Elaboration and in operando stuctural characterizations of a 3D microbattery made of thin films deposited by atomic layer deposition (ALD)

Afin de subvenir aux besoins énergétiques des nouvelles technologies électroniques nomades et miniatures, le développement de microdispositifs de stockage électrochimique d’énergie suffisamment performants telles que les microbatteries (MB) Li-ion est nécessaire. Pour ce faire, l’élaboration de MB Li-ion en topologie tridimensionnelle est une voie attractive qui permet le déploiement de surface spécifique tout en conservant l’empreinte surfacique initiale (de l’ordre du mm2), exacerbant ainsi la densité d’énergie délivrée par la MB. Cette solution est rendue possible grâce au développement de technique de dépôt couches minces telle que l’ALD qui est capable de réaliser des dépôts conformes. Dans le cadre de cette thèse, un électrolyte solide (Li3PO4) a été développé et optimisé de façon conforme, par ALD, sur un substrat de silicium structuré au préalable par des techniques de micro-fabrication. Une électrode positive de type spinelle (LiMn1.5Ni0.5O4) a également été élaborée par pulvérisation cathodique RF. Les performances ont été optimisées en fonction des paramètres de dépôt sur un substrat Si/Al2O3/Pt. Une capacité volumique de 63 µAh.cm-2.µm-1 a ainsi été mesurée pour un dépôt de 420 nm à 0,01 mbar recuit sous air à 700°C. Enfin, un prototype de cellule électrochimique en vue d’un suivi in situ/operando par DRX d’une électrode en couche mince, a été proposé.In order to address the demand on energetic needs to sustain nomad and miniaturized electronic devices, micro-devices performance for energy storage such as Li-ion microbatteries (MB) have to be improved. An attractive way to meet the required performance consists in using 3D topology increasing the specific surface while keeping the initial surface footprint (in the mm2 range) which is significantly enhancing the delivered energy density of the MB. The development of thin film technologies such as ALD enabling conformal deposition makes it possible. In the framework of this thesis, a solid electrolyte (Li3PO4) has been developed and optimized by ALD, on a 3D micro-architectured silicon substrate obtained by microfabrication techniques. A positive electrode (LiMn1.5Ni0.5O4) has also been developed and optimized as a function of the deposition parameter by RF sputtering deposition on a Si/Al2O3/Pt substrate. A volumetric capacity of 63 µAh.cm-2.µm-1 has been measured for a film of 420 nm thick obtained at 0.01 mbar and then annealed at 700°C under air atmosphere. Finally, a prototype has been proposed to realize an electrochemical cell for the purpose of in situ/operando follow-up by XRD of a thin film electrode deposited on silicon substrate

Evidence of PtSi phase formation during the annealing of LiMn1.5Ni0.5O4 thin films

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Tuning the Cation Ordering with the Deposition Pressure in Sputtered LiMn1.5Ni0.5O4 Thin Film Deposited on Functional Current Collectors for Li-Ion Microbattery Applications

International audienceThe development of high voltage spinel LiMn1.5Ni0.5O4 (LMNO) sputtered thin films on functional current collector was reported within the framework of this study. We have first solved the technological issue due to the PtSi phase which originates from the interdiffusion between silicon wafer and chromium/platinum current collector to form PtSi phase under annealing treatment. By substituting the Cr layer with a very dense and pinhole free Al2O3 thin film deposited by ALD acting as a barrier diffusion between the silicon substrate and the LMNO layer, the synthesis process (sputtered thin films annealed under air at 700 °C) has been validated. In the second part of this study, the behavior of the sputtered LMNO thin films as a function of the deposition pressure and the film thickness has been investigated. The deposition pressure has been found to play a key role on the Mn–Ni cations ordering in spinel-like structures (P4332 ordered vs Fd3̅m disordered spinel) and consequently on the electrochemical performance. We have thus shown that LMNO thin films deposited at 10–2 mbar and annealed at 700 °C deliver a normalized capacity of 65 μAh·cm–2·μm–1 with good capacity retention upon cycling thanks to its disordered spinel structure. Moreover, the Coulombic efficiency has been shown to be highly dependent on the film thickness for high voltage LMNO thin film electrodes. To the best of the authors’ knowledge, this work is one of the most complete study combining structural and electrochemical characterizations of the LMNO thin film obtained by sputtering deposition on Si/Al2O3/Pt functional current collectors

Assessment of Radiation Effects on Attitude Estimation Processing for Autonomous Things

International audienceThis paper investigates and assesses neutron radiation effects on the attitude estimation (AE) processing, typically embedded in inertial navigation systems (INS) and upcoming autonomous things. Findings highlight the importance of radiation-induced critical failures that can upset the on-board AE processing, and consequently the inertial navigation. Radiation tests and analyses were conducted by considering as on-board AE processing the execution of classical AE algorithm on a multi-core computer hardware exposed to 14-MeV neutron and thermal neutron radiation. Three computing strategies and different case-study scenarios were tested and compared. Results suggest that the contribution of radiation-induced soft errors to be mitigated on the embedded AE processing is essentially related to single-event functional interrupts that can lead the inertial navigation to critical failures

Sputtered LiMn1.5Ni0.5O4 thin film for Li-ion microbattery

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Atomic Layer deposition of thin films materials for 3D solid state Li-ion microbattery

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Step conformal solid electrolyte deposited by ALD on robust 3D silicon scaffold for on chip Li-ion microbattery

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«Etude de couches minces ferroélectriques alpha-La₂WO₆»

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Investigating the Reliability Impacts of Neutron-induced Soft Errors in Aerial Image Classification CNNs Implemented in a Softcore SRAM-based FPGA GPU

This work has been partially supported by: MultiRad (PAI project funded by Région Auvergne-Rhône-Alpes) and IRT Nanoelec (ANR-10-AIRT-05 project funded by French PIA).International audienc