Publications Scientifiques

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Adsorption and diffusion of oxygen atom on UN2(100) surface and subsurface : a density functional theory study (DFT and DFT + U)
(Springer, 2014) Zergoug, Toufik; Abaidia, Seddik-El-Hak; Nedjar, A.; Mokeddem, Mohamed Yazid
In the present work, adsorption and dif fusion of oxygen (O) atom on uranium dinitride (UN2) is studied to map out the preferential UN2(100) surface site. The first principle method based on density functional theory (DFT) within the generalized gradient approximation PBE and the covariant version energy functional PBE + U correction were used. The supercell approach and a coverage dependence of the adsorption structures and energetic were studied in detail for several monolayers’ (ML) range. Potential energy surfaces (PES) corresponding to the interaction between O atom and UN2(100) on surface and subsurface for several sites and layers (Top U and Top N slabs) were calculated and favorable sites were identified with their maxima energy stable positions, which were then analyzed. For all positions, the PES show the same system behavior, when the O atom is sufficiently far from the UN2 surface, and the energy of the system tends to the sum of free UN2 slab and free oxygen atom energies. In return, when the distances decrease, strong interactions appear with presence of important potential wells. Calculation results showed that favored on-surface site for O atom adsorption were found to be near the bridge one for the UN (Top U slab) corresponding to five layers, uranium terminated and top one for (Top N slab) corresponding to six layers nitrogen terminated, the maximum system energy is situated at a position of about 1.2 and 1.5 Å from the surface for the two layers types calculations respectively. For subsurface results, only Top N presents a favorable incorporation site at the hollow position and the penetration of O atom is about −0.5 Å from the surface. DFT + U study confirms all the results obtained by DFT calculations; that is, the maxima site positions for oxygen atom and the adhesion energy values per atom are of the same order of magnitudes. The adsorption energy per oxygen atom and the mean distance from the top surface gradually decrease with the coverage of O atoms for both on-surface cases, Top U and Top N slabs, with oxygen occupying the favorable site. For the Top N slab hollow site, the incorporation of oxygen through the surface becomes effective from a coverage of 3/8 ML with an encrustation of about −0.3 Å
Aluminium-induced crystallization of amorphous silicon films deposited by DC magnetron sputtering on glasses
(2011) Kezzoula, F.; Hammouda, A.; Kechouane, M.; Simon, p.; Abaidia, Seddik-El-Hak; Keffous, A.; Cherfi, R.; Menari, H.; Manseri, A.
Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) films were deposited by DC magnetron sputtering technique with argon and hydrogen plasma mixture on Al deposited by thermal evaporation on glass substrates. The a-Si/Al and a-Si:H/Al thin films were annealed at different temperatures ranging from 250 to 550 °C during 4 h in vacuum-sealed bulb. The effects of annealing temperature on optical, structural and morphological properties of as-grown as well as the vacuum-annealed a-Si/Al and a-Si:H/Al thin films are presented in this contribution. The averaged transmittance of a-Si:H/Al film increases upon increasing the annealing temperature. XRD measurements clearly evidence that crystallization is initiated at 450 °C. The number and intensity of diffraction peaks appearing in the diffraction patterns are more important in a-Si:H/Al than that in a-Si/Al layers. Results show that a-Si:H films deposited on Al/glass crystallize above 450 °C and present better crystallization than the a-Si layers. The presence of hydrogen induces an improvement of structural properties of poly-Si prepared by aluminium-induced crystallization (AIC)
Cooling enhancement of planar-balanced magnetron cathode
(Springer, 2017) Salhi, M’hamed; Abaidia, Seddik-El-Hak; Mohamedi, Brahim; Laouar, Sofiane
Effect of Ar/N2 flow ratio on the microstructure and mechanical properties of Ti-Cr-N coatings deposited by DC magnetron sputtering on AISI D2 tool steels
(Elsevier, 2021) Kehal, Abdelkrim; Saoula, Nadia; Abaidia, Seddik-El-Hak; Nouveau, Corinne
Ti-Cr-N coatings were deposited on Si (100) and AISI D2 tool steel substrates by reactive DC magnetron co-sputtering technique from titanium and chromium target in mixed Ar/N2 atmosphere. The Ar/N2 ratio effects on the chemical composition, structure, morphology, intrinsic stress and mechanical properties of the Ti-Cr-N coatings were investigated. The growing process of Ti-Cr-N coatings can be divided into three stages: Stage I, in poisoning mode (low flow ratio 1 < Ar/N2 ≤ 1.4), Stage II, in transition mode (intermediate flow ratio 1.4 ≤ Ar/N2 ≤ 3) and Stage III in metallic mode (Ar/N2 > 3). For all samples, XRD analysis shown the formation of mixed nitrides phases. In stage I, Ti2N, TiN0.3, and hexagonal-Cr2N phases were observed. In Stage II, TiN0.3, Cr2N, and cubic-TiN phases were formed, while only TiN and Cr2N are observed in stage III. The coatings deposited with Ar/N₂ ratio of 3 shows the largest hardness of 24 GPa which is attribute to the dense structure and smoother surface morphology. The properties of the films are discussed in terms of evolution growth stages resulting by the variation of Ar/N2 flow ratios
Effect of extended phosphorus diffusion gettering on chromium impurity in HEM multicrystalline silicon
(2012) Khelifati, Nabil; Bouhafs, Djoudi; Boumaour, Messaoud; Abaidia, Seddik-El-Hak; Palahouane, Baya
We have investigated the extended phosphorus diffusion gettering (PDG) effect on chromium impurities (Cr) in p-type multicrystalline silicon (mc-Si) grown by Heat Exchanger Method (HEM). The study was made after phosphorous diffusion and according to different extended annealing temperatures. The secondary ion mass spectrometry (SIMS) analysis revealed a significant accumulation of 52Cr in heavily phosphorus doped (HPD) region. Using quasi-steady state photoconductance (QSSPC) technique, the apparent lifetime dependent minority carrier density curves have been obtained. The results showed an increment of the bulk minority carrier lifetime for specific annealing temperatures. Appropriate calculations based on QSSPC results allowed us to determine the lifetime curves associated to gettered impurities. Their fitting by Shockley-Read-Hall (SRH) model reveal that the origin of the lifetime increment is the reduction of interstitial chromium (Cri) density in the bulk. Furthermore, the estimation of electron to hole capture cross-section ratio (k=σn/σp) through the modelling of apparent lifetime curves using Hornbeck–Haynes model, confirmed the effectiveness of Cri gettering and identified the nature of dominant recombination centres after gettering process
Effect of TiN thin films deposited by oblique angle sputter deposition on sol-gel coated TiO2 layers for photocatalytic applications
(Elsevier, 2024) Naas, Lazhari-Ayoub; Bouaouina, Boudjemaa; Bensouici, Fayçal; Mokeddem, Kamel; Abaidia, Seddik-El-Hak
TiO2 monolayer and TiN/TiO2 bilayer coatings were deposited on soda-lime glass prepared by mixing two techniques, TiO2 was deposited by sol-gel dip-coating and TiN film was deposited by oblique angle deposition using reactive magnetron sputtering at α=45° Structural analysis showed typical peaks of TiO2 anatase phase and cubic (Na-Cl type) structure of TiN. Roughness value of 3 nm was obtained for the TiN/TiO2 bilayer film with a rise and elongated grains size. It was found that the optical band gap energy decreases after coupling the TiN sub-layer which is explained by the incorporation of N atoms into TiO2 structure. At constant UV irradiation time, the photo-degradation of methylene blue rate increased for TiN/TiO2 film by 4 % compared to TiO2 film
An estimate of a frequency characterizing the electrochemical stability of a gold electrode modified by MHDA thiol in different ways
(Croatian Chemical Society, 2021) Chaibi, Sarah; Zabat, Mokhtar; Hadjersi, Toufik; Abaidia, Seddik-El-Hak; Zine, Nadia; Yaakoubi, Nourdin; Errachid, Abelhamid
A theoretical investigation aimed at estimating a characteristic frequency in the medium-low frequency domain in which the impedance response of a given interface measured by electrochemical impedance spectroscopy (EIS) is almost constant, constitutes the basic idea of this work. A theoretical model was subsequently applied to the data resulting from EIS measurements performed on gold electrodes modified by various ways of 16-mercaptohexadecanoic acid (MHDA) thiol functionalization. Analysis of these data revealed a direct relationship between the way the substrate was modified and this characteristic frequency
First principle study of oxygen diffusion on uranium nitride UN(001) surface with uranium or nitrogen vacancies
(Bentham Science Publishers, 2015) Zergoug, Toufik; Abaidia, Seddik-El-Hak; Nedjar, A.
High performance silicon nanowires/ruthenium nanoparticles micro-supercapacitors
(Elsevier, 2019) Bencheikh, Yasmina; Harnois, Maxime; Jijie, Roxana; Addad, Ahmed; Roussel, Pascal; Szunerits, Sabine; Hadjersi, Toufik; Abaidia, Seddik-El-Hak; Boukherroub, Rabah
The continuous increase of small electronic devices calls for small energy storage components, commonly known as micro-supercapacitors, that can ensure autonomous operation of these devices. In this work, we propose a simple and straightforward method to achieve high energy and power densities of a silicon-based micro-supercapacitor, consisting of silicon nanowires decorated with ruthenium nanoparticles (Ru/Si NWs). The Si NWs are obtained through the common vapor-liquid-solid (VLS) growth mechanism, while a simple electroless process is used to deposit Ru nanoparticles. While silicon nanostructuration allows to increase the surface area, coating with Ru NPs introduces a pseudocapacitance necessary to attain high energy and power densities. The Ru/Si NWs micro-supercapacitor exhibits a specific capacitance of 36.25 mF cm−2 at a current density of 1 mA cm−2 in a neutral Na2SO4 electrolyte and a high stability over 25 000 cycles under galvanostatic charge-discharge at 1 mA cm−2. A solid state supercapacitor is then fabricated with symmetric electrodes separated by a polyvinyl alcohol/sulfuric acid electrolyte. The device displays a specific capacitance of ∼18 mF cm−2 at a current density of 1 mA cm−2 and a specific power density 0.5 mW cm−2. This solid-state nanowire device also exhibits a good stability over 10 000 galvanostatic charge-discharge cycles
Influence of the organic solvents on the properties of the phosphoric acid dopant emulsion deposited on multicrystalline silicon wafers
(2007) Bouhafs, D.; Moussi, A.; Boumaour, M.; Abaidia, Seddik-El-Hak; Mahiou, L.; Messaoud, A.
This study is devoted to the formation of an n+p emitter for multicrystalline silicon (mc-Si) solar cells for photovoltaic (PV) application. The atomization technique has been used to make the emitter from H3PO4 phosphoric acid as a doping source. The doping emulsion has been optimized using several organic solvents. H3PO4 was mixed with one of these solutions: ethanol, 2-butanol, isopropanol alcohol and deionized water. The volume concentration of H3PO4 does not exceed 20% of the total volume emulsion. The deposit characteristics of the emulsion change with the organic solvent. H3PO4 : 2-butanol gives the best deposited layer with acceptable adherence and uniformity on silicon surface. Fourier transform infrared characterizations show the presence of organic and mineral phosphorous bonds in the formed layer. The obtained emitters are characterized by a junction depth in the range 0.2–0.75μm and a sheet resistance of about 10–90 / . Such a low cost dopant source combined with a continuous spray process can effectively reduce the cost per Wp of the PV generator
Interlayer exchange coupling between FeCo and Co ultrathin films through Rh(001) spacers
(American Physical Society, 2015) Blizak, S.; Bihlmayer, G.; Blügel, S.; Abaidia, Seddik-El-Hak
Microstructure, corrosion and magnetic behavior of an aged Dual-Phase stainless steel
(Springer, 2018) Ziouche, Aicha; Haddad, A.; Badji, Riad; M. Zergoug, M. Zergoug; Zoubiri, N.; Bedjaoui, W.; Abaidia, Seddik-El-Hak
N+ silicon solar cells emitters realized using phosphoric acid as doping source in a spray process
(2006) Bouhafs, D.; Moussi, A.; Boumaour, M.; Abaidia, Seddik-El-Hak; Mahiou, L.
The spray technique is used to realize the n+ emitter from phosphoric acid H3PO4 as a doping source. Emulsions have been prepared using several organic solvents. It was found that H3PO4:2-butanol mixture provides the most uniform deposited layer. The sheet resistance and the n+ profile were measured with a four point probe and the Hall profiling, respectively. The variety of emitters obtained are characterized by a sheet resistance ranging from 10 to 86 Ω/□ and a junction depth of about 0.2 to 0.7 μm which can be adequate for emitters in a polycrystalline silicon solar cell process
Oxygen diffusion and migration in clean and defective uranium nitride UN (0 0 1) surfaces
(Elsevier, 2018) Zergoug, T.; Abaidia, Seddik-El-Hak; Nedjar, A.
This study focuses on the diffusion of atomic and molecular oxygen through the uranium mono-nitride UN (0 0 1) surface. The adsorption of oxygen at the most favorable sites has been checked on different surface states namely: clean surface and surfaces containing defects such as inclusion atoms. Inclusions atoms are positioned at a uranium U atom vacancy or at a nitrogen N atom vacancy location of the UN (0 0 1) surface. Neptunium, plutonium, protactinium, silver and neodymium which are the most probable nuclear reactions (n, U) products have been selected as U atom substitute. Some light elements such as carbon, chromium and silicon were used to replace an N atom. The first principle calculation, based on Density Functional Theory (DFT) was used, taking into account the Generalized Gradient Approximation (GGA) and the Projector-Augmented Wave (PAW) to describe the exchange-correlation functional. The purpose of this work is to verify the oxygen adsorption energy variations performed across all the studied surfaces. The most favorable sites of UN (0 0 1) clean and defective surfaces to oxygen O atom diffusion were preliminary identified. In the second step, atomic dynamical Potential Energy Surface (PES) was used to study the interaction between O atom and UN (0 0 1) surfaces at these sites. Finally, Nudged Elastic Band (NEB) method was used in order to investigate the migration of O atom through the UN (0 0 1) surfaces. The results show that at the bridge site, the adsorption and incorporation energies of oxygen atom on and in the UN (0 0 1) surfaces respectively, do not substantially vary with the type and position of the studied impurities. But, at the N vacancy site, the adsorption energy of the O atom decreases practically when UN (0 0 1) surfaces contain inclusion atoms compared to the clean surface case. Furthermore, the NEB calculations show discrepancies for the Minimum Energy Path (MEP) during the migration of the O atom at the bridge site through the studied UN (0 0 1) surfaces and depending on the type and position of the added impurities. Among the studied MEPs, protactinium is found to be the most suitable barrier to the diffusion of oxygen through the UN surface as an inclusion on UN (0 0 1)
Pulsed eddy current signal analysis of ferrous and non-ferrous metals under thermal and corrosion solicitations
(Springer, 2017) Ziouche, A.; Zergoug, M.; Boucherrou, N.; Boudjellal, H.; Mokhtari, M.; Abaidia, Seddik-El-Hak
Residual stress, mechanical and microstructure properties of multilayer Mo 2 N/CrN coating produced by R.F Magnetron discharge
(Elsevier B.V., 2017) Bouaouina, Boudjemaa; Besnard, A.; Abaidia, Seddik-El-Hak; Haid, F.
We have investigated the effect of the period thickness of the multilayer Mo 2 N/CrN deposited on Si substrate produced by reactive magnetron sputtering. Mo 2 N presents a face centered cubic structure and CrN an orthorhombic one. The residual stress of the coatings was determined by the measurement of the substrate curvature. The microstructure of the multilayer was investigated from the X-ray diffraction and scanning electron microscopy (cross section images). The residual stresses resulting from the deposition of the different bi-layer thickness were measured and correlated to the structural properties of the coating as well as the nanoindentation analysis of the coating. The stresses are compressive and tensile for the individual Mo 2 N and CrN layer respectively. The result shows that an increase of the multilayer coatings Mo 2 N/CrN thicknesses induce an increase of the hardness and the elastic modulus, in the other hand the tensile stress increases. The shift of the XRD diffraction peak (1 1 1) of Mo 2 N at high angle which means the reduction of the residual stress is in good agreement with the residual stresses measurements
Silicon nanowire-hydrogenated TiO2 core-shell arrays for stable electrochemical micro-capacitors
(Elsevier, 2021) Bencheikh, Yasmina; Addad, Ahmed; Coffinier, Yannick; Kumar, Umesh; Roussel, Pascal; Szunerits, Sabine; Hadjersi, Toufik; Amin, Mohammed A.; Abaidia, Seddik-El-Hak; Boukherroub, Rabah
In this paper, we fabricated silicon nanowire-TiO2 core-shell arrays in a two-step process. First, silicon nanowire arrays (SiNW) were prepared in HF/AgNO3 aqueous solution using metal-assisted chemical etching of bulk silicon. Then, atomic layer deposition (ALD) technique was applied to coat a 20 nm thin shell TiO2 film. The TiO2/SiNW substrates were afterward annealed at 400°C in hydrogen atmosphere for 4 h and tested as electrode materials for electrochemical micro-capacitors. The electrochemical features of the constructed H−TiO2/SiNW electrode were assessed in an aqueous 1 M Na2SO4 electrolyte solution and revealed that the specific capacitance increased six times compared to non-annealed TiO2/SiNW and 20-fold compared to a reference SiNW electrode under the same operating conditions. Importantly, H−TiO2/SiNW also displayed a high stability over 30,000 cycles at 0.1 mA cm−2 with an overall decrease of 19% of the initial capacitance. The hydrogen treatment increased the density of hydroxyl group and enhanced the carrier density on TiO2 surface improving the capacitive properties of H−TiO2/SiNW
Sputter deposition of titanium and nickel thin films in radio frequency magnetron discharge characterized by optical emission spectroscopy and by rutherford backscattering spectrometry
(Elsevier, 2017) Salhi, M.; Abaidia, Seddik-El-Hak; Mammeri, S.; Bouaouina, Boudjemaa