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

PhD : selection by topics

Technology and physics of devices for the large-scale fabrication of Si-CMOS process based qubits

Département Composants Silicium (LETI)

Laboratoire de Caractérisation et Test Electrique

01-10-2019

SL-DRT-19-0570

mikael.casse@cea.fr

The fabrication of spin quantum bits has recently been demonstrated from an industrial Silicon-On-Insulator (SOI) CMOS platform, marking an important first step for the fabrication of a quantum computer in Si. Indeed, a massive production of qubits will be necessary for the future quantum processors. These qubits, to be functional, must imperatively be cooled down to a few tens of mK. Measuring the physical properties of qubits is currently done on individual devices, and requires a lot of time. The preselection of qubit devices potentially functional from the physical and technological parameters measured at 300K and down to 4K, using faster measurements and compatible with a quasi-industrial approach, remains a challenge. Mass production of qubits necessitates tools and electrical characterization methods to produce large data statistics. The subject of the phD thesis proposed is focused on the electrical characterization (from 300K to 4K-1K) of transistor devices, designed to be functional qubits at very low temperature. The goal is to make the link with the characterization of the qubits themselves at a few tens of mK. This work will open new paths of optimization for the qubit-CMOS technology (technological variants, architecture of transistors, etc.), in order to achieve a greater scale integration. The thesis will benefit from a unique work environment in Grenoble in the field of "quantum computing" *. The thesis will be performed in the electrical characterization team in CEA-Leti, in close collaboration with the process integration team and researchers in qubit physics of INAC (CEA) and the Néel Institute (CNRS). *cf. https://quantum.univ-grenoble-alpes.fr/

Study by transmission electron microscopy of the intergranular phases in NdFeB magnets for their magnetic property optimization

Département des Technologies des NanoMatériaux (LITEN)

Laboratoire de Nanocaractérisation et Nanosécurité

01-10-2019

SL-DRT-19-0571

laure.guetaz@cea.fr

The deployment of renewable energies and limitation of greenhouse gas emission involve a growing use of permanent magnets to build the cores of electrical machines. However, the most powerful magnets (NdFeB sintered) require a non-sustainable use of critical raw materials (Dy, Tb). Optimizing the magnet microstructure is widely recognized as the most promising route to mitigate the dependency to these problematic materials. In this context, knowledge of the chemical composition and structure of the phases along the grain boundaries has become crucial to better understand the magnetic properties of magnets and improve the process route. The main objective of the thesis is to study the microstructure of sintered magnets developed at CEA-Grenoble and, more particularly, to precisely characterize the intergranular phases. The PhD will used the different facilities available on the nano-characterization platform (PFNC). Specifically, she/he will use advanced electronic microscopy techniques such as nanodiffraction and STEM/HAADF (scanning transmission electron microscopy/high angle annular dark field) coupled with X-EDS (Xray energy dispersive spectroscopy) that allow analysis of the structure and the chemistry composition at the atomic scale. Secondly, from the identification of phases located at grain boundaries, she/he will use the data to set up micro-magnetic simulation. This work carried out in close collaboration with the team in charge of the magnet manufacturing will make it possible to propose an optimization of the magnet composition and process parameters.

VHF converter incorporating innovative passive components

Département Systèmes

Laboratoire Electronique Energie et Puissance

01-10-2019

SL-DRT-19-0573

sebastien.carcouet@cea.fr

The aim of the thesis is to develop a very high frequency converter (> 10 MHz) and exploiting innovative passive components. The increase in frequency allows the use of smaller passive components in value, size and weight. Indeed, the higher the frequency is, the lower the energy is stored and exchanged per cycle, the lower the volume of the inductor and / or capacity is and the higher the power density of the converter is. Moreover, a high switching frequency allows a faster converter response to operating condition changes (shorter response time). However, when the converters operate at more than 10MHz, commonly used structures, even conventional resonant structures, are no longer suitable even via Zero Voltage Switching (ZVS). This is why a new inverter topology, breaking with half or full bridge topologies is being considered. The objective of the thesis is to design, model and experimentally validate new high frequency DC / DC converter topologies using piezoelectric materials whose quality factor is high. The power level considered is from a few tens to a few hundred watts.

III-V materials etch process development for power device application

Département Technologies Silicium (LETI)

Laboratoire Gravure

01-09-2019

SL-DRT-19-0574

patricia.pimenta-barros@cea.fr

Formation of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructrures is the key-point for successful development of GaN-based power-electronics such as High Electron Mobility Transistors (HEMT) and diodes. Plasma-etching steps are considered as critical in fabrication for such devices. The aim of this thesis is to understand the etch mechanism of III-V materials using traditional etch chemistry and its impact on the film damage. An atomic layer etching (ALE) process developed at LETI will also be studied. This ALE process consists in etching the III-V material with cyclic steps. The first step is a chlorine based process to chemically modified the film at its surface, then an argon plasma is performed to selectively remove the modified layer. The goal of the thesis is to develop and characterize these plasma etch processes. This understanding of plasma surface interaction function of the etch chemistry will be studied on CEA-LETI etch tools using complementary useful characterization techniques like XPS, Tof SIMS, TEM-EELS?

Hyperspectral microscopy and single-shot optical coherence tomography with a static Fourier transform imaging spectrometer

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Imagerie et Systèmes d'Acquisition

01-09-2019

SL-DRT-19-0576

jean-charles.baritaux@cea.fr

Fourier Transform Spectroscopy measures the degree of coherence of light to recover the spectrum. A Fourier Transform spectrometer is said static when the fringe pattern is recorded in a single shot with no displacement of mechanical parts. Recently this concept was extended to Hyperspectral Imaging (HSI) for Space applications using a new configuration of static interferometer positioned in front of a focal plane array. Aside from HSI, another possibility that has not yet been investigated is to use this static interferometer for Optical Coherence Tomography (OCT). This PhD project is a collaboration between the Department of Astrophysics of the University of Grenoble and CEA Leti. We propose to investigate this new OCT approach, and its coupling to HSI in a fast bimodal system that could address many applications in Diagnostic and Bioimaging. The student will work on the development of a microscope integrating this new kind of interferometer, as well as the numerical processing of the interference patterns. Applications from students with a solid background in optics and data processing are welcome. A strong interest in biophotonics, and bioimaging is expected.

Evaluation of Metal -Organic Frameworks as new materials for Li-ion batteries

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

Laboratoire Matériaux

01-09-2019

SL-DRT-19-0584

david.peralta@cea.fr

Metal-Organic Frameworks (MOFs) are hybrid and porous materials which are mainly studied for purification and catalysis applications. However some researchers are currently prospecting for using these materials for electrochemistry applications. In this case, MOFs are directly tested as new active electrode materials in Li-ion batteries or MOFs are calcined to produce metallic oxide for supercapacitor. Recently, CEA introduced the idea to use Metal-Organic Frameworks for recycling of spent batteries with the aim to synthetize electroactive materials. The PhD position will focus on highlighting the fundamental mechanism of synthesis of such materials in different media. The selected student will work in the battery materials laboratory which is specialized in materials synthesis and characterizations. Chemical materials skills are mandatory.

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