NMR-MAS offers many prospects for a detailed understanding of the mechanisms of tritium incorporation and trapping in many materials of interest to the nuclear industry (metals, plastics, cements, etc.). Helium-3, produced by the decay of tritium, is another isotope that is easily detected by NMR.



The aim of this thesis is to develop and explore the potential of tritium NMR for a wide range of materials currently being studied, in collaboration with the main actors of the CEA's tritium fields.
Theoretical study of graphene electrodes for Molecular Electronics

SL-DRF-20-0929

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Groupe Mésocopie Modélisation et Thermoélectricité

Saclay

Contact :

Yannick DAPPE

Starting date : 01-10-2020

Contact :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Thesis supervisor :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Personal web page : http://iramis.cea.fr/spec/Pisp/yannick.dappe/

Laboratory link : http://iramis.cea.fr/spec/GMT/

Molecular Electronics constitute nowadays a very active field of research, either for fundamental aspects in these new systems which allow exploring new Physics at the atomic scale, than for the possible applications in terms of innovative electronic devices. Indeed, beyond the ability to reproduce silicon based components (diodes, transistors, …), molecules can also bring new types of electric response due to the great number of quantum degrees of freedom, which are tunable according to the considered molecule. Indeed, the quantum nature of these objects as well as the new associated functionalities open fascinating perspectives to build future electronics. Consequently, those new researches have led to important developments in the field of Molecular Electronics, in particular regarding the control and manipulation of electronic transport through a molecular junction. Most of the molecular junctions are based on molecules connected to metallic electrodes (gold, platinum, silver…). However, it has been demonstrated in several occasions that the connection between molecule and electrode has a non-negligible influence on the electric conductance of the system. In that manner, recent developments have proposed to make use of new materials like graphene, which is really well-known for its fantastic electric conduction properties, as electrodes for molecular junctions. Hence, it has been observed that the connection to a graphene electrode allows to significantly increase the junction conductance for long molecular chains, and therefore to reduce the energetic cost of such junction.



The main objective of this PhD lies in this frame by the theoretical study of asymmetric molecular junctions based on graphene or MoS2, as well as the study of molecular wires lifted off a surface using a STM tip. By using Density Functional Theory (DFT), we will determine the equilibrium configuration of the molecular junction and the corresponding electronic properties, before in a second time to calculate the electronic transport from the obtained structures, using a Keldysh-Green formalism. The purpose will be to understand the mechanism of conductance increase with respect to classical junctions, and to compare them to existing experimental results. The different expected behaviors in these systems allow studying the Physics of electronic transport at the atomic scale, and could be exploited for the conception of new devices at the single molecule scale.

Nickelates: a New Superconducting Oxide Family

SL-DRF-20-0520

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Dorothée COLSON

Jean-Baptiste MOUSSY

Starting date : 01-10-2020

Contact :

Dorothée COLSON
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 73 14

Thesis supervisor :

Jean-Baptiste MOUSSY
CEA - DRF/IRAMIS

01-69-08-72-17

Personal web page : http://iramis.cea.fr/Pisp/dorothee.colson/

Laboratory link : http://iramis.cea.fr/spec/lno/

The discovery of high-Tc superconductivity in cuprates [1] has motivated the study of oxides with similar crystalline and electronic structure with the aim of finding additional superconductors and understanding the origins of this unconventional superconductivity. Isostructural examples include the superconducting Sr2RuO4 ruthenate or the electron-doped Sr2IrO4 iridate even if a zero-resistance state has not yet been observed in this last compound [2]. Recently, the superconductivity in the infinite layer Nd0.8Sr0.2NiO2 nickelate [3] has also been observed by using a soft-chemistry topotactic reduction of the perovskite precursor phase. The discovery of this superconducting phase (around 10-15 K) should allow to progress in the understanding of the mechanisms involved in high-Tc superconductors.



During this PhD thesis, the student will perform the crystalline growth of pure and (Nd/Sr) substituted NdNiO3(001) thin films on single-crystal SrTiO3(001) substrates by pulsed laser deposition (PLD). Once grown, the student will test reducing treatments allowing the formation of the expected infinite layer phase. A peculiar attention will be given to the structural and physical properties of oxide thin films by using in situ electron diffraction (RHEED), photoemission spectroscopy (XPS/UPS) or ex situ techniques such as near-field microspcopy (AFM), magnetism (SQUID, VSM). The electronic properties of samples will then be studied as a function of temperature (resistivity, Hall coefficient, current-voltage characteristics) in order to analyze the superconducting behavior.



[1] J. G. Bednorz and K. A. Müller, Z. Phys. B 64, 189 (1986).

[2] Y.J. Yan et al., Phys. Rev. X. 5, 041018 (2015).

[3] D. Li et al. Nature. 572, 624 (2019).
Ab initio simulations of spin polarized STM images

SL-DRF-20-0930

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Groupe Mésocopie Modélisation et Thermoélectricité

Saclay

Contact :

Yannick DAPPE

Starting date : 01-10-2020

Contact :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Thesis supervisor :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Personal web page : http://iramis.cea.fr/Pisp/yannick.dappe/

Laboratory link : http://iramis.cea.fr/spec/GMT

Since its discovery more than 30 years ago by Binnig and Rohrer [1], the Scanning Tunnelling Microscope (STM) has become a tool of choice, not only for the study of atomic structures of surfaces or surface nanostructures, but also for the determination of the electronic properties of these systems. However, the complexity of the experimentally obtained images frequently requests an advanced theoretical support in order to reach a correct interpretation of the experimental data. In that respect, the determination of the atomic and electronic structure based on Density Functional Theory (DFT) calculations constitutes a very interesting and complementary tool for the characterization of these systems. The purpose of this PhD is to continue further the numerical developments in terms of STM images simulation by taking into account the spin polarization effects. Indeed, the study of magnetic nanostructures is of paramount importance in nowadays research due to the numerous applications in information and communication technologies. In this work, the goal will be to introduce the spin polarization in a DFT code, and then to continue the previously performed developments to determine the spin polarized current between the STM tip and the considered system. These developments will be later compared to reference experimental systems.
Simulation of quantum transport in two-dimensional magnetic materials

SL-DRF-20-0926

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Groupe Mésocopie Modélisation et Thermoélectricité

Saclay

Contact :

Alexander SMOGUNOV

Starting date : 01-09-2020

Contact :

Alexander SMOGUNOV
CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Thesis supervisor :

Alexander SMOGUNOV
CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Personal web page : http://iramis.cea.fr/Pisp/alexander.smogunov/

Laboratory link : http://iramis.cea.fr/spec/GMT

The goal of the thesis is to develop a general and efficient code for theoretical study of electron transport in two-dimensional (2D) systems (such as graphene) and, in particular, in recently discovered magnetic 2D materials such as CrI3, Fe3GeTe2 and others [1] – the subject of great interest from both fundamental point of view but also for possible technological applications. The code will be based on realistic multi-orbital tight-binding model where needed parameters will be extracted from ab initio DFT (Density Functional Theory) calculations. The main DFT tool to be used is the Quantum-ESPRESSO (QE) package [2] – one of the most accurate electronic structure codes based on plane wave expansion of electronic wave functions. Several approaches to quantum transport such as Non-equilibrium Green's function formalism, the wave function scattering method, or the direct time evolution of electron wave packets will be explored and implemented in the transport code. Many interesting phenomena such as an effect of external magnetic field, time-dependent potentials, impurities or atomic vibrations (phonons) on spin-dependent electron propagation are going to be addressed based on accurate quantum-mechanical description.



[1] M. Gibertini, M. Koperski, A. F. Morpurgo, K. S. Novoselov, Magnetic 2D materials and heterostructures, Nature Nanotechnology14, 408 (2019)

[2] P. Giannozzi et al., QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials, Phys.: Condens. Matter 21, 395502 (2009)
Ab initio simulation of transport phenomena in atomic-scale junctions

SL-DRF-20-0372

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Groupe Mésocopie Modélisation et Thermoélectricité

Saclay

Contact :

Alexander SMOGUNOV

Starting date : 01-09-2019

Contact :

Alexander SMOGUNOV
CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Thesis supervisor :

Alexander SMOGUNOV
CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Personal web page : http://iramis.cea.fr/Pisp/alexander.smogunov/

Laboratory link : http://iramis.cea.fr/spec/GMT

We will develop a code for theoretical study of transport phenomena in open quantum nanosystems made of two generic macroscopic reservoirs connected by a single atomic-scale junction – the subject of great interest from both fundamental point of view but also for various technological applications.



Two macroscopic electrodes could be, for example, semi-infinite metallic (magnetic) surfaces or two-dimensional materials (such as graphene) with in-plane transport regime, while a junction could be a chain of atoms or a single (magnetic) molecule. Several transport channels across a junction, such as electron or phonon (atomic vibrations) propagation, will be treated on the same quantum-mechanical footing using Non-equilibrium Green’s functions formalism [1]. The code will be based on realistic tight-binding model with parameters extracted from ab initio DFT (Density Functional Theory) calculations. The main DFT tool to be used is the Quantum ESPRESSO (QE) package [2] – one of the most accurate electronic structure codes based on plane wave expansion of electronic wave functions. Our code will be an extension of quantum transport code PWCOND [3] (which is a part of QE) to address more general transport phenomena and to treat larger scale quantum systems. It should allow, in particular, to evaluate electronic and thermal currents as a function of applied voltage or temperature gradients and thus to explore various thermoelectric phenomena. In addition, electron-electron or electron-phonon interactions inside the junction could be naturally incorporated into the model which would make possible to address also the Kondo physics or to investigate energy conversion and exchange mechanisms between electronic and phononic degrees of freedom.



[1] J. C. Cuevas and E. Scheer, Molecular Electronics: An Introduction to Theory and Experiment, World Scientific (2010)

[2] P. Giannozzi et al., QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials, Phys.: Condens. Matter 21, 395502 (2009)

[3] A. Smogunov, A. Dal Corso, E. Tosatti, Ballistic conductance of magnetic Co and Ni nanowires with ultrasoft pseudo-potentials, Phys. Rev. B 70, 045417 (2004)

Ultrafast dynamics in multiferroics

SL-DRF-20-1138

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

jean-yves Chauleau

Michel VIRET

Starting date : 01-10-2020

Contact :

jean-yves Chauleau
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 72 17

Thesis supervisor :

Michel VIRET
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 71 60

Personal web page : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=jchaulea

Laboratory link : http://iramis.cea.fr/spec/lno/

The objectives of this PhD are the study of the ultrafast time evolution (sub-picosecond) of the magneto-electric antiferromagnets when subjected to various types of ultrafast stimuli such as intense femtosecond light pulses (UV, visible, infrared), terahertz pulses or ultrafast pure spin-current bursts. Indeed, antiferromagnets (AF), whose intrinsic dynamics directly lies in the THz range) are currently in the limelight thanks to recent breakthroughs underlining the effect of spin currents on the AF order parameter. This work could open new horizons towards ultrafast control of the AF order, either in an all-optical fashion or using spins.
Theoretical studies of novel graphene based nanostructures

SL-DRF-20-0999

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Groupe Mésocopie Modélisation et Thermoélectricité

Saclay

Contact :

Yannick DAPPE

Starting date : 01-05-2020

Contact :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Thesis supervisor :

Yannick DAPPE
CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Personal web page : http://iramis.cea.fr/Pisp/yannick.dappe/

Laboratory link : http://iramis.cea.fr/spec/GMT/

A PhD position is open in the “Groupe de Modélisation et Théorie” at SPEC (UMR 3680 CNRS – CEA Saclay).

This theoretical work is dedicated to the study of new carbon materials like graphene nano-meshes (perfectly periodical network of sized holes within the lattice) shape/size controlled graphene flakes and graphene nanoribbons. All these structures are of crucial interest in several modern issues like optics, nanoelectronics and spintronics.

It consists in the study of both atomistic and electronic structures of these new materials, aiming to determinate electronic transport and optical properties.

Investigations will be performed with Density Functional Theory (DFT) and tight-binding models. The goal is to determine electronic structure at different levels of accuracy, enabling robustness of predictions for a large range of systems sizes. From this well established electronic structure, the transport properties will firstly be determined within a Green functions formalism. Scanning tunneling microscopy (STM) images as well as tunnel current spectroscopies will also be simulated, in order to compare and analyze experimental data.

Optical response of these materials will be studied from previous DFT results. Absorption or luminescence properties will be calculated help to a combined DFT/tight-binding formalism. A large part of the work here will consist in the development of the tight binding model needed to study the largest structures.

The research performed during this project will be performed within a long-time collaboration network involving experimental teams located in the Saclay area: chemistry groups at CEA-Nimbe and ICMMO, STM/STS at ISMO and optics measurements at LAC.

The PhD student theoretical work will then be performed within this collaboration, ensuring excellent experiment/theory feedbacks and comparisons.

The candidate must have followed condensed matter studies, with a numerical and theoretical background. He/she also should show interest in experimental techniques involved in this project.
new material for energy: oxynitride thin fims for photoelectrodes

SL-DRF-20-0533

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Hélène MAGNAN

Antoine BARBIER

Starting date : 01-10-2020

Contact :

Hélène MAGNAN
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 04

Thesis supervisor :

Antoine BARBIER
CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Personal web page : http://iramis.cea.fr/Pisp/helene.magnan/

Laboratory link : http://iramis.cea.fr/spec/LNO/

More : http://iramis.cea.fr/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=1996&id_unit=0&id_groupe=196

Uranium detection at trace level in water

SL-DRF-20-0465

Research field : Solid state physics, surfaces and interfaces
Location :

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Marie-Claude CLOCHARD

Starting date : 01-10-2020

Contact :

Marie-Claude CLOCHARD
CEA - DRF/IRAMIS/LSI/LSI

0169334526

Thesis supervisor :

Marie-Claude CLOCHARD
CEA - DRF/IRAMIS/LSI/LSI

0169334526

Personal web page : http://iramis.cea.fr/Phocea/Membres/Annuaire/index.php?uid=clochard

Laboratory link : https://portail.polytechnique.edu/lsi/fr/recherche/physique-et-chimie-des-nano-objets

More : https://portail.polytechnique.edu/lsi/fr/recherche/physique-et-chimie-des-nano-objets/elaboration-de-membranes-polymeres-nanoporeuses

72% of french nuclear plants are 31 to 40 years old. Even if an extension of their lifetime is now on study, their dismantlement should be considered. The study of soil pollution by heavy metals from aqueous soil leachates (rain waters - NF-EN-12457-2) should address on-site analyses with reliable and ultrasensitive methods. Since a decade, the LSI is developping a sensor of heavy metal ions based on nanoporous polymer membranes able to trap numerous metal ions by complexation with chemical functions localized in the porosity by radio-induced grafting. A peculiar focus on Uranium ions detection in different waters (fresh and salted) will be studied by analytical techniques dealing with electrochemistry, photoluminescence and spectroscopy such ICP-MS. New functionalities and/or improvement of the nanoporous sensors (fabrication process and functioning)will be also investigated.
Thermally charged ionic supercapacitor with VACNT - Vertically aligned carbon nanotube electrodes

SL-DRF-20-0511

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

Saclay

Contact :

Sawako NAKAMAE

Starting date : 01-10-2020

Contact :

Sawako NAKAMAE
CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Thesis supervisor :

Sawako NAKAMAE
CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Personal web page : http://iramis.cea.fr/Pisp/sawako.nakamae/

Laboratory link : https://iramis.cea.fr/spec/sphynx/

Experimental research project in the field of renewable energy science (waste-heat recovery). Study, development and characterization of ionic-liquid supercapacitors, made with nanostructured carbon électrodes (VACNT : vertically aligned carbon nanotube).



Domain: Physics, Materials Science, Fluid Physics, Physical Chemistry.
Local magnetic microscopy by integration of magnetoresistive sensors

SL-DRF-20-1135

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Aurélie Solignac

Myriam PANNETIER-LECOEUR

Starting date : 01-10-2020

Contact :

Aurélie Solignac
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 95 40

Thesis supervisor :

Myriam PANNETIER-LECOEUR
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 74 10

Personal web page : http://iramis.cea.fr/Pisp/aurelie.solignac/

Laboratory link : http://iramis.cea.fr/spec/LNO/

In order to characterize the local magnetic properties of magnetic materials such as steels, nanoparticles or magnetic rocks, an ultrasensitive and quantitative magnetic microscope has been developed at the Laboratory of Nanomagnetism and Oxides. This microscope combines a local scanning probe microscope of the AFM (Atomic Force Microscope) type and a magnetic sensor integrated in an AFM cantilever. The magnetic sensors used are giant and tunneling magnetoresistance (MR) sensors based on spin electronics and capable of detecting magnetic fields of the order of nT/vHz. The AFM allows monitoring the height of the tip and its displacement, while the MR sensor integrated in the AFM tip measures the magnetic field at each position on the sample.



This innovative tool has so far been applied to the nanometrology of static magnetic fields on a local scale. During this thesis the aim is to investigate other possible applications using a specific property of MR sensors: their wide frequency range in detection from DC to several hundred MHz or even GHz. Thus the magnetic susceptibility properties of unique magnetic nanoparticles can be studied, especially in the context of the use of nanoparticles in biomedical applications for example (biochips, strip tests...). A second targeted application is magnonics or the use of spin waves (rather than charges) to transport and process information with a minimum of energy loss. MR sensors are indeed very good candidates to be miniaturizable detectors of these spin waves and allow their mapping.



In the framework of this thesis, developments will be necessary in order to optimize the response of the sensors according to the targeted application. The performance of the sensors will be studied in terms of magnetoresistance and noise when integrated in flexible cantilever. The thesis will include a clean room microfabrication aspect and a magnetotransport and noise measurement aspect, which will be performed in the shielded magnetic chamber of the Ultra Low Noise platform. The microscope and the sensor detection electronics will also have to be adapted to high frequency measurements in order to exploit the potential of the microscope for innovative applications.

From spectra to total energies: a new approach to calculate the electronic ground state

SL-DRF-20-0554

Research field : Solid state physics, surfaces and interfaces
Location :

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Lucia REINING

Starting date : 01-10-2020

Contact :

Lucia REINING
CNRS - LSI/Laboratoire des Solides Irradiés

0169334553

Thesis supervisor :

Lucia REINING
CNRS - LSI/Laboratoire des Solides Irradiés

0169334553

Personal web page : https://etsf.polytechnique.fr/People/Lucia

Laboratory link : https://etsf.polytechnique.fr

The total energy of a system, and total energy differences, are at the basis of numerous key properties of materials, such as their stability or compressibility, and influence phenomena all over physics, chemistry or biology, such as protein folding. Theoretical predictions are crucial for materials design, but in many cases, the required precision is not reachable with the available computational resources.



The aim of the proposed thesis is to explore a novel way for the calculation of total energies, which makes use of the fact that many details of the ground state wavefunction are integrated out when the energy is calculated. Starting from standard many-body pertubation theory, the equations that lead to the total energy are modified from the very beginning in such a way that contributions which should integrate out are never calculated. On the basis of the developments of this formalism, which is ongoing in the group, an important part of the thesis project is to design and realize the numerical implementation. In order to be applicable to realistic systems, this novel approach will be included in a parallel, scalable ab intio code, as well integrated into a bigger platform.
Ultrafast pure spin current transport through antiferromagnetic insulators

SL-DRF-20-1137

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

jean-yves Chauleau

Jean-Baptiste MOUSSY

Starting date : 01-11-2020

Contact :

jean-yves Chauleau
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 72 17

Thesis supervisor :

Jean-Baptiste MOUSSY
CEA - DRF/IRAMIS

01-69-08-72-17

Personal web page : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=jchaulea

Laboratory link : http://iramis.cea.fr/spec/lno/

Pure spin-currents are playing a major role in modern spintronics. Mastering their ultrafast and efficient transport allows to extend spintronics concepts to the terahertz range. The main objective of this PhD is to address the underlying mechanisms of the dynamics of spin-current transport through antiferromagnetic insulators. These materials are now attracting a substantial interest mainly due to their ultrafast capabilities. We propose here to explore the different characteristics of the terahertz pure spin-current transport in antiferromagnets using time-resolved optical techniques (magneto-optics and second harmonic generation) and terahertz spectroscopy.
Realization and study of functional nano-circuits at artificial laminar multiferroic interfaces by nanolithography

SL-DRF-20-1132

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l’Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Antoine BARBIER

Starting date : 01-10-2020

Contact :

Antoine BARBIER
CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Thesis supervisor :

Antoine BARBIER
CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Personal web page : http://iramis.cea.fr/Pisp/137/antoine.barbier.html

Laboratory link : http://iramis.cea.fr/spec/LNO/

Limiting resources and diverging world energy consumptions are challenging problems that the next generation of technologies absolutely need to address to reach sustainable growth. A reduction of materials use can be achieved by realizing multifunctional nanometric laminar heterostructures which are easy to recycle. In this work, we will consider full oxide artificial multiferroic stacks including a ferroelectric and a ferrimagnetic layer. Near field piezo-force (PFM) microscopy tip nanolithography writing, will be used to create embedded conduction channels within an otherwise insulating material. We wish to realize, exploit and understand interface conduction and local charge trapping phenomena at such interfaces to realize functional nano-circuits and investigate them under working conditions. The proposed thesis work consists of a close collaboration between CEA/SPEC, SOLEIL synchrotron and CEMES and is funded as part of an ongoing ANR project. Single crystalline samples will be realized at CEA by molecular beam epitaxy assisted by atomic oxygen plasma, PFM writing and lithography processes. The local behaviour of these samples, including under functioning conditions, will be examined using the most advanced synchrotron radiations techniques and in particular spectromicroscopy, X-ray diffraction and absorption, respectively on beamlines HERMES, DIFFABS and LUCIA in a close collaborative approach and complementary to theoretical DFT predictions realized at CEMES. The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, magnetometry, near field microscopy, lithography as well as in the above mentioned state of the art synchrotron radiation techniques.

 

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