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

PhD : selection by topics

Components and optical systems for the activation of pixelated holograms, application to retinal display

Département d'Optronique (LETI)

Laboratoire pour la Visualisation et l'Eclairage

01-10-2019

SL-DRT-19-0876

christophe.martinez@cea.fr

The PhD is forming part of a research activity in our laboratory about retinal projection for Augmented Reality (AR) applications. Current AR devices (smart glasses) are limited in their design by the constraints given by the optical systems. The use of the device in a social context is still difficult to be implemented commercially because of the lack of aesthetic that discourages the user. To overcome these limitations related to the pupil management in the axial optical systems, CEA Leti is investigating the use of pixelated holograms, distributed on the surface of the glass and addressed by a grid of single mode waveguides and electrodes. The PhD will focus on the development of the technological brick related to the activation of the holograms. The work will consist in the recording of pixelated holograms on the holographic printer of the laboratory. A series of optical set-up will then be implemented to demonstrate the dynamic addressing of the holographic function. These set-ups will concern first simple free space propagation with the use of DLP and will progressively migrate to integrated photonics devices in relation to our development in Silicon Photonics and Liquid Cristal Devices. The use of these set-ups concerns retinal projection but the PhD student will also be in charge to investigate other domains of application (3Dimaging/sensing, Lidar technologies, ?).

Study and Optimisation of combined cold and heat production for thermal networks

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Systèmes Solaires Haute Température

01-10-2019

SL-DRT-19-0877

nicolas.lamaison@cea.fr

Heating demand represents a major part of the total energy consumption (about 40% in France for example). In parallel, residential and tertiary cold demand keeps increasing (+80% for the next 10 years at the European scale). Moreover, the ever-increasing integration of photovoltaic or wind electricity may eventually lead to over voltage and thus instabilities of the power grid. Finally, it is well proven that energy storage is more efficient and cheaper using thermal rather than electrical means. Thus, smart synergies must be found between these two energy carrier. In that context, the present PhD thesis aims at studying the combined production of cold and heat for District Thermal Networks (DTN) using a thermal/electrical co-optimization framework. First, we will focus on the different production/conversion technologies available for the thermal and electric carriers such as simultaneous heating and cooling heat pumps (SHC-HP), absorption heat pumps (A-HP), electrical resistance, etc? and for storage. We will define the advantages and breakdowns of each system depending on the domain of application. The most promising system in terms of applicability will be then studied in details in a second phase. We will particularly develop a sizing methodology, based on MILP methods (Mixed Integer Linear Programming). With the latter, the potential conflictual objectives of production (heat vs cold) will be accounted for in the problem formulation and thus in the sized system. To do so, a physico-mathematical systematic approach accounting for uncertainties will be implemented. Finally, we will study the system from an operational point of view both numerically and experimentally, notably to evaluate the real level of performance of the sized system.

Development of an ultrasonic sensor dedicated to odour analysis

Département Composants Silicium (LETI)

Laboratoire Composants Micro-Capteurs

01-09-2019

SL-DRT-19-0886

bruno.fain@cea.fr

The development of Micromachined Ultrasonic Transducers (MUT) was first dedicated to acoustics for biomedical applications. Today, they are of great interest for a much wider spectrum of applications, such as fingerprint sensor and echolocalization, because of their unique properties compared to bulk transducers : size, ease of integration, potentially low cost. The MEMS section of the CEA-LETI is devoted to MEMS design, fabrication and test. Current work include the development of innovative capacitive and piezoelectric micromachined transducer (cMUT / pMUT). The candidate will join the MEMS sensor lab to investigate the potential of current cMUT sensor for gas and odour analysis. He/she will establish the relevance of current sensor by electrical and optical characterization (impedance analyzer, laser vibrometry, digital holography microscopy). Analytical model and numerical simulation will be developed to support the interpretation of the results. The candidate will be able to propose novel design for the next generation of gas / odour sensors. The fabrication process will be achieved within the 8 inches MEMS Platform of CEA-LETI with the strong support of the CEA teams. The characterization will confirm and refine the models. The relevance of the devices for the targeted applications (environmental or biomedical field) will be evaluated on a dedicated gas test setup, in collaboration with a start-up. For this purpose, the Ph.D. student is expected to have strong background in mechanics. He will tackle both scientific and technological challenges. He should be an autonomous team player.

Van der Waals epitaxy of CdTe on 2D materials

Département Technologies Silicium (LETI)

Laboratoire

01-10-2019

SL-DRT-19-0887

philippe.ballet@cea.fr

2D materials nowadays attract a great amount of research because of their unique properties directly derived from their graphene-like electronic structure and crystalline organization. These materials have strong in-plane chemical bounds while extremely weak, van der Waals type, out-of-plane interaction describing them a 2D sheets of monolayer material. 2D material epitaxy on conventional 3D semiconductors may thus occur without any lattice parameter mismatch strain. The opposite is also true when depositing a 3D onto a 2D. The PhD work consists in studying in details these new epitaxial systems with the proposal of realizing the strain free epitaxial growth of photovoltaics CdTe or infrared sensitive HgCdTe on 2D layers. These materials (2D and 3D) will be grown by molecular beam epitaxy allowing for an in-situ control of the interface. The growth mode of 3D(CdTe)/2D and 2D/3D(HgCdTe) will be first independently studied with the goal of providing a full 3D(CdTe)/2D/3D(HgCdTe) heterostructure where the 3D(CdTe) will promote, through the very thin 2D, the crystalline structure and orientation for the ultimate growth of HgCdTe. Inserting a weakly bonded 2D material also offer promising new functions by enabling the HgCdTe layer to be detached and transferred onto another substrate opening the way towards new optoelectronic applications. The thesis scientific environment will be brought to a broader range by considering the availability and proximity of the nano-characterization platform (CEA-PFNC) where skilled teams and last generation of equipment are dedicated to revealing the chemical nature and crystallographic structure of the epitaxial stacks.

Holistic and multidisciplinary design optimization of the positive energy buildings with alternative models

Département des Technologies Solaires (LITEN)

01-10-2019

SL-DRT-19-0891

antoine.leconte@cea.fr

The future Thermal Regulation aims to design energy-generating buildings while limiting CO2 emissions. Beyond the energy and environmental aspects, socio-economic criteria are crucial to optimize the design of a building. Despite their importance, these criteria are very rarely taken into account in optimization processes because they are difficult to quantify with conventional calculation approaches. For example, occupant behavior depends on the technologies implemented, which makes it necessary to adapt the scenarios used in the dynamic simulations accordingly. These modeling assumptions are important because they determine the optimal solutions obtained. Designing energy-generating buildings also introduces new stakeholders and legal frameworks. Representative models of these different disciplines must therefore be defined and properly associated. The holistic approach to the optimized design of buildings is ultimately very underdeveloped due also to the calculation time due to dynamic simulations and the many decision parameters. The substitution model approach is a recent approach to solving this problem. It has already been applied to optimize quantifiable quantities such as environmental aspects (energy, comfort, CO2 ...) and financial aspects. Now, it becomes essential to integrate the multidisciplinary approach for a better representation of the reality through the socio-economic and legal aspects. This is the challenge of the proposed thesis that will implement a global model and multidisciplinary performance criteria, within a methodology of optimization of criteria both quantitative and qualitative, with substitution models.

Characterization of all-solid-state batteries using neutron and synchrotron facilities

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

Laboratoire Matériaux

01-10-2019

SL-DRT-19-0894

lionel.picard@cea.fr

In view to increasing both energy density and safety of lithium batteries, all solid state battery systems are currently of interest, either based on the use of polymer or inorganic electrolyte materials, or the combination of them as hybrid electrolytes. Research activities in this field are already well established at CEA-Grenoble, such as the developments of ionic conductive ceramic materials and single-ion conductive polymers. In this frame, the PhD student will aim at supporting this work through better understanding of the hybrid electrolyte system. The objectives of the PhD student will be the in depth characterisation of the structure and properties of such systems, including local/nanoscale organisation, organic-inorganic interfaces and electrolyte-electrode interfaces. The studies will use materials already available at CEA and novel cathodes from UMICORE, as well as new material under development. The student will employ cutting-edge neutron and synchrotron techniques, such as small angle scattering, tomography, micro-beam and imaging techniques, to characterise the hybrid materials both ex situ and operando in devices and propose potential optimisation to the systems.

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