Service de Physique de l'Etat Condensé

SPEC PhD subjects

28 sujets IRAMIS//SPEC

Dernière mise à jour : 19-04-2018


• Mesoscopic physics

• Soft matter and complex fluids

• Solid state physics, surfaces and interfaces

 

Out-of-equilibrium thermoelectric transport in quantum conductors

SL-DRF-18-0459

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Geneviève FLEURY

Alexander SMOGUNOV

Starting date : 01-10-2017

Contact :

Geneviève FLEURY

CEA - DRF/IRAMIS/SPEC/GMT

0169087347

Thesis supervisor :

Alexander SMOGUNOV

CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Personal web page : http://iramis.cea.fr/spec/Pisp/genevieve.fleury/

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

This subject is now receiving CEA funding as a "flagship" topic. The selection of the candidatures received will be made at the beginning of spring 2018.



Seebeck and Peltier thermoelectric effects provide an eco-friendly way of converting heat into electricity and vice-versa. Thus it is possible with the Seebeck effect to harvest waste heat for producing electricity. Conversely, the Peltier effect enables local cooling of a device by investing electrical power. For a long time, thermoelectric conversion has been limited by a poor efficiency and therefore, practical applications have till date remained rare. Interest in the field has been recently rekindled by the discovery of new promising materials, by progress in nanostructuration, and by the growing societal concern about energy issues.



The purpose of this theoretical PhD thesis is to study analytically and numerically thermoelectric conversion in low-dimensional mesoscopic systems. We will consider the regime far from equilibrium where important thermoelectric effects are expected. In particular, we will investigate systems under dynamic time-dependent forcing. From a methodological standpoint, we will use the numerical tools and the analytical formalism developed at CEA-Grenoble (X. Waintal's team) for the study of (out-of-equilibrium) time-resolved quantum transport (see https://kwant-project.org/). We will adapt it to the case of thermoelectric transport and apply it to various systems (quantum dots, quantum point contacts, nanowires…).

Quantum heat transport in graphene Van der Waals heterostructures

SL-DRF-18-0412

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Nano-Electronique (GNE)

Saclay

Contact :

François PARMENTIER

Patrice ROCHE

Starting date : 01-10-2018

Contact :

François PARMENTIER

CEA - DRF/IRAMIS/SPEC/GNE

+33169087311

Thesis supervisor :

Patrice ROCHE

CEA - DRF/IRAMIS/SPEC/GNE

0169087216

Laboratory link : http://nanoelectronics.wikidot.com/research

The goal of this project is to explore quantum transport of heat in new states of matter arising in ultra-clean graphene in high magnetic fields, using ultra-sensitive electronic noise measurements.



The ability to obtain ultra-clean graphene (a two-dimensional crystal made of Carbon atoms in a honeycomb lattice) samples has recently allowed the observation of new phases of condensed matter in graphene under high magnetic fields. In particular, new states of the quantum Hall effect were observed at low charge carrier density [1], where interactions and electronic correlations can either make graphene completely electrically insulating, or give rise to the quantum spin Hall effect. In the latter, the bulk of the two-dimensional crystal is insulating, while electronic current is only carried along the edges of the crystal, with opposite spins propagating in opposite directions. The exact nature of those various states is still not fully understood, as one cannot probe the properties of the insulating regions by usual electron transport measurements.



We propose a new approach to probe those phases, based on the measurement of quantum heat flow carried by chargeless excitations such as spin waves, at very low temperature. Our method will consist in connecting the graphene crystal to small metallic electrodes which will be used as heat reservoirs. The temperature of each reservoir will be inferred by ultra-sensitive noise measurements [2], allowing us to extract the heat flow.



The first step of this project will consist in fabricating the samples made of graphene encapsulated in hexagonal boron nitride [3]. This technique, which we have recently developed in our lab, allows to obtain large-area, ultra-clean graphene flakes. In parallel, an experimental platform for low-temperature, high magnetic field, ultra-high sensitivity noise measurements will be set up.



[1] Young et al., Nature 505, 528-532 (2014).

[2] Jezouin, Parmentier et al., Science 342, 601 (2013).

[3] Wang et al., Science 342, 614 (2013).

Data-driven model-learning for suspensions of micro-swimmers

SL-DRF-18-0902

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Hugues CHATE

Starting date : 01-09-2018

Contact :

Hugues CHATE

CEA - DSM/IRAMIS/SPEC/SPHYNX

0169087535

Thesis supervisor :

Hugues CHATE

CEA - DSM/IRAMIS/SPEC/SPHYNX

0169087535

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

The past ten years have seen the emergence of Active Matter – composed of particles that convert energy from an ambient source into systematic movement – as a distinct topic in nonequilibrium statistical physics, motivated mainly by the need to understand and imitate individual and collective motility. Experiments are still relatively few, but, increasingly, large datasets obtained in controlled conditions are obtained with the aim of testing theoretical ideas and results. The time is ripe to try to build models from data, aiming at full quantitative agreement so that the effect of experimental control parameters on model parameters is made explicit. This is challenging and important since models, especially continuous ones, typically contain many terms parameters so that there is no one-to-one correspondence with experimental ones.



We will use high-throughput experimental data on bacterial suspensions (‘big data’, from collaborators in Shanghai and Hong Kong) to build quantitative models/theories.



The PhD work will consist of following two main avenues toward the overarching goal of building a direct quantitative link between experiments and theory. The first one, based on traditional model building based on multidimensional optimization of a set of target quantifiers, is already under way. The second one, based on automatic model learning, is more challenging and risky, as it will explore how to use machine-learning techniques to build a model ‘automatically’. The comparison between the results obtained using both routes will be particularly interesting. Analytical work necessary to derive kinetic and hydrodynamic theories from simple interacting swimmers models, including stochastic terms, will be developed in parallel.

Thermoelectric phenomena in ionic liquids and nanofluids

SL-DRF-18-0370

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Sawako NAKAMAE

Starting date : 01-10-2018

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

More : https://www.magenta-h2020.eu

Dissipation, cascades and singularities in turbulence

SL-DRF-18-0272

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Bérengère DUBRULLE

Starting date : 01-10-2017

Contact :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

Thesis supervisor :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

Personal web page : http://iramis.cea.fr/Pisp/berengere.dubrulle/index.html

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

Many phenomena in nature involve motion of viscous flows, which are widely believed to be described by Navier-Stokes equations (NSE). These equations are used for instance in numerical simulations of flows in astrophysics, climate or aeronautics. These equations are the cornerstones of many physical and engineering sciences, and are routinely used in numerical simulations. From a mathematical point of view, however, it is still unclear whether the Navier-Stokes equations are a well-posed problem in three dimensions, i.e. whether their solutions remain regular over sufficient large time or develop singularities.



Historically, the search for singularities in NSE was initiated by Leray who introduced the notion of weak solutions (i.e. in the sense of distribution). This notion was used to prove that the mathematical singular set has a one-dimensional Haussdorff measure equals to zero in space-time. Therefore, if these singularities exist, they must be extremely localized events in space and time. This makes their direct detection an outstanding problem. For some times, the best suggestive evidence of their existence was provided by the observation that the energy dissipation rate in turbulent flows tends to a constant at large Reynolds numbers This observation is at the core of the 1941 Kolmogorov theory of turbulence, and was interpreted by Onsager as the signature of singularities with local scaling exponent h=1/3. Later, it was conjectured that the singularities are organized into a multifractal set. Analysis of measurements of 3D numerical or 1D experimental velocity fields showed that the data are compatible with the multifractal picture, with a most probable h close to 1/3. However, this analysis could not reveal any information on the space-time statistics of (possible) singularities.



A major breakthrough was achieved when Duchon and Robert performed a detailed energy balance for weak solutions of INSE, and compute the contribution stemming from an eventual lack of smoothness. They show that it can be lumped into a single term that quantifies the "inertial" energy dissipation, i.e. the energy dissipated by non-viscous means.

The purpose of this thesis is to test these mathematical results in a numerical turbulent swirling flow to infer properties of the energy dissipation in a turbulent flow.

Optical measurements of dissipation and energy fluxes in turbulent flows

SL-DRF-18-0872

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Sébastien AUMAÎTRE

Starting date : 01-10-2018

Contact :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

Thesis supervisor :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

Personal web page : http://iramis.cea.fr/Pisp/sebastien.aumaitre/

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

The aim of this proposal is the study of power fluctuations in turbulent flow. The usual theoretical approaches have shown that the stationarity of the flow, implying the balance of the power injected large scales with the power dissipated at small scales, constrains the power spectrum of the velocity. However, one needs to go beyond to explain the complexity and the intermittency of turbulent flow. One can consider the statistical properties of the fluctuations of powers involved in turbulent flow. Especially one can explore the correlations implied by the stationarity on the fluctuations of injected and dissipated power and theirs consequences on the structure of the flow. The challenge is to estimate the fluctuations of dissipated power resolved in time. To do so, we would like to develop an innovative optical technics implying diffusive wave spectroscopy and ultra-fast image acquisition. This technics will be complemented by usual measurement technics in order to estimate simultaneously the injected power and to probe the structure of the flow.

Tunable multicomponent supramolecular magnetic self-assembly for spintronics

SL-DRF-18-0337

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Fabien SILLY

Starting date : 01-10-2018

Contact :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Thesis supervisor :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Personal web page : http://iramis.cea.fr/Pisp/fabien.silly/index.html

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

The autonomous ordering and assembly of molecules on atomically well-defined surfaces is an important technique for evolving applications in nanotechnology. The objective of this PhD project is to create tunable open molecular architectures to control the ordering of magnetic nano-objects on metal surfaces. The idea is to use experimental parameters to switch to one magnetic structure to another. These structures will be characterized using scanning tunneling microscopy in ultra-high vacuum and spin polarized scanning tunneling spectroscopy. Theses tunable nanostructures are model candidates to study magnetism at the nanometer scale.

Theoretical study of graphene electrodes for Molecular Electronics

SL-DRF-18-0818

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

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Yannick DAPPE

Starting date : 01-10-2018

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.

All oxide magnetic junctions

SL-DRF-18-0643

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Aurélie Solignac

Thomas Maroutian

Starting date : 01-10-2018

Contact :

Aurélie Solignac

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 95 40

Thesis supervisor :

Thomas Maroutian

Université Paris Sud - Centre de Nanosciences et de Nanotechnologies (C2N)

01 69 15 78 38

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

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

Generation of hot electrons of plasmonic origin: Physics and applications

SL-DRF-18-0292

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Ludovic DOUILLARD

Starting date : 01-10-2018

Contact :

Ludovic DOUILLARD

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 36 26

Thesis supervisor :

Ludovic DOUILLARD

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 36 26

Personal web page : http://iramis.cea.fr/Pisp/ludovic.douillard/

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

Physics and applications of hot electrons of plasmonic origin



At small scale, the interaction of light with a metal object results in the occurrence of remarkable resonances within the absorption spectrum, the plasmon resonances. These resonances correspond to collective oscillations of the charge carriers [Mie 1908] and constitute a research domain in itself known as Plasmonic. Beyond its interest in the manipulation of the near optical field, a metal object at plasmonic resonance is a source of hot electrons whose electronic properties can be used to achieve non classical chemistry reactions at the local scale.



This work aims to study the fundamental physics of the emission of hot electrons by a nanometric metal object in connection with applications, particularly medical ones such as the anticancer photodynamic therapies. It is a work of experimental character in close collaboration to a relevant partnership of physicists, chemists, biologists and oncologists from different Institutions (CEA, CentraleSupélec, Saint-Louis Hospital). It will benefit from the experience acquired by the CEA IRAMIS SPEC group in LEEM / PEEM (Low Energy Electron / PhotoEmission Electron Microscopy) microscopies, the principle of which is based directly on the acquisition of the distribution of the photoelectrons emitted in response to a plasmon resonance decay [Douillard 2012, 2011] and is therefore a unique technique of choice for this study.



The objectives are to answer fundamental questions related to the emission of hot electrons by a metal particle under ultrafast multiphoton optical excitation. In particular, this involves determining the emission dynamics of the charge carriers (pump probe experiment) and their physical distributions : spatial mapping of the emission hot spots at the nano-object scale and energy mapping through the determination of the kinetic energy spectra. The ultimate goal takes place in the context of a project devoted to medical oncology and more specifically on the optimization of anticancer therapies under development, namely the photothermal and photodynamic therapies.



Keywords: hot electrons, plasmon, laser, PEEM, LEEM



[Mie 1908] G. Mie, Ann. Phys. (Leipzig) 25 (1908) 377

[Douillard 2012, 11] C. Awada, et al. J. of Phys. Chem. C 16 (2012) 14591 DOI 10.1021/jp303475c, L. Douillard, F. Charra. J. of Phys. D: Applied Physics 44 (2011) 464002 DOI:10.1088/0022-3727/44/46/464002, C. Hrelescu, et al. Nano Lett. 11 (2011) 402–407 DOI: 10.1021/nl103007m



Laboratoire d’accueil CEA IRAMIS SPEC UMR 3680

Correspondant CEA chargé du suivi de la thèse ludovic.douillard@cea.fr

Ecole doctorale Ondes et Matière, Univ. Paris Saclay.

Magnetic properties of differently-shaped metal nanocrystals

SL-DRF-18-0336

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Fabien SILLY

Starting date :

Contact :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Thesis supervisor :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Personal web page : http://iramis.cea.fr/Pisp/fabien.silly/index.html

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

The structure and shape of metal nanocrystals govern their magnetic properties at the nanometer scale. The objective of this PhD project is to grow differently-shaped metal nanocrystal and investigate their magnetic properties. These structures will be characterized using scanning tunneling microscopy in ultra-high vacuum, spin polarized scanning tunneling spectroscopy and synchrotron spectroscopy. Theses tunable nanostructures are model candidates to study magnetism and observe new magnetic phenomena at the nanometer scale.

Superparamagnetic transitions in 3D superlattices of magnetic nanocrystals

SL-DRF-18-0451

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

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

caroline RAEPSAET

Sawako NAKAMAE

Starting date : 01-10-2018

Contact :

caroline RAEPSAET

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169082423

Thesis supervisor :

Sawako NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

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

Interactions between magnetic nanocrystals give rise to a large variety of magnetic behaviors, grouped together in a new field of physics called "supermagnetism." In this PhD project, we propose an experimental study of supermagnetic transitions; i.e., superspin glass (SSG) and dipolar superferromagnetism (SFM), in supracrystals (SC) of cobalt nanoparticles (NP) controlled by structural constraints.



We are working with 3D supracrystals, which are artificial solids which building block is not the atom but the nanoparticle. As in atomic solids, nanocrystals are organized in a specific structure such as face centered cubic (cfc) structure. The dipolar moments of nanocrystals are thus found on regular supra-lattice sites, and interact with one another through dipolar interactions. The geometric simplicity of these supracrystals offers a “real” and “simple” system that can be modelled numerically and theoretically. Supracrystal samples are prepared at the MONARIS UPMC/CNRS laboratory, with controlled NP and SC crystallinity and morphology conditions.



The proposed study concerns the experimental study of the evolution of the magnetic states of supracrystals of Co nanoparticles. Two measurements methods will be used, globally, by SQUID (Superconducting Quantum Interference Device) magnetometry and microscopically, using miniature Hall-probes. With the latter technique, we hope to detect the ferromagnetic transition in a single domain supracrystal, a decisive experimental proof of the existence dipolar SFM.



The main issue of this work concerns fundamental physico-chemistry, by evidencing the dipolar SFM in 3D superlattices. Predicted by theoretical studies, it hasn’t been observed yet. This experimental study will require a strong collaboration with the theoreticians, for interpreting the experimental results as well as validating the modelization. SFM supracrystals will find applications in the medical field, for data storage…



The competences required for the proposed study will include NP magnetism, magnetic measurements techniques (ultra-sensitive magnetometry integrating very low noise measurements), cryogenic technics, statistical analysis and experimental results interpretation. Motivated candidates will have the possibility to participate to the NP and SC synthesis, and to their structural characterization (SAXS, MET, MEB…).

Lab on chip magnetoresistive biosensors for early and fast diagnosis

SL-DRF-18-0766

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Guenaelle Jasmin-Lebras

Claude FERMON

Starting date : 01-10-2018

Contact :

Guenaelle Jasmin-Lebras

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 65 35

Thesis supervisor :

Claude FERMON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 01

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

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

The development of technology of early diagnosis, at the same time fast and sensitive, allowing the detection of very small quantities of (sub) micrometric biological objects (cells, bacteria, proteins etc…) is a real challenge in the medical domain. One possible method consists to label these biological objects with magnetic particles. This feature can be combined with magnetic detection, where magnetoresistive sensors, developed in our lab (LNO) to measure very low magnetic signals, can be integrated within microfluidic channels to detect these magnetically labelled biological objects.

During this PhD, the student will optimize the current lab on chip to increase the efficiency of the tests and to detect very small biological objet like bacteria and proteins . He will use the cleaning room technicals to make the GMR sensors and the microfluidic channels. He will adapt the electronic and the microfluidic parameters to optimize the signal noise ratio (SNR). In collaboration with the LERI (DRF/JOLIOT/SPI) specialized for several years in the development of fast tests of detection, he will functionalize magnetic particles with various antibodies managed against various biological objects

Ultra low field Magnetic Resonance Imaging

SL-DRF-18-0386

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Claude FERMON

Starting date : 01-10-2018

Contact :

Claude FERMON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 01

Thesis supervisor :

Claude FERMON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 01

We have developed magnetic hybrid sensors based on the association of a superconducting loop to a micron size giant magnetoresistive sensor. These sensors will allow exploring a new field: Nuclear Magnetic Resonance and Magnetic Resonance Imaging at very low fields (of the order of a milliTesla).



A full head very low field MRI prototype has been built and has demonstrated the approach. The goal of the PhD will be firstly to participate to the installation of the system at Neurospin and implement fast acquisition schemes. In addition, a work on the next generation of magnetic sensors based on tunnel magnetic junctions will be performed to improve the signal to noise of the system.

Characterization of the interface electronic structure of ultra-thin ferroelectric HfZrO2 films for low power, CMOS-compatible, non-volatile memories

SL-DRF-18-0824

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS)

Saclay

Contact :

Claire Mathieu

Nicholas BARRETT

Starting date : 01-10-2018

Contact :

Claire Mathieu

CEA - DRF/IRAMIS/SPEC/LENSIS

+33 1 69 08 47 27

Thesis supervisor :

Nicholas BARRETT

CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

Personal web page : http://iramis.cea.fr/Pisp/claire.mathieu/

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

The Internet of Things (IoT) requires intelligent, fast and energy efficient handling of sensory, inhomogeneous data. eFlash is the standard non-volatile memory (NVM), however, it suffers from low write speed, high power, low endurance and vulnerability to radiation.



FeRAM has the highest endurance among all NVM candidates, low energy per bit and power consumption making it a candidate to replace Flash in embedded applications.



Within the framework of the H2020 European project 3eFERRO, led by the CEA, we will use new ferroelectric HfO2-based materials to develop a competitive and versatile FeRAM technology for eNVM solutions.

The formation of an interface layer (IL) can be of crucial important to ultimate device performance and is one of the major challenges for materials engineering of FE HfO2.



Advanced characterization tools, including both soft and hard X-ray photoemission will describe the IL formation and its effect on for example band line-up, leakage and defect levels. Synchrotron radiation induced photoemission using both soft and hard X-rays will be used. Results of structural, chemistry and trap investigations will allow understanding how the defects and ILs affect the material parameters and device characteristics.

FE domain imaging in doped HfO2 and HfZrO2 will be performed using low energy and photoemission electron microscopy (LEEM and PEEM) to investigate the ferroelectricity at the nanoscale.



The thesis will require close collaboration with the partners in the 3eFERRO project. The successful candidate will participate actively in regular project meetings. The candidate will also carry out the synchrotron radiation campaigns at, for example, Soleil (Saint Aubin), Elettra (Trieste), Petra-3 (Hambourg).

Highly spin-polarized electron transport in organic molecule-based magnetic junctions

SL-DRF-18-0443

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

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Alexander SMOGUNOV

Starting date : 01-05-2018

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 propose to study theoretically spin-polarized electron transport in tunnel junctions made of organic molecules connecting two ferromagnetic electrodes – the subject of great interest in the field of organic/molecular spintronics [1]. The particular stress will be made on the possibility to optimize and to control the degree of spin-polarization of electric current and the magnetoresistance of a junction – very important properties in spintronics – by a clever choice of molecules themselves or by some external stimuli such as a temperature (via interaction of electrons with molecule vibrations), an electric field (a gate), or a mechanical strain exerted on the molecule by electrodes. We will especially exploit a symmetry aspect of electronic orbitals of a molecule – the idea which we have recently proposed [2] – which can allow to spin-filter the electric current in the most efficient way. The combination of ab initio DFT (Density Functional Theory) electronic structure methods, as implemented in the Quantum ESPRESSO (QE) package [3], with model electron transport calculations, based on the Keldysh formalism, will be used during the project. Various new functionalities and features such as, for example, an electron-phonon coupling at the molecule or a thermal transport, will be implemented in both QE and electron transport codes.



[1] A. R. Rocha et al., Towards molecular spintronics, Nature Mater. 4, 335(2005); S. Sanvito,

Molecular spintronics, Chem. Soc. Rev. 40, 3336 (2011); V. Alek Dediu et al., Spin routes in

organic semiconductors, Nature Mater. 8, 707 (2009);

[2] A. Smogunov and Y. J. Dappe, Symmetry-Derived Half-Metallicity in Atomic and Molecular

Junctions, Nano Lett. 15, 3552 (2015);

[3] P. Giannozzi et al., QUANTUM ESPRESSO: a modular and open-source software project for

quantum simulations of materials, Phys.: Condens. Matter 21, 395502 (2009).

Theoretical investigation of the magnetic anistropy of hybrid systems for molecular spintronics

SL-DRF-18-0045

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

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Cyrille BARRETEAU

Starting date : 01-12-2017

Contact :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Thesis supervisor :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Personal web page : http://iramis.cea.fr/Pisp/cyrille.barreteau/

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

Nanomagnetism is an active field at the frontier of various domains. It consists in the study (and use) of the magnetism of nanometer sized systems. Magnetic properties of nano-objects generally strongly differ from their bulk counterpart. A major issue is to control/manipulate their magnetic properties. One of the fundamental properties of magnetic materials is their magnetic anisotropy which is characterized by their easy axis but also anisotropic magnetoresistance (AMR). It has been recently demonstrated that the interaction between a magnetic thin film and adsorbed molecules can greatly modify the anisotropy of the film due to hybridization between the molecule and the surface atoms of the substrate. Recent experiments have also shown that large AMR can be achieved in “simple” systems such as nano-conctrictions of nickel connected via a benzene molecule.

In this internship we propose to study via electronic structure methods (ab-initio and/or tight-binding) the magnetic anisotropy of few simple systems. We will first consider cobalt and iron thin films in interaction with simple molecules. More complex systems will be further investigated. The final goal is to find systems molecule/substrate with optimal properties in view of possible applications.

Ab initio simulations of spin polarized STM images

SL-DRF-18-0886

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

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Yannick DAPPE

Starting date : 01-10-2018

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.

New electronic states in single crystals and thin films of iridates

SL-DRF-18-0419

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Jean-Baptiste MOUSSY

Dorothée COLSON

Starting date : 01-10-2018

Contact :

Jean-Baptiste MOUSSY

CEA - DRF/IRAMIS/SPEC/LNO

01-69-08-92-00

Thesis supervisor :

Dorothée COLSON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 73 14

Personal web page : http://iramis.cea.fr/spec/Pisp/jean-baptiste.moussy/

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

More : http://iramis.cea.fr/spec/Pisp/dorothee.colson/

Iridates (e.g. Sr2IrO4, Sr3Ir2O7 ...) have recently attracted attention due to the presence of a strong spin-orbit coupling and strong electronic interactions that give rise to original physical properties such as, the high critical temperature superconductivity or the state of topological insulator (insulator with metallic surface states). Especially, the identification of a topological phase in these oxides should allow exploring new ways to manipulate the spin of electrons, a key point for applications in spintronics.



The aim of this thesis project is to study the emergence of Mott insulators, magnetic and topological properties in single crystals, single layers and heterostructures of iridates. More precisely, the objectives of the thesis will be to synthesize new compounds of the iridates family (e.g.Sr3Ir2O7) in the form of single crystals and thin films to explore their electronic properties (new topological phases, new Mott insulators, etc).



For the development of single crystals, the self-flux method will be chosen. Sr3Ir2O7 crystals of pure compound will be synthesized and electron doping will be achieved through cationic substitutions (for example: Sr/La). Then, the crystals will be characterized by different techniques: X-ray diffraction, electron microprobe and magnetic measurements (SQUID, VSM magnetometry). For thin films, we will use a new ultrahigh vacuum growth technique developed in the laboratory: the pulsed laser deposition (PLD) method with a laser beamworking in the nanosecond or femtosecond regime. PLD is a well-known technique for the epitaxial growth of oxide thin films (cuprates, manganites, ferrites ...), which is based on the ablation by a laser beam of the target of the material to be deposited on a monocrystalline substrate.



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 microscopy (AFM), magnetism (SQUID,VSM).



The electronic properties of samples (crystals and films) will then be studied in collaboration with the LPS-Orsay, including electrical measurements and the quantum spin Hall effect, which is the signature of a topological state.

Epsilon-Near-Zero modes in metamaterials for optoelectronics

SL-DRF-18-0399

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Simon VASSANT

Starting date : 01-10-2018

Contact :

Simon VASSANT

CEA - DRF/IRAMIS/SPEC/LEPO

+33 169 089 597

Thesis supervisor :

Simon VASSANT

CEA - DRF/IRAMIS/SPEC/LEPO

+33 169 089 597

Personal web page : http://iramis.cea.fr/Pisp/simon.vassant/index.php

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

Our team has already demonstrated theoretically and experimentally the interest of specific electromagnetic modes (epsilon-near-zero modes) for optoelectronics. These modes allow the confinement of light in a layer of sub-wavelength thickness (less than the penetration depth of the light), and thus maximize the interaction between photon and the matter.



The subject of PhD deals with the design, realization and characterization of artificial materials (metamaterials) to realize and control these electromagnetic modes.



Two approaches will be considered:

- The first is based on quantum cascade detector concepts, in partnership with C2N, ONERA, the Institut d'Optique and the 3-5 Lab (Thalès) as part of an ANR project funded from 2018 to 2022.

- The second, more exploratory, proposes to use supra-molecular assemblies on graphene. This technique is at the heart of the laboratory's expertise.



The doctoral student will have to model the structures to be created (using available numerical codes), then will have to manufacture and characterize the samples made. Part of the manufacturing will be done in clean room.

Ab initio simulation of transport phenomena in atomic-scale junctions

SL-DRF-18-0899

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

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Alexander SMOGUNOV

Starting date : 01-09-2018

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)

ToughGlasses: Researching tomorrow’s glasses today

SL-DRF-18-0227

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

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Cindy ROUNTREE

Starting date : 01-10-2018

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/

The 3 years of this PhD subject are today funded by an ANR project. Decision by the laboratory over a candidature will be given early (beginning of spring 2018).



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 SiO2-B2O3-Na2O (SBN) glasses provide the necessary structure to enhanced SCC behavior? ToughGlasses aim is to fill this gap and to unravel the secret behind enhanced SCC behavior.



The Ph.D. candidate will have the opportunity to study the physical, mechanical and stress-corrosion cracking properties of APS glasses. The primary objective of this study will be to observe stress corrosion crack propagation in situ and the analysis of fracture surfaces in several pristine and APS glasses. Hence, providing information on environmental limit of stress corrosion cracking and understanding of how the crack growth occurs in APS glasses. This method was previously used in our group to study 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 conjunction with the primary objective, the candidate will have the occasion to characterize the elastic properties of the samples and their structures (Raman, NMR spectroscopy, X-ray absorption …) with various collaborators including collaborators in CEA, DEN and University of Rennes. This will allow for a comparison of the fracture behavior of glasses with other macroscopic and microscopic properties.



Logistically, the candidate will be co-advised by C. L. Rountree at CEA and F. Célarié at Université de Rennes 1. Glass formation and preliminary tests will occur at Université de Rennes 1 and stress corrosion cracking tests along with other tests will be carried out at CEA. In conclusion, the theme of this project is the 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.



Some Relevant Publications:

1) “SiO2-Na2O-B2O3 density: A comparison of experiments, simulations, and theory.”

M. Barlet, A. Kerrache, J-M Delaye, and C. L. Rountree Journal of Non-Crystalline Solids. 382, 32, (2013)

2) "Hardness and Toughness of Sodium Borosilicate Glasses via Vicker's indentations”

M. Barlet, J-M. Delaye, T. Charpentier, M. Gennisson, D. Bonamy, T. Rouxel, C.L. Rountree

Journal of Non-Crystalline Solids. 417–418:66-69 (June 2015).

DOI:10.1016/j.jnoncrysol.2015.02.005

3) “Role of evaporation rate on the particle organization and crack patterns obtained by drying a colloidal layer”

K. Piroird, V. Lazarus, G. Gauthier, A. Lesaine, D. Bonamy and C. L. Rountree

Europhysics Letters, 113:38002 (February 2016).

4) “From network depolymerization to stress corrosion cracking in sodium-borosilicate glasses: Effect of the chemical composition.”

M. Barlet, J.-M. Delaye, B. Boizot, D. Bonamy, R. Caraballo, S. Peuget and C. L. Rountree

Journal of Non-Crystalline Solids. 450:174-184 (15 October 2016).

Molecular dynamics simulations of amorphous phase separated glasses

SL-DRF-18-0877

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

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Cindy ROUNTREE

Starting date : 01-10-2018

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.

Characterization Electro-mechanical Control of Charged Domain Walls

SL-DRF-18-0825

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS)

Saclay

Contact :

Nicholas BARRETT

Starting date : 01-10-2018

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/nick.barrett/

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

Ferroelectrics are insulating by nature but the recent discovery of domain wall conduction has triggered a new era for these materials: domain walls exhibit very different electronic properties and can be controlled (written or erased) under application of low power electrical fields. They are naturally nano-sized and therefore highly scalable. The conceptual breach is based here on the domain wall itself becoming the active element of the device. Under certain conditions charged domain walls can be created with true metallic conduction, orders of magnitude higher than in bulk domains through quasi 2D electron gas at the domain wall. The conductivity may be chemically or electrically controlled. The aim of the project is to realize, study and control such charged domain walls in BaTiO3 and in BiFeO3.



Water photo-electrolysis assisted by an internal potential

SL-DRF-18-0353

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

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.

Failure behavior in mechanical metamaterials bone-inspired

SL-DRF-18-0887

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

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

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.

In operando study of ferrite - perovskite multiferroic encapsulated microstructures

SL-DRF-18-0351

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Antoine BARBIER

Starting date : 01-10-2018

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 multiferroïc 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 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 behavior of these inclusions under functioning conditions will be examined using the most advanced synchrotron radiations techniques and in particular spectro-microscopy, 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 and magnetometry, as well as in the above mentioned state of the art synchrotron radiation techniques.

Magnetic skyrmion dynamics in nanostructures

SL-DRF-18-0911

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

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Grégoire de Loubens

Starting date : 01-10-2018

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

More : http://www.cnrs-thales.fr/spip.php?article64&lang=fr

Magnetic skyrmions are topological singularities appearing in magnetic materials with strong Dzyaloshinskii-Moriya interaction (DMI), which favor non-colinear configurations of the magnetization. These topological objects are interesting candidates for information storage and processing, as they are naturally coupled to spintronics. Nevertheless, their stability and dynamics still have to be investigated. Recently it has been demonstrated that such structures having typical size of a few tens of nanometers could be stabilized at room temperature in nanodisks patterned from multilayers with perpendicular magnetic anisotropy and strong DMI. Their excitation spectrum has also been calculated, but never measured so far. The main objective of this thesis will thus be to experimentally probe the spin-wave excitation modes in individual nanostructures hosting single skyrmions. Another aspect will be to investigate radio frequency devices based on skyrmions, since frequency generation and detection as well as signal processing could benefit from their specific magnetization dynamics.



This thesis work will be conducted in close collaboration between the Service de Physique de l’État Condensé (CEA/CNRS) and the Unité Mixte de Physique CNRS/Thales, in the framework of the ANR project TOPSKY, which started at the end of 2017. It will be co-directed by Grégoire de Loubens (SPEC) and Vincent Cros (UMPhy).

 

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