Minimizing modifications at III-V pattern sidewalls after plasma etching for heterointegrated optoelectronics and nonlinear photonics
This project will focus on understanding plasma-induced damage at the sidewalls of micro-nano-patterned III-V semiconductors to find relevant technological solutions capable to minimize this damage. There is a clear need of knowledge on by which mechanisms and to what extent the plasma etching process modifies the III-V pattern sidewalls and the consequences it has on the device optical performances. The selected III-V semiconductor will be aluminium gallium arsenide which exhibits excellent optoelectronic properties and strong nonlinear parametric gain.
The student will be mainly focused on understanding how the key plasma process parameters influence the structural and chemical changes at the III-V sidewalls, as well as changes of optical properties. This will require the development of a methodology for a 3D quantitative characterization of the sidewalls at the nanoscale, based on Auger microscopy and cathololuminescence. The main objective will be to correlate plasma-induced structural defects and modifications of the optoelectronics properties. The second step will consist in developing optimized plasma etching processes for III-V semiconductors, exploring alternative plasma technologies. You will also be involved in the development of processes for restoring and passivating the AlGaAs sidewalls.
Detection of traces of narcotics in saliva by electrochemiluminescence on diamond electrodes
The consumption of narcotics is becoming a problem for road safety because 23% of road deaths in France occur in an accident involving at least one driver who tested positive. Thus, one objective of road safety in consultation with the concerned ministries (Ministry of Transport, Ministry of Interior, Ministry of Health and Ministry of Economy) is to improve the fight against road insecurity linked to narcotics consumption. In particular, this involves increasing and facilitating roadside checks using a portable device dedicated to controlling the use of narcotics on the roadside, similar to what is already done for breathalyzer tests. Such a device is not commercially available today. The main prerequisites of this device will be to provide reliable, immediate confirmation results with evidentiary value for the courts as well as a purchase cost compatible with large-scale deployment on French road networks. In this context, the subject of study proposed aims to study the possible detection of traces of narcotics in saliva using electroluminescence on a boron-doped diamond electrode. This method is considered promising for such an application because it potentially allows extremely low detection thresholds to be reached and, in accordance with legislative requirements, offers multiple possibilities aimed at achieving high selectivity towards chemical targets, with a high detection capacity. miniaturization of equipment and a relatively low cost of apparatus compared to analytical tools such as mass spectrometer, IMS, etc.
Plastic recycling enabled by toxic additives extraction using green solvents
It is important to develop the scientific knowledge and stimulate innovations to recycling Plastics. The extremely large variety of plastic based objects that we use in our daily life are made of a wide range of plastic materials covering many different polymers, many different formulations. Plastics objects are also used for many purposes and there is therefore the need of various ways to collect, sort and treat them.
Methods of recycling of plastics are generally divided into four categories: primary, secondary, tertiary, and qua-ternary (see Figure 9). Primary recycling or closed loop recycling method is considered when the materials after recycling present equal or improved properties compared to the initial or virgin materials. When the recyclates present a decrease in the properties level, one may spook about secondary or down-cycling method. In tertiary (also known as chemical or feedstock) recycling method, the waste stream is converted into monomers or chemicals that could be advantageously used in the chemical industries. Finally, quaternary (also known as thermal recycling, energy recovery, and energy from waste) recycling method corresponds to the recovery of plastics as energy and is not considered as recycling for Circular Economy.
Various processes can be considered for chemical recycling which present different level of maturity. Hence this project that will study the decontamination of various PVC formulations using green solvents, and more particularly supercritical CO2
This work located in Saclay, France, in the heart of the University Paris-Saclay and will benefit from a very multidisciplinary and international environment.
This work will benefit from the prestigious framework of the France 2030 funding, and more precisely the PEPR Recycling (https://www.cnrs.fr/fr/pepr/pepr-recyclabilite-recyclage-et-reincorporation-des-materiaux-recycles ). It will be supervised by Dr. Jean-Christophe P. Gabriel: linkedin.com/in/jcpgabriel).
Optimization of Li metal/electrolyte for the next generation of all-solid-state battery
CEA Tech Nouvelle-Aquitaine, created in 2013, set up a new laboratory, since more than two years, focused on both the development of materials and the high throughput screening to accelerate the discovery of materials for the next generations of Li-ion batteries. For that, the CEA Tech Nouvelle-Aquitaine acquires different vacuum deposition equipment (sputtering, evaporation, atomic layer deposition) integrated in glovebox and different automated characterization techniques (SEM-EDX, profilometer, XRD, LIBS and confocal microscope later).
The Li metal/electrolyte interface constitutes one of the main challenges to overcome for the next generation of all-solid-state battery. The reactions of decompositions at the interface associated to uneven plating/stripping of Li ions lead to quick cell failure. One of the avenue for stabilizing it is to use a protective layer, which must feature numerous physical-chemical properties. In this context, this internal CEA project aims at setting up a combinatorial synthesis methodology associated to high throughput characterizations in order to accelerate the discovery of new protective layers at the Li metal/electrolyte interface.
We are seeking for an outstanding applicant who will be in charge of setting up the whole methodology, from the synthesis to the physical-chemical-electrochemical characterizations of the materials. She/he will have at her disposal a new state-of-the-art infrastructures. She/he will collaborate with other CEA labs located at LITEN (Grenoble, France).
New nanostructurated fluorescent materials for the detection of volatile organic compounds.
The presence in indoor environments of many substances and (geno-)toxic, allergenic and infectious agents with pathogenic effects is well known. The on-site detection of these
substances has become a strong need, related to public health concerns. To respond to this need and enable the development of sensitive and selective ’field-deployable chemical sensors’, different technological solutions are being considered (conductimetric, electrochemical, piezoelectric, electro-mechanical, optical based systems…). Among all these methods, those based on the use of fluorescence phenomena are particularly interesting because of the inherently high sensitivity (lower limit of detection) of the technique and the possibility it offers to develop low cost, small size and low
energy consuming devices.
The proposal falls into this context and aims at evaluating the potentialities of new nanostructurated organic materials for the detection of indoor air trace pollutants by fluorescence change monitoring. This work will be done in straight collaboration with the Laboratoire Chimie des Polymères (UMR7610-CNRS/UPMC Paris VI) specialized in the synthesis
of functionalized organogels. More precisely, we propose to develop new highly porous supramolecular materials serving either as substrate for the sensitive fluorescent polymer or functionalised so as to directly detect and recognize the vapor pollutant.
The physico-chemical properties of these new materials will be examined by different techniques. Their performances in the presence of target pollutants (formaldehyde, acetaldehyde) and potentially interferants will be evaluated. Finally, the most interesting materials will be integrated into a functional prototype.
Development of new processes for the fabrication of advanced interconnect structures of solar cells
The fabrication of solar cells with high performances at a reduced cost is a key challenge addressed by many research institutions and industrials worldwide. Many technological solutions are being investigated. Among them, a promising approach consists in forming narrower metal lines to limit shadowing of active areas of the cells. This work aims at replacing serigraphy by new fabrication processes able to reduce line width. For this purpose, the conducting substrate is coated by an insulating mask in which the lines are defined. The metal is then directly plated selectively onto the weakly conducting portions of the substrate, i.e. the lines, using electrolytic reactions. The process conditions will be adapted with regard to the nature of the initial conducting surfaces.
Multi-scale modelling of the structure and mobility of small defect clusters in metals
Recently, we have proposed a three dimensional periodic structure for self-interstitial clusters in body-centered-cubic metals, as opposed to the conventional two dimensional loop morphology [1]. The underlying crystal structure corresponds to the C15 Laves phase. Using Density Functional Theory and interatomic potential calculations, we have demonstrate that in a–iron these C15 aggregates are highly stable and immobile and that they exhibit large antiferromagnetic moments. They form directly in displacement cascades and they can grow by capturing self-interstitials. They thus constitute an important new element to account for when predicting the microstructural evolution of iron base materials under irradiation.
Despite their low concentration, these clusters are expected to play a crucial role in the behavior of iron and ferritic steels under irradiation and many questions remain to be elucidate: which clusters are the most stable in intermediate sizes, which are the reaction pathways which link the traditional clusters to new ones, how the new clusters interact with the dislocation loops, which are the effects of finite temperatures etc
xenon measurement by Cavity RingDown Spectroscopy to improve safety in the fast neutron reactors
Safety is a key point of the IVth generation nuclear reactors. Therefore new analytical methods are investigated for reliably detecting tracers of a nuclear reactor malfunction. This postdoctoral work aims at studying an innovative laser absorption method, Cavity RingDown Spectroscopy CDRS, to measure gaseous tracers indicating a reactor malfunction. This study is part of the research and development activity of the Physical Chemistry Department (DPC), which is partly involved in improving and developing tools and analytical methods. The optical system studies are a collaboration work with the "Laboratoire Interdisciplinaire de Physique" of the Grenoble University (France), which is a leader research laboratory in trace gas detection by laser absorption methods CRDS (Cavity RingDown Spectroscopy) and OF-CEAS (Optical Feedback Cavity Enhanced Absorption Spectroscopy).
A glow discharge was coupled to a Cavity RingDown measurement. After plasma conditions optimization, the optical set-up is able to measure below 1 part per billion Xe/Ar mixing ratios. The optical saturation of the xenon electronic transition should be considered to quantify each isotope. The optimized CRDS measurement will be characterized. The set-up could further measure krypton isotopes.
A. Pailloux & al., depot de brevet 11 62436 (2011)
P. Jacquet, A. Pailloux, submitted to J. Anal. Atom. Spectrom. (2013)
N. Sadeghi, J. Plasma Fusion Research 80 (9), pp 767-776 (2005)
Silicon nanowire elaboration for microelectronic applications
In order to realize high capacity integrated capacitor, one approach consists in developing electrode with high specific surface. In this work, we propose to perform capacitor integrating silicon nanowires. The first part of this study will be devoted to the understanding and to the optimization of Si nanowires CVD growth process. In parallel, properties of nanowires obtained by electrochemical silicon etching will be assessed and will be compared to CVD nanowires characteristics. According to the electrical performances, different strategies (metallization Silicuration…) will be envisaged in order to enhance their electrical conductivity.
New Sustainable Carbon Catalysts for PEMFC
The aim of the project is to develop and test for ORR, a mesoporous and graphitised graphene aerogel based material, presenting a hierarchical structuring allowing a better material transfer and graphitic domains increasing the durability and conductivity of the final material, and functionalised by Pt-NPs.
These graphene-based structures developed at IRIG/SyMMES possess surface chemistries and micro/meso/macro porosities that depend on the synthesis, functionalisation and drying methods used. The aim will be to increase their degree of graphitisation, and then to deposit Pt-NPs by chemical means. The electrocatalytic properties of these materials will then be tested.
Advanced meso-structural characterisation of these materials by scattering (X-ray or neutrons) methods will enable to investigate the structural properties of these new electro-catalysts. These properties will thenbe correlated to their electrocatalytic properties, and performances in fuel cell systems. This knowledge will be gained through ex-situ and operando analyses.