In situ synchrotron X-ray monitoring of the growth of defect-free two-dimensional materials by liquid-metal catalytic routes
The postdoctoral research project is part of a four-year European FET-Open project called LMCat (http://lmcat.eu/) bringing together five European labs, including the ESRF and the CEA-INAC, to develop the growth of defect-free two-dimensional materials by liquid-metal catalytic routes. A central lab will be established at the ESRF to develop an instrumentation/methodology capable of studying the ongoing chemical reactions on the molten catalyst. The growth by chemical vapor deposition at high pressure and temperatures will be characterized in situ, by means of two main techniques: Raman and X-ray scattering (Grazing Incidence X-Ray Scattering and Reflectivity). It will be complemented by theoretical calculations performed in Munich. The successful candidate will be in charge; together with a PhD student, of the in situ synchrotron X-ray scattering measurements, using the ESRF ID10 liquid scattering beamline (http://www.esrf.eu/UsersAndScience/Experiments/CBS/ID10) and the P08 beamline of PETRA-III (photon-science.desy.de/facilities/petra_iii/beamlines/p08_highres_diffraction/index_eng.html), in Desy.
You should hold a PhD in physics, chemistry or material science or closely related science. Previous experience of complex instrumental environment, MBE or CVD growth methods and / or with synchrotron X-ray scattering / diffraction / reflectivity, especially on liquids, will be an advantage. You should be motivated to work with an international team of young researchers with an experimental setup at the forefront of instrumental development, and ready to travel in Germany (Hambourg) for extended periods to perform some of the experiments. A good practice of English is mandatory. You should also have:
This is a full time, 3 year contract.
Please submit a 1 page cover letter stating the motivation, research experience and goals, ; a curriculum vitae, and contact information for 3 references.
Simulation of semimetal nanowires
The candidate’s mission will be:
• Simulation using ab-initio tools of the structure of bismuth nanowire bands of different diameters (from 1 nm to 10 nm).
• Extraction of parameters as effective masses, density of states, band offsets for these nanowires.
• Implementation of these parameters in a NEGF simulator to simulate bismuth nanowire transistors with variable diameter.
• Ab-initio simulation of the bismuth-dielectric nanowire interface and study of various elements of chemical passivation.
• This work will be done in collaboration with LETI / DCOS / SCME / LSIM (Philippe Blaise)
• The candidate will interact with an experimental team that will produce the simulated devices and will help to supervise one or more doctoral students, in collaboration with IMEP.
• The candidate will interact with the LTM to help predict the properties of the grid bismuth-insulator interface and implement the IMEP results in the simulator.
Physisorption of chemical species on sensitive surfaces during transfer in controlled mini-environment in microelectronics industry
A characterization platform based on the connection concept between process and characterization tools through the use of a transfer box under vacuum was implemented allowing a quasi in-situ characterization of substrates (wafers) of the microelectronics. Currently, this transfer concept based simply on static vacuum inside a carrier box is satisfactory regarding the residual O or C on the surface of especially sensitive materials (Ge, Ta, Sb, Ti…) and the MOCVD layers growth on GST or III/V surfaces. Its optimization for more stringent applications (molecular bonding, epitaxy…) in terms of contamination surface prevention requires studies the understanding of the physico-chemical evolution of the surfaces.
The proposed work will be focused on physico chemical studies of the evolution and molecular contamination of surfaces during transfers and will take place in clean room. XPS, TD-GCMS and MS coupled to the carrier itself (to be implemented) will be used to address the sources (wall, seals, gaseous environment…) of the adsorbed chemical species implied and to determine the physisorption mechanisms on the substrates. The studied surfaces will be sensitive to the contaminants in such a way than the box environment impact will be extracted and studied parameters will be the nature of polymer seal used, the carrier box thermal conditioning, the vacuum level, the use of low pressure gaseous environment in the carrier (gas nature, pressure level…).
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.
Bio-compatible, bio-resorbable microbatteries for medical applications
In the framework of its activities dedicated to embedded micro-batteries, LETI initiates prospective research in the field of micro-batteries for medical applications, and in particular as energy power sources for implantable micro-devices. In this context, a collaborative project, including LETI labs and an academic Partner (ICMCB, Bordeaux), is aiming at designing, manufacturing and studying prototypes of bio-resorbable primary microbatteries.
The main tasks will include (i) a contribution to the design of the thin film electrochemical cell by the selection of adequate biocompatible materials (able to generate the targeted electrical power, corrodible and able to solubilize in the body), (ii) the manufacture of the cell constituents (electrodes, electrolyte, substrate) as thin films (sputtering, electrochemical plating, doctor blade coating) and their characterization,(iii) the achievement of full prototype cells and the study of their in vitro behaviour.
The work will be carried out at ICMCB (Bordeaux) in a joint CEA/ICMCB team, in collaboration with LETI labs in Grenoble.
Atomic sensors based on metastable 4He
Detection of weak magnetic fields opens the way to new techniques of medical imaging, geophysics and chemistry. Optically pumped magnetometers are currently the most accurate and precise sensors for magnetic fields [1]. Our lab works on optically-pumped magnetometers based on a thermal gas of helium-4 metastables, a spin-one electronic species. Our main achievement in last years has been the design and space qualification of the most recent generation of magnetometers available for spatial exploration, which were launched by ESA Swarm mission [2].
We are now starting a new project in order to explore further applications of magneto-optical effects of metastable helium. Indeed, dichroism and birefringence have been observed on 4He from the very first times of optical pumping [3] but, in strong contrast with alkali [4], the nonlinear regimes which can be reached from the introduction of 1083 nm lasers have been hardly studied. These regimes open new possibilities for realizing not only magnetometers but also other kind of useful sensors which address a broader range of industrial applications.
We are looking for a motivated postdoc candidate willing to work towards a better understanding of these effects but also towards harnessing them for building ultra-precise sensors. The applicant should have a PhD in physics, ideally with a good background in experimental atomic physics and/or laser physics. Our lab is well equipped and staff engineers will be available to assist the post doc on technical aspects related to optics, design of electronics and magnetic materials. The results will be divulgated in form both of journal publications and of patents.
[1] Kominis et al., Nature 422 (2003)
[2] http://smsc.cnes.fr/SWARM
[3] Laloë, Leduc, Minguzzi, Journal de Physique, 30 (1969)
S. Pancharatnam, J. Phys. B: At. Mol. Phys. 1 (1968).
[4] Budker et al., Rev. Mod. Phys. 74 (2002)
Wireless biological sensor using 2D materials (Graphene , Molybdenium disulfide)
The main goal of the post-doctoral position is the fabrication of a biological sensor using 2D materials and that can be remotely addressed thanks to a RF antenna simultaneously fabricated alongside the biosensor.
The post-doctoral associate will be in charge of the fabrication and characterization of the prototype. Starting from well-designed modelling, he/she will first establish a design architecture for the sensor and RF antenna. Once designed and sized, the post-doctoral associate will adapt existing transfer protocol of 2D materials to develop an innovative fabrication process for the sensor. He/she will then fabricate the first prototypes of the sensors. Consecutively he/she will validate first the remote addressing of the sensor via the RF antenna. Secondly he/she will lead biodétection tests to assess the sensitivity of the fabricated sensors. Finally, he/she will try to integrate Transition Metal Di-chalcogenides 2D materials (such as MoS2) to graphene sensors inside a hybrid 2D materials biological sensor. The goal here will be to boost operational sensitivity.
Charge to spin conversion in HgTe topological insulators
The intrinsic spin-momentum locking of Dirac fermions at the surface or interface of topological insulators opens the path towards novel spintronic effects and applications.
Strained HgTe/CdTe is a model topological insulator and a very good candidate to design and demonstrate new spintronic devices exploiting the very large charge to spin conversion efficiency expected for such 2D systems. This postdoc position aims at realizing the first demonstration of the direct charge to spin conversion in topological HgTe nanostructures and use this demonstration as a building block for spin based logic elements.
Design of new extractant molecules for uranium and plutonium separation
The subject of this postoctoral position is related to the optimization of the process used to separate uranium and plutonium from spent nuclear fuels. In the so called PUREX process currently in operation at La Hague reprocessing plant in France, the TBP (tri-n-butylphosphate) is used as extractant in the solvent extraction system. This molecule shows high affinity for uranium and plutonium at oxidation states VI and IV and allows to reach high decontamination factors versus fission products. Nevertheless, the separation of U from Pu requires the use of reducing and anti-nitrous reagents to allow the back-extraction of Pu(III). In order to improve the process, researches are under way to design new extractant molecules which would allow to separate U and Pu without redox chemistry and with high selectivity versus fission products (Ru, Tc, Cs, lanthanides, etc) and other actinides (especially Np). The objective of the postdoctoral associate will be to select the molecules, to determine synthesis routes and to perform their synthesis using equipment available in the LCPE laboratory (micro-wave, flash chromatography, NMR, HPLC-MS, GC-HRMS) at the CEA Marcoule.
Modeling silicon-on-insulator quantum bits
Quantum information technologies on silicon have raised an increasing interest over the last five years. CEA is pushing forward its own original platform based on the “silicon-on-insulator” (SOI) technology. The information is stored in the spin of carrier(s) trapped in quantum dots, which are etched in a thin silicon film and are controlled by metal gates. SOI has many assets: the patterning of the thin film can produce smaller, hence more scalable qubits; also, the use of the silicon substrate beneath as a back gate provides extra control over the quantum bits (qubits).
Many aspects of the physics of silicon spin qubits are still poorly understood. It is, therefore, essential to complement the experimental activity with state-of-the-art modeling. For that purpose, CEA is actively developing the "TB_Sim" code. The aims of this 2-year post-doctoral position are to model spin manipulation and readout in SOI qubits, and to model decoherence and relaxation at the atomistic scale using TB_Sim. This modeling work will be strongly coupled to the experimental activity in Grenoble. The candidate will have access to experimental data on state-of-the-art devices.