PhD : selection by topics
Mathematics - Numerical analysis - Simulation
Biochemistry
Optics - Laser optics - Applied optics
Solid state physics, surfaces and interfaces
Biotechnologies,nanobiology
Biotechnology, biophotonics
Analytic chemistry
Electronics and microelectronics - Optoelectronics
Materials and applications
Thermal energy, combustion, flows
Mechanics, energetics, process engineering
Physical chemistry and electrochemistry
Medical imaging
Instrumentation
Electromagnetism - Electrical engineering
Radiation-matter interactions
Chemistry
Automatics, Remote handling
Nuclear physics
Ultra-divided matter, Physical sciences for materials
Neutronics
Biotechnologies,nanobiology
Biotechnology, biophotonics
Biochemistry
Materials and applications
Solid state physics, surfaces and interfaces
Electronics and microelectronics - Optoelectronics
Theoretical Physics
Ultra-divided matter, Physical sciences for materials
Chemistry
Solid state physics, chemistry and nanosciences >> Materials and applications
19 propositions.
Disruptive processes for ultrathin silicon layer transfer
The Smart-CutTM technology, invented in LETI, is the most efficient process for the production of SOI substrates at an industrial scale. Its principle is based on the fracture in a brittle silicon layer performed by ion implantation of light ions. Due to SOI specifications (Si top silicon layer thikness, uniformity....) provided by the semiconductor roadmap, constraints on the mastery of processes are becoming increasingly stringent. In this context, the objective of this thesis work conducted within the framework of a collaboration between the CEA / LETI and CNRS / CEMES will explore disruptive processes and adapted to these new constraints to obtain silicon fracture. It will therefore develop the new processes and perform studies to characterize them and to understand the mechanisms involved. We are seeking a motivated candidate with a taste for various experiments combining technological work on microelectronics tools and undamental studies to understand the mechanisms of the processes studied.
See the summary of the offernterconnection reliability of 3D silicon systems on flexible substrate for medical applications
CEA-LETI develops micro-electronic systems with very high integration: this activity consists in stacking and interconnecting components in order to create electronic circuits in three dimensions. This type of 3D integration opens the door to the development of more efficient integrated systems that are smaller, faster and consume less. Thus, the 3D circuits have real benefits not only for mobile applications but also for medical applications. In the context of medical applications, one of the solutions explored is the stacking of silicon components on flexible substrates. Indeed, this type of technology perfectly suits to the development of medical implants or smart dressing. The thesis work will be achieved in the frame of 3D electronic circuit development on flexible substrates for medical applications. The research will focus on applied electro-mechanical characterization, multi-physics simulation and reliability.
See the summary of the offerAdvanced integration technology for power electronics modules
CEA-LETI is strongly committed to develop and transfer advanced technologies to manufacturing. Among its numerous field of expertises, Advanced Substrates Lab ? CEA is focusing its technological expertise to develop and apply direct bonding at wafer level to enlarge and improve semiconductor packaging toolboxes. On its side G2Elab ? UMR CNRS/G-INP/UJF (Grenoble Electrical Engineering Lab) is searching for discovering and improving the knowledge and the techniques related to the production and management of the electrical energy. Both entities are today engaged toward the development of news packaging techniques of power electronics modules for improving their performances, compactness and cost solution. Based on the development and the use of a new technology based on direct bonding at wafer level applied to 3D integration of vertical power devices, Si/SiC and possibly GaN, a PhD position is offered to do research on innovative power converters modules, for automotive and solar energy applications. The objectives of this PhD position is to develop the complete process integration of an innovating module based on advanced direct bonding and layer transfer technologies of power devices on solid metal wafers. Thermal, electrical and mechanical simulations will be realized to define the best material and circuits configuration. Then, the complete process integration technologies will be realized based on LETI's state-of-the-art semiconductors process line. Finally, after the full integration, characterization will be done and results will be analysed to understand the mechanisms involved in the technology and to assess the overall potentiality of the power modules especially in terms of electromagnetic perturbation.
See the summary of the offerSurface preparation on III-Nitrides materials
III-V semiconductors are widely used in high-power and high-frequency electronics because of their superior electron velocity with respect to the more common semiconductors silicon. They also have a direct bandgap, making them useful for optoelectronics or solar devices. III-V materials are therefore widely investigated at CEA-LETI in many French or European innovative projects with several industrial partners. These projects use production tools dedicated for microelectronic and Si-based technologies. Regarding cleaning and surface preparation of III-V materials, several chemistries borrowed from Si technology have been investigated and are now adopted for organics, particles or metallic contamination removal. But cleaning of III-V compounds remains a challenge compared to Si-based technologies. Interactions between those substrates and chemical solutions as basic surface phenomena mechanisms need to be understood. This thesis will focus on the study of phosphides or arsenides like InP, GaAs, InGaAs, InGaAsP, or gallium nitride GaN or indium antimonide InSb. The thesis will take place in the environment of the technological platform of CEA-LETI and the PhD student will have access to adequate and up to date characterization tools. Initially, the proposed work aims to evaluate fundamental behaviour of these materials in liquid phase. Surface proprieties will be measured using Zeta potential measurements, XPS, SEM, AFM, XRD, ATR, MIR FTIR, TEM and ellipsometry. Different chemistries will be tested and the performances of the wet chemical cleaning sequence developed will be characterize in terms of metallic or particle removal efficiency using SP1 or SP2 tools and TXRF (Total X-ray Reflexion Fluorescence) or ICP-MS (induced coupled plasma ? mass spectrometry) methods.
See the summary of the offerOriented growth and positioning of silicon nanowires on 2D supports
This thesis aims to study the oriented growth of Si nanowires by catalytic CVD on any type of substrate. The idea is for instance, to use a thin layer of ordered mesoporous silica as a template for the growth of nanowires. This solution would have the advantage of being compatible with a wide variety of substrates and with conventional microelectronic technologies. Different approaches will be used to relaize the silica with the catalyst positioned in the porosity. Then, the growth of nanowires will be studied and the different nano-objects synthetized will be characterized.
See the summary of the offerAlternative methods for epitaxial growth of GaN on Silicon for LED applications
Blue Leds, used for Solid State Lighting, are based on the use of semiconducting materials from the III-Nitride family (GaN and related alloys). In commercial LEDs, the optically active layers are deposited mainly on sapphire substrates, but industrial companies and R&D laboratories are presently assessing silicon as an alternative substrate. Indeed, silicon is less expensive and can be made in very large dimensions (up to 12 inches). Nevertheless, using silicon as a substrate meets two difficulties. The first is related to the high dislocation density resulting from the large lattice parameter difference between nitride materials and silicon, the second being related to their large difference in Coefficient of Thermal Expansion (CTE) which leaves the layer into high tensile stress conditions, leading to crack formation. . To deal with these problems, we want to use silicon substrates on which a mask will be deposited, in the holes of which the growth of GaN will be initiated locally. In order to reach the objectives of dislocation and tensile stress reduction, the thesis work will consist in defining and optimising the mask itself and the growth parameters. As such, the proposed thesis consists in a comprehensive work mainly based on MOVPE epitaxial growth of the GaN layers, complemented by characterization studies to assess the morphological, structural and optical quality of the layers and to follow the process evolution. The proposed work is part of the research carried out in the « Laboratoire des Composants pour Eclairage » (LCE) in LETI, whose objective is to propose innovative solutions for solid stale lighting, and will be done in close collaboratyion with the reserachers and engineers of the lab.The work will also be carried out in close collaboration with the CNRS team from LTM (Laboratoire des Technologies pour le Microélectronique), lab in which the growth process on patterned substrates has been initially developped.
See the summary of the offerPerovskite thin films optimisation for microsystems : doping and new electrodes
Thin films of perovskite structure as Pb(Zr,Ti)O3 (PZT) are becoming genuinely important for microsystems: high-K capacitors, piezoelectric devices, electrocaloric systems or pyroelectric sensors. Although they require very elaborated technology, their properties are so interesting that more and more people from both academic and industry study and develop them. One of the main drawbacks of these materials is that bulk still exhibits better properties than thin films. The main ideas to improve these lasts are 1) subtle composition modification by doping and 2) electrodes nature. In this PhD, we propose to perform PZT thin films with different dopants together with uncommon electrodes. The aim is to simplify the technological route by getting rid of the standard platinum electrodes that hinder the spreading of perovskite materials into microsystems. As it has been observed for bulk, doping can help understanding and improving the dielectric constant, the piezoelectric coefficients and the reliability of PZT. To do so, several labs from CEA that have been studying perovskite films for more than 10 years will be involved in this work: DCOS (Grenoble) for films elaboration and simulation, DTSI (Grenoble) and IRAMIS (Saclay) for all advanced characterizations (XPS, XPEEM, SIMS, XRD).
See the summary of the offerEnergy harvesting device on ultrathin substrate for biomedical applications
The PhD research will deal with thin-film photovoltaic cells on ultrathin and mechanically flexible substrates, for powering energy-autonomous miniature devices, in particular for biomedical applications. The ultrathin, flexible and robust photovoltaic cells will allow new integration concepts, and will be able to supply power for wearable or even implantable medical devices. The objective of the PhD research will be two-fold. First, the PhD student will focus on novel types of flexible substrates, namely ultrathin glass or ceramic foils. Such substrates present significant advantages compared to the more conventional metal or polymer foils. An important part of the study will focus on the properties of the back electrical contact deposited on ultrathin glass or ceramic foils. Several scientific and technological challenges have to be addressed, in particular controlling mechanical stress, microstructure, chemical composition and electrical properties of the back electrode. Second, the PhD student will explore a new crystallization annealing technique for photovoltaic thin film absorber synthesis. Compared to conventional processes, this new technique leads to a decrease of the number of process steps and a reduction of raw material consumption, hence a significantly lower manufacturing cost. A crucial aspect of the research will be to study the physical mechanisms related to reactive gas control in a prototype equipment which is available at CEA LITEN.
See the summary of the offerAdvanced concepts for structural modification of amorphous silicon layers and their application on heterojunction solar cells
Amorphous / crystalline silicon heterojunction solar cell technology (HET) has become a very promising because it combines easily industrialized processes avec very high efficiency (> 23%). The key of heterojunction solar cells is the deposition of hydrogenated amorphous silicon (a-Si: H) on a substrate of monocrystalline silicon. This allows obtaining excellent surface passivation and reaching open circuit voltage values (Voc) higher than 730mV. This thesis is focused on using innovative methods to dope and more generally to improve the structural properties of a-Si:H. The three processes approached for this goal are: ion implantation, irradiation and micro or full Laser crystallization. The aim of the work is to get stacks of a-Si: H with better passivation, improved conductivity and higher transparency for high efficiency HET cells by these innovative technologies. The application will be the single or bifacial heterojunction cells and rear contact heterojunction solar cells.
See the summary of the offer3D Tomographic Reconstruction on Non-standard Trajectoires
The tomographic reconstruction was initially developed for a 360° circular trajectory. Advances in the medical field lead to the use of helicoidal paths and therefore some reconstruction algorithms were adapted. In the field of non destructive testing (NDT), the technological advances lead to the use of robotic positioning systems in the process of automatization the testing procedure. For this case, the acquisition trajectories may vary and in the same time mechanical constraints may impact the trajectory. The main objective of this work is to propose, adapt and optimize CT reconstruction methods for non-standard trajectories. Both analytical and iterative algorithms are of interest, especially GPU accelerated versions. Two important problems arise: missing data when compared to traditional acquisitions implies the ill-posedness of the inversion problem and secondly the positioning of the source-object-detector system becomes critical. For the first aspect pre-processing techniques such as inpainting can be used or a direct handling of the missing data by the reconstruction algorithm will be investigated. For the second aspect, detection and calibration techniques should be implemented in order to ensure the correct positioning. The developed algorithms will be validated on synthetic and experimental data generated and acquired with the tools and devices available in our laboratory.
See the summary of the offerModelling of the radiation of ultrasonic guided waves in a thin structure in view of its nondestructive examination
Elastic guided waves (GW) propagate at long range, permitting the examination of large structures. Their complex behaviour makes it necessary to conduct simulation studies to help interpreting results and to improve nondestructive testing (NDT) methods that use them. The CEA LIST develops the CIVA software for NDT simulation and the models on which simulations are based. One module simulates GW-NDT of structures having a single guiding direction (pipeline, rail). Models are based on semi-analytic finite element (SAFE) techniques for the guided propagation, coupled to finite elements for calculating local interaction with defects. The thesis aims at extending this module to the case of thin parts that guide waves in all directions. A model for predicting the field radiated by ultrasonic transducers will be developed and by reciprocity, will predict their sensitivities in reception. A formulation for coupling this model to a model of interaction of a GW with a defect in such structures, in progress, is to be developed too. The overall model shall be able to deal with testing configurations involving curved anisotropic parts. Validation experiments will be made in collaboration with experimentalists at CEA. The theoretical work will be developed in the framework of a long term collaboration with specialists of aapplied mathematics.
See the summary of the offerStudy of extrinsic doping in high operating temperature (HOT) HgCdTe photodetectors
CEA/Leti is, in collaboration with the Grenoble based company Sofradir, one of the world leaders in the research and development of Infrared photodetectors made in the II-VI semi-conductor HgCdTe. One of the main challenges in this field is the increase in operating temperature of the detectors. Theoretically, the highest operating temperature in HgCdTe photodiodes should be achieved in extrinsically doped material. The characteristics of such detectors made so far have however failed to meet the expected performance level. The reason for this has been attributed to defects that are generated by the introduction of the dopants. The present thesis will be made in the context of the development of new means to incorporate and activate dopants in HgCdTe. In the beginning, the work will be concentrated on the structural (x-ray and electron microscopy) and physical (minority carrier life-time and hall-effect measurements) characterisation of samples prepared by the different techniques. In a second phase, the student will participate in the design and characterisation of innovative high-operating temperature photodiodes based on the developed material.
See the summary of the offerdegradation diagnosis of planar breathing micro fuel cells
LCSN Laboratory (CEA Grenoble LITEN) develops planar breathing fuel cells for low power supply (1-50Watt) since ten years. The work, done in a close relationship with an industrial partner, has led to the development of the fuel cell basic building blocks. First commercialization stage is targeted within 3 to 4 years. In this context, it is crucial for us to study / analyze and improve the performances and the ageing of these prototypes. The PhD work will mainly consist in studying the ageing of fuel cell core as well as of functional prototypes. It will also be necessary to participate in improving the devices, to propose innovative solutions. This work will be articulated according to three phases - Test strategy: the test strategy will be developed in agreement with the functional devices constraints, in a real working mode. - Test analyses: the results exploitation will be made through electrochemical characterization methods. In addition, ?post mortem? analyses of the devices will be done via characterization of the core fuel cell materials as well as the integration materials. Characterization techniques such as SEM, TEM, RBS and XPS will be used. It will also be an objective to study the impact of various contaminants on the fuel cells behavior. - Integration / materials: from these tests and characterization, new materials and/or architecture will be proposed and explored.
See the summary of the offerDevelopment of silicon highly integrated capacitors
The IPDiA company (Caen, France) is manufacturing silicon integrated capacitors with outstanding performances of reliability and linearity (temperature, voltage) suitable for very high-end markets like medical, aeronautics, or petrol. This PhD aims to optimize the capacitance density (goal of 1µF/mm2), the electrical performances and the robustness of a new generation of integrated capacitors. Differents dielectrics stacks have been identified but their silicon integration as well as the design of the capacitors need to be optimized. The PhD will be part of a common lab between IPDiA and CEA-Leti, academic supervisor will be G2ELab laboratory.
See the summary of the offerAdvanced Patterning process development for sub 14nm CMOS technology
For sub 14nm CMOS technology, Optical lithography based Patterning techniques are limited in terms of minimum dimension and minimum pitch. Alternative techniques, such as ebeam lithography, spacer patterning & direct self assembly, are able to overcome the sub 14nm challenges. One of the key points of such patterning techniques is to have innovative plasma etch processes that will enable the integration of these solutions. Plasma etching processes are able to transfer mask dimension into multi layers stack with a good control of the anisotropy & the selectivity towards the used materials. The goal of this PhD is to study & develop plasma etching processes for alternatives patterning techniques (Ebeam, DSA, Spacer patterning) to reach the sub 14nm dimension for line/space features.
See the summary of the offerDesign and Characterization of Memory Circuits and Macro-Cells based on organic Materials for Printed Electronics
The work of this PhD is devoted to de design and characterization of a non-volatile memory circuit in the frame of the memory and logic technologies developed within the Laboratory of Printed Components (LCI) of the CEA-LITEN. Improvements in material synthesis for organic electronics enable now the fabrication of circuits, intended for applications on large surfaces and on substrates of all types (flexible or conformable, etc). In this context the building block for information storage are still required for the autonomous circuits (Internet of Things, RFID, Sensor Tags). The aim this PhD is to design and characterize Circuits and macro cells for memory application based on the logic and ferroelectric and resistive nonvolatile memory printable technologies developed at CEA-LITEN.
See the summary of the offerDevelopment of advanced interconnections for power applications and study of their reliability
To respond to requirements for environmental protection and alternative energies (solar panels, wind energy, electrical vehicles), CEA-LETI is developing power devices based on HEMT GaN technology (High Electron Mobility Transistor on Gallium Nitride semiconductor). On top of these GaN transistors, a metallic network (also called interconnects) is fabricated to bring current and voltage to the source and drain electrodes of the components. These interconnects must withstand high current (100A), high voltage (600V), and elevated working temperatures (>250°C). Such operating conditions can lead to metallic reliability issues (diffusion, electro-migration?). This work is focused on the development of advanced interconnections for GaN power transistors and the study of their reliability. After an analysis of the specifications required for these interconnects (current density, electrical field, temperature, geometries...), the work will consist of identifying appropriate materials (eg: aluminium, copper?) and technologies to fabricate them. The interconnect structures produced will be characterized by several physico-chemical and electrical methods. Accelerated aging tests will help to study failure mechanisms. Through optimization of the technological process steps, this work will permit the fabrication of efficient and reliable interconnects.
See the summary of the offerMulti strained channels integration for 10nm FDSOI CMOS
This PhD thesis is focused on the evaluation of different strain techniques for boosting the electrical performance of FDSOI CMOS for sub 10nm generation nodes.
See the summary of the offerSurface micro-nanostructuring by local enhancement of the laser field
The interaction between a light beam and particles of very small size is an area of innovation in the field of surface micro-nanostructuring. Indeed, under certain conditions of laser irradiation, there is formation of a photonic nanojet under the irradiated particle associated to a concentration of electromagnetic field. The local reinforcement of the laser field can lead to an ablation of the substrate, localized melting or curing of photosensitive species. The objective of this thesis is to control the formation and characteristics of photonic nanojet forming underneath different types of particles and in interaction with the substrate. Through this approach, generic processes of surface structuring, multi-material, multi-scale, multi-functional, large area and low cost are targeted. Work will take place at CEA/LITEN whose applications are related to the fields of energy and nanomaterials in close collaboration with the Hubert Curien laboratory for its expertise in the area of optics, modeling and lasers. Two research axes will be carried out at the theoretical and experimental levels, one aiming at structuring by removal of material and the other one by adding material on the host substrate.
See the summary of the offer