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PhD subjects

32 sujets IRAMIS

Dernière mise à jour : 16-07-2018


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• Solid state physics, surfaces and interfaces

 

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

Laboratoire Nano-Magnétisme et Oxydes

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).

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

Laboratoire d'Electronique et nanoPhotonique Organique

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.

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

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

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).

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

Groupe Mésocopie Modélisation et Thermoélectricité

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.

Exploring spin fluctuations in photosensitive molecules

SL-DRF-18-0416

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

Laboratoire Léon Brillouin

Groupe Interfaces et Matériaux

Saclay

Contact :

Gregory CHABOUSSANT

Starting date : 01-10-2018

Contact :

Gregory CHABOUSSANT

CNRS-UMR 12 - LLB - Laboratoire de Diffusion Neutronique

01 69 08 96 51

Thesis supervisor :

Gregory CHABOUSSANT

CNRS-UMR 12 - LLB - Laboratoire de Diffusion Neutronique

01 69 08 96 51

Personal web page : http://iramis.cea.fr/Pisp/gregory.chaboussant/

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

In the general framework of nanomagnetism, this research subject deals with fundamental properties of new magnetic materials (molecular magnetic clusters, magnetic nanoparticles) displaying very interesting functional properties like photo-commutation or the precise control of magnetization at the molecular level (data storage).



These “switchable” molecular solids are promising materials for high-density optical memory devices. Molecular materials with so-called “spin transition” properties are capable to drastically change their magnetic state upon temperature variation or under light radiation (photomagnetism). This transition is induced by an electronic state conversion of the magnetic atoms (from low-spin to high-spin state).



We have undertaken study using Small Angle Neutron Scattering (SANS) to probe structural and magnetic properties of coordination nanoparticles (CNPS’s) which are novel systems that open new possibilities for the design of molecule-based bistable objects where magnetism may be controlled or tuned by an external perturbation (light, temperature, field, etc.). Neutron scattering experiments will be carried out at the LLB neutron source (CEA Saclay, south of Paris) and/or at the Institute Laue-Langevin (Grenoble).

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

Laboratoire d'Etude des NanoStructures et Imagerie de Surface

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).

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

Laboratoire Nano-Magnétisme et Oxydes

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.

Hybrid carbon nanotube optoelectronic devices for silicon photonics

SL-DRF-18-0445

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 : 01-10-2018

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).

Ab initio study of electronic properties of Calcium Oxalate

SL-DRF-18-0461

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Francesco SOTTILE

Starting date : 01-10-2018

Contact :

Francesco SOTTILE

Ecole Polytechnique - UMR 7642

0169334549

Thesis supervisor :

Francesco SOTTILE

Ecole Polytechnique - UMR 7642

0169334549

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

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

More : https://portail.polytechnique.edu/lsi/fr/recherche/spectroscopie-theorique

Calcium Oxalate is a chemical compound found in plants (used to detoxify from calcium excess), in human-driven procedures (like in beer brewing, when it produce the famous beerstones), and constitutes the most common compound of human kidney stones. In particularly linked to the latter application, for its evident medical interest, the scope of this PhD work is to study the structure, electronic and dielectric properties of the different flavours of calcium oxalate, from the anhydrous do the mono- di- and tri-hydrate polimorphisms.



Objectives of the work include the provision of reference optical and loss spectra for the different phases and structure, as well as the proposition of new experiments, both with X-ray (Inelastic X-ray scattering) and electrons probe (Electron Energy Loss Spectroscopy). The PhD candidate has a strong background in solid-state physics, and will work within Time-Dependent Density Functional Theory and Many-Body Perturbation Theory.

Development of density functionals for observables

SL-DRF-18-0478

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Lucia REINING

Starting date : 01-10-2018

Contact :

Lucia REINING

CNRS - LSI/Laboratoire des Solides Irradiés

0169334553

Thesis supervisor :

Lucia REINING

CNRS - LSI/Laboratoire des Solides Irradiés

0169334553

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

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

Density Functional Theory (DFT) [1] tells us that the external potential, and therefore all observables, are functionals of the ground state density. The exact functionals are of course not known, and much effort goes into the design of suitable approximations. However, these are mostly limited to functionals for the total energy, and other observables are usually approximated by using a single Kohn-Sham Slater determinant [2] instead of the many-body ground-state wave function.



Here we are exploring possibilities to build density functionals that would directly yield observables. The main ingredients of our approach are an inversion of the diagrammatic expansion of many-body perturbation theory, and the design of a “connector” that allows us to profit from calculations which are performed once and forever in a model system [3,4]. We have already shown that using the connector idea we can describe many-body effects that go beyond the capabilities of usual DFT approximations, such as double-plasmon excitations in loss spectroscopies. If successful, besides its intellectual interest this strategy might have a strong impact in the field of materials design.



This thesis will combine conceptual, analytical and numerical work. Since it is based on a new strategy, we expect to obtain important results even without setting up a very complicated framework.





[1] W. Kohn, "Nobel Lecture: Electronic structure of matter - wave functions and density functionals", Rev. Mod. Phys. 71, 1253 (1999).

[2] W. Kohn and L. J. Sham, "Self-Consistent Equations Including Exchange and Correlation Effects", Phys. Rev. 140, A 1133 (1965)

[3] M. Vanzini, L. Reining, and M. Gatti, “Dynamical local connector approximation for electron addition and removal spectra”, arXiv:1708.02450

[4] M. Panholzer, M. Gatti, and L. Reining, “Non-local and non-adiabatic effects in the charge-density response of solids: a time-dependent density functional approach”, arXiv:1708.02992

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

Laboratoire d'Electronique et nanoPhotonique Organique

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 description of non-linear processes in magnetic materials

SL-DRF-18-0364

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Valérie VENIARD

Starting date : 01-10-2018

Contact :

Valérie VENIARD

CNRS - LSI/Laboratoire des Solides Irradiés

01 69 33 45 52

Thesis supervisor :

Valérie VENIARD

CNRS - LSI/Laboratoire des Solides Irradiés

01 69 33 45 52

Personal web page : http://etsf.polytechnique.fr/People/Valerie

Second harmonic generation (SHG) is a process where two photons are absorbed by a material and a photon of twice the energy of the incoming photons is emitted. This spectroscopy is used to study the optical properties of materials because it reveals additional information, compared with linear optical spectroscopies.



Due to dipole selection rules, SHG is forbidden in centro-symmetric materials and it is possible to obtain a structural and electronic characterization for these systems. However the absence of time-inversion symmetry in antiferromagnetic materials leads to new contributions in second harmonic generation, thus revealing the arrangement of spins in the solid. SHG becomes a powerful tool to study of ultra-fast demagnetization processes.



There are few satisfactory theoretical descriptions for SHG in magnetic materials, since spin-orbit coupling, electron-electron interactions and local field effect must be treated on the same footing. To study this process, we have developed a formalism within the framework of Density Functional Theory (DFT). In this thesis, we will focus on the electron-electron interaction, described by an exchange-correlation kernel fxc which must be approximated. We will explicitly deal with spin-orbit coupling, describing electronic orbitals by a 2D spinor. We will study these effects for a typical antiferromagnetic material, namely Cr2O3.

Atomistic modelleing of the growth of III-V nitride alloys for high power high frequency components

SL-DRF-18-0740

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

Centre de recherche sur les Ions, les Matériaux et la Photonique

Centre de recherche sur les Ions, les Matériaux et la Photonique

Saclay

Contact :

Jun CHEN

Starting date : 01-10-2018

Contact :

Jun CHEN

Université de Caen - CIMAP - Centre de Recherche sur les Ions, les Matériaux et la Photonique

02 33 80 85 21

Thesis supervisor :

Jun CHEN

Université de Caen - CIMAP - Centre de Recherche sur les Ions, les Matériaux et la Photonique

02 33 80 85 21

Personal web page : http://cimap.ensicaen.fr/spip.php?article204

Laboratory link : http://cimap.ensicaen.fr/spip.php?rubrique99

More : http://cimap.ensicaen.fr/

The wurtzite III-V nitride semiconductors (Al, Ga, In)N exhibit important physical properties, indeed, their band gap alloys to cover wavelengths from deep ultraviolet to near infrared, moreover, they have a ceramic character, which a high mechanical and thermal stability. Therefore, they are at the basis of electronic components that may also be used in harsh environments. For the fabrication of optimized high power, high frequency transistors, InAlN barrier have been forecast to constitute the best candidate, however obtaining highest quality layers still constitutes a challenge. In this scope, the topic of the proposed PhD research is to model the growth of such alloys using atomistic modelling through molecular dynamics. The developed tools will be integrated within our existing multiscale system for the investigation of materials properties. This theoretical work will be completed by extensive investigations of the alloys by transmission electron microscopy in close collaboration with industrial partners who carry out the growth optimization for these materials.

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

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.

All oxide magnetic junctions

SL-DRF-18-0643

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

Service de Physique de l'Etat Condensé

Laboratoire Nano-Magnétisme et Oxydes

Saclay

Contact :

Aurélie Solignac

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/

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

Laboratoire Nano-Magnétisme et Oxydes

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.

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

Laboratoire d'Electronique et nanoPhotonique Organique

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.

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

Groupe Mésocopie Modélisation et Thermoélectricité

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.

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

Laboratoire Nano-Magnétisme et Oxydes

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

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

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

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…).

Exploration of honeycomb tellurates

SL-DRF-18-0896

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

Laboratoire Léon Brillouin

Groupe Diffraction Poudres

Saclay

Contact :

Françoise DAMAY-ROWE

Starting date : 01-10-2018

Contact :

Françoise DAMAY-ROWE

CNRS-UMR 12 - LLB - Laboratoire de Diffusion Neutronique

01 69 08 49 54

Thesis supervisor :

Françoise DAMAY-ROWE

CNRS-UMR 12 - LLB - Laboratoire de Diffusion Neutronique

01 69 08 49 54

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

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

Layered honeycomb materials offer an extremely large variety of exotic magnetic behaviours, linked with the frustrated topology of the lattice, from quantum spin liquids to non colinear or dimerized magnetic orderings.



The goal of the proposed study is to study new tellurium oxides with a honeycomb structure, derived from PbSb2O6. The main challenge will be to link the crystal structure and the magnetic ground state with the observed macroscopic properties and theoretical predictions. In addition, for long-range ordered compounds, physical characterizations including dielectric properties and polarization measuresments will be carried out, in view of multiferroic applications.



The main experimental technique will be neutron scattering, which allow one to get informations on both the crystal and magnetic lattices, and on their corresponding excitations.

Design of auxiliary systems for the calculation of observables

SL-DRF-18-0479

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

Laboratoire des Solides Irradiés

Laboratoire des Solides Irradiés

Saclay

Contact :

Matteo GATTI

Starting date : 01-10-2018

Contact :

Matteo GATTI

CNRS - LSI

0169334538

Thesis supervisor :

Matteo GATTI

CNRS - LSI

0169334538

Personal web page : http://etsf.polytechnique.fr/People/Matteo

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

Density Functional Theory [1] tells us that the external potential, and therefore all observables, are functionals of the ground state density. The exact functionals, however, are not known, and one has to find approximations. Existing work mostly concentrates on the total ground state energy and on the electron density. To obtain the density, Kohn and Sham [2] have proposed the idea to use an “auxiliary system”. This is a simplified non-interacting system with a potential that is designed such that its density equals the true density of the real system. Of course, also this effective potential has to be approximated, and much research effort goes into finding better and better Kohn Sham potentials. In order to access also observables other than the density, we have proposed [3] to generalize the Kohn-Sham idea of an auxiliary system, and we have recently shown that this is a successful strategy [4,5]. In this thesis we will try to design auxiliary systems for observables that have to date never been calculated in this way; for example, we will examine how spin degrees of freedom are folded into effective potentials that have no explicit spin dependence.



[1] W. Kohn, "Nobel Lecture: Electronic structure of matter - wave functions and density functionals", Rev. Mod. Phys. 71, 1253 (1999).

[2] W. Kohn and L. J. Sham, "Self-Consistent Equations Including Exchange and Correlation Effects", Phys. Rev. 140, A 1133 (1965)

[3] M. Gatti, V. Olevano, L. Reining, and I. V. Tokatly, “Transforming Nonlocality into a Frequency Dependence: A Shortcut to Spectroscopy”, Phys. Rev. Lett. 99, 057401 (2007)

[4] M. Vanzini, L. Reining, and M. Gatti, “Dynamical local connector approximation for electron addition and removal spectra”, arXiv:1708.02450

[5] M. Panholzer, M. Gatti, and L. Reining, “Non-local and non-adiabatic effects in the charge-density response of solids: a time-dependent density functional approach”, arXiv:1708.02992

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

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

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.

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

Groupe Mésocopie Modélisation et Thermoélectricité

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.

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

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.

Thermal approach of liquid/solid and liquid/air interfaces

SL-DRF-18-0782

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

Laboratoire Léon Brillouin

Groupe de Diffusion Neutron Petits Angles

Saclay

Contact :

Laurence NOIREZ

Starting date : 01-09-2018

Contact :

Laurence NOIREZ

CNRS-UMR 12 - LLB01/Laboratoire de Diffusion Neutronique

01 69 08 63 00

Thesis supervisor :

Laurence NOIREZ

CNRS-UMR 12 - LLB01/Laboratoire de Diffusion Neutronique

01 69 08 63 00

Personal web page : http://iramis.cea.fr/Pisp/laurence.noirez/

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

This experimental PhD training is proposed in the frame of a collaborative program CEA-Pays de la Loire Region. The aim is to propose a new physical and physico-chemistry approach of solid / liquid or liquid / air interfacial mechanisms. At the interface of a liquid and a solid, the imbalance between the inter-molecular energies and the surface energies (attractive and repulsive) creates an intermediate zone where the liquid-liquid and liquid-solid interactions are in competition. While the literature on the subject are abundant and the developments continuously increasing, the interfacial mechanisms involved are still obscure. In particular the questions around the thermal interfacial properties are now emerging being at the heart of modern electronic devices. Pioneering experiments conducted in collaboration between the Léon Brillouin Laboratory and the Institute of Molecules and Materials of Le Mans have recently shown that, when approaching the liquid / solid interface, a variation in temperature is observable [1]. The temperature variation depends on the nature of the solid and the liquid in contact. This major discovery is a new field of investigation for the understanding of energy transfer mechanisms. It can lead to the development of passive energy converters and new technological solutions

In the frame of the PhD training it will be proposed to explore the characteristics of this novel interfacial property, its potentialities and locks. A bottom-up strategy is adopted consisting in describing how the first liquid molecules interact with the atoms of the solid in the case of high or low energy surfaces and how the energy is transferred from solid to far in the liquid. Model surfaces of different topography and of varied surface chemistry will be defined and used in order to control and characterize the surface forces (electrical, ionic or acid-base). Modern techniques of thermal analysis and of surface Raman micro-spectrometry combined with chemometric techniques will be used jointly to experimentally highlight the interfacial phenomena at several lengthscales. The candidate will also benefit of established international collaborations with worldwide leading individuals in modelling of soft matter properties from molecular up to mesoscopic and macroscopic scales. Rapid progress in understanding the mechanisms governing thermal equilibria is expected.

This program will be suitable for a student with solid skills in liquid physics, physico-chemistry of polymers or materials with a strong motivation for original experimental approaches to liquids, an interest in instrumentation and the use of Large Instruments (LLB, Soleil, ESRF) for scattering techniques.

1. L. Noirez, P. Baroni, J.F. Bardeau, Appl. Phys. Lett. 110 (2017) 213904.

2. L. Noirez, P. Baroni, J. Colloid and Surface, in press 2018.



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

Laboratoire Nano-Magnétisme et Oxydes

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.

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

Laboratoire d'Etude des NanoStructures et Imagerie de Surface

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.



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

Laboratoire d'Electronique et nanoPhotonique Organique

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.

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

Groupe Mésocopie Modélisation et Thermoélectricité

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)

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

Groupe Mésocopie Modélisation et Thermoélectricité

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).

Time resolved Spin-Charge Interconversion at Rashba Interfaces

SL-DRF-18-0953

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 : 01-10-2018

Contact :

Michel VIRET

CEA - DSM/IRAMIS/SPEC/LNO

01 69 08 71 60

Thesis supervisor :

Michel VIRET

CEA - DSM/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/

Spintronics relies on the discrimination of spin up and down carriers originally generated by charge currents in metallic ferromagnets. Recent developments aim to get rid of this source of dissipation by manipulating pure spin currents without their charge counterpart. One convenient way of achieving this is to use the spin-orbit coupling (SOC) interaction based on the Rashba effect. This stems from the joint action of the SOC and built-in electric potentials in two-dimensional electron gases existing at surfaces, interfaces or semiconductor quantum wells. Moreover, similar physics is at play in topological insulators, materials which are insulating in the bulk but conducting at their surfaces due to broken symmetry inducing topological states.



The PhD subject proposed here will consist in measuring the spin charge conversion as spins are injected by ferromagnetic resonance and laser induced ultra-fast excitation of a ferromagnet. Both techniques are mastered in our laboratory and the latter is very promising as it can give very interesting information concerning time-resolved injection and spin lifetime with a time resolution of 100fs. The LAO/STO samples come from the University of Geneva, Bi/Ag systems are made in the university of Zaragoza while new oxide systems based on irridates are synthesized in our group by Pulsed Laser Deposition.

 

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