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Wassim Fouad Kafrouni

Assistant professor
Chemistry - Biochemistry department - Section IV - Zahle
Speciality: Chemistry
Specific Speciality: Chimie Physique des Materiaux

Teaching 7 Taught Courses
Education
2005 - 2009: Doctorat en Sciences des Matériaux (spécialité couches minces)

Université Montpellier 2
spécialité couches minces par plasma

PhD

2004 - 2005: DEA

Université Montpellier 2

Chimie Moléculaire et Élaboration du Solide

1999 - 2003: Maitrise en chimie generale

Université Libanaise
Chimie

Publications 7 publications
T Tillocher, W. Kafrouni, J Ladroue, P Lefaucheux, M Boufnichel, P Ranson and R Dussart Optimization of submicron deep trench profiles with the STiGer cryoetching process: reduction of defects IOP PUBLISHING 2011

The STiGer process is a time-multiplexed cryogenic etching method designed to achieve high aspect ratio structures on silicon. SF6 or SF6/O2 plasmas are used as etch cycles and SiF4/O2 plasmas are used as passivation cycles. Trenches with a critical dimension of 0.8 µm have been etched to a depth of 38 µm with an average etch rate of 1.8 µm min−1. These features exhibit both undercut and a defect which is called extended scalloping. We describe this defect specific to the STiGer process and we discuss its origin: the extended scalloping is composed of anisotropic cavities developed on the sidewalls of the feature top (typically in the first 2–3 µm below the mask). It originates from ions scattered at the feature entrance that hit the top profile and remove the passivation layer where it is weakest. Then, we propose two methods to reduce this extended scalloping. The first consists in adding a low oxygen flow in the etching cycle. It favors a low additional passivation which reduces scalloping. The second technique consists in gradually increasing the SF6 flow from a low value to the nominal value. Consequently, the process starts with a low etch rate and an efficient passivation.

Wassim Kafrouni, Vincent Rouessac, Anne Julbe, Jean Durand; Synthesis and characterization of silicon carbonitride films by plasma enhanced chemical vapor deposition (PECVD) using bis(dimethylamino)dimethylsilane (BDMADMS), as membrane for a small molecule gas separation 2010

Abstract Silicon carbonitride thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) from bis(dimethylamino)dimethylsilane (BDMADMS) as a function of X = (BDMADMS/(BDMADMS + NH3)) between 0.1 and 1, and plasma power P (W) between 100 and 400 W. The microstructure of obtained materials has been studied by SEM, FTIR, EDS, ellipsometrie, and contact angle of water measurements. The structure of the materials is strongly depended on plasma parameters; we can pass from a material rich in carbon to a material rich in nitrogen. Single gas permeation tests have been carried out and we have obtained a helium permeance of about 10−7 mol m−2 s−1 Pa−1 and ideal selectivity of helium over nitrogen of about 20.

V. Rouessac*, W. Kafrouni, A. Julbe and J. Durand PECVD a-SiNXCY:H thin films for hydrogen selective membranes 2010

Microporous thin films deposited by PECVD from a gas mixture of silazanes and ammonia, on alumina asymmetric porous flat supports were studied as selective membranes for light gas separation. Microstructural characterization of the materials deposited on Si wafers and gas permeance of the membranes as a function of synthesis conditions are reported and discussed. First results reveal that an accurate choice of both the ammonia/silazane ratio and the plasma electric power lead to promising a-SiNXCY:H membranes with thickness less than 150 nm, helium permeance P(He) = 9.1 10-8 mol.m-2.s-1.Pa-1 and He/N2 ideal selectivity over 30 at 150°C with DP = 105 Pa. Furthermore, the hydrophobic/philic properties of these materials can be adjusted through their chemical composition which can be stabilized up to 500°C in air. Thin films and membranes obtained from different silazanes and ammonia/silazane ratios are compared and correlations between the derived material structures/compositions and the corresponding membrane properties are pointed out.

V. Rouessac, W. Kafrouni, J. Motuzas, M. Drobek, C. Charmette, J. Durand, A. Julbe Un matériau non-oxyde ultramicroporeux pour la séparation de l’hydrogène à plus de 300°C ? 2010

Les méthodes de production d’hydrogène nécessitent souvent en aval une étape de purification. L’utilisation de membranes est une approche très intéressante car elle permet de travailler en continu et tout en augmentant le rendement ou en abaissant la température des réactions de production d’hydrogène par déplacement des équilibres thermodynamiques. Des couches minces obtenues par PECVD en partant d’un mélange de silazane et d’ammoniac et déposées sur des supports d’alumine poreux et asymétriques sont étudiées comme membranes permsélectives aux gaz légers. Les caractéristiques microstructurales de ces matériaux déposés sur wafer de silicium seront rapportées et discutées, en relation avec les conditions de synthèse (puissance électrique du plasma, composition et mélange des gaz, post-traitement hydrothermal), et avec les performances des membranes dérivées (perméabilité, permsélectivité). Les premières analyses révèlent que des choix précis du rapport ammoniac/silazane et de la puissance plasma conduisent à des membranes a-SiCXNY:H très prometteuses dont l’épaisseur est inférieure à 100 nm. De plus, ces matériaux originaux semblent chimiquement stables jusqu’à 500°C sous air et leur balance hydrophile/hydrophobe peut être ajustée par leur composition chimique.

Wassim Kafrouni, Vincent Rouessac, Anne Julbe, Jean Durand; Synthesis of PECVD a-SiCXNY:H membranes as molecular sieves for small gas separation 2009

Plasma enhanced chemical vapor deposition (PECVD) a-SiCXNY:H thin films have been studied as molecular sieve membranes for light (hydrogen, helium) gas separation at room temperature up to 150 °C. The microstructure of the deposited materials and their thermal stability have been characterized as a function of the electric plasma power and the ratio between the vapor precursors – hexamethyldisilazane and ammonia – using SEM, Fourier transformed infrared spectroscopy (FTIR), EDS, thermo-gravimetric analysis (TGA) and ellipsometry. Single gas permeation tests have also been carried out. An ideal selectivity of helium over nitrogen of 50 has been obtained at 150 °C with a helium permeance of about 10−7 mol m−2 s−1 Pa−1. These promising PECVD materials developed for gas separation also revealed a chemical stability up to 500 °C, even in oxidative atmosphere.

Wassim Kafrouni, Vincent Rouessac *, Anne Julbe, Jean Durand PECVD SILICON NITRIDE MEMBRANES FOR GAS SEPARATION AT LOW AND INTERMEDIATE TEMPERATURES 2007

Plasma enhanced chemical vapor depostion (PECVD) a-SiNX:H layers are strongly studied for low-temperature surface passivation in silicon solar cells, for waveguides in optical communications and for gate dielectrics in microelectronics. Here we present a new potential application of such film as membrane for small gas separation at intermediate temperature.

A. Kassibaa, M. Makowska-Janusikb, J. Alauzun, W. Kafrouni, A. Mehdi, C. Reyé, R.J. Corriu, A. Gibauda EPR investigations of mesoporous silica doped with metal transitions ions 2006

Abstract Electron paramagnetic resonance (EPR) experiments were performed on mesoporous silica powders in which (1,4,8,11-tetraazacyclotetradecane) cyclam groups were incorporated. These functionalised groups allow an easy binding with copper and nickel ions. Comparative studies are carried out on samples functionalised by cyclam groups located either inside the pores or in the walls of the mesoporous structures. Copper and nickel EPR parameters, including g-tensors and hyperfine components are determined and relevant electronic, magnetic and structural information are obtained. The EPR spectra intensities and line-widths are investigated on the temperature range [4 K,300 K] to clarify the relative dispersion or agglomeration of the doping ions in the matrices as well as their possible thermally activated mobility and ions pairing. As a support of the experimental EPR investigations, numerical simulations of the geometry of metallic ion environments and their electronic properties are carried out and discussed. The possibility of dynamic Jahn Teller (JT) effect in the temperature range [200, 60 K] is discussed for the nickel doped matrices where the low temperature quenched JT configuration is thought to favour the formation of Ni3+ pairs.

Languages
Arabic

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English

Professional working proficiency

French

Native or bilingual proficiency