Electric field and ab initio simulations, application to RRAM
Since several years, LETI/DCOS is engaged in a simulation effort of microscopic phenomena at the heart of oxide-based RRAM operation (made of HfO2, Ta2O5, Al2O3). The correct description of an external electric field applied to a MIM device (Metal-Insulator-Metal) is now possible thanks to two methods one by an orbital separation approach [1] the other by using the non equilibrium green function formalism [2]. In this work, we propose to develop and to handle these methods by combining already existing simulation approaches. The main goal is to study the degradation mechanisms of an oxide by following the oxygen atoms movements coupled directly to the applied external electric field. These mechanisms are not known and this study will support the optimization and characterization efforts already engaged at LETI on RRAM functional prototypes. The targeted simulations tools are SIESTA for the DFT part, and TB_SIM for the electronic transport part.
[1] S. Kasamatsu et al., « First principle calculation of charged capacitors under open-circuit using the orbital separation approach, PRB 92, 115124 (2015)
[2] M. Brandbyge et al., « Density functional method for nonequilibrium electron transport », PRB 65, 165401 (2002)
Design and implementation of force feedback by electrical sense for remote operation with submarines or aerial robots
Since few years, the Bio-inspired Robotics group of the IRCCyN Robotics team is developing a bio-inspired perception mode found on some freshwater tropical fish: the electrical sense. This active sense is based on the distortions measures, due to environment, of an electric field produced by the fish. Based on this principle Irccyn developed in the context of a European project called Angels, the first autonomous underwater robot capable of moving by means of the electrical sense . In the future, CEA TECH and Irccyn want to extend this first result in multiple directions, including the remote operation of submarines manipulators and aerial robots domains. The force feedback should be emulated by the use of the electrical sense. Integrated in the Bio-inspired robotics team of IRCCYN , post -doctoral fellow will contribute to the development of the electric sense and its use for underwater and aerial teleoperation . He will participate in the design and development of new sensors inspired by electric fish and their use for underwater telerobotics. The results of its work will underpin the industrial demonstrator system (teleoperation offshore) to be developed under the project CEA TECH / IRCCYN Bio-inspired robotics.
Eco-innovation of insulating materials by AI, for the design of a future cable that is long-lasting, resilient, bio-sourced and recyclable.
This topic is part of a larger upcoming project for the AI-powered creation of a new electrical cable for future nuclear power plants. The goal is to design cables with a much longer lifetime than existing cables in an eco-innovative approach.
The focus is on the cable insulation because it is the most critical component for the application and the most sensitive to aging. The current solution is based on adding additives (anti-rad and antioxidants) to the insulation to limit the effects of irradiation and delay aging as much as possible. However, there is another solution that has never been tested before: self-repairing materials.
The project to which this topic is attached aims to design and manufacture several test model of insulation specimens. With several test characterization protocols, in order to verify the gain in terms of reliability and resilience. The results obtained will begin to fill a future database for the AI platform Expressif, developed at CEA List, which will be used to design the future cable.
Aging study of silicon nanowires used as piezoresistive detection gauges for achieving inertial MEMS sensors.
Today’s sensors are present in all areas: housing, automotive... Thanks to recent developments in microelectronics, new generations of sensors combine high performance, small size and low cost. In this context, CEA-LETI has proposed an innovative concept called M&NEMS for the realization of inertial sensors such as accelerometers, magnetometers and gyroscopes. The M&Nems concept combines MEMS and NEMS to take advantage of the great inertia generated by a MEMS mass and the high detection sensitivity of piezoresistive silicon nanowires. Demonstrators have already been carried out and have shown the good potential of the M&Nems concept. One of the main challenges which remain to overcome is the reliability of sensors based on this concept and specifically the reliability of the piezoresistive nanowires. The research work will be mainly focused on the study of the failure modes of these piezoresistive nanowires gauges i.e. the identification of physical phenomena and the development of failure models. In order to do this study, a first preliminary work will be focused on the physical mechanisms which manage the electrical conduction in the nanowires: piezoresistivity, charge trapping, relaxation field effect ... The work will then continue by the study of the failure modes of nanowires, the goal will be to understand and model the physical aging of these nanowires: it will be possible to rely on the knowledge of the physics of nanowires conduction but also play with the physical parameters of these nanowires such as silicon doping, the process fabrication, the packaging technique, the thermomechanical stresses, the scale effect due to surface / volume ratio, or the surface condition. Finally, models of aging will allow proposing and validating technological choices to ensure the nanowires lifetime depending on operating conditions of the sensors.
Study of cooling solutions for compact electronic systems
3D technologies (i.e. electronic components vertically stacked) constitute an axis of global research, both at the architectural and manufacturing level. The Grenoble area is at the heart of these technological breakthroughs with world first prototypes that make Cea-Leti one of the leaders in these advanced technologies.
One of the critical points of this innovative technology is to control the thermal management in such 3D components regardless of the final application. Nowadays conventional solutions like adding a fan cannot fit all the thermal requirements, and may be of limited effectiveness. More integrated solutions are now unavoidable and can be considered from two points of view: heat can be managed directly at the component-level in silicon chips that make up the 3D-stack, or it can be managed at package level. Ideally, the two approaches should be combined.
The first objective of this study is to achieve an exhaustive state of the art and evaluate the potential of the different solutions for the components developed at Leti. This evaluation will be based on thermal simulations and a critical analysis based on technological feasibility, consumption, efficiency, cost,… and lead to choose the most appropriate solution.
The second part of the work will be dedicated to the implementation of this solution. Relying on experts of silicon and packaging technologies, the candidate will be responsible for contributing to the design of the component (design and implementation) and its characterization.
This position is for a researcher with a strong background in the areas of thermal and microelectronic components. This position requires analysis skills, a large autonomy and unifying skills.
Realistic motion generation for anthropomorphic systems
This work is devoted to Digital Human motion generation, for manufacturing (specifically, for design, maintenance, operator training, workstation design and ergonomics, ...), health (postures for surgery, rehabilitation, ...), or entertainment industry (animation for games, movies,...).
Based on complementary skills and developments of Gepetto LAAS team, and CEA LIST team, in terms of path planning (HPP), dynamic motion control of anthropomorphic systems, the objective of this post doc is to combine both approaches, a global one, dealing mainly with geometric and quasi-static constraints and characteristics, and a local one, dealing with dynamics and taking into account human movement characteristics (motor primitives, minimizing cost criteria, etc ...).
Dual layer transfer of piezoelectric films for advanced RF devices
The aim of these workds is to study and develop an innovating concept of piezoelectric thin films multilayer transfer for RF applications.The applicant will be responsible for the development of the entire fabrication sequence of these multilayer structures and of the 3D RF components. To this end, he or she must master the physical mechanisms involved in the film transfer technology and design the complete architecture through simulation of the expected RF filters properties. Once the structure is defined and the technology backbone is mastered, the candidate will collaborate with Leti technology experts to identify the necessary process developments. He or she will then ensure their implementation in the fabrication technology platform and support the achievement of the most critical steps.
The development of this fabrication sequence will allow the generation of substrates whose features meet device specifications. The functionality of the substrates will then be demonstrated through the fabrication and characterization of RF devices that are relevant to the target applications.
Model evolution management and mastering
Designing ever more complex systems needs for new paradigms in order to face all the new challenges as improving safety while reducing time and cost to market. Paradigms, mainly active models and model transformations, promoted by model-driven engineering are providing efficient solutions to deal with those issues. However, as promoted in the series of international workshops on model and evolution (www.modse.fr), model (co-)evolution and consistency management become crucial activities to cope with the natural changes of any system. In fact, there is an increasing need for more disciplined techniques and engineering tools to support a wide range of model evolution activities, including model-driven system evolution, model differencing, model comparison, model refactoring, model inconsistency management, model versioning and merging, and (co-)evolution of models.
As part of this project, the LISE want especially to consider model evolution management under both next perspectives:
- The first issue is to enable modelers to manage the evolution of their models. They should be able to follow the changes that have been made within a model by providing as for example “track changes” mode in the modeling environment.
- The second issue concerns the problem of model versioning. The users need here to manage and use multiple versions of their models in a collaborative way.
Evolution of the surface layers resulting from the physico-chemical interactions between low pH concrete and clays: experiments and modeling
The design of an industrial facility for storage of radioactive wastes in geological environment is an important issue taken into account in the French nuclear energy sector. In this context the cementitious materials are an important (packages, structures).
The main objective of the proposed study is to characterize alterations of the materials in the concrete-clay interfaces, caused by chemical exchanges. At the current stage, a comprehensive approach was initiated taking into account simultaneously the chemistry of the storage site and concrete considered for this application, based on commercial cements or innovative binders (low pH) formulated specifically. On these low pH materials in particular, questions remain as to their mineralogical and microstructural evolution. An experimental program (dedicated testing, microscopic characterization), supplemented by digital simulations, will increase the essential knowledge for use of these materials.
This project will involve both of the specialists of cementitious materials of the CEA, and researchers at the laboratory Hydrasa of the University of Poitiers.