Strain driven Group IV photonic devices: applications to light emission and detection

Straining the crystal lattice of a semiconductor is a very powerful tool enabling controlling many properties such as its emission wavelength, its mobility…Modulating and controlling the strain in a reversible fashion and in the multi% range is a forefront challenge. Strain amplification is a rather recent technique allowing accumulating very significant amounts of strain in a micronic constriction, such as a microbridge (up to 4.9% for Ge [1]), which deeply drives the electronic properties of the starting semiconductor. Nevertheless, the architectures of GeSn microlasers under strong deformation and recently demonstrated in the IRIG institute [2] cannot afford modulating on demand the applied strain and thus the emission wavelength within the very same device, the latter being frozen “by design”. The target of this 18 months post doc is to fabricate photonic devices of the MOEMS family (Micro-opto-electromechanical systems) combining the local strain amplification in the semiconductor and actuation features via an external stimulus, with the objectives to go towards: 1-a wide band wavelength tunable laser microsource and 2-new types of photodetectors, both in a Group IV technology (Si, Ge and Ge1-xSnx). The candidate will conduct several tasks at the crossroads between fabrication and optoelectronic characterization:
a-simulation of the mechanical operation of the expected devices using FEM softwares, and calculation of the electronic states of the strained semiconductor
b-fabrication of devices at the Plateforme Technologique Amont (lithography, dry etching, metallization, bonding), based on results of a
c-optical and material characterization of the fabricated devices (PL, photocurrent, microRaman, SEM…) at IRIG-PHELIQS and LETI.
A PhD in the field of semiconductors physics or photonics, as well as skills in microfabrication are required.

[1] A. Gassenq et al, Appl. Phys. Lett.108, 241902 (2016)
[2] J. Chrétien et al, ACS Photonics2019, 6, 10, 2462–2469

Modeling silicon and germanium spin qubits

Silicon/Germanium spin qubits have attracted increasing attention and have made outstanding progress in the past two years. In these devices, the elementary information is stored as a coherent superposition of the spin states of an electron in a Si/SiGe heterostructure, or of a hole in a Ge/SiGe heterostructure. These spins can be manipulated electrically owing to the intrinsic (or to a synthetic) spin-orbit coupling, and get entangled through exchange interactions, allowing for the implementation of a variety of one- and two-qubit gates required for quantum computing and simulation. The aims of this postdoctoral position are to strengthen our understanding and support the development of electron and hole spin qubits based on Si/Ge heterostructures through analytical modeling as well as advanced numerical simulation. Topics of interests include spin manipulation & readout, exchange interactions in 1D and 2D arrays, coherence and interactions with other quasiparticles such as photons. The selected candidate will join a lively project bringing together > 50 people with comprehensive expertise covering the design, fabrication, characterization and modeling of spin qubits. He/She is expected to start early 2023, for up to three years.

Post doctoral/Research engineer position in esophageal tissue engineering using bioprinting techniques

Due to disease such as cancer or accidents such as caustic burns, the esophagus is sometimes irreversibly damaged and the only option is to remove it and replace it by using the stomach and part of the digestive tract, which often leads to serious complications and even in the best cases to poor functional results and poor quality of life. The most advanced current developments in tissue engineering for the esophagus is the use of decellularized donor tissue and clinical trials are ongoing at St Louis Hospital in this area. This approach however still presents some limitations, in particular related to donor shortage and inflammatory response. In order to prepare the next generation approach, the lab initiated a project funded by MSD Avenir to build an esophagus substitute using 3D printing. This bottom-up approach which uses bioinks as a starting material allows full control over 3D architecture and the construct can be thus personalized to the patient’s morphology and pathology, including smaller sizes for pediatric patients, in unlimited supply which is a great advantage over donor tissue. We have patented a formulation based on both natural and synthetic polymers which shows similar mechanical properties when compared to native esophagi, good suturability as well as high porosity to allow cell colonization. It also presents slow degradation as the ultimate aim is that it be replaced with native regenerated tissue over time.

We are seeking a highly motivated and autonomous post-doctoral fellow or research engineer to continue this project and characterize long term culture on this scaffold by re-epithelializing the interior of the tube and seeding primary endothelial and muscular cells on the outer part. Characterizations will include both material mechanical testing and long term cell behavior, morphology and analysis of any toxicity.

Location; St Louis Hospital, Paris

Catalytic properties at the nanoscale probed by time-resolved Bragg coherent diffraction imaging

The postdoctoral research project is part of a five-year ERC-funded project called CARINE (Coherent diffrAction foR a Look Inside NanostructurEs towards atomic resolution: catalysis and interfaces – to develop and apply new coherent diffraction imaging (CDI) capabilities. The main objective of the project is to image nanostructures in situ during reaction and to reveal their structure evolution in time and at the nanoscale to probe bulk, surface and interface effects, as well as defects. Catalysts play a key role in approximatively 90% of industrial chemical processes. The development of heterogeneous catalysis with selectivity targeting the 100% is a constant challenge as well as understanding the durability and ageing of the catalyst itself. However, the catalytic process and the associated structural changes still remain poorly understood. Understanding how catalyst structure is affected by the adsorbed layer under reaction conditions is therefore of utmost importance to formulate catalyst structure-performance relations that guide the design of better catalysts.

Postdoctoral position on the modeling of silicon spin qubits

A post-doctoral position is opened at the Interdisciplinary Research Institute of Grenoble (IRIG) of the CEA Grenoble (France) on the theory and modeling of silicon spin quantum bits (qubits). The selected candidate is expected to start at the beginning of year 2022, for up to two years.
Quantum information technologies on silicon have raised an increasing interest over the last few years. Grenoble is pushing forward an original platform based on the “silicon-on-insulator” (SOI) technology. In order to meet the challenges of quantum information technologies, is essential to support the experimental activity with state-of-the-art modeling. For that purpose, CEA is actively developing the “TB_Sim” code. TB_Sim is able to describe very realistic qubit structures down to the atomic scale when needed using atomistic tight-binding and multi-bands k.p models for the electronic structure of the materials. The aims of this postdoctoral position are to strengthen our understanding of spin qubits, and to progress in the design of efficient and reliable Si and Si/Ge spin qubit devices and arrays using a combination of analytical models and advanced numerical simulations with TB_Sim. Topics of interest include spin manipulation & readout in electron and hole qubits, exchange interactions in 1D and 2D arrays of qubits and operation of multi-qubit gates, sensitivity to noise (decoherence) and disorder (variability). This work takes place in the context of the EU QLSI project and will be strongly coupled to the experimental activity in Grenoble and among the partners of CEA in Europe.

Nanofabrication of spintronic spiking neurons

In the frame of the French national ANR project SpinSpike, Spintec laboratory is opening a postdoctoral researcher position. The candidate will work in collaboration with UMPhy CNRS-Thales and Thales TRT. The objective is the realization of proof-of-concept magnetic tunnel junction based artificial spiking neurons able to generate spikes and propagate them between coupled artificial neurons.
The candidate should have a strong background in nanofabrication and should be familiar with common techniques of optical and e-beam lithography as well as different etching techniques. The candidate can also be involved in the electrical characterization of the devices.
The position is expected to start on April 1, 2021 and go on for up to 2 years jointly between the RF team and MRAM teams of Spintec. The contract will be managed by CEA and funded by ANR Agency.
We offer an international and competitive environment, state-of-the-art equipment, and the possibility to perform research at the highest level. We promote teamwork in a diverse and inclusive environment and welcome all kinds of applicants. Further information about Spintec laboratory .

Simulation of thermal exchange between fluid and structure in turbulent channels

There is presently a huge effort in Europe for the Development of high power (PW range), high repetition rate (1-10 Hz) lasers: the ELI project in three countries of Eastern Europe , the Apollon program in France have the objective to install multipetawatt high repetition rate lasers for scientific research and applications in various fields of physics. These large projects result in – and demand – an increased mastering of most challenging issues in laser technology; at high repetition rate one of the greatest issues consists in the cooling of the laser amplifiers for the highest repetition rates. In order to master this technology, CEA (Grenoble and Saclay, with a collaboration with Grenoble/LEGI) has decided to start an R&D program, with the following tasks to perform: (i) simulation of the cooling of amplifiers; (ii) validation of the calculations; (iii) design of an appropriate cooling system dedicated to future high power high repetition rate lasers: for this, cryogenic helium gas is a very interesting fluid, as working at low temperature for laser amplification allows a better thermal conductivity of the amplifiers (consequently a better uniformity of their temperature), and an increased efficiency of the laser amplification.
This postdoc position is associated with the first (simulation) task.

Nano-imaging with deep neural networks

The postdoctoral research project is part of a five-year ERC-funded project called CARINE (Coherent diffrAction foR a Look Inside NanostructurEs towards atomic resolution: catalysis and interfaces – to develop and apply new coherent diffraction imaging (CDI) capabilities. We want to develop and apply machine learning and, more generally, data science approaches for imaging and characterisation of nanoscale systems. Coherent x-ray diffraction imaging is a strong new tool to probe the structure of nanomaterials in a non-destructive way with a spatial resolution of 10 nm. The reconstruction problem, known as “phase retrieval”, is typically solved by iterative algorithms that do not always converge. Machine learning will be applied to different tasks like e.g. phase retrieval, super-resolution, phase unwrapping, etc, to unambiguously reverse the diffraction patterns and image the structure of 3D object with nm-resolution.