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PhD subjects

19 sujets IRAMIS

Dernière mise à jour : 17-09-2019


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• Solid state physics, surfaces and interfaces

 

Theoretical study of the physical and optical properties of some titanium oxide surfaces for gas sensing applications

SL-DRF-19-0532

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Nathalie VAST

Starting date : 01-10-2019

Contact :

Nathalie VAST
CEA - DRF/IRAMIS/LSI/LSI

01 69 33 45 51

Thesis supervisor :

Nathalie VAST
CEA - DRF/IRAMIS/LSI/LSI

01 69 33 45 51

Personal web page : https://www.polytechnique.edu/annuaire/fr/users/nathalie.vast

Laboratory link : https://portail.polytechnique.edu/lsi/fr/recherche/theorie-de-la-science-des-materiaux

The international community under the auspices of the United Nation Framework Convention on Climate Change (UNFCCC) is engaged in developing the policy to reduce greenhouse gases (GHGs) emission and minimize the risks of climate change. Consequently, it is very important to develop a low power, high performance sensor suitable to monitor the GHGs for proper mitigation. A common and existing method for sensing the concentration of gases is by using semiconducting metal oxides like SnO2, ZnO, and TiO2. Some models emphasize the importance of charge transfer in the sensing mechanism, but an study from first principles, including the electronic coupling with phonons, is necessary to understand quantitatively the adsorption process and the consequent optical response of the system.



The optical response and electron-phonon coupling will be in investigated with methods based on the time-dependent density functional theory on which the host team has developed an expertise. Numerical simulations will be performed with the Quantum ESPRESSO package. Part of the project may consist of theoretical and numerical implementations. The Ph.D. subject requires the candidate to be highly motivated by modelling, computing and programming.
Theoretical study of coupled electronic and heat transports to design thermoelectric materials at ambient temperature

SL-DRF-19-0533

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Nathalie VAST

Starting date : 01-10-2019

Contact :

Nathalie VAST
CEA - DRF/IRAMIS/LSI/LSI

01 69 33 45 51

Thesis supervisor :

Nathalie VAST
CEA - DRF/IRAMIS/LSI/LSI

01 69 33 45 51

Personal web page : https://www.polytechnique.edu/annuaire/fr/users/nathalie.vast

Laboratory link : https://portail.polytechnique.edu/lsi/fr/recherche/theorie-de-la-science-des-materiaux

Thermoelectricity have proven to offer a viable solution for the generation of electrical power (Seebeck effect) and to the problem of overheating in nanodevices (Peltier effect). New technological and scientific efforts are needed to find low-cost efficient materials that will develop the use of thermoelectric devices working at ambient temperature. Numerical simulations, which are the heart of this Ph.D. subject, provide a highly valuable tool to reach this end.



The theoretical method that will allow the prediction of the effect of nanostructuring on the figure of merit ZT will be developed and an integrated simulation tool to evaluate both the diffusive and the phonon-drag contributions to the Seebeck coefficient i.e., the contribution due to electron-phonon coupling, will be provided. This fully ab initio approach will be applied to germanium (abundant and non-toxic) and bismuth (among the material with the highest Seebeck coefficient), achieving a parameter-free description of thermoelectricity for these materials, their nanostructures and their compounds (Si-Ge alloys and Bi2Te3).



The BTEs (Boltzmann transport équations) for the electronic and the phonon system, coupled through electron-phonon interaction, will be solved beyond standard approximations. The phonon-phonon anharmonicity and the phonon scattering with surfaces and interfaces in nanostructures will be taken into account, with the aim of tayloring the phonon system to increase the thermoelectric effect.The electron-phonon coupling will be computed with a recent method based on the interpolation in the Wannier space. Finally, the DFT-based results for the electron-phonon coupling will be coupled to a Monte Carlo transport code, opening the

possibility to model even complex nano-devices based on the materials that will be theoretically studied.
Theoretical study of graphene electrodes for Molecular Electronics

SL-DRF-19-0779

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 : 01-10-2019

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.

Linear magnetoelectric and multiferroic properties in A4A’2O9 antiferromagnets

SL-DRF-19-0539

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

Laboratoire Léon Brillouin

Groupe Diffraction Poudres

Saclay

Contact :

Françoise Damay

Starting date : 01-10-2019

Contact :

Françoise Damay
CEA - DRF/IRAMIS/LLB/GDP

0169084954

Thesis supervisor :

Françoise Damay
CEA - DRF/IRAMIS/LLB/GDP

0169084954

Personal web page : http://iramis.cea.fr/Pisp/francoise.damay/

Laboratory link : http://www-llb.cea.fr/

The general context of this PhD work is the search for new multiferroics, compounds in which magnetisation and electric polarization are coupled, allowing for instance a magnetic field to modify the polarization, of an electric field to change magnetization.



In the proposed work, a new family of promising multiferroics will be investigated, namely niobiates and tantalates of general formula A4A'O9 with A a divalent transition metal. In work published in 2018, it was shown that in particular Fe4Ta2O9 exhibits both multiferroic and linear magneto-electric properties, depending on the temperature range. This suggests different spin/charge couplings that remain to be explored and understood. Experimental techniques will be devoted to the understanding of the relations ships between crystal and magnetic structures and physical properties: for the most part, the student will deal with magnetization, dielectric constant and polarization measurements, coupled with X-ray and neutron diffraction experiments versus temperature.
Electronic properties of two-dimensional semiconductors

SL-DRF-19-0735

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 : 01-10-2019

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/

Two-dimensional materials (graphene, phosphorene, BN monolayers…), which have atomic thickness, have been attracting enormous attention from the scientific community since 2004. Among them, 2D semiconductors such as monolayers of transition metal dichalcogenides (MoS2, MoSe2, WS2…) have a high potential for future applications in electronics, optics, and as materials for renewable energies (MoS2 is for example an excellent catalyst for hydrogen production). These materials exist at the natural state (within 3D natural crystals that can be exfoliated down to individual monolayers) and/or can be synthetized in the laboratory, in particular using chemical vapor deposition (CVD). In both cases, 2D materials present inhomogeneities (edges, defects, folds, vacancies, double-layers...). Yet at that scale, such features can drastically impact their properties (the charge mobility, the luminescence yield, the catalytic efficiency...). It is thus important to study these properties with local techniques that allow understanding the role of inhomogeneities and to either reduce or maximize their impact. In this context, the LICSEN team of the NIMBE Unit synthetizes monolayer MoS2 (by CVD) and study its electronic properties within devices such as field-effect transistors as well as its electro-catalytic properties by electrochemistry. In this PhD project, conducted in strong collaboration with other academic partners, we aim at developing new measurement techniques for the study of ultrathin semiconductors at the local scale using notably high-contrast microscopy on antireflection substrates [1,2] and local probe techniques coupled to electrical measurements (EFM, KPFM).



[1] Campidelli et al., Backside absorbing layer microscopy: Watching graphene chemistry, Science Advances 3, e1601724 (2017).

[2] Jaouen et al., Ideal optical contrast for 2D materials observation using antireflection absorbing substrates, submitted

Atomic Transport in Nanocrystalline Metals

SL-DRF-19-0705

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Vassilis PONTIKIS

Gianguido Baldinozzi

Starting date : 01-10-2019

Contact :

Vassilis PONTIKIS
CEA - DRF/IRAMIS

0169082904

Thesis supervisor :

Gianguido Baldinozzi
CNRS-Ecole Centrale-Supelec Paris - SPSMS


Personal web page : https://www.researchgate.net/profile/Vassilis_Pontikis

This project aims at unravelling the atomic scale mechanisms of mass transport and recrystallization in nano-crystalline metallic samples via atomic scale simulations relying on near-transferable n-body potentials adapted to noble metals. It is legitimate to ask whether the grain growth in nano-crystalline metallic materials relies upon the same mechanisms observed in microcrystalline materials or the grain growth in nano-crystalline materials involves a different “new” physics. The available experiments do not support the idea that crystal growth in metallic nano-crystals can be simply extrapolated from the processes observed in micrometric crystals, but no definitive answer is available about the underlying physical mechanisms. Computational experiments focusing on atomic transport in nano-crystalline systems will be compared with experiments and theoretical models, which have evidenced the unexpected existence in metallic nano-crystals of a linear grain growth below a critical grain size.
Fracture properties of bone-inspired mechanical metamaterials: toward lightweight and resistant solids

SL-DRF-19-0465

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 :

Daniel BONAMY

Starting date :

Contact :

Daniel BONAMY
CEA - DSM/IRAMIS/SPEC/SPHYNX

0169082114

Thesis supervisor :

Daniel BONAMY
CEA - DSM/IRAMIS/SPEC/SPHYNX

0169082114

Personal web page : http://iramis.cea.fr/Pisp/2/daniel.bonamy.html

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

The quest toward high-performance materials combining lightness and mechanical strength gave rise to a flurry of activity, driven in transport industries, for instance, driven by the desire to reduce CO2 emissions and develop fuel-efficient vehicles. In this context, the meta-materials or architectured materials offer considerable potential (e.g. micro-lattice invented at Caltech and produced by Boeing) and significant progresses have been achieved recently.



The idea explored here is to obtain a new class of materials by introducing a scale invariant (fractal) porosity inspired by the structure of bones. Special attention will also be paid at to which extend and how such a porous structure is reflected in terms of "risks", i.e. statistical fluctuations around average behavior. The final objective is to come up with rigorous rationalization tools to define one or more optima in terms of lightness, resistance to cracking, and risks (in the sense defined above) in this new class of materials.



Our previous research has provided a new formalism, at the interface between continuum mechanics and statistical physics, which permits (in simple cases) to take into account explicitly material spatial inhomogeneities and induced statistical aspects. We will seek to adapt this formalism to the case of fractal porosity. The study will rely on numerical approaches based on Random Lattice models of increasing complexity. Particular attention will be paid to a proper characterization of the statistical fluctuations around the average breaking behavior. The approach will then be confronted to experiments carried out on 2D printed samples of fractal porosity broken by means of an original experimental device developed in our laboratory and giving access to both fracture toughness and its statistical fluctuations.



This Ph.D. thesis takes place astride Statistical Physics, Continuum Mechanics and Materials Science. The candidate will have the opportunity to use, - and to familiarize himself with -, both the theoretical and experimental techniques developed in these three fields. Collaboration with the FAST laboratory in Paris-Saclay University is being currently developed. This PhD topic, combining both fundamental aspects and potential industrial applications, will permit the candidate to find job openings either in the academic field or in industry.
Electromechanical control of surface topological domain walls

SL-DRF-19-0384

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

Service de Physique de l'Etat Condensé

Laboratoire d'Etude des NanoStructures et Imagerie de Surface

Saclay

Contact :

Nicholas BARRETT

Starting date : 01-10-2019

Contact :

Nicholas BARRETT
CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

Thesis supervisor :

Nicholas BARRETT
CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

Personal web page : http://iramis.cea.fr/Pisp/87/nick.barrett.html

Laboratory link : http://iramis.cea.fr/spec/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2075

In ferroelectric or ferroelastic materials, domains form to minimize the electrostatic and mechanical contributions to the free energy, separated by Domain Walls (DW). DWs break translational symmetry to exhibit astonishing and very different properties compared to their parent materials, including conductivity, superconductivity and polarity. As a result, they could become a completely novel paradigm for nanoelectronics, in which the wall is the active element of the device. A reproducibly switchable 2D polar or conducting object in a dielectric medium would provide a route to extremely high storage densities with very low switching power per bit. The thesis will address walls between ferroelastic and ferroelectric domains.

Bulk single crystal ferroelectrics (BaTiO3), ferroelastics (CaTiO3) and epitaxial thin films (ferroelectrics BaTiO3, PbTiO3 and ferroelastic CaTiO3) will be studied. Low Energy and Photoemission Electron Microscopy will map the electrical topography, local chemistry and electronic structure of the domain walls. Dedicated set-ups for in-situ imaging of domain walls as a function of applied stress and electric field will be used for in operando experiments. In collaboration with Prof. Ekhard Salje (University of Cambridge) a mechanical model based will be used to simulate the emergence of polarity from strain gradients.

Ultra-fast Spintronics with antiferromagnetic insulators

SL-DRF-19-0913

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

Service de Physique de l'Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Michel VIRET

Starting date : 01-10-2019

Contact :

Michel VIRET
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 71 60

Thesis supervisor :

Michel VIRET
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 71 60

Personal web page : http://iramis.cea.fr/Pisp/michel.viret/

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

Among the ordered electronic states that occur in solid-state materials, magnetism is uniquely robust, persisting to well above room temperature in a wide variety of materials. Ferromagnets are now routinely used in the field of information technology. On the other hand, antiferromagnets (AF), which compose the overwhelming majority of magnetically ordered materials, have not been considered as candidates for active elements. In these materials, the magnetic moments of atoms align in a regular pattern with neighbouring spins pointing in opposite directions. Because of their zero net moment, antiferromagnets are rather insensitive to a magnetic field and difficult to probe. Thus, their intrinsic properties, and especially AF domains formation and the mobility of their domain walls, are poorly known.



In the last few years, it has been demonstrated that metallic antiferromagnets can lead to giant-magnetoresistance effects (resulting from spin-orbit-coupling), which validates their use as “spintronic elements”. On the other hand, insulating antiferromagnets are much more common than their conducting counterparts because super-exchange interactions in insulators are mainly antiferromagnetic. Direct control of AF properties requires unpractically large magnetic fields, not commonly available in a laboratory. The recent development of the spin transfer torque effect produced by spin polarized currents provides an ideal way of generating (the equivalent of) a staggered field, ideal to control the AF order. This should allow to toggle AF domains and influence the AF dynamical properties, but this has not yet been demonstrated.



The PhD work proposed here aims at assessing the potential of AF insulators in spintronics. These materials will be manipulated using pure spin currents generated through a newly discovered effect based on the ultra-fast demagnetization of an adjacent ferromagnetic layer. Both excitation and measurement will be carried out using a femtosecond laser.

Numerical simulations will also be developed through on an existing home-made code based on the dynamical resolution of the Landau-Lifshitz-Gibert equation on localised spins.

Molecular dynamics simulations of amorphous phase separated glasses

SL-DRF-19-0033

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 :

Cindy ROUNTREE

Starting date : 01-10-2019

Contact :

Cindy ROUNTREE
CEA - DRF/IRAMIS/SPEC/SPHYNX

+33 1 69 08 26 55

Thesis supervisor :

Cindy ROUNTREE
CEA - DRF/IRAMIS/SPEC/SPHYNX

+33 1 69 08 26 55

Personal web page : http://iramis.cea.fr/Pisp/cindy.rountree/

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

More : http://iramis.cea.fr/spec/index.php

ToughGlasses is a fundamental research project motivated by the need to improve and assess glasses mechanical durability over the long term. Glasses are integral parts our daily lives (buildings, cars, dishes…) along with being integral parts of heat resistant technologies, protection panels (smart phones, plasma screens…), low-carbon energies (protection for solar panels) and satellites in outer space to name a few. These systems and others undergo a variety of damage (consumer use, sand storms, external irradiations, high temperatures…) which can lead to premature failure and/or alterations of the physical and mechanical properties. Frequently, post-mortem failure studies reveal material flaws, which were propagating via Stress Corrosion Cracking (SCC). A recent question arriving in the field has been: Can the Amorphous Phase Separation (APS) of SiO_2-B_2 O_3-Na_2 O (SBN) glasses provide the necessary structure to enhanced SCC behavior? This thesis project aim is to fill this gap and to unravel the structural secrets behind enhanced SCC behavior.



The Ph.D. candidate will use Molecular Dynamics simulations to study the physical, mechanical and fracture properties of APS glasses. The primary objective of this study will be to use MD simulations to characterize the structure and failure properties of APS glasses and link these to experimental SCC studies. Hence, providing information on how the intrinsic structure of the glasses plays a role on the fracture properties of APS glasses. This method of comparing and contrasting MD simulations and stress corrosion cracking experiments has been used several times within our group to reach novel understandings of the process zone size versus the crack front velocity in pure silica (SiO2) and several SBN samples. Repeating this study for SBN APS glasses compositions will aid in the understanding of how the physical structure of glasses alters the mechanical properties.



In parallel, a second thesis student will conducting experimental studies (e.g. examining physical, mechanical and fracture properties) on the same materials. Both thesis students will work together in comparing and contrasting experimental and simulation results. Thus, researchers and developers will have a better idea of how small scale structural changes scale up to devise failures.



Logistically, the candidate will be advised by C. L. Rountree at CEA, SPEC. Simulations will be carried out on local HPC computers and eventually on large-scale HPC computers. The development of methods to form APS glasses will be part of the doctoral candidate’s tasks. Results concerning the structural formation of APS glasses will be compared and contrasted with thermodynamic results gathered from CALPHAD methods. In conclusion, the theme of this project is a comprehension of the source of the changes in the macroscopic property, and in particular how to control the stress corrosion cracking properties by varying the structure of glasses through Amorphous Phase Separation.

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

SL-DRF-19-0483

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.
Water photo-electrolysis assisted by an internal potential

SL-DRF-19-0755

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 : 01-10-2017

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

Photo-electrolysis is a very seductive solution to produce hydrogen using solar energy. Metal oxides are promising candidates for photoanode, but simple oxides present some limiting factors which can explain their relatively low efficiency for hydrogen production.



In this experimental thesis, we propose to use the spontaneous electric field of a ferroelectric compound to better separate photogenerated charges within the photoanode. In this study, we will investigate model samples (epitaxial thin films prepared by molecular beam epitaxy) and will study the influence of the electric polarization orientation with respect to the surface of the electrode (upward, downward, unpolarized, multi domains) on the photo-electrochemical efficiency. Moreover in order to understand the exact role of electrical polarization, we will measure the lifetime of the photogenerated charges and the electronic structure for the different state of polarization using synchrotron radiation. This thesis work is in the framework of long term research project where the CEA is associated with synchrotron SOLEIL, and University of Bourgogne for a modelisation of the systems.
Ab initio simulations of spin polarized STM images

SL-DRF-19-0780

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 : 01-10-2019

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.
In operando study of ferrite - perovskite multiferroic encapsulated microstructures

SL-DRF-19-0808

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/137/antoine.barbier.html

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

More : http://iramis.cea.fr/spec/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2545&id_unit=9&id_groupe=179

Perovskite ferroelectric oxides coupled with magnetic ferrites belong to the new class of artificial multiferroic materials. Their high potential for applications in spintronics and energy conversion makes their study a challenging topic. The nature of the coupling, especially during operation under an external field, remains largely unexplored. The proposed thesis work consists of a close collaboration between CEA/SPEC and SOLEIL synchrotron (HERMES beamline). The ferrite inclusions in a single crystalline perovskite film will be realized at CEA by molecular beam epitaxy assisted by an atomic oxygen plasma or thermal treatment. The behaviour of these inclusions under functioning conditions will be examined using the most advanced synchrotron radiations techniques and in particular spectromicroscopy, absorption, X-ray diffraction and magnetic dichroism, respectively on beamlines HERMES, DIFFABS and DEIMOS in a close collaborative approach. The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, magnetometry as well as in the above mentioned state of the art synchrotron radiation techniques.
Ab initio simulation of transport phenomena in atomic-scale junctions

SL-DRF-19-0723

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)

Hybrid carbon nanotube optoelectronic devices for silicon photonics

SL-DRF-19-0721

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 :

Arianna FILORAMO

Starting date : 01-10-2019

Contact :

Arianna FILORAMO
CEA - DRF/IRAMIS/NIMBE/LICSEN

01-69-08-86-35

Thesis supervisor :

Arianna FILORAMO
CEA - DRF/IRAMIS/NIMBE/LICSEN

01-69-08-86-35

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

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

Thanks to their outstanding electrical, mechanical and chemical characteristics, carbon nanotubes have been demonstrated to be very promising building blocks for future nanoelectronic technologies. In addition, recently their optical properties have attracted more attention because of their typical fundamental optical transition in the NIR [1-2] in a frequency range of interest for the telecommunications. The idea is to combine their particular optical features, inferred by their one-dimensional character, with their assessed exceptional transport and mechanics characteristics for hybrid optoelectronics/optomechanics application [3-5]. However, before that this can be realized some fundamental studies are necessary. Here, we will consider the mechanism involved in the electroluminescence and photoconductivity: both the carrier injection and the mechanisms leading to radiative recombination are to be considered. We will perform studies onto semiconducting nanotubes that we will extract from the pristine mixture by a method based on selective polymer wrapping [6-14]. Then, hybrid opto-mecanichal integrated devices will be considered. This will be realized thanks to the expertise of the associated laboratories. CEA-LICSEN (Laboratory of Innovation in Surface Chemistry and Nanosciences) is part of the DRF (Fundamental Research Department) division of CEA and develops pioneer research in molecular electronics and surface chemistry, with specific know how in carbon nanotubes and their nanofabrication and self-assembly techniques. CEA- LETI (LCO) (Laboratoire des Capteurs Optiques et Nanophotonique) is part of the LETI at CEA Tech (Technological Research Department) division of CEA which is specialized in nanotechnologies and their applications, with specific know-how in photonic, nano-systems (NEMS) and optomechanics.





[1] S. M. Bachilo et al. Science 298, 2361 (2002) ;

[2] O’Connell M. J. et al., Science 297, 593 (2002) ;

[3] Freitag et al., NanoLetter 6, 1425 (2006) ;

[4] Mueller et al., NatureNanotech. 5, 27 (2010) ;

[5] S.Wang et al. Nano Letter 11, 23 (2011);

[6] Nish, A. et al. Nat. Nanotechnol. 2, 640 (2007) ;

[7] Chen, F. et al. Nano Lett. 7, 3013 (2007) ;

[8] Nish, A. et al. Nanotechnology 19, 095603 (2008) ;

[9] Hwang, J.-Y. et al., J. Am. Chem. Soc. 130, 3543-3553 (2008) ;

[10] Gaufrès E. et al., Appl. Phys. Lett. 96, 231105 (2010) ;

[11] Gao, J. et al. Carbon 49, 333 (2011);

[12] Tange M. et al. ACS Appl. Mater. Interfaces 4, 6458 (2012)

[13] Sarti F. et al Nano Research 9, 2478 (2016)

[14] Balestrieri M. et al Advanced Functional Materials 1702341 (2017).

Detection of micronic and submicronic objects with a labo on chip based on GMR sensors

SL-DRF-19-0361

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

Service de Physique de l'Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Guenaelle Jasmin-Lebras

Stéphanie SIMON

Starting date : 01-02-2018

Contact :

Guenaelle Jasmin-Lebras
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 65 35

Thesis supervisor :

Stéphanie SIMON
CEA - DRF/Joliot/DMTS/SPI/LERI

01 69 08 77 04

Personal web page : http://iramis.cea.fr/Pisp/guenaelle.jasmin-lebras/

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

The development of early diagnosis techniques is a real challenge in the medical or defence domain. The aim is to obtain a lab on chip able to quickly detect, in a simple, sensitive and specific way, various rare biological objects in response to an urgent need for clinical diagnosis and/or biosecurity. For this purpose, the approach proposed by LERI and LNO is very innovative. It is based on the combination of specific labelling of antibodies developed at the LERI with magnetic nanoparticles and their dynamic detection with magnetic sensors based on highly sensitive spin electronics. This topic is currently the subject of a thesis, which has carried out the proof of concept study for the specificity of the test using a model of a murine myeloma cells. A new, more efficient device, with sensors on both sides of the microfluidic channel, has been developed. During this new thesis carried out in collaboration with the LERI, the aim will be to demonstrate that this lab on a chip is able to achieve sufficient performance to detect smaller biological objects like bacteria.

The LERI has already developed antibodies against various bacteria (Bacillus thuringiensis gram(+) bacterial spores, Salmonella Typhimurium gram(-) bacteria) used as models for the study of biological threat bacteria. At the LERI, the student will functionalize magnetic particles with various antibodies against these bacteria.

At the LNO, the student will aim to develop laboratories on a chip and evaluate their performance and robustness. He/she will have to learn how to manufacture them using the different techniques available in the department (clean room, laser cutting, deposit machines). He/she will have to design a transportable shielded device against magnetic noise in order to perform measurements at the LERI in a high microbiological safety level 2 environment. It will adapt the simulation and acquisition programs to the simultaneous detection of a bacterium by two sensors.

Hematite based photoelectrodes for low power consumption solar water splitting

SL-DRF-19-0476

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 : 01-10-2019

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/

Laboratory link : https://speclno.org/oxide%20nanorod.php

More : https://www.synchrotron-soleil.fr/fr/lignes-de-lumiere/HERMES

Hydrogen production by water splitting is a clean and viable approach to the world’s energy needs, yet it is very greedy in electrical energy consumption necessary to overcome the water redox potential. In order to reduce the energy consumption, we study the possibility of employing solar radiation, which, absorbed by identified and optimized semiconductor oxides, generates electron-hole pairs that will participate to redox reactions in a photo-electrolysis cell. Using a photo-anode and a photo-cathode in tandem configuration, hydrogen production could naturally occur via solar water splitting, without any electrical energy input to initiate the reaction.



The PhD student will first optimize the growth of hematite-based photo-electrodes by aqueous chemical growth. This method allows obtaining nanostructured films in the form of nano-rods, which are oriented perpendicularly to the substrate. Photo-anodes and photocathodes will be obtained by doping hematite with Ti and Mg or Zn, respectively. Photo-electrochemical activity will be correlated with surface morphology using techniques such as SEM and AFM, or with the surface potential measurements using the KPFM. In addition, a micro-spectroscopic approach using the STXM at the HERMES beamline at SOLEIL synchrotron, will allow probing the chemical composition and the electronic structure of the photo-electrodes at nanometric scales. These techniques will reveal the microscopic origin of the photoconduction properties. Moreover, they will provide the keys of optimizing the photo-electrodes via the physico-chemical parameters.
Magnetization dynamics of nanostructures in strongly out-of-equilibrium regimes

SL-DRF-19-0955

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

Service de Physique de l'Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Grégoire de Loubens

Starting date : 01-10-2019

Contact :

Grégoire de Loubens
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 71 60

Thesis supervisor :

Grégoire de Loubens
CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 71 60

Personal web page : http://iramis.cea.fr/Pisp/gregoire.deloubens

Laboratory link : https://www.speclno.org

This thesis aims at investigating, understanding and controlling the linear and nonlinear regimes of magnetization dynamics in individual nanostructures made of magnetic materials with very weak damping. An original near field microscopy technique developed in the host laboratory to detect the spin dynamics at the nanoscale will be employed to perform experiments, and analytical tools as well as micromagnetic simulations will be used for their interpretation. This work will take place in the framework of an ANR project whose goal is to demonstrate the manipulation of high amplitude coherent spin waves in devices combining concepts of magnonics and spintronics.



Keywords: magnetization dynamics; nanomagnetism; spintronics; magnonics; nonlinear dynamical systems

Methods: magnetic force microscopy; high frequency techniques; micromagnetic simulations

 

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