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PhD subjects

8 sujets IRAMIS/LSI

Dernière mise à jour :


• Additive manufacturing, new routes for saving materials

• Solid state physics, surfaces and interfaces

• Theoretical Physics

• Ultra-divided matter, Physical sciences for materials

 

4D printing of thermo-magnetic composite materials using light-driven additive manufacturing techniques

SL-DRF-24-0649

Research field : Additive manufacturing, new routes for saving materials
Location :

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Giancarlo RIZZA

Starting date : 01-03-2024

Contact :

Giancarlo RIZZA
CEA - DRF/IRAMIS/LSI/LSI

01.69.33.45.10

Thesis supervisor :

Giancarlo RIZZA
CEA - DRF/IRAMIS/LSI/LSI

01.69.33.45.10

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

Laboratory link : https://portail.polytechnique.edu/lsi/fr/page-daccueil

More : https://www.linkedin.com/in/giancarlo-rizza-phd-48338410a/

This PhD research project explores the cutting-edge field of 4D printing, a field that integrates smart materials into additivemanufacturing processes. The aim is to create nanocomposite objects with multifunctional capabilities, enabling them to change shapeand properties in response to external stimuli.

In this PhD project, we will primarily focus on liquid crystal elastomers (LCEs) as the active matrix. LCEs are a versatile class ofprogrammable polymer materials that can undergo reversible deformation under various stimuli, such as light, heat, electric fields, andmagnetic fields, transitioning from disordered to oriented phases. Because of their actuation properties, LCEs are promising candidatesin applications like artificial muscles in medicine and soft robotics.

Consequently, the project's first objective is to devise a method for 3D printing LCE resins using light-driven printing processes, includingdigital light processing (DLP), direct ink writing (DIW), and two-photon polymerization. The project also explores the possibility of co-printing using two laser sources with different wavelengths. This will result in designed objects capable of programmed deformationsand reversibility. To further enhance the actuation capabilities of the LCE matrices, magnetic particles will be incorporated into thethermoresponsive LCE resin. Thus, the second objective of the project is to develop a strategy for self-assembling and spatiallyorienting embedded magnetic nanoparticles in LCE resins during light-driven printing processes (DLP, DIW, 2PP). Ultimately, the thirdobjective of this project is to combine these two strategies to create sophisticated multifunctional soft machines and devices suitable forcomplex environments. Experiments will follow an incremental trial-and-error research approach, with the aim of improving machinelearning models by designing purpose-built objects.

The envisioned research work can be summarized into the following macro-steps:
- Specification of target shape-changes depending on the multiple stimulation scenarios
- Selection of active particles, formulation of the LCE, and synthesis of the particles
- Development of hybrid additive manufacturing strategies with possible instrumentation
- Printing proofs-of concept and conducting mechanical and actuation tests
- Characterization of composite structures
- Development of simulation models
- Realization of a demonstrator (e.g., crawling robot, actuators for the automotive sector…)
TeraHertz surface plasmonic resonators

SL-DRF-24-0344

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

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Yannis Laplace

Starting date : 01-10-2024

Contact :

Yannis Laplace
Ecole Polytechnique - Laboratoire des Solides Irradiés LSI - UMR 7642

0169334512

Thesis supervisor :

Yannis Laplace
Ecole Polytechnique - Laboratoire des Solides Irradiés LSI - UMR 7642

0169334512

Personal web page : https://www.polytechnique.edu/annuaire/laplace-yannis

Laboratory link : https://portail.polytechnique.edu/lsi/fr/recherche/nouveaux-etats-electroniques/terax-lab

More : https://portail.polytechnique.edu/lsi/fr/recherche/nouveaux-etats-electroniques/

Scientific and technological development of the Terahertz (THz) frequency range, a domain of the electromagnetic spectrum that is located in between microwaves and infrared photonics, is timely and subjected to an intense research activity recently. We have recently developed TeraHertz cavities using a plasmonic mechanism based on the surface plasmons of a doped semiconductor. We have demonstrated the remarkable property of these resonators of being able to confine TeraHertz photons in record volumes of the order of 10-7 times smaller than the diffraction limit. This plasmonic mechanism also allows the functionalization and tunability of the cavities thanks to external parameters such as the electric or magnetic field or the temperature, among others. The aim of this thesis will be to develop THz plasmonic cavities and in particular to study their nonlinear behaviour when subjected to intense THz pulses. The aim will be to TeraHertz frequency conversion based on this nonlinearity.
Theoretical study of the physical and optical properties of some titanium oxide surfaces for greenhouse gas sensing applications

SL-DRF-24-0569

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

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Nathalie VAST

Starting date : 01-10-2024

Contact :

Nathalie VAST
CEA - DRF/IRAMIS/LSI

01 69 33 45 51

Thesis supervisor :

Nathalie VAST
CEA - DRF/IRAMIS/LSI

01 69 33 45 51

Personal web page : http://nathalie-vast.fr

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

More : https://portail.polytechnique.edu/lsi/en/research/materials-science-theory

The international community is engaged in developing the policy to reduce greenhouse gases (GHGs) emission, in particular carbon dioxide (CO2), in order to reduce the risks associated to the global warming. Consequently, it is very important to find low-cost processes to dissociate and then capture carbon dioxide (CO2), as well as to develop low power, high performance sensors suitable to monitor GHGs reductions.A common and existing method for sensing the concentration of gases is achieved by using semiconducting metal oxides surfaces (MOS) like SnO2, ZnO, and TiO2. Moreover, one route to achieve CO2 dissociation is plasma assisted catalytic decomposition. However, surface defects, and in particular oxygen vacancies and charged trapped therein, play an important role in the (photo)reactivity of MOS. The way optical properties of surfaces are modified by such defects is not completely understood, nor is the additional effect of the presence of the gas. In some models, the importance of charge transfer is also emphasized.

In this Ph.D. work, theoretical methods will be used to model the surface with defects and predict the optical properties. The objective is threefold: To apply the theoretical frameworks developed at LSI for the study of defects to predict the defect charge states in bulk; To study the effect of the surface on the defect stability; to study bulk and surface optical properties, and find out spectroscopic fingerprints of the molecular absorption and dissociation near to the surface. Materials/gas under considerations are oxides like titanium oxide, eventually deposited on a layer on gold, and carbon dioxide. The theoretical method will be the time dependent density functional perturbation theory method (TDDFPT) developed at LSI in collaboration with SISSA, Trieste (Italy).

Ref.: I. Timrov, N. Vast, R. Gebauer, S. Baroni, Computer Physics Communications 196, 460 (2015).
Spin-current to charge-current interconversion devices: theoretical and experimental optimization of the efficiency

SL-DRF-24-0503

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

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Jean-Eric WEGROWE

Starting date : 01-10-2024

Contact :

Jean-Eric WEGROWE
CEA - LSI/Laboratoire des Solides Irradiés

0169334555

Thesis supervisor :

Jean-Eric WEGROWE
CEA - LSI/Laboratoire des Solides Irradiés

0169334555

Personal web page : https://www.polytechnique.edu/annuaire/wegrowe-jean-eric

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

The major argument for promoting the development of spin electronics is the low power dissipation. The aim of the thesis is to determine and optimize the power efficiency of these devices. We focus the study on the power dissipated by two kinds of devices. On the one hand, the devices allowing the reversal of the magnetization of a magnetic layer by a transverse spin current, namely the Spin-Orbit Torque effect (SOT), and on the other hand the devices based on topological materials.

In this context, the definition of useful power - or efficiency - is an open problem. Indeed, the thermodynamics of this type of non-equilibrium system involves cross-effects between the degrees of freedom of the electric charge carriers, those of the spin of these carriers, as well as those of the magnetization of the adjacent layer.

We have developed a variational method in order to establish the stationary state of a Hall bar and the power dissipated in a load circuit. Preliminary measurements have recently validated the prediction in the case of the anomalous Hall effect. The project aims to generalize the study to SOT and topological materials.

Coupled electron and phonon dynamics in 1d and 2d materials for potential thermoelectric applications: quantum confinement and external phonon bath effects

SL-DRF-24-0535

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

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Jelena SJAKSTE

Starting date : 01-10-2024

Contact :

Jelena SJAKSTE
CNRS - DRF/IRAMIS/LSI/LSI

+33169334511

Thesis supervisor :

Jelena SJAKSTE
CNRS - DRF/IRAMIS/LSI/LSI

+33169334511

Personal web page : https://www.polytechnique.edu/annuaire/sjakste-jelena

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

Today, in the context of climate change and the search for frugal numerical technologies, there is an urgent need to develop a portfolio of thermoelectric materials offering thermal stability, especially for the temperature range 300-400 K, where a large amount of heat is wasted into the environment. Compared to bulk materials, low-dimensional materials, such as nanowires and thin films, offer interesting possibilities for improvement of their thermoelectric properties. In this theoretical project, we aim to describe the coupled dynamics of hot electrons and phonons in low dimensional materials via an approach based on Density Functional Theory and on the solution of coupled Boltzmann transport equations for electrons and phonons. The focus of the project will be to describe main effects of reduced dimensionality and the role of interface and substrate on thermoelectric transport properties in 1D and 2D dimensional materials. The choice of materials is motivated by the potential applicability in the field of next generation energy harvesting, as well as by the ongoing collaborations with experimentalists. Recently, GEEPS researchers have demonstrated that 2D Bi2O2Se allows to achieve a thermoelectric power which is 6-fold larger and closer to room temperature operation than that measured recently by another team. This preliminary result is very encouraging and, at the same time, raises fundamental questions on the physical reasons which led to such outstanding power factor. This is what our theoretical project aims to elucidate.
Modelling point defects for quantum application including electron-lattice interaction and surface effect

SL-DRF-24-0570

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

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Nathalie VAST

Starting date : 01-10-2024

Contact :

Nathalie VAST
CEA - DRF/IRAMIS/LSI

01 69 33 45 51

Thesis supervisor :

Nathalie VAST
CEA - DRF/IRAMIS/LSI

01 69 33 45 51

Personal web page : http://nathalie-vast.fr

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

More : https://portail.polytechnique.edu/lsi/en/research/materials-science-theory

The rise of room-temperature applications - nanoscale magnetometry, thermometry, single photon emission, solid-state implementation of qubits - of the negatively charged nitrogen-vacancy NV- center in diamond has motivated a renewed interest in the search, with theoretical methods, of other point defects - in diamond in another material- with a desired property for quantum application, e.g. a bright photoluminescence adna long coherence time of the spin ground state.

However, the fact that the local atomic structure of the defect ground-state or of the excited states is hardly accessible with direct experimental techniques prevents a direct understanding of the thermodynamics stability of defect charge states in the bulk, and of the expected quantum property. This makes the on-demand control of the defect charge state challenging, a problem even more complex near to the surface, because band bending induces a surface modification of the charge state and surface states of ubiquitous defects may be present.

In this Ph.D. work, theoretical methods will be used to predict the defect charge states and explore the effect of the proximity of the surface on the thermodynamic stability and on the spin structure. The objective is threefold: To apply the theoretical framework developed at LSI and predict the defect charge states in bulk; To study changes in the charge state brought by the proximity of the surface; To extend the Hubbard model used to compute the excited states and to account for the electron-lattice interaction in order to compute the zero-phonon line also for the excited states that cannot be predicted by the DFT only. Materials under considerations are carbides -diamond and silicon carbide- and borides - elemental boron and boron compounds. The theoretical method will rely on the Hubbard model developed at LSI in collaboration with IMPMC, and density functional theory (DFT) calculations.
Innovative concepts for particles plasma acceleration and radiation emission in laser – overdense plasma interaction at ultra-high intensity

SL-DRF-24-0638

Research field : Theoretical Physics
Location :

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Michèle RAYNAUD

Starting date : 01-10-2024

Contact :

Michèle RAYNAUD
CEA - DRF/IRAMIS/LSI/LSI


Thesis supervisor :

Michèle RAYNAUD
CEA - DRF/IRAMIS/LSI/LSI


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

Laboratory link : https://portail.polytechnique.edu/lsi/fr/research/la-recherche-au-lsi

The present PHD work aims at exploring theoretically and numerically the generation of fast particle beams in ultra-relativistic (above 10^21 W/cm2) laser-overdense solid interaction by using properly-structured or shaped targets. Surface characteristics inducing local electromagnetic modes more intense than the laser field and where nonlinear and relativistic effects play a major role will be investigated.

On the basis of the work already carried out, the new scheme for particle acceleration will be extended in the ultra-relativistic regime of laser plasma interaction. It may lead to groundbreaking ultra-short synchronized light and electron sources with applications in probing ultrafast electronic processes. In this context, this theoretical and numerical study will allow to suggest new experimental schemes feasible on the Apollon facility and multi-PW lasers.
Structural evolution under electron irradiation of lamellar hydroxydes and hydrates

SL-DRF-24-0532

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Laboratoire des Solides Irradiés (LSI)

Laboratoire des Solides Irradiés (LSI)

Saclay

Contact :

Marie-Noelle De Noirfontaine

Starting date : 01-10-2024

Contact :

Marie-Noelle De Noirfontaine
CNRS - DRF/IRAMIS/LSI


Thesis supervisor :

Marie-Noelle De Noirfontaine
CNRS - DRF/IRAMIS/LSI


Personal web page : https://www.polytechnique.edu/annuaire/de-noirfontaine-marie-noelle

Laboratory link : https://portail.polytechnique.edu/lsi/fr/recherche/defauts-desordre-et-structuration-de-la-matiere

The societal context of the study is the optimization of cementitious matrices for nuclear waste conditioning. These cementitious matrices are composed of hydrated minerals, some of which are lamellar (portlandite Ca(OH)2, brucite Mg(OH)2, brushite CaHPO4.2H2O, gibbsite Al(OH)3...). Very few data exist in the literature on the structural damage of these hydrated lamellar minerals under electron irradiation. The aim of the proposed thesis is to experimentally investigate irradiation-induced structural modifications in various types of compounds, with a view to gaining a better understanding of the damage mechanisms of these compounds under irradiation, and to identify irradiation sensitivity criteria in order to ultimately optimize the chemical and mineralogical composition of the materials.

 

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