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

PhD : selection by topics

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New overlay techniques for advanced technologies measurement

Département des Plateformes Technologiques (LETI)

Laboratoire Microscopie Mesures et Défectivité

01-09-2021

SL-DRT-21-0956

yoann.blancquaert@cea.fr

Advanced nano characterization (.pdf)

Overlay (OVL) is one of the key parameters to be monitored during the microelectronic components fabrications. Currently, this parameter is monitored by imaging techniques or by scatterometry. For the most advanced technologies - CMOS10nm and beyond - these techniques, although accurate (<0.4nm in 3 sigma), have difficulty to meet the needs of the process. Other techniques need to be evaluated by simulations and experimentally to achieve lower accuracies. CD-SAXS and CD-SEM are the two techniques that need to be evaluated for this ultimate metrology. The accuracy of current techniques will be evaluated, new measurement methodologies will be defined and inter-technique reference standards will be created. This subject is in the continuity of ongoing European collaborations and programs.

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Distributed intrusion detection in a constrained edge network context

Département Intelligence Ambiante et Systèmes Interactifs (LIST)

Laboratoire Systèmes Communiquants

01-09-2021

SL-DRT-21-0965

alexis.olivereau@cea.fr

Cyber security : hardware and sofware (.pdf)

The objective of the proposed PhD thesis is to define a distributed, autonomous, and reactive security system able to reconfigure itself in real time in order to take into account in particular the possible attacks, the traffic pattern to be monitored and its own resources. In this system, intrusion detection probes are essential components. They implement anomaly-based detection using artificial intelligence, capable of detecting weak signals in a potentially very high-speed environment. The analyses of the different probes are correlated in order to increase the overall capacity to identify malicious behavior on the scale of the network to be protected. Finally, the question of energy efficiency is to be considered both at the level of individual probes and that of the orchestration of the global monitoring function. PhD thesis subject proposed in the framework of the European GREENEDGE project: https://greenedge-itn.eu/wp-content/uploads/2021/03/ESR11_description.pdf All applications must be submitted via the GREENEDGE project website: https://greenedge-itn.eu/phd-hiring-call/

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Interconnection reducing or removing the use of non sustainable material to reduce photovoltaic footprint

Département des Technologies Solaires (LITEN)

Laboratoire des applications modules

01-10-2021

SL-DRT-21-0966

vincent.barth@cea.fr

Solar energy for energy transition (.pdf)

Photovoltaic (PV) industry consumes nearly 10% of the world's silver production (2019 data) and its constant growth is likely to create a short-term problem. Silver is mainly used in the interconnection of photovoltaic cells, specifically for the metallization. Today heterojunction cells provide the highest efficiency and a low temperature coefficient. These characteristics allow to obtain an excellent LCOE (Levellized Cost Of Energy). However, mandatory use of low temperature silver paste which are less conductive and cannot be easily soldered requires to deposit more silver and the problem of silver consumption is further amplified. Different approaches can be explored to solve this problem. Increasing wires number, cutting the cells or using low temperature soldering methods are the first solutions. Replacement of silver by other conductive particles are another way. The thesis proposes to explore the different approaches and after an LCA analysis to develop the most interesting one for a sustainable development of PV.

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Development of two-dimensional (2D) GaSe / InSe heterostructures for the realization of new concepts of nano- and opto-electronic devices that save on critical elements III

Département des Plateformes Technologiques (LETI)

Laboratoire des Matériaux pour la photonique

01-11-2021

SL-DRT-21-0973

berangere.hyot@cea.fr

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

With the very strong growth in the number of connected objects, which should almost triple, from 8.74 billion in 2020 to 25.4 billion in 2030, access to raw materials is becoming a major economic and geopolitical issue for the field of nanoelectronics. In order to develop sustainable nanoelectronics, it becomes necessary to design and produce devices (memories, optoelectronic components, etc.) by reducing or substituting their critical constituent elements. The notion of criticism can cover many aspects; a raw material can be classified as critical because of the available world reserves, production monopolies and possible associated geopolitical conflicts, the economic weight of the material on the balance of one or more countries or even ethical reasons (working conditions or environmental impact of extraction conditions). For example, many light emitting and light sensors devices (laser sources, light emitting diodes, photodetectors / imagers, etc.) are based on III-V semiconductors (alloys composed of elements from columns III and V of the periodic table). However, some of these elements, such as gallium (Ga) and indium (In), are now considered critical by the European Commission and it is urgent to reduce their consumption. Two-dimensional (2D) or lamellar III-VI (GaSe and InSe) semiconductors made up of only a few atomic monolayers now appear very promising for designing new architectures of optical sensors or memory cells that save on III elements. Compared to a conventional III-V component, a gain of 5 orders of magnitude can be expected on the consumption of Ga and In. Today, most devices based on III-VI materials presented in the literature are prepared by mechanical exfoliation of bulk crystals of GaSe or InSe, a technique allowing to carry out proofs of concept (the typical average dimension of exfoliated crystals is a few µm) but incompatible with the large scale and low cost manufacture of these components. The objective of the thesis is to work on the development of MOCVD growth of III-VI materials and their heterostructures directly on large-dimension silicon substrates (diameter = 300 mm). It should be noted that the combination of this growth technique with the use of silicon substrates makes the results of this work directly compatible with the production tools of microelectronics. The structural properties of these heterostructures will be investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) and Raman spectroscopy. Their physical properties (electronic or optoelectronic) will be explored through the production of suitable devices. A previous study made it possible to overcome a certain number of difficulties linked to the integration of these materials and to implement various technological bricks (lithography, identification of compatible chemistries?) for the realization of functional devices. We will focus in this new thesis on the realization of two types of devices: optoelectronic devices (mainly photodetectors) and memory cells (or memristors). In both cases, we plan to work on vertical heterostructures where the properties of the silicon substrate will be taken advantage of. The expectations of these devices are wavelength selectivity adjustable from UV to IR and good conversion efficiency for photodetectors and a low operating voltage for memory cells allowing low-power electronics applications (neural networks for example). A theoretical approach involving ab initio calculations of GaSe / InSe superlattices with determination of the electronic and optical properties of different structures will support the experimental development described above and may serve as a guide in the design of new functional heterostructures (whether dedicated to photodetection or resistive memories). The candidate, depending on his/her sensitivity, can either get involved in the development of these mathematical models or participate in their analysis with the collaborators in charge of the study.

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Synthesis and photophysical characterization of new cyclophane molecules

Département Métrologie Instrumentation et Information (LIST)

Laboratoire Capteurs et Architectures Electroniques

01-09-2021

SL-DRT-21-0991

guillaume.bertrand@cea.fr

During our recent developments in the field of radiation detection for nuclear instrumentation, we showed a benefic effect of cyclophane doping in plastic scintillators for neutron/gamma discrimination. The goal of this thesis is to perform a systematic study, both theoretical and experimental; of this phenomenon by synthesizing a library of polyaromatic cyclophane molecules. These molecules are for most of them new and will form the ground for the future theoretical and applicative exploration. Hence, a strong background in organic chemistry is required for this PhD. The other ambition of this thesis is to build a theoretical framework for the numerous photophysical processes that can occur in cyclophane molecules, with a very peculiar structure. This work will be based on a collaboration between three laboratories: CEA Saclay, for the nuclear detection application (DRT/LCAE); ENS Paris-Saclay, for photophysics research (PPSM); and Université de Versailles-Saint-Quentin, for organic chemistry (ILV/SORG).

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Diffuse Reflectance Spectroscopy using an array of Germanium photodiodes

Département d'Optronique (LETI)

Laboratoire d'Imagerie thermique et THz

01-09-2021

SL-DRT-21-1008

luc.andre@cea.fr

Photonics, Imaging and displays (.pdf)

With the increasing demand for autonomous vehicles, LETI-DOPT has developed a large portfolio of state of the art optical components including low cost focal plane sensitive in the SWIR range [900-1600nm]. In parallel, LETI-DTBS gathered a strong expertise in Diffuse Reflectance Spectrometry to measure the concentration of various chromophore in biological tissue. Formerly tuned in the visible range, this technique could be shifted in the SWIR range to detect water, oil or sugar, and benefit from the technological effort for optical components and finally propose low cost and robust biosensors. As the worldwide diabetics population is today estimated larger than 400 Million people, the targeted biosensors would represent a major breakthrough from an industrial and societal point of view. In this perspective, the robustness is a strong plus. In order to qualify then to improve it, we propose a two-pronged approach. In a first time, the candidate will work on an available lab setup made from fibered components from the shelf: black body source, spectrometer featuring an InGaAs cooled camera, and post-processing based on a Monte-Carlo algorithm. The Device Under Test is synthetic, homogenous and its optical properties are well-known. The goal is to qualify the setup: a strong simulation part of scattering medium is expected. In a second time, a design of the focal plane is expected in close collaboration with the team in charge of the realization. Last, the focal plane could be bonded on a read-out circuit to be embedded on a portable prototype. The overall response will be qualified in more complex heterogenous media, to finally asses the biosensor in realistic biological tissue.

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