Laifa boufendi - Academia.edu (original) (raw)
Papers by Laifa boufendi
Lisa Wörner 1, 2, Lénaïc Couëdel 2, Maxime Mikikian 1, Alexei V. Ivlev 2, Tania Hagl 2, Mierk Sch... more Lisa Wörner 1, 2, Lénaïc Couëdel 2, Maxime Mikikian 1, Alexei V. Ivlev 2, Tania Hagl 2, Mierk Schwabe 2, Hubertus M. Thomas 3, Vladimir E. Fortov 4, Andrey M. Lipaev 5, Vladimir I. Molotkov 6, Oleg Petrov 7, Alexander Skvortsov 8, Laifa Boufendi 1, Gregor E. Morfill 9
HAL (Le Centre pour la Communication Scientifique Directe), May 1, 2018
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 14, 2011
HAL (Le Centre pour la Communication Scientifique Directe), Dec 1, 2006
Ce travail porte sur differents aspects de physique et de physico-chimie associes a la generation... more Ce travail porte sur differents aspects de physique et de physico-chimie associes a la generation de poudres dans les decharges radiofrequences (rf) basse pression en melange argon-silane. Ce phenomene constitue une source de contamination reconnue recemment comme tres critique dans les procedes de traitement de surfaces utilises dans l'industrie de la micro-electronique (circuits integres) et de la macro-electronique (ecran plat de visualisation). Un reacteur, equipe d'un ensemble de diagnostics, a ete specialement concu pour cette etude. Il est decrit en detail dans la premiere partie de cette these. La seconde partie est consacree a l'etude de l'apparition et de la croissance des particules par microscopie electronique en transmission et a travers l'analyse de leur morphologie. Cinq differentes phases dans la croissance ont ete identifiees. Cette etude est completee par la mise en uvre d'un nouveau diagnostic, base sur l'evaporation par laser des particules, permettant la detection des premieres cristallites qui apparaissent dans le plasma. La troisieme partie est quant a elle devolue a la caracterisation du plasma en presence et en l'absence de poudres. De meme que nous avons focalise notre interet sur le comportement collectif du nuage de particules dans le plasma
Molecular Crystals and Liquid Crystals, 2002
Multiwall nanotubes were functionalized using plasma treatments, chemical oxidation, ball milling... more Multiwall nanotubes were functionalized using plasma treatments, chemical oxidation, ball milling and thermal treatments. In optimized conditions, plasmas modify nanotubes surface chemistry with a great selectivity. Vickers microindentation and tension tests performed on epoxy resin loaded with multiwall nanotubes allow comparison of the influence of nanotubes surface chemistry and microtexture on loaded resin mechanical properties.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 25, 2019
The Japan Society of Applied Physics, Feb 6, 2014
This work is devoted to the study of light scattering in biological tissues. It aims to determine... more This work is devoted to the study of light scattering in biological tissues. It aims to determine indicators that permit to differentiate between cancerous and normal tissues of a human organ and to seek a mean of therapy transport. For this, we analyzed the intensity and the spectral variation of the scattered light as a function of its scattering direction. This work gives some main results of the experiment and the simulation. We stepped impressive to discriminate between cancerous and normal tissues of a human organ, such as: Vesicle, Breast.
HAL (Le Centre pour la Communication Scientifique Directe), 2006
La chargeélectrique résiduelle des poudresà l'extinction d'un plasma poussiéreux aété mesurée dan... more La chargeélectrique résiduelle des poudresà l'extinction d'un plasma poussiéreux aété mesurée dans une décharge radio-fréquence. La force de gravité aété compensée par l'application d'une force de thermophorèse de même intensité et de direction opposée. Des poudres chargées positivement ou négativement ainsi que des poudres non chargées ontété observées. Ces charges résiduelles peuvent se maintenir pendant plus de 1 minute après l'arrêt de la décharge. La chargeélectrique résiduelle moyenne pour des poudres d'environ 200 nm de rayon aété mesuréeà environ −5e pour une pression de 1, 2 mbar et −3e pour une pression de 0, 4 mbar. La chargeélectrique résiduelle sur les poudresétant reliée aux phénomènes de diffusion (ambipolaire et libre) des espèces chargées du plasma (ions etélectrons), des mesures de densitéélectronique dans des plasmas post-décharges d'argon pur et d'argon/méthane (plasma poussiéreux) ontété effectuées afin de comprendre l'influence des poudres sur les mécanismes de perte desélectrons. Ces mesures ont montré que la présence de poudres provoque d'abord une augmentation rapide de la densitéélectroniqueà l'arrêt du plasma suivie d'une décroissance accélérée.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 13, 2010
The present work is part of an endeavour to perform laboratory simulations of the chemistry of Ti... more The present work is part of an endeavour to perform laboratory simulations of the chemistry of Titan, satellite of Saturn. In the atmosphere of Titan, composed of N2 and CH4, solid particles are produced by photochemistry and charged particles from Saturn's magnetosphere. We mimic this chemistry using a low-pressure capacitively coupled plasma (CCP), produced in a gas mixture representative of Titan's atmosphere. The production of solid particles in these discharges has already been observed, together with the delay in their formation and their effect upon the electron density. Here, we present a first contribution to this global task, by characterizing pure nitrogen CCPs (with a simpler chemistry) RF discharges. The study involves both modelling and diagnostics of the discharge plasma, aiming to compare simulations and measurements.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 12, 2018
The present work is part of an endeavour to perform laboratory simulations of the chemistry of Ti... more The present work is part of an endeavour to perform laboratory simulations of the chemistry of Titan, satellite of Saturn. In the atmosphere of Titan, composed of N2 and CH4, solid particles are produced by photochemistry and charged particles from Saturn's magnetosphere. We mimic this chemistry using a low-pressure capacitively coupled plasma (CCP), produced in a gas mixture representative of Titan's atmosphere. The production of solid particles in these discharges has already been observed, together with the delay in their formation and their effect upon the electron density. Here, we present a first contribution to this global task, by characterizing pure nitrogen CCPs (with a simpler chemistry) RF discharges. The study involves both modelling and diagnostics of the discharge plasma, aiming to compare simulations and measurements.
Optik, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Physics of Plasmas, Dec 1, 2013
ABSTRACT Residual charges of individual microparticles forming dense clouds were measured in a RF... more ABSTRACT Residual charges of individual microparticles forming dense clouds were measured in a RF discharge afterglow. Experiments were performed under microgravity conditions on board the International Space Station, which ensured particle levitation inside the gas volume after the plasma switch-off. The distribution of residual charges as well as the spatial distribution of charged particles across the cloud were analyzed by applying a low-frequency voltage to the electrodes and measuring amplitudes of the resulting particle oscillations. Upon "free decharging" conditions, the charge distribution had a sharp peak at zero and was rather symmetric (with charges concentrated between -10e and +10e), yet positively and negatively charged particles were homogeneously distributed over the cloud. However, when decharging evolved in the presence of an external DC field (applied shortly before the plasma switch-off) practically all residual charges were positive. In this case, the overall charge distribution had a sharp peak at about +15e and was highly asymmetric, while the spatial distribution exhibited a significant charge gradient along the direction of the applied DC field.
Bulletin of the American Physical Society, Oct 7, 2010
Submitted for the GEC10 Meeting of The American Physical Society Negative ions and nanoparticle f... more Submitted for the GEC10 Meeting of The American Physical Society Negative ions and nanoparticle formation in low pressure rf plasmas JOHANNES BERNDT, GREMI Universite d'Orleans, E. KOVACEVIC, G. WATTIEAUX, L. BOUFENDI, GREMI, Universite d'Orleans, France-The formation of nanoparticles in low temperature and low pressure plasmas is a complex process involving a great variety of different neutral and charged species. The understanding of the underlying mechanisms is an essential requirement for a controlled initiation or suppression of nanoparticle growth. In this contribution we focus on nanoparticle formation in a capacitively coupled discharge operated in different mixtures of noble gases with either hydrocarbons or silane as precursor gas. Despite the complexity of nanoparticle formation and its dependence on the specific chemistry, it is generally believed that negative ions play a crucial role in the early stage of this process. The role of negative ions for the nucleation of nanoparticles and their impact on the discharge characteristics (electron density, self bias etc.) is investigated both experimentally and theoretically. The investigations are performed for continuous and pulsed discharges.
Lisa Wörner 1, 2, Lénaïc Couëdel 2, Maxime Mikikian 1, Alexei V. Ivlev 2, Tania Hagl 2, Mierk Sch... more Lisa Wörner 1, 2, Lénaïc Couëdel 2, Maxime Mikikian 1, Alexei V. Ivlev 2, Tania Hagl 2, Mierk Schwabe 2, Hubertus M. Thomas 3, Vladimir E. Fortov 4, Andrey M. Lipaev 5, Vladimir I. Molotkov 6, Oleg Petrov 7, Alexander Skvortsov 8, Laifa Boufendi 1, Gregor E. Morfill 9
HAL (Le Centre pour la Communication Scientifique Directe), May 1, 2018
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 14, 2011
HAL (Le Centre pour la Communication Scientifique Directe), Dec 1, 2006
Ce travail porte sur differents aspects de physique et de physico-chimie associes a la generation... more Ce travail porte sur differents aspects de physique et de physico-chimie associes a la generation de poudres dans les decharges radiofrequences (rf) basse pression en melange argon-silane. Ce phenomene constitue une source de contamination reconnue recemment comme tres critique dans les procedes de traitement de surfaces utilises dans l'industrie de la micro-electronique (circuits integres) et de la macro-electronique (ecran plat de visualisation). Un reacteur, equipe d'un ensemble de diagnostics, a ete specialement concu pour cette etude. Il est decrit en detail dans la premiere partie de cette these. La seconde partie est consacree a l'etude de l'apparition et de la croissance des particules par microscopie electronique en transmission et a travers l'analyse de leur morphologie. Cinq differentes phases dans la croissance ont ete identifiees. Cette etude est completee par la mise en uvre d'un nouveau diagnostic, base sur l'evaporation par laser des particules, permettant la detection des premieres cristallites qui apparaissent dans le plasma. La troisieme partie est quant a elle devolue a la caracterisation du plasma en presence et en l'absence de poudres. De meme que nous avons focalise notre interet sur le comportement collectif du nuage de particules dans le plasma
Molecular Crystals and Liquid Crystals, 2002
Multiwall nanotubes were functionalized using plasma treatments, chemical oxidation, ball milling... more Multiwall nanotubes were functionalized using plasma treatments, chemical oxidation, ball milling and thermal treatments. In optimized conditions, plasmas modify nanotubes surface chemistry with a great selectivity. Vickers microindentation and tension tests performed on epoxy resin loaded with multiwall nanotubes allow comparison of the influence of nanotubes surface chemistry and microtexture on loaded resin mechanical properties.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 25, 2019
The Japan Society of Applied Physics, Feb 6, 2014
This work is devoted to the study of light scattering in biological tissues. It aims to determine... more This work is devoted to the study of light scattering in biological tissues. It aims to determine indicators that permit to differentiate between cancerous and normal tissues of a human organ and to seek a mean of therapy transport. For this, we analyzed the intensity and the spectral variation of the scattered light as a function of its scattering direction. This work gives some main results of the experiment and the simulation. We stepped impressive to discriminate between cancerous and normal tissues of a human organ, such as: Vesicle, Breast.
HAL (Le Centre pour la Communication Scientifique Directe), 2006
La chargeélectrique résiduelle des poudresà l'extinction d'un plasma poussiéreux aété mesurée dan... more La chargeélectrique résiduelle des poudresà l'extinction d'un plasma poussiéreux aété mesurée dans une décharge radio-fréquence. La force de gravité aété compensée par l'application d'une force de thermophorèse de même intensité et de direction opposée. Des poudres chargées positivement ou négativement ainsi que des poudres non chargées ontété observées. Ces charges résiduelles peuvent se maintenir pendant plus de 1 minute après l'arrêt de la décharge. La chargeélectrique résiduelle moyenne pour des poudres d'environ 200 nm de rayon aété mesuréeà environ −5e pour une pression de 1, 2 mbar et −3e pour une pression de 0, 4 mbar. La chargeélectrique résiduelle sur les poudresétant reliée aux phénomènes de diffusion (ambipolaire et libre) des espèces chargées du plasma (ions etélectrons), des mesures de densitéélectronique dans des plasmas post-décharges d'argon pur et d'argon/méthane (plasma poussiéreux) ontété effectuées afin de comprendre l'influence des poudres sur les mécanismes de perte desélectrons. Ces mesures ont montré que la présence de poudres provoque d'abord une augmentation rapide de la densitéélectroniqueà l'arrêt du plasma suivie d'une décroissance accélérée.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 13, 2010
The present work is part of an endeavour to perform laboratory simulations of the chemistry of Ti... more The present work is part of an endeavour to perform laboratory simulations of the chemistry of Titan, satellite of Saturn. In the atmosphere of Titan, composed of N2 and CH4, solid particles are produced by photochemistry and charged particles from Saturn's magnetosphere. We mimic this chemistry using a low-pressure capacitively coupled plasma (CCP), produced in a gas mixture representative of Titan's atmosphere. The production of solid particles in these discharges has already been observed, together with the delay in their formation and their effect upon the electron density. Here, we present a first contribution to this global task, by characterizing pure nitrogen CCPs (with a simpler chemistry) RF discharges. The study involves both modelling and diagnostics of the discharge plasma, aiming to compare simulations and measurements.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 12, 2018
The present work is part of an endeavour to perform laboratory simulations of the chemistry of Ti... more The present work is part of an endeavour to perform laboratory simulations of the chemistry of Titan, satellite of Saturn. In the atmosphere of Titan, composed of N2 and CH4, solid particles are produced by photochemistry and charged particles from Saturn's magnetosphere. We mimic this chemistry using a low-pressure capacitively coupled plasma (CCP), produced in a gas mixture representative of Titan's atmosphere. The production of solid particles in these discharges has already been observed, together with the delay in their formation and their effect upon the electron density. Here, we present a first contribution to this global task, by characterizing pure nitrogen CCPs (with a simpler chemistry) RF discharges. The study involves both modelling and diagnostics of the discharge plasma, aiming to compare simulations and measurements.
Optik, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Physics of Plasmas, Dec 1, 2013
ABSTRACT Residual charges of individual microparticles forming dense clouds were measured in a RF... more ABSTRACT Residual charges of individual microparticles forming dense clouds were measured in a RF discharge afterglow. Experiments were performed under microgravity conditions on board the International Space Station, which ensured particle levitation inside the gas volume after the plasma switch-off. The distribution of residual charges as well as the spatial distribution of charged particles across the cloud were analyzed by applying a low-frequency voltage to the electrodes and measuring amplitudes of the resulting particle oscillations. Upon "free decharging" conditions, the charge distribution had a sharp peak at zero and was rather symmetric (with charges concentrated between -10e and +10e), yet positively and negatively charged particles were homogeneously distributed over the cloud. However, when decharging evolved in the presence of an external DC field (applied shortly before the plasma switch-off) practically all residual charges were positive. In this case, the overall charge distribution had a sharp peak at about +15e and was highly asymmetric, while the spatial distribution exhibited a significant charge gradient along the direction of the applied DC field.
Bulletin of the American Physical Society, Oct 7, 2010
Submitted for the GEC10 Meeting of The American Physical Society Negative ions and nanoparticle f... more Submitted for the GEC10 Meeting of The American Physical Society Negative ions and nanoparticle formation in low pressure rf plasmas JOHANNES BERNDT, GREMI Universite d'Orleans, E. KOVACEVIC, G. WATTIEAUX, L. BOUFENDI, GREMI, Universite d'Orleans, France-The formation of nanoparticles in low temperature and low pressure plasmas is a complex process involving a great variety of different neutral and charged species. The understanding of the underlying mechanisms is an essential requirement for a controlled initiation or suppression of nanoparticle growth. In this contribution we focus on nanoparticle formation in a capacitively coupled discharge operated in different mixtures of noble gases with either hydrocarbons or silane as precursor gas. Despite the complexity of nanoparticle formation and its dependence on the specific chemistry, it is generally believed that negative ions play a crucial role in the early stage of this process. The role of negative ions for the nucleation of nanoparticles and their impact on the discharge characteristics (electron density, self bias etc.) is investigated both experimentally and theoretically. The investigations are performed for continuous and pulsed discharges.