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Offers : 20

SiNW composites in high energy density lithium-ion batteries

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Start date : 1 October 2018

offer n° SL-DRF-18-0291

The lithium-ion battery (LiB) technology, used for portable electronics as well as electrical vehicles, is based on continuously changing materials to improve their energy storage capacity, life span and safety. Silicon is interesting as an active material because it can absorb up to 10 times more lithium than carbon, the usual material in the negative electrode of commercial LiB. Besides silicon can be mixed with carbon in the electrode. Only silicon in the form of nanosized particles or wires can make long-standing battery electrodes, because mechanical constraints during the charge/discharge cycles induce silicon fracturing into disconnected powder. But on the other hand, nanosized silicon offers a large surface area to surface side-reactions, leading to lithium immobilization and performance loss.

In the present PhD project, two recent CEA technologies will be associated: a method for silicon nanowire growth at large scale (patents 2014-2016), and a process for making silicon-carbon composites in which nanosized silicon is embedded in carbon microparticles. The student will be in charge of material synthesis, characterization and performance tests in LiB. In order to optimize synthesis processes and LiB life span, he/she will try to understand the reactivity of all components of the composite during LiB cycling by electronic microscopy, spectroscopy and electrochemistry.

  • Keywords : Engineering science, Materials and applications, Ultra-divided matter, Physical sciences for materials, INAC, SyMMES
  • Laboratory : INAC / SyMMES
  • CEA code : SL-DRF-18-0291
  • Contact : cedric.haon@cea.fr

Antiferromagnetic spintronics

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Start date : 1 October 2018

offer n° SL-DRF-18-0274

Antiferromagnetic materials (antiparallel alignment of the atomic magnetic moments) could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics and are capable of generating large magneto-transport effects. Intense research efforts are being invested in unraveling spin-dependent transport properties in antiferromagnetic materials. Whether spin-dependent transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges to address.

The nature of the elements constituting the antiferromagnetic material and the quality of the interfaces will be the adjustable parameters. We will consider mainly the efficiency of spin injection and the interfacial filtering, the absorption of spins in the core of the material and the absorption characteristics lengths, the order temperatures and the magnetic susceptibility, and the efficiency of the spin-orbit coupling via the spin Hall effect.

This PhD thesis work is experimental. It will build on the many techniques of fabrication (sputtering, molecular beam epitaxy, clean room nanofabrication) and characterization (magnetometry, ferromagnetic resonance, transport) at SPINTEC and benefit from the collaboration with our partner laboratories for experiments with a resonant cavity and for access to complementary materials.

  • Keywords : Solid state physics, surfaces and interfaces, INAC, SPINTEC
  • Laboratory : INAC / SPINTEC
  • CEA code : SL-DRF-18-0274
  • Contact : vincent.baltz@cea.fr

Quantum transport in voltage-biased topological Josephson junctions

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Start date : 1 October 2018

offer n° SL-DRF-18-0281

Topological phases of matter have attracted much interest in recent years. Topological superconductors are of particular interest because they may host Majorana bound states [1]. Josephson junctions have been proposed as probes of topological superconductivity, and possible signatures of such Majorana bound states in topological Josephson junctions have indeed been observed [2,3,4]. However, important aspects related to the effect of the environment on the properties of the junction are still not fully understood. The aim of the thesis is to make progress in the understanding of quantum transport in voltage-biased topological Josephson junctions in the presence of an electromagnetic environment.

  • Keywords : Theoretical physics, Mesoscopic physics, Theoretical Physics, INAC, PHELIQS
  • Laboratory : INAC / PHELIQS
  • CEA code : SL-DRF-18-0281
  • Contact : manuel.houzet@cea.fr

Interaction effects on topological properties of multiterminal Josephson junctions

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Start date : 1 October 2018

offer n° SL-DRF-18-0289

There is currently an active search for new phases of matter that admit topologically protected edge states. A promising route to realize them consists in combining conventional materials into appropriate heterostructures. Multiterminal Josephson junctions between conventional superconductors may be considered as topological materials themselves. As an example, 4-terminal junctions can accommodate topologically protected zero-energy bound states, which form so-called Weyl singularities. Their existence may be revealed through a quantized transconductance, like in the quantum Hall effect, but without magnetic field. The aim of the project will be to explore further this recent idea by investigating theoretically the robustness of this prediction in the presence of local Coulomb repulsion within the junction. In particular, the fate of Weyl singularities will be analyzed within an actual quantum-dot model for the junction.

  • Keywords : Theoretical physics, Mesoscopic physics, Theoretical Physics, INAC, PHELIQS
  • Laboratory : INAC / PHELIQS
  • CEA code : SL-DRF-18-0289
  • Contact : julia.meyer@univ-grenoble-alpes.fr

System-level simulation and exploration flow for non-volatile neuromorphic architectures

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Start date : 1 October 2018

offer n° SL-DRF-18-0278

Hardware neural network implementation is a hot topic in research and is now considered as strategic for several international companies. Leading projects in neuromorphic engineering have led to powerful brain-inspired chips such as SyNAPSE, TrueNorth and SpiNNaker. Most of these technologies work well in centralized computing farms but will not fit embedded systems or Internet-of-Things (IoT) requirements, due to their energy consumption. Heterogeneous integration between CMOS and emergent technologies is seen as an opportunity to go past this limitation. In particular, Magnetoresistive Random-Access Memory (MRAM) is considered one of the most promising Non-Volatile Memory (NVM) technology expected to mitigate energy consumption when integrated in computing architectures. However, we still miss a high-level perspective on how NVM actually benefits energy efficiency and how it can be improved any further.

In this context, the aim of the thesis is to enable exploration of NVM-based neuromorphic accelerators by defining a framework for the joint, high-level modelling of digital logic and NVM-based functions. The framework will enable exploration of new architectural choices based on NVM properties to understand how they affect the performance/energy/area trade-off.

The thesis will be supervised by Professor Benoît Miramond (University Côte d’Azur, LEAT, Sophia Antipolis) and co-supervised by François Duhem (CEA/Spintec, Grenoble).

Applicants should have background in RTL development, system architecture, electronics and programming language such as C/C++ (SystemC appreciated).

  • Keywords : Engineering science, Computer science and software, Electronics and microelectronics - Optoelectronics, INAC, SPINTEC
  • Laboratory : INAC / SPINTEC
  • CEA code : SL-DRF-18-0278
  • Contact : francois.duhem@cea.fr
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