Radiative forcing in the 21st century due to ozone changes in the troposphere and the lower stratosphere

Radiative forcing due to changes in ozone is expected for the 21st century. An assessment on changes in the tropospheric oxidative state through a model intercomparison ("OxComp'') was conducted for the IPCC Third Assessment Report (IPCC-TAR). OxComp estimated tropospheric changes in ozone and other oxidants during the 21st century based on the "SRES'' A2p emission scenario. In this study we analyze the results of 11 chemical transport models (CTMs) that participated in OxComp and use them as input for detailed radiative forcing calculations. We also address future ozone recovery in the lower stratosphere and its impact on radiative forcing by applying two models that calculate both tropospheric and stratospheric changes. The results of OxComp suggest an increase in global-mean tropospheric ozone between 11.4 and 20.5 DU for the 21st century, representing the model uncertainty range for the A2p scenario. As the A2p scenario constitutes the worst case proposed in IPCC-TAR we consider these results as an upper estimate. The radiative transfer model yields a positive radiative forcing ranging from 0.40 to 0.78 W m(-2) on a global and annual average. The lower stratosphere contributes an additional 7.5-9.3 DU to the calculated increase in the ozone column, increasing radiative forcing by 0.15-0.17 W m(-2). The modeled radiative forcing depends on the height distribution and geographical pattern of predicted ozone changes and shows a distinct seasonal variation. Despite the large variations between the 11 participating models, the calculated range for normalized radiative forcing is within 25%, indicating the ability to scale radiative forcing to global-mean ozone column change

Irradiation ionique et auto-organisation de la matière

The topics adressed in this manuscript deal with different uses of ion irradiation techniques for structuring and functionalizing materials. Two examples are more specifically addressed : semiconductor nanostructuration through surface self-organization process, and ordering magnetic FePt alloys, of interest for instance in magnetic data storage. New research ways address modern problems related to materials for solar energy These issues are explored with the help of optical spectrometry and ion irradiation. Firstly we studied silicon heterojunction solar cells and worked out the crystalline silicon surface passivation issue. Using ion irradiation, we introduce on purpose defects at the amorphous/crystal interface for studying the degradation of the electronic properties. We observed that moderate annealing after ion irradiation allows an improved robustness of the passivation up to 400°C. Another topic will concern defects engineering in hybrid perovskite materials with a double goal : a better understanding of the luminescence intrinsic mechanisms, intimately related to electronic processes, as well as a possible electronic doping effect through the control of point defects concentration. Therefore, my future research activities will concern the impact of defects on electronic properties and their contribution to materials science. The favored tools for that purpose will be ion irradiation and photoluminescence spectroscopyLes thématiques abordées dans ce mémoire concernent différentes utilisations de l’irradiationionique pour la structuration et la fonctionnalisation des matériaux. Deux exemples sontplus particulièrement développés : nanostructuration des semi-conducteurs, en particulier dusilicium, par auto-organisation de surface, et mise en ordre d’alliages magnétiques FePt, d’intérêtpar exemple pour le stockage magnétique de l’information. Des perspectives sont dessinéesautour de la spectrométrie optique et de l’irradiation ionique à travers des thématiques trèsactuelles concernant les matériaux pour l’énergie solaire photovoltaïque. Nous nous sommesintéressés aux cellules solaires à hétérojonction a-Si :H/c-Si et à la question de la passivationde surface du silicium cristallin que nous avons pu aborder sous l’angle de l’irradiation ionique.Nous introduisons délibérément des défauts à l’interface amorphe/cristal pour étudierla dégradation des propriétés électroniques des cellules. Nous avons pu mettre en évidence uneffet intéressant des recuits à température modérée (250-400°C) qui permettent d’améliorer lapassivation du c-Si et sa tenue en température. Une autre approche concerne l’ingéniérie desdéfauts dans les perovskites hybrides avec un double objectif : une meilleure compréhensiondes mécanismes intrinsèques de luminescence, et donc des propriétés électroniques, ainsi qu’unpossible effet de dopage électronique de ces matériaux. L’orientation qui se dessine donc pourmes futures activités de recherche concernera le rôle des défauts et leur apport en science desmatériaux. Les outils privilégiés seront l’irradiation ionique et la spectrométrie de photoluminescence

Effect of Defect Production on Photoluminescence Properties in He ion Implanted Methylammonium Lead Tri-Iodide Perovskite Layers

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Effect of Defect Production on Photoluminescence Properties in He ion Implanted Methylammonium Lead Tri-Iodide Perovskite Layers

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Flux growth and physical properties characterizations of Y1.866Eu0.134O3 and Lu1.56Gd0.41Eu0.03O3 single crystals

Y1.866Eu0.134O3 and Lu1.56Gd0.41Eu0.03O3 single crystals of the cubic rare-earth sesquioxide phase were grown for the first time by a new flux method, in air and at temperatures between 1250 and 1100 degrees C. Magnetic susceptibility measurements performed in the former crystals suggest that a preferential dissolution of Eu3+ cations occurs on the C-2-site. Transmission measurements established the promising optical quality of the samples, especially for Lu1.56Gd0.41Eu0.03O3 in the red spectral range where most of the scintillation light is emitted. The Lu1.56Gd0.41Eu0.03O3 single crystal, grown and tested for the first time, is an efficient X-ray scintillator and its characteristics seem promising for X-ray imaging with medium spatial resolution, in terms of light output and low afterglow. Emission and transmission spectra were measured and Eu3+ Judd-Ofelt analysis was performed in both crystals. (C)2015 Optical Society of Americ

Judd-Ofelt analysis of luminescence emission from Li6Eu1−xSmx(BO3)3Li_6Eu_{1-x}Sm_x(BO_3)_3 single crystal

A detailed spectroscopic study of Eu3+ ions in the monoclinic Li6Eu1-xSmx(BO3)3 (LSEBx) crystals is reported. The symmetry of the local environment of Eu3+ activators has been confirmed within the framework of the standard Judd-Ofelt theory, using Ω2, Ω4 and Ω6 intensity parameters derived from emission spectra data analysis. With these intensity parameters various radiative properties, like spontaneous emission probability, branching ratio, stimulated emission cross-section and radiative lifetime, have been calculated. The maximum stimulated emission cross section corresponding to the 5D0 → 7F2 transition is 3×10-21 cm2 at 611 nm. Under UV excitation, the LSEBx crystals provide intense red photoluminescence intensity. These results revealed that LSEBx might be potential materials for optical applications

Optical spectroscopy and magnetic behaviour of Sm3+ and Eu3+ cations in Li6Eu1-xSmx(BO3)3 solid solution

A new borate solid solution series of powders, Li6Eu1-xSmx(BO3)3 (LSEBx, x = 0.35, 0.5, 0.6, 1), were synthesized by solid-state reaction, characterized and their luminescent properties were investigated. The absorption spectra indicate that absorption takes place mainly from the Sm3+6H5/2 ground state, with a strong band at 405 nm. The photoluminescence spectra reveal that the Eu3+ red emission intensity strongly depends on the Sm3+ content x. Judd-Ofelt theory was applied to experimental data for the quantitative determination of phenomenological parameters Ωi (i = 2, 4, 6) Judd Ofelt parameters, radiative transition rates and emission quantum efficiency. Owing to the energy transfer from Sm3+ to Eu3+ the intense red light detected at 613 nm at room temperature under UV or blue light excitation, was improved by ∼35% as compared with Sm3+-free samples. This energy transfer was confirmed by faster decay times of Sm3+ as energy donors. Moreover, the energy transfer between Sm3+ and Eu3+ is unidirectional and irreversible, implying that the energy transfer wastage between Sm3+ and Eu3+ is very low. Magnetic susceptibility (χ) measurements of LSEBx were carried out in the temperature range 2-320 K and are used to compare calculated and experimental energy levels

Reversible nature of photo-induced phase segregation and origin of long carrier lifetime in triple cation mixed halide perovskite films

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Reversible nature of photo-induced phase segregation and origin of long carrier lifetime in triple cation mixed halide perovskite films

conférence en visioInternational audienc

Radiative Recombination in Quadruple Cation Organic-Inorganic Mixed Halide Perovskite Layers: Electron Irradiation Induced Ageing Effects

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