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277 results on '"Hoummada, K."'

9. Nickel stanogermanides thin films: Phases formation, kinetics, and Sn segregation.

Author

Khelidj, H., Portavoce, A., Hoummada, K., Bertoglio, M., Benoudia, M. C., Descoins, M., and Mangelinck, D.

Subjects
X-ray diffraction measurement, MAGNETRON sputtering, OHMIC contacts, THIN films, FINITE differences, GERMANIUM films
Abstract

Ge1−xSnx thin films with a Sn content of x ≥ 0.1 present a direct bandgap, which is very interesting for the fabrication of efficient photonic devices. The monostanogermanide phase, Ni(GeSn), is promising to form ohmic contact in GeSn-based Si photonic devices. However, the formation kinetics of Ni stanogermanides and the incorporation of Sn in Ni–GeSn phases are not fully understood. In this work, Ni thin films were deposited on Ge and Ge0.9Sn0.1 layers grown in epitaxy on an Si(100) substrate using magnetron sputtering technique. In situ x-ray diffraction measurements were performed during the solid-state reaction of Ni/Ge and Ni/Ge0.9Sn0.1. 1D finite difference simulations based on the linear parabolic model were performed to determine the kinetics parameters for phase growth. The nucleation and growth kinetics of Ni germanides are modified by the addition of Sn. A delay in the formation of Ni(GeSn) was observed and is probably due to the stress relaxation in the Ni-rich phase. In addition, the thermal stability of the Ni(GeSn) phase is highly affected by Sn segregation. A model was developed to determine the kinetic parameters of Sn segregation in Ni(GeSn). [ABSTRACT FROM AUTHOR]

Published
2024
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10. Structural, dielectric, ferroelectric and tuning properties of Pb-free ferroelectric Ba0.9Sr0.1Ti1-xSnxO3

Author

Zaitouni, H., Hajji, L., Mezzane, D., Choukri, E., Gagou, Y., Hoummada, K., Charai, A., Alimoussa, A., Rožič, B., Marssi, M. El, and Kutnjak, Z.

Subjects
Condensed Matter - Materials Science
Abstract

A series of Pb-free ferroelectric materials Ba0.9Sr0.1Ti1-xSnxO3 (BSTS-x) with 0 < x < 0.15 was successfully prepared via solid-state reaction method. The effect of Sn substitution on the crystal structure, microstructure, dielectric behavior, ferroelectric and tunable features of BSTS-x ceramics were systematically investigated. Room temperature (RT) x-ray diffraction (XRD) analysis using the Rietveld refinement method reveals that all the synthesized BSTS-x ceramics were well crystallized into single perovskite structure. The results show a tetragonal phase for 0.00 < x < 0.02, which evolves to orthorhombic and tetragonal coexisting phases for 0.05 < x < 0.07. The composition x = 0.10 showed a mixture of tetragonal, orthorhombic and rhombohedral phases at RT, while a single cubic phase is observed for x = 0.15. The crystal phases determined by XRD were confirmed by Raman spectroscopy. Enhanced dielectric permittivity with a maximum value of {\epsilon}'~ 35000 is observed for x = 0.10 at RT. The ferroelectric behavior of BSTS-x ceramics was investigated through polarization hysteresis loops and tunability measurements. High tunability of 63% at RT and under the low DC-applied electric field of 1.40 kV/cm is achieved for x = 0.10.

Published
2020
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18. High Curie temperature Mn 5 Ge 3 thin films produced by non-diffusive reaction

Author

Assaf, E., Portavoce, A., Hoummada, K., Bertoglio, M., and Bertaina, S.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Strongly Correlated Electrons
Abstract

Polycrystalline Mn 5 Ge 3 thin films were produced on SiO 2 using magnetron sputtering and reactive diffusion (RD) or non-diffusive reaction (NDR). In situ X-ray diffraction and atomic force microscopy were used to determine the layer structures, and magnetic force microscopy, superconducting quantum interference device and ferromagnetic resonance were used to determine their magnetic properties. RD-mediated layers exhibit similar magnetic properties as MBE-grown monocrystalline Mn 5 Ge 3 thin films, while NDR-mediated layers show magnetic properties similar to monocrystalline C-doped Mn 5 Ge 3 C x thin films with $0.1 \leq x \leq 0.2.$ NDR appears as a CMOS-compatible efficient method to produce good magnetic quality high-curie temperature Mn 5 Ge 3 thin films.

Published
2017
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25. Absence of boron aggregates in superconducting silicon confirmed by atom probe tomography

Author

Hoummada, K., Dahlem, F., Kociniewski, T., Boulmer, J., Dubois, C., Prudon, G., Bustarret, E., Courtois, H., Debarre, D., and Mangelinck, D.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Superconducting boron-doped silicon films prepared by gas immersion laser doping (GILD) technique are analyzed by atom probe tomography. The resulting three-dimensional chemical composition reveals that boron atoms are incorporated into crystalline silicon in the atomic percent concentration range, well above their solubility limit, without creating clusters or precipitates at the atomic scale. The boron spatial distribution is found to be compatible with local density of states measurements performed by scanning tunneling spectroscopy. These results, combined with the observations of very low impurity level and of a sharp two-dimensional interface between doped and undoped regions show, that the Si:B material obtained by GILD is a well-defined random substitutional alloy endowed with promising superconducting properties., Comment: 4 pages

Published
2011
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40. Anti-polar state in BiFeO3/NdFeO3 superlattices.

Author

Khaled, M. A., Arnold, D. C., Dkhil, B., Jouiad, M., Hoummada, K., El Marssi, M., and Bouyanfif, H.

Subjects
SUPERLATTICES, ENERGY density, TRANSMISSION electron microscopy, ENERGY storage, X-ray diffraction
Abstract

Antiferroelectrics are promising materials for high energy density capacitors, and the search for environmentally friendly and efficient systems is actively pursued. An elegant strategy to create and design new (anti)ferroic system relies on the use of nanoscale superlattices. We report here the use of such a strategy and the fabrication of nanoscale BiFeO3/NdFeO3 superlattices and in depth characterization using high-resolution x-ray diffraction and transmission electron microscopy. The structural analysis at the atomic scale demonstrates that such superlattices host anti-polar ordering most likely described by an antiferroelectric-like Pbnm symmetry. Temperature dependence of the anti-polar state and structural transition further hint that the stability of the anti-polar state is controlled by the BiFeO3 layer thickness within the stacking and, in a more moderate way, by interlayer strain. Discovery of such a polar arrangement in superlattices and the possible generalization to the whole rare-earth family pave the way to new platforms for energy storage applications as well as nano-electronic devices. [ABSTRACT FROM AUTHOR]

Published
2021
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