Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Optimisation de l'électrode Ni-YSZ à hydrogène pour une durabilité améliorée des cellules à oxydes solides

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Production d'Hydrogène

01-10-2020

SL-DRT-20-0602

karine.couturier@cea.fr

Advanced hydrogen and fuel-cells solutions for energy transition (.pdf)

Solid oxide cells (SOCs) are electrochemical devices operating at high temperature that can directly convert fuel into electricity (fuel cell mode ? SOFC) or electricity into fuel (electrolysis mode ? SOEC). In recent years, the interest on SOCs has grown significantly thanks to their wide range of technological applications that could offer innovative solutions for the transition toward a renewable energy market. Indeed, the SOCs present various advantages, such as a good reversibility, a large fuel flexibility and a very high efficiency. Despite these advantages, the degradation in performances of SOCs is still too high to envisage the industrial deployment of this technology. Among the different degradation phenomena, the microstructural evolution of the fuel electrode, which is classically made of Nickel and Yttria stabilized Zirconia (Ni-YSZ cermet), is recognized to contribute significantly to the cell ageing. In this PhD thesis, the degradation mechanisms of the Ni-YSZ electrode will be studied. For this purpose, an integrated experimental and modelling approach will be adopted coupling (i) electrochemical testing, (ii) modeling and (iii) advanced post-test microstructural characterization. Once the mechanisms of degradation precisely understood, solutions for mitigating the degradation will be proposed via material and microstructural optimizations.

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Low-frequency wireless power transmission for autonomous systems

Département Systèmes (LETI)

Laboratoire Autonomie et Intégration des Capteurs

01-09-2020

SL-DRT-20-0615

pierre.gasnier@cea.fr

Cyber physical systems - sensors and actuators (.pdf)

Wireless power transmission (WPT) technologies are expanding rapidly, particularly for wireless charging of electrical systems (phones, electric vehicles, etc.). However, these technologies have a limited transmission range and their high operating frequency prohibits any transmission of energy in the presence or through conductive media (metal walls or seawater), which limits their adoption in complex environments (industrial, military...). The low-frequency WPT technology we propose is based on an electromechanical system comprising two coils and a magnet. This type of technology has the advantage of being able to power wireless sensor nodes for a variety of applications (health monitoring of structures in isolated environments is one example among others). The purpose of the thesis is to study the addition of a piezoelectric converter at the receiver side. This so-called "hybrid" system (electromagnetic/piezoelectric) will take advantage of each converter, in order to improve the receiver's performance and ultimately increase the maturity of the technology (increase in range, power densities, etc.). In this context, the thesis will consist in studying, developing and testing the performance of hybrid WPT solutions. The candidate will develop analytical and numerical models to identify the parameters of influence of the coupled system and compare its performance to the literature. The candidate will also have to develop adapted innovative energy conversion electronics. A joint optimization of the electromechanical system and its associated electronics will lead to the development of a complete high-performance wireless power transmission system. The final goal of the thesis is to analyze and understand the advantages and limitations of this hybrid technology. A multidisciplinary profile oriented towards physics and mechatronics is sought for this thesis. In addition to a solid theoretical background, the candidate must have teamwork skills and an ability for experimentation. The student will integrate the Systems Division of CEA-Leti, within a team of researchers with strong expertise in the development and optimization of electronic and mechatronic systems combining innovative solutions for energy harvesting, wireless power transmission, low-power electronics and sensor integration for the development of autonomous systems.

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Degradation Mechanisms of the Lanthanum Strontium Cobalt Ferrite Used as Oxygen Electrode in Solid Oxide Cells

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Production d'Hydrogène

01-10-2020

SL-DRT-20-0622

bertrand.morel@cea.fr

Advanced hydrogen and fuel-cells solutions for energy transition (.pdf)

Solid oxide cells (SOCs) are electrochemical devices operating at high temperature that can directly convert fuel into electricity (fuel cell mode ? SOFC) or electricity into fuel (electrolysis mode ? SOEC). In recent years, the interest on SOCs has grown significantly thanks to their wide range of technological applications that could offer innovative solutions for the transition toward a renewable energy market. Indeed, the SOCs present various advantages, such as a good reversibility, a large fuel flexibility and a very high efficiency. Despite these advantages, the degradation in performances is still too high to envisage the industrial deployment of this technology. Among the different degradation phenomena, the destabilization of the oxygen electrode, classically made of Lanthanum Strontium Cobalt Ferrite (LSCF), is recognized to contribute significantly to the cell ageing, especially when operated in electrolysis mode. In this context, the aim of the PhD thesis is to investigate the mechanisms controlling the electrode phase demixing and the diffusion of chemical elements. For this purpose, an experimental and modeling approach will be adopted including electrochemical testing and advanced post-test characterizations. Nano-imaging by synchrotron X-ray fluorescence and diffraction will be conducted on the aged electrodes. The acquired data will be implemented in an existing multiscale model to analyze the degradation mechanisms. Finally, recommendations in terms of materials and manufacturing conditions will proposed to improve the cell lifetime.

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Development of innovative chalcogenide material etching processes for non-volatile memories and photonic

Département des Plateformes Technologiques (LETI)

Laboratoire Gravure

01-09-2020

SL-DRT-20-0625

christelle.boixaderas@cea.fr

Emerging materials and processes for nanotechnologies and microelectronics (.pdf)

The patterning steps (etching / stripping / cleaning) have adverse effects on the properties of chalcogenide films. It is therefore essential to study this patterning brick in order to propose new dry etching solutions and associated post treatments. After a first phase of bibliographic research and training in clean room on tools necessary for future works, the student will propose a methodology allowing the understanding of the mechanisms of etching of the reference process and modifications of the GeSbTe (and other alloys) by surface analyzes (bottom and sidewall of the structures) It will propose and implement improvements to the reference process (chemistry, plasma parameters, etc.) that will ensure that the chalcogenide remains intact during the flow of memory fabrication. Then, he will have to choose the integrations and materials for a test vehicle in memory and Photonics. The challenge will be to make improvements to the reference process of the memory stack based on the study of the previous phase: stack etching, stripping, management of waiting times between stages. Finally, it would be interesting to measure the impact of the changes by electrical results on the memory cells (gain / loss on the intrinsic characteristics of a PCM memory).

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Development of cellulose-based materials for the conception of biomedical devices by stereolithograpy

Département des Technologies des NanoMatériaux (LITEN)

Laboratoire de Formulation des Matériaux

01-11-2020

SL-DRT-20-0628

sebastien.rolere@cea.fr

Health and environment technologies, medical devices (.pdf)

The development of innovative medical devices mainly relies on the use of high performance multifunctional materials. These materials should display high biocompatibility and controlled degradability, and advantageously specific biological properties, such as muco-adhesion, antimicrobial features, or bioaffinity. Such advanced materials are keys for biomedical research activities. Additive manufacturing technologies are particularly well-suited for the technical specifications of biomedical devices. Notably, StereoLithography Apparatus (SLA) allows the processing of complex geometries from UV-light curing of liquid materials. SLA is currently under consideration to develop biomedical devices from cellulose materials. Cellulose is a biocompatible bio-based polymer, extracted from renewable resources. Cellulose chemical structure possesses many hydroxyl functional groups for potential chemical modification and further biomolecules attachment. The aim of the present project is the design and fabrication, using SLA, of biomedical devices able to present various bio-specific properties, from chemically-modified cellulose materials.

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Ferroelectric Tunnel Junctions (FTJs) for Memory Applications and Ultra-Low Power Neuromorphic Circuits

Département Composants Silicium (LETI)

Laboratoire de Composants Mémoires

01-10-2020

SL-DRT-20-0635

laurent.grenouillet@cea.fr

Artificial intelligence & Data intelligence (.pdf)

The recent discovery of ferroelectricity in hafnium oxide (HfO2) thin films generates a strong interest to save information in a non volatile way for ultra-low power memories, via the application of an electric field to switch the material's electrical polarization. More recently, preliminary results demonstrating HfO2-based ferroelectric tunnel junctions (FTJs) were reported with this CMOS-compatible and scalable material. Here the ferroelectric layer enables to modulate the tunneling current passing through the junction, depending on its polarization. This opens numerous perspectives to those new devices. The objectives of the PhD work will be to fabricate, characterize and model ferroelectric tunnel junctions to better understand the physics of those devices, and then optimize their performance. The optimized devices will then be co-integrated in the form of arrays above complex CMOS circuits to serve as artificial synapses in an ultra low power neuromorphic processor. This work will be performed in collaboration with european partners in the framework of H2020 BeFerroSynaptic EU project.

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