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The Secondary Electron Emission (SEE) process plays an important role in the performance of various devices. Mitigating the multipactor phenomenon that may occur in radio-frequency components is a concern in many fields such as space technologies or electron microscopy. SEE is also a concern in the accelerator physics community, where the beam lines stability can strongly be affected by this phenomenon*,**. In that scope, the escaped depth and thus the range of emitted electrons is of great interest. Our goal, by means of simulations is to provide a better knowledge of SEE. We have developed a Monte Carlo electron transport code for low energy electrons [~eV, ~10keV], that is part of the Dec. 2020 release of GEANT4***. It has been used to study the practical range of low energy electrons. Our goal is to formulate, below ~10 keV, an analytic range vs. energy expression, and to relate it to fundamental physcial parameters such as the mean free paths of electrons in matter. The goal is to provide simple practical extrapolated range formula that can help to understand SEE phenomenon., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Low energy electrons of few tens of eV may cause Multipactor breakdowns in waveguides driven by the Secondary Electron Emission Yield (SEY) of the walls. This risk is lowered by using low emissive surfaces and this topic has been studied experimentally and with numerical simulations. The dependence of the SEY on surface properties is well known*. Surface morphology has been widely used to reduce the SEY by forming roughness patterns on the surface**. All patterns do not have the same efficiency so their analysis in terms of SEY is relevant. Monte-Carlo simulation codes can be used to study the processes behind the SEY. The MicroElec module of GEANT4 has recently been extended with more materials and processes and validated with experimental data for SEY calculations**. In this work, simulation results are shown for a bulk sample capped with different roughness patterns. The effects of the shape parameters on the SEY are studied for typical dimensions between 20 µm and 100 µm. The results are checked with experimental SEY measurements on samples with similar roughness patterns., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

International audience; A comprehensive approach is developed for the simulation of single particle displacement damage in silicon. The first step corresponding to Monte Carlo simulation of the primary interaction is presented.

International audience; This work investigates MGy Total Ionizing Dose effects in CMOS technologies. Large TID-induced electrical shifts are observed in devices with thin dielectrics. Trapping and detrapping properties are discussed using dedicated irradiation/annealing experiments

International audience; This study focus on an innovative procedure allowing to regenerate highly irradiated optical fibers used in nuclear facilities by recovering the fiber transmission acting only from one of the two fiber ends.

International audience; There is an increasing interest in developing cameras for surveillance systems to monitor nuclear facilities or nuclear waste storages [1]. Particularly, for today’s and the next generation of nuclear facilities increasing safety requirements consecutive to Fukushima Daiichi’s disaster have to be considered. For some applications, radiation tolerance needs to overcome doses in the MGy(SiO2) range whereas the most tolerant commercial or prototypes products based on solid state image sensors withstand doses up to few kGy [2]. The objective of this work is to present the radiation hardening strategy developed by our research groups to enhance the tolerance to ionizing radiations of the various subparts of these imaging systems by working simultaneously at the component and system design levels.Developing radiation-hardened camera implies to combine several radiation-hardening strategies. In our case, we decided not to use the simplest one, the shielding approach. This approach is efficient but limits the camera miniaturization and is not compatible with its future integration in remote-handling or obotic systems. Then, the hardening-by-component strategy appears mandatory to avoid the failure of one of the camera subparts at doses lower than the MGy.Concerning the image sensor itself, the used technology is a CMOS Image Sensor (CIS) designed by ISAE team with custom pixel designs used to mitigate the total ionizing dose (TID) effects that occur well below the MGy range in classical image sensors (e.g. Charge Coupled Devices (CCD), Charge Injection Devices (CID) and classical Active Pixel Sensors (APS)), such as the complete loss of functionality, the dark current increase and the gain drop. We’ll present at the conference a comparative study between these radiation-hardened pixel radiation responses with respect to conventional ones, demonstrating the efficiency of the choices made. The targeted strategy to develop the complete radiation hard camera electronics will be exposed. Another important element of the camera is the optical system that transports the image from the scene to the image sensor. This arrangement of glass based lenses is affected by radiations through two mechanisms: the radiation induced absorption andthe radiation induced refractive index changes. The first one will limit the signal to noise ratio of the image whereas the second one will directly affect the resolution of the camera. We’ll present at the conference a coupled simulation/experiment study of these effects for various commercial glasses and present vulnerability study of typical optical systems to radiations at MGy doses. The last very important part of the camera is the illumination system that can be based on various technologies of emitting devices like LED, SLED or lasers. The most promising solutions for high radiation doses will be presented at the conference.In addition to this hardening-by-component approach, the global radiation tolerance of the camera can be drastically improve by working at the system level, combining innovative approaches eg. for the optical and illumination systems. We’ll present at the conference the developed approach allowing to extend the camera lifetime up to the MGy dose range.[1] Cho, Jai Wan; Choi, Young Soo; Jeong, Kyung Min, “Monitoring Performance of the Cameras under the High Dose-Rate Gamma Ray Environments”, Health Physics:May 2014 - Volume 106 - Issue 5 - pS47-S58[2] Armani, J.M., Barrochin, P. ; Joffre, F. ; Gaillard, R. ; Saigne, F. ; Mainguy, J.L., “Enhancement of the total dose tolerance of a commercial CMOS active pixel sensor by use of thermal annealing”, Radiation and Its Effects on Components and Systems (RADECS 2011 Proceedings), pp. 340-344,2011.

International audience; We investigate the impact of performance boosters using mechanical stress on the Single-Event Transient (SET) response of nanometer scaled Fully-Depleted Silicon-On-Insulator (SOI) devices. Laser SET measurements show that the active silicon layer thickness is the most important contributor to the SET response of highly scaled Ultra-Thin SOI (UTSOI) devices compared to the impact of strain. This is then demonstrated by dedicated TCAD calculations performed without taking into account any strain engineering technique. Finally, heavy ion-induced charge collection mechanisms are analyzed through the measurement of fast transients to get additional insights into the impact of short channel effects on the SET response of nanometer scaled SOI devices

International audience; The quest for high-mobility MOSFET channel material has led electronic material researchers to replace silicon by germanium in advanced technologies. This field of research has been the subject of many studies in recent years (see for example [1]). One of the main problem of the rise of germanium as a possible material is its oxide, GeO2, and its interface with the latter, because of the larger defects density in Ge:GeO2 than in Si:SiO2. In this study, we performed first principles calculations on defects and dopants in crystalline and amorphous GeO2. Calculations based on the Density Functional Theory (DFT) using the Local Density Approximation (LDA) are performed through the PWscf code from the Quantum ESPRESSO distribution [2]. These calculations allow us to have access to the atomic configurations of defects and dopants and to their energy properties. Starting from the wavefunctions and from the atomic configurations obtained in DFT, we use the SaX code version 2.0 [3] to apply the GW approximation to obtain a right value of the band gap and to evaluate the effects of point defects, dopants and impurities on the electronic properties of GeO2. Finally, the optical properties (particularly the absorption spectra) of pure and doped GeO2 are given including excitonic effects with resolution of the Bethe-Salpeter equation (BSE). A particular attention will be given to the levels introduced by dopants and defects in the electronic structure of Germania and their effects in terms of charge capture will be discussed. We already successfully applied this methodology to oxygen vacancies in pure and Germanium doped silica [4] and the results obtained will be discussed and compared to the results coming from this previous study and from literature. [1] M. Houssa, A. Satta, E. Simoen, B. De Jaeger, M. Caymax, M. Meuris, and M. Heyns, in Germanium Based Technologies: From Materials to Devices, edited by C. Claeys and E. Simoen Elsevier, Amsterdam, 2007, p. 233. [2] P. Giannozzi et al., J. Phys. Condens.Matter, 21, 395502 (2009). [3] L. Martin-Samos and G. Bussi, Comp. Phys. Com., 180, 1416 (2009). [4] N. Richard et al., J. Phys.: Condens. Matter, 25, 335502 (2013).

International audience; Abstract-- A hardening method is proposed to enable the use of CMOS image sensors for Fusion by Inertial Confinement Diagnostics. The mitigation technique improves their radiation tolerance using a reset mode implemented in the device. The results obtained evidence a reduction of more than 70% in the number of transient white pixels induced in the pixel array by the mixed neutron and γ-ray pulsed radiation environment.

International audience; We investigate Single-Event Transients (SET) in various designs of multiple-gate devices: FinFETs and nanowires. Heavy ion experimental results are explained by using a thorough charge collection analysis of fast transients measured on dedicated test structures. Multi-level simulations are performed to get new insights into the charge collection mechanisms in multiple-gate devices. Implications for multiple-gate device design hardening are finally discussed.

International audience; We report an experimental study demonstrating the feasibility to produce both pure and Ge-doped silica nanoparticles (size ranging from tens up to hundreds of nanometers) using nanosecond pulsed KrF laser ablation of bulk glass. In particular, pure silica nanoparticles were produced using a laser pulse energy of 400 mJ on pure silica, whereas Ge-doped nanoparticles were obtained using 33 and 165 mJ per pulse on germanosilicate glass. The difference in the required energy is attributed to the Ge doping, which modifies the optical properties of the silica by facilitating energy absorption processes such as multiphoton absorption or by introducing absorbing point defects. Defect generation in bulk pure silica before nanoparticle production starts is also suggested by our results. Regarding the Ge-doped samples, scanning electron microscopy (SEM) and cathodoluminescence (CL) investigations revealed a good correspondence between the morphology of the generated particles and their emission signal due to the germanium lone pair center (GLPC), regardless of the energy per pulse used for their production. This suggests a reasonable homogeneity of the emission features of the samples. Similarly, energy dispersive X-ray spectroscopy (EDX) data showed that the O, Ge and Si signals qualitatively correspond to the particle morphology, suggesting a generally uniform chemical composition of the Ge-doped samples. No significant CL signal could be detected in pure silica nanoparticles, evidencing the positive impact of Ge for the development of intrinsically emitting nanoparticles. Transmission electron microscope (TEM) data suggested that the Ge-doped silica nanoparticles are amorphous. SEM and TEM data evidenced that the produced nanoparticles tend to be slightly more spherical in shape for a higher energy per pulse. Scanning transmission electron microscope (STEM) data have shown that, regardless of size and applied energy per pulse, in each nanoparticle, some inhomogeneity is present in the form of brighter (i.e., more dense) features of a few nanometers