Browsing by Author "BENOUDIA Mohamed Cherif (Co-Auteur)"
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Item Direct Observations of the Structural Properties of Semiconducting Polymer: Fullerene Blends under Tensile Stretching(Materials, 2020-07-10) ALIOUAT Mouaad Yassine; BENOUDIA Mohamed Cherif (Co-Auteur)We describe the impact of tensile strains on the structural properties of thin films composed of P BT4T-2OD -conjugated polymer and PC71BM fullerenes coated on a stretchable substrate, based on a novel approach using in situ studies of flexible organic thin films. In situ grazing incidence X-ray di raction (GIXD) measurements were carried out to probe the ordering of polymers and to measure the strain of the polymer chains under uniaxial tensile tests. A maximum 10% tensile stretching was applied (i.e., beyond the relaxation threshold). Interestingly we found di erent behaviors upon stretching the polymer: fullerene blends with the modified polymer; fullerene blends with the 1,8-Diiodooctane (DIO) additive. Overall, the strain in the system was almost twice as low in the presence of additive. The inclusion of additive was found to help in stabilizing the system and, in particular, the – packing of the donor polymer chains.Item Equiaxed grain structure formation during directional solidification of a refined Al-20wt.%Cu alloy: In situ analysis of temperature gradient effects(Journal of Crystal Growth, 2022-03-27) SOLTANI Hadjer; BENOUDIA Mohamed Cherif (Co-Auteur)Three series of directional solidification experiments on refined Al-20wt.%Cu alloys have been carried out with different temperature gradients, and for each of them a wide range of cooling rates were applied. The experiments were performed in horizontal configuration to minimize the impact of gravity-driven phenomena and characterized in situ and in real-time by using the X-radiography technique. The influence of the temperature gradient on the microstructure formation (impact of Temperature Gradient Zone Melting: TGZM), the nucleation distance, the average grain size and morphology (elongation factor and grain orientation) have been analysed quantitatively. The experimental results are discussed with current theoretical models and similar experimental works.Item Ge(Sn) growth on Si(001) by magnetron sputtering(Materials Today Communications, 2020-11-26) BENOUDIA Mohamed Cherif (Co-Auteur)The semi-conductor Ge1–xSnx exhibits interesting properties for optoelectronic applications. In particular, Ge1–xSnx alloys with x ≥ 0.1 exhibit a direct band-gap, and integrated in complementary-metal-oxide semiconductor (CMOS) technology, should allow the development of Si photonics. CMOS-compatible magne tron sputtering deposition was shown to produce monocrystalline Ge1–xSnx films with good electrical properties at low cost. However, these layers were grown at low temperature (< 430 K) and contained less than 6 % of Sn. In this work, Ge1–xSnx thin films were elaborated at higher temperature (> 600 K) on Si(001) by magnetron sputtering in order to produce low-cost and CMOS-compatible relaxed pseudo-coherent layers with x ≥ 0.1 exhibiting a better crystallinity. Ge1–xSnx crystallization and Ge1–xSnx crystal growth were investigated. Crys tallization of an amorphous Ge1–xSnx layer deposited on Si(001) or Ge(001) grown on Si(001) leads to the growth of polycrystalline films. Furthermore, the competition between Ge/Sn phase separation and Ge1–xSnx growth prevents the formation of large-grain Sn-rich Ge1–xSnx layers without the formation of β-Sn islands on the layer surface, due to significant atomic redistribution kinetics at the crystallization temperature (T = 733 K for x = 0.17). However, the growth at T = 633 K of a highly-relaxed pseudo-coherent Ge0.9Sn0.1 film with low impurity concentrations (< 2 × 1019 at cm–3 ) and an electrical resistivity four orders of magnitude smaller than undoped Ge is demonstrated. Consequently, magnetron sputtering appears as an interesting technique for the integration of optoelectronic and photonic devices based on Ge1–xSnx layers in the CMOS technology.Item Ge(Sn) growth on Si(001) by magnetron sputtering(Materials Today Communications, 2020) BENOUDIA Mohamed Cherif (Co-Auteur)The semi-conductor Ge1−xSnx exhibits interesting properties for optoelectronic applications. In particular, Ge1−xSnx alloys with x ≥ 0.1 exhibit a direct band-gap, and integrated in complementary-metal-oxide-semiconductor (CMOS) technology, should allow the development of Si photonics. CMOS-compatible magnetron sputtering deposition was shown to produce monocrystalline Ge1−xSnx films with good electrical properties at low cost. However, these layers were grown at low temperature (< 430 K) and contained less than 6% of Sn. In this work, Ge1−xSnx thin films were elaborated at higher temperature (> 600 K) on Si(001) by magnetron sputtering in order to produce low-cost and CMOS-compatible relaxed pseudo coherent layers with x ≥ 0.1 exhibiting a better crystallinity. Ge1−xSnx crystallization and Ge1−xSnx crystal growth were investigated. Crystallization of an amorphous Ge1−xSnx layer deposited on Si(001) or Ge(001) grown on Si(001) leads to the growth of polycrystalline films. Furthermore, the competition between Ge/Sn phase separation and Ge1−xSnx growth prevents the formation of large-grain Sn-rich Ge1−xSnx layers without the formation of β-Sn islands on the layer surface, due to significant atomic redistribution kinetics at the crystallization temperature (T = 733 K for x = 0.17). However, the growth at T = 633 K of a highly-relaxed pseudo-coherent Ge0.9Sn0.1 film with low impurity concentrations (< 2 × 1019 at cm−3) and an electrical resistivity four orders of magnitude smaller than undoped Ge is demonstrated. Consequently, magnetron sputtering appears as an interesting technique for the integration of optoelectronic and photonic devices based on Ge1−xSnx layers in the CMOS technologyItem Impact of gravity on directional solidification of refined Al-20wt.%Cu alloy investigated by in situ X-radiography(Journal of Alloys and Compounds, 2020) BENOUDIA Mohamed Cherif (Co-Auteur)Gravity effects such as natural convection in the liquid phase and buoyancy forces acting on the solid phase have a strong influence on the grain structure and microstructure formation dynamics during the solidifi cation of metal alloys. It is thus very useful to undertake experimental studies that will provide benchmark data for a deeper understanding of the role of such gravity effects. In this paper, we study the formation of the equiaxed grain structure during refined Al-20wt.%Cu solidification in a temperature gradient for three different configurations: horizontal, vertical upward and vertical downward solidification. The key grain characteristics, namely grain size, grain elongation and grain growth orientation, were determined for all experiments. A comparative analysis was performed to identify the dominant effects of gravity using the experiment in horizontal configuration as reference case. The impact of buoyancy on the grain structure formation was highlighted for the experiment in vertical upward configuration, inducing a final grain structure with a wider grain size distribution. For the experiment in vertical downward configuration, the final grain structure is composed of thinner and longer grains. The origin of these differences was linked to the impact of grain flotation and solute flows on the equiaxed microstructure development. © 2020 Elsevier B.V. All rightsItem Impact of growth velocity on grain structure formation during directional solidification of a refined Al-20 wt.%Cu alloy(Journal of Crystal Growth, 2020) BENOUDIA Mohamed Cherif (Co-Auteur)The paper presents detailed analyses of solidification experiments performed on a refined Al-20 wt.%Cu alloy using the SFINX (Solidification Furnace with IN situ X-radiography) laboratory facility. Directional solidifica tions of a sheet-like sample were carried out in a horizontal configuration, with the main surface of the sample parallel to the ground. The sample was solidified for a wide range of cooling rates to obtain various grain structures, from columnar to elongated and equiaxed. The formation of the grain structure was observed in-situ and in real-time by X-radiography, which allows the dynamic of solidification phenomena to be thoroughly analyzed. Based on the radiographs, quantitative measurements were performed to accurately describe the so lidified grain structure, namely the nucleation position, nucleation rate, grain size, grain elongation factor and growth orientation. The experiments showed that increasing the growth velocity leads to a decrease of both the grain size and grain elongation factor, resulting in a more homogeneous and isotropic grain distribution. The grain characteristic parameters were also sensitive to variations of the temperature gradient in the Field-of-View. The results were discussed by analyzing the impact of the solidification parameters on the constitutionally undercooled liquid zone ahead of the solidification frontItem In situ measurements of the structure and strain of a π-conjugated semiconducting polymer under mechanical load(Journal of Applied Physics, 2020) BENOUDIA Mohamed Cherif (Co-Auteur)In this work, in situ studies of organic thin films under stretching are developed. A high efficiency PffBT4T-2OD π-conjugated polymer (PCE11) was coated directly on a stretchable substrate in order to examine the impact of tensile strain on the structural properties. For that purpose, in situ grazing incidence x-ray diffraction coupled with optical microscopic observations have been carried out to measure the structural parameters of PCE11 and to probe the mechanical behavior of polymer chains under uniaxial tensile load. It is observed that in the range between 0% and 15%–20% of stretching, the polymer chains become more oriented. Meanwhile, an increase in negative values of deformation, i.e., compression of the polymer chains along the film normal was measured. Beyond this range of stretching, the polymer order declined and the stress was relaxed. This relaxation is explained by the increased number of cracks spreading over the entire film as observed using optical microscopy.Item Nickel stanogermanides thin films: Phases formation, kinetics, and Sn segregation(Journal of Applied Physics, 2024) BENOUDIA Mohamed Cherif (Co-Auteur)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).Item Structural and mechanical evaluation of a new Ti‑Nb‑Mo alloy produced by high‑energy ball milling with variable milling time for biomedical applications(The International Journal of Advanced Manufacturing Technology, 2023) BENOUDIA Mohamed Cherif (Co-Auteur)The main focus of this work is to investigate the impact of varying milling times (2 to 18 h) on the structural and mechanical properties of the developed Ti-Nb-Mo alloy. The morphology, phase composition, microstructure, and mechanical behavior of milled and sintered Ti-25Nb-25Mo alloy samples were characterized systematically using x-ray diffraction, scanning electron microscope, optical microscope, and Vicker microhardness. It was noted that the quantity of the β-Ti phase increased as the milling time increased. After 12 h of milling, the synthesized alloys exhibited a spherical morphology and texture with homogeneous distribution. The milled alloys' structural evolution and morphological changes were found to be dependent on their milling duration. Morphological analysis revealed that the crystallite size and mean pore size decreased when the milling duration increased, reaching minimum values of 51 nm and < 1 μm, after 12 and 18 h respectively. As the milling time increased, the grain size decreased, resulting in an increase in density, microhardness, and elastic modulus. Ti-25Nb-25Mo will presents good anti-wear ability and higher resistance to plastic deformation due to enhanced mechanical characteristics (H/E, and H3/E2). Hence, the developed Ti-25Nb-25Mo alloys with reduced elastic modulus and desirable mechanical properties were found to be a promising option for biomedical applications.Item Thickness Effect on the Solid-State Reaction of a Ni/GaAs System(Nanomaterials, 2022) BENOUDIA Mohamed Cherif (Co-Auteur)Ni thin films with different thicknesses were grown on a GaAs substrate using the mag netron sputtering technique followed by in situ X-ray diffraction (XRD) annealing in order to study the solid-state reaction between Ni and GaAs substrate. The thickness dependence on the formation of the intermetallic phases was investigated using in situ and ex situ XRD, pole figures, and atom probe tomography (APT). The results indicate that the 20 nm-thick Ni film exhibits an epitaxial relation with the GaAs substrate, which is (001) Ni//(001) GaAs and [111] Ni//[110] GaAs after deposition. Increasing the film’s thickness results in a change of the Ni film’s texture. This difference has an impact on the formation temperature of Ni3GaAs. This temperature decreases simultaneously with the thickness increase. This is due to the coherent/incoherent nature of the initial Ni/GaAs interface. The Ni3GaAs phase decomposes into the binary and ternary compounds xNiAs and Ni3 xGaAs1 x atabout 400 C.Similarly to Ni3GaAs, the decomposition temperature of the second phase also depends on the initial thickness of the Ni layer.