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

PhD : selection by topics

Co-optimization of a bio-inspired image sensor and scene analysing technics

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)

Laboratoire Adéquation Algorithmes Architecture

01-10-2017

SL-DRT-17-0002

laurent.soulier@cea.fr

Artificial vision systems (camera(s) and processor(s)) have recognition capabilities well below those achieved by biological systems (eye - cortex). Moreover, biological systems are able to process information within a few milliseconds, which is still out of range of electronic systems, even though their electronic image sensors are far from achieving the resolution of human eyes (few dozen megapixel against more than one hundred million). This thesis aims at addressing the challenge posed by the biology by designing integrated bio-inspired sensor architectures. Our approach is based three assumptions: first, resolution biological imaging sensors is not uniform, the best resolved zone (the fovea) is dedicated to the acquisition of the areas of interest of the scene; secondly, pre-processing from the sensor are used to compress the information; finally, the processing of information is context and prior knowledge dependent. This exploratory thesis, aims to devise, within the frame of these hypothesis, breakthrough solutions with respect to the state of the art, to endow autonomous artificial systems (drones of all kinds (UAV, UGV, ...), machine tools, smart camera) of ability to perception of their complex environment, while using only limited resources, i.e. those of embedded systems. The candidate should have strong tastes or skills in image processing and digital architectures.

Polyaniline composite membranes for redox-flow batteries

Département des Technologies Solaires (LITEN)

01-09-2017

SL-DRT-17-0003

angel.kirchev@cea.fr

The availability of low cost proton exchange membranes (PEM) with high cation selectivity is one of the most acute problems in the development of affordable redox-flow batteries. The usual strategy in the development of PEM materials includes co-polymerisation and further chemical functionalisation of various organics, which are subsequently melted or solution cast to form a thin membrane (Nafion® can be considered as the most typical for example). The redox-flow battery specifics allow the use of the polyaniline (PANI) as a promising alternative proton conducting material. The synthesis of this polymer (especially the electrochemical polymerisation) is very cheap and guarantees low final cost of the product. The use of PANI as proton exchange system is possible because the bi-polar flow reactor can be designed avoiding the physical contact between the membrane and the electrode (for example sandwiching the membrane between two glass mat tissue layers). In this way, the electric conductivity of PANI is eliminated and the latter operates only as proton exchange polymer. The nature of the partially or the fully oxidized protonated PANI is particularly suitable for composite membranes: this form of the polymer is insoluble in water, acid solutions and most of the typical organic solvents. The thesis objectives will focus on the development and characterization of such composite membranes using electrochemical cells and redox-flow battery cells employing different electrochemical couples. The molecular structure of the PANI supposes much faster proton transport due to the very dense distribution of the proton exchange groups ? theoretically each aniline monomer element can be protonated, providing very dense distribution of sites for proton hoping. Thus the study of the ?isolated? proton conductivity of the PANI apart from its electric conductivity will be another objective of the thesis, which is interesting from fundamental point of view, because almost all of the published literature on PANI discusses either its electric or mixed conductivity.

New architecture MEMS microphone realization

Département Composants Silicium (LETI)

Laboratoire Composants Micro-Capteurs

01-09-2017

SL-DRT-17-0005

loic.joet@cea.fr

While MEMS microphones performances stagnate, specifications imposed by voice recongnition or noise cancellation are still not addressed. The counter-electrode, placed in front of the membrane to realize a capacitive detection, is the main limit, by disturbing acoustic path. Several ways are explored to remove the electrode and increase performances: - Detection change: piezoelectricity (Vesper), piezoresistivity (CEA-Léti) - Capacitive comb all around the membrane (Infineon) A new architecture patented by CEA conserves capacitive detection and its avantages while removing induced noises. The thesis work is to design, produce and test a first device taking advantage of this architecture.

Toward the Next generation of Non Volatile Phase-Change Memory Targeting Ultra-Low Power Consumption

Département Composants Silicium (LETI)

Laboratoire de Composants Mémoires

01-10-2017

SL-DRT-17-0009

gabriele.navarro@cea.fr

The goal of the PhD is to contribute to the development of the next generation of Non-Volatile Phase Change Memory (PCM) that target low power applications. Since this technology bases its functionality on the Joule heating, the thermal optimization of the PCM cell becomes the key point of this work. In this context, the candidate will contribute to the following tasks: multi-physical simulations to understand the impact of the interfaces and the thermal barriers on the programming current of the cell; physicochemical characterization of the different materials envisaged as thermal barriers; analysis of new phase change materials by DRX, FTIR, TEM, photo-thermal radiometry, etc. ; electrical characterization of memory devices integrating optimized thermal barriers and innovative phase change materials; development and fabrication of an "ultimate" PCM device that can be the precursor of the new generation of PCM devices. In addition, the student will be involved in the collaboration with external laboratories, experts at the international level in the field of heat transport.

New thin film solid electrolytes with high ionic conductivity for lithium-ion microbatteries

Département Composants Silicium (LETI)

Laboratoire Micro-Batteries Embarquées

01-10-2017

SL-DRT-17-0013

frederic.lecras@cea.fr

The aim of the work will be the development of new glassy inorganic electrolytes able to meet both conductivity and process requirements for the realization of microbatteries with enhanced performance. These sulfide or oxide type materials, based on network formers comprising a metal or semi-metal element, will be deposited as thin films by radio-frequency magnetron sputtering of home-made targets, using an equipment connected to a glovebox. Different strategies dealing with materials composition (type of network former, synergic effect of mixed formers) and/or structure (glass-ceramics) will be carried out to get optimal performance in terms of ionic and electronic transport, chemical and electrochemical stability. Numerous techniques will be used to determine the chemical composition of the thin films (ICP, Rutheford Back-scaterring Spectroscopy, Electron Probe Micro Analysis, Auger spectroscopy, ?) and to characterize their structure (X-ray diffraction, Raman spectroscopy, XPS, TEM,?) and their morphology (MEB-FEG). Impedance spectroscopy measurements performed at different temperatures will allow determining conduction properties (ionic conductivity, activation energy). In the course of this study, the behavior of selected electrolytes will be assessed in real microbatteries. The work will be carried out in the CEA/CNRS team located at ICMCB (Bordeaux).

All-solid-state lithium(-ion) microbatteries for high temperature applications

Département Composants Silicium (LETI)

Laboratoire Micro-Batteries Embarquées

01-10-2017

SL-DRT-17-0026

frederic.lecras@cea.fr

The aim of this thesis is the development of all-solid-state microbatteries suitable for high temperature operation (80-200°C), as power supplies for sensors located in severe environments. The first part of the work will aim at assessing the behaviour (electrochemical cycling, impedance) of conventional Li/LiPON/LiCoO2 microbatteries operating at various temperature, as a function of time, cycles and state-of-charge, in order to determine the level of performance of these devices and to highlight thermally-activated aging phenomena. Then, a thorough physico-chemical characterization of these microbatteries and their constituents will be carried out by various means (STEM-EELS, SEM-FIB, Auger nano-probe, XRD, Raman spectroscopy, XPS, ToF-SIMS,?) in order to identify the origin of these phenomena. The second part of the thesis work will focus on the improvement of the microbattery design - especially by means of a proper choice of electrode and/or electrolyte materials - able to enhance the robustness of the device and to make it more appropriate to specific purposes. Therefore, new thin film electrode/electrolyte materials will be prepared by PVD (sputtering) in a dedicated equipment connected to a glove-box. The thermal stability of these materials will be assessed (DSC, XRD, Raman spectroscopy,?) at first individually, then for couples of electrode/electrolyte materials in order to highlight the possible evolution of their interface (XPS, ToF-SIMS, Auger spectroscopy). Finally, the more promising systems (secondary or primary batteries) will be completed and their electrochemical behaviour at high temperature will be studied. The thesis will be carried out at ICMCB in Bordeaux (Laboratory of Condensed Matter Chemistry) in a joint CEA/CNRS team, having expertise in the fields of all-solid-state microbatteries and thin film materials.

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