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Offers : 100

Crystalline quality improvment of first building blocks of a UV LED

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Start date : 1 September 2017

offer n° SL-DRT-17-0839

Emission in UVC range is important for applications such as water disinfection. Mercury lamps are nowadays used but one of their drawbacks is the use of Hg and their size. AlGaN based UV light emitting diodes (LEDs) seems to be the best candidate for their replacement. However, UV LED performances for emission around 260 nm did some progress but stay low. Three points of the LED structure can be incriminated: 1) AlN or AlGaN buffer bad crystalline quality, 2) quantum well internal quantum efficiency, 3) p doped AlGaN. We can also add issues with light extraction.

During this PhD thesis, we propose to tackle points 1) and 2). The thesis should follow two parts. The first one will be about crystalline quality improvement of AlGaN buffer by using AlGaN pyramids (dislocation filtering). The second part will focus on AlGaN well microstructure modification in order to increase localization effects. For each significant improvement, a UV LED demonstrator may be realized.

  • Keywords : Engineering science, Optics - Laser optics - Applied optics, Solid state physics, surfaces and interfaces, DOPT, Leti
  • Laboratory : DOPT / Leti
  • CEA code : SL-DRT-17-0839
  • Contact : amelie.dussaigne@cea.fr

Realization of low leakage & low cost top transistor level in a 3D sequential integration

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Start date : 1 October 2017

offer n° SL-DRT-17-0908

An alternative approach to conventional planar integration for future nodes is 3D sequential integration also called 3D VLSI or CoolCube integration. Compared to TSV-based 3D ICs, it offers the possibility to stack devices with alignment precision at the nm range enabling 3D contacts at the device level. CoolCube integration is deeply studied in the Silicon division (DCOS) in LETI and a first demonstration on 300mm wafers have been realized, with a top transistor level integrating all the features compatible with high power & high performance logic applications (defect free Si monocrystal, high-k/metal gate stack, raised source & drain).

However, CoolCube is a versatile integration and other applications (e.g. automotive or neuromorphic applications) do not need such high performance features which are cost effective. Relaxed top transistor level on Poly-Si film is a solution for these low leakage applications but raises technological challenges as it must be done with a limited thermal budget in order to preserve the bottom transistor layer integrity.

  • Keywords : Engineering science, Electronics and microelectronics - Optoelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-17-0908
  • Contact : laurent.brunet@cea.fr

The nucleotides pool imbalance as a biomarker of stress

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Start date : 1 October 2016

offer n° SL-DRF-17-0717

Several methods have been developed to study the genotoxicity of endogenous or exogenous stresses. To determine if such stresses could alter DNA (genotoxicology) the methods consist in the measurement of DNA lesions or their consequences (cell cycle arrest, micronuclei, mutations, chromosomal aberrations,). In our laboratory we have developed several approaches to determine the genotoxicity of ionizing (radiobiology) and non-ionizing (photobiology) radiations, nanoparticles (nanotoxicology), and HAPs (environmental toxicology). Our data and those from the abundant literature are difficult to rationalize, but all these stresses induce very low levels of DNA lesions. Thus DNA lesions or alterations could not be used as a marker of exposure to these stresses. Intriguingly, the effects of stresses on the nucleotides pool imbalance has been poorly studied. Actually, an imbalance of the nucleotide pool is known to significantly affect cell division and survival, as confirmed by the use of 5-fluorouracil (a thymine analog) in chemotherapy, due to its ability to inhibit thymine synthase and thus to induce a nucleotides pool imbalance.

The objective of that project is to develop a highly specific and quantitative method to measure at the cellular level the amounts of the different nucleotides, and to study the variations of their concentrations following exposure of isolated cells to various conditions of stress.

For such a purpose, first an HPLC coupled through electrospray ionization to tandem mass spectrometry (HPLC-MS/MS) method (routinely used in the laboratory to quantify DNA lesions) will be develop to quantify natural nucleotides including mono-, di- and tri-phosphate derivatives, for both ribo- and desoxy-ribonucleotides. In a second step, the analytical method will be also applied to the measurement of less abundant nucleotide derivatives, including natural compounds such as AMPc, GMPc, FAD, SAM, Acyl-CoA, as well as modified nucleotides including for example 8-oxodGTP (arising from the oxidation of dGTP). Using such an approach, the concentrations of the above mentioned nucleotides will be determined in cells (in vitro) treated under several conditions of stress, for different doses and concentrations. The final objective is to determine if the nucleotides pool imbalance could be used as a good biomarker of stress.

  • Keywords : Life Sciences, Radiobiology, Toxicology, INAC, SyMMES
  • Laboratory : INAC / SyMMES
  • CEA code : SL-DRF-17-0717
  • Contact : jean-luc.ravanat@cea.fr

Biomimetic optical-nose development: from chemistry to artificial intelligence

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Start date : 1 October 2017

offer n° SL-DRF-17-0975

Electronic noses (eNs) have emerged as promising tools for the analysis of volatile organic compounds (VOCs) with potential applications in a wide range of domains such as biomedicine. However, so far, their performance is still far behind that of the human nose.

In this thesis, we propose a new paradigm to prepare sensing materials by combining two recognition principles used in the human nose: specific recognition and cross-reactive interaction, with the aim to greatly improve the performances of eNs and to explore their potential applications in biomedical domains.

Herein, peptides will be used as building blocks for the preparation of sensing receptors. On the one hand, based on a biomimetic approach, we aim to obtain sensing receptors that can mimic binding properties of olfactory receptors, and on the other hand, based on a combinatorial approach developed in our laboratory, we aim to prepare cross-reactive receptors with great diversity giving correlated signals (landscapes). In particular, fundamental studies will be conducted to better understand and control the chemical and physical phenomena implicated in the interaction between peptides and VOCs. This will be achieved using surface analysis and thin layer characterization techniques available at PFNC. Surface plasmon resonance imaging will be used as the optical system for the analysis of various VOCs, with a special emphasis on the problematic of anosmia-related issues. A particular theoretical effort in data analysis will be made for establishing appropriate criteria for classification purposes by using cognitive approaches and artificial intelligence via collaboration with local scientists.

  • Keywords : Solid state physics, surfaces and interfaces, INAC, SyMMES
  • Laboratory : INAC / SyMMES
  • CEA code : SL-DRF-17-0975
  • Contact : yanxia.hou-broutin@cea.fr

Structure-properties correlations in hybrid perovskites for photovolataics

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Start date : 1 October 2017

offer n° SL-DRF-17-0971

In the last five years solar cells based on hybrid perovskites have gained a tremendous research interest. This is principally due to the spectacular evolution of their power conversion efficiency, reaching more than 22% today, and to the possibility of low cost processing. On the other hand, the parameters governing the electronic properties of the hybrid perovskites as a function of their chemical structure and of the mechanisms determining the solar cell device operation are still poorly understood. Only by addressing these points it will be possible to leverage current challenges related to the limited long-term stability of perovskite solar cells and to the substitution of toxic lead in their composition.

In this context our team allies complementary competences spanning from advanced materials characterization using laboratory techniques and large infrastructures (ESRF, ILL) to the realization and test of photovoltaic devices on the Hybrid-EN platform. The present thesis builds on our experience with hybrid perovskite solar cells, which we acquired in the past 2-3 years.

  • Keywords : Ultra-divided matter, Physical sciences for materials, INAC, SyMMES
  • Laboratory : INAC / SyMMES
  • CEA code : SL-DRF-17-0971
  • Contact : stephanie.pouget@cea.fr
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