Mohamed ZANOUNI - Profile on Academia.edu (original) (raw)

Papers by Mohamed ZANOUNI

Tunable Properties of the Stable SiSeS Janus Monolayer Under Biaxial Strain: First-principles Prediction

Optik

A DFT study of electronic, optical and thermoelectric properties of Ge-halide perovskites CsGeX3 (X=F, Cl and Br)

Computational Condensed Matter, Mar 1, 2022

Effect of indium doping on the structural, optical and electrochemical behaviors of CeO2 nanocrystalline thin films

Optical Materials

Strain effects on the structural, electronic, optical and thermoelectric properties of Si 2 SeS monolayer with puckered honeycomb structure: A first‐principles study

International Journal of Quantum Chemistry, 2022

Journal of Superconductivity and Novel Magnetism, 2022

Methylammonium lead iodide, CH 3 NH 3 PbI 3 , is currently a front-runner as light absorber in hy... more Methylammonium lead iodide, CH 3 NH 3 PbI 3 , is currently a front-runner as light absorber in hybrid solar cells. Despite the high conversion efficiency, the stability of CH 3 NH 3 PbI 3 is still a major obstacle for commercialization application. In this work, the geometry, electronic structure, thermodynamic, and mechanical property of pure and Cs-doped CH 3 NH 3 PbI 3 have been systematically studied by first-principles calculations within the framework of the density functional theory (DFT). Our studies suggest that the (CH 3 NH 3) + organic group takes a random orientation in perovskite lattice due to the minor difference of orientation energy. However, the local ordered arrangement of CH 3 NH 3 + is energetic favorable, which causes the formation of electronic dipole domain. The band edge states of pure and Cs-doped CH 3 NH 3 PbI 3 are determined by (PbI 6) − group, while A-site (CH 3 NH 3) + or Cs + influences the structural stability and electronic level through Jahn-Teller effect. It has been demonstrated that a suitable concentration of Cs can enhance both thermodynamic and mechanical stability of CH 3 NH 3 PbI 3 without deteriorating the conversion efficiency. Accordingly, this work clarifies the nature of electronic and mechanical properties of Cs-doped CH 3 NH 3 PbI 3 , and is conducive to the future design of high efficiency and stable hybrid perovskite photovoltaic materials.

First-principles study on electronic and thermoelectric properties of Janus monolayers AsXC3 (X: Sb, Bi)

Computational Condensed Matter, 2022

Les memoires flash non volatiles - utilisees dans les ordinateurs, les telephones portables ou le... more Les memoires flash non volatiles - utilisees dans les ordinateurs, les telephones portables ou les cles USB - peuvent etre constituees de nanostructures semiconductrices (SC) ou metalliques inserees dans une matrice isolante. Elles necessitent l’elaboration d’heterostructures de type "oxyde/metal/oxyde/SC" et la maitrise de chaque interface. Dans ce cadre, nous avons etudie les premiers stades de la croissance de nanostructures de Fer elaborees par epitaxie par jet moleculaire (EJM) sur les substrats d’oxyde (high-k) cristallins LaAlO3(001) et LaAlO3(111). Les proprietes chimiques et structurales ont ete determinees, in-situ, par spectroscopie de photoelectrons X (XPS), diffraction de photoelectrons X (XPD) et diffraction d’electrons (RHEED et LEED) puis ex-situ par microscopie electronique en transmission (TEM). Une etude par simulation des profils XPD, basee sur la theorie de la diffusion multiple, a ete menee a l’aide du programme de calcul Ms-Spec. L’etude de la croiss...

Electronic structure, optical and thermoelectric properties of Ge2SeS monolayer via first-principles study

Physica E: Low-dimensional Systems and Nanostructures, 2021

Na adsorption on bismuthene monolayer for battery applications: A first-principles study

FlatChem, 2021

Abstract Energy storage technologies in electric vehicles and electronic devices have generated a... more Abstract Energy storage technologies in electric vehicles and electronic devices have generated an urgent need for alternative rechargeable batteries such as lithium-ion batteries (LIBs). The cost and limited resources of lithium in the earth's crust may be hindered by the LIBs applications. Due to abundant sodium resources and their similar electrochemical mechanisms, sodium-ion batteries (SIBs) are considered a potential alternative to lithium-ion batteries for large-scale renewable energy storage applications. Herein, based on first-principles density functional theory (DFT), the properties of Na atoms adsorbed on a bismuthene monolayer (ML) have been investigated. Our results exhibited the V site is the optimal adsorption position of Na atoms on ML-Bi with a negative adsorption energy of -1.55 eV and a significant charge transfer. As the adsorption energy of Na increases, the crystal structure of bismuthene tends to be changed significantly and reveals a tendency to form alloys. Also, semiconductor-to-conductor transitions have been observed. Of interest, the diffusion barrier of Na atoms in the NaxBi monolayer system was found to be very low (0.18 eV). This latter would facilitate the insertion/extraction of ions into the electrode material and improves the rate of charge and discharge. These predicted findings can pave the way for experimental studies leading to strong decision-making in the development of battery technology.

Results in Physics, 2021

We have employed the first-principles calculations and quasi-harmonic Debye model to investigate ... more We have employed the first-principles calculations and quasi-harmonic Debye model to investigate the effect of the pressure on anisotropic elasticity and thermodynamic properties of FeAl 3 . According to Christoffel's equation, the wave velocity anisotropy of FeAl 3 as a function of pressure was also studied. Based on 3D surfaces and 2D projection contours, the anisotropy of shear modulus for FeAl 3 changes significantly with the increasing pressure, and increases more obviously on [0 0 1] direction than that on [1 0 0] direction under high pressure. The thermodynamic properties calculations show that the volume of FeAl 3 decreases with the increasing temperature and pressure. The bulk modulus decreases with the increasing temperature, and increases with the increasing pressure. On the contrary, the thermal expansion coefficient, the heat capacities, and Grüneisen constant increase with the increasing temperature, and decrease as pressure increases. It is found that the bulk modulus and Grüneisen constant display strong pressure dependence, while the heat capacities are sensitive to the temperature. And the thermal expansion coefficient is affected simultaneously by the pressure and temperature.

Undulated silicene and germanene freestanding layers: why not?

Journal of Physics: Condensed Matter, 2020

Silicene and germanene freestanding layers are usually described as a honeycomb lattice formed by... more Silicene and germanene freestanding layers are usually described as a honeycomb lattice formed by two hexagonal sub-lattices presenting a height difference, namely the layer buckling. In this work, first-principles calculations show that silicene and germanene can be rippled at 0K with various wavelengths, without any compressive strain of the layer. For germanene, the height difference between two Ge atoms from the same sub-lattice can be as high as 4.7 Å for an undulation length of 81 Å. The deformations are related to slight (lower than 1.7°) bond angle modifications, and the energy cost is remarkably low, lying between 0.1 and 0.8 meV per atom. These undulations modify the electronic structure, opening a gap of 15 meV.

Surface and Interface Analysis, 2015

The grafting of trialkoxysilane molecules should also give rise to the formation of a siloxane ne... more The grafting of trialkoxysilane molecules should also give rise to the formation of a siloxane network at the substrate's surface when trialkoxysilanes are used. Other candidates that might be able to act as adhesion promoters at metallic surfaces are dimethylalkoxysilanes. The advantage of dimethylalkoxysilanes is that only one silanol group is produced during the hydrolysis step, leading to the formation of a grafted monolayer onto the steel. Moreover, the chemical grafting of stainless steel, which exhibits a low surface reactivity, is of great interest for industrial applications such as adhesive bonding or coatings. The objective of this work was to chemically graft dimethylalkoxysilanes onto AISI 316L stainless steel and to analyze the grafted layer by X-ray photoelectron spectroscopy (XPS). Investigation of the hydrolysis of these molecules in aqueous solutions was also performed by proton nuclear magnetic resonance spectroscopy (1 H NMR). The grafting of 3-(ethoxydimethylsilyl)propylamine (APDES) and 3-glycidoxypropyldimethylethoxysilane (GPDES) was achieved onto stainless steel after a controlled hydrolysis reaction. A pH inferior or equal to 5 was necessary to obtain a sufficient hydrolysis of silanes. XPS results have evidenced the grafting of the silanes onto stainless steel. The signal of the Si 2p peak clearly showed the formation of a covalent bond between APDES and the stainless steel surface through the O atoms giving rise to a uniform layer of adsorbed molecules. Moreover, this grafted layer is strongly stable as no removal of the alkoxysilane was observed after immersion in hot water which is very critical for these molecules.

Journal of Physics: Conference Series, 2014

We report the epitaxial growth of one Silicon monolayer on the LaAlO3(111) substrate, a high-κ cr... more We report the epitaxial growth of one Silicon monolayer on the LaAlO3(111) substrate, a high-κ crystalline oxide. Structural and chemical properties were investigated in-situ using reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). The deposition was achieved by molecular beam epitaxy in the temperature range RT-500 • C. A two-dimensional epitaxial growth mode is observed for a deposition at temperature between 300 • C and 500 • C. The deposited single layer is formed by two dimensional (2D) structures of Si.

Influence of annealing process and its associated atomic migrations on the Si/LaAlO3(001) nanostructure nucleation

Thin Solid Films, 2014

physica status solidi (c), 2014

Non-volatiles flash memories embedding nanocrystals are promising devices. These memories are mad... more Non-volatiles flash memories embedding nanocrystals are promising devices. These memories are made of semiconducting or metallic nanostructures inserted in an insulating matrix. SiO 2 , traditionally used as an insulator, is gradually replaced by high-dielectric materials called "high-k" oxides, to reduce leakage currents. In this context, we used a crystalline lanthanum aluminate (LaAlO 3) oxide. The magnetic properties of nanoparticles of Fe can increase the storage capacity in the memories compared to the semiconductor nanostructures as Si or Ge. Memories combining these two materials require complex monolithic structures such as "LaAlO 3 /Fe/LaAlO 3 / Si(001)". In this context we have studied the initial growth of Fe on a solid substrate of LaAlO 3 (001). Fe deposits were performed by molecular beam epitaxy (MBE) at different substrate temperatures. Chemical and structural properties were investigated by X-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). The temperature dependence study indicates that the growth of Fe on LaAlO 3 is epitaxial with a single epitaxial relationship in a tight temperature window around 500 °C. The plane (001) of Fe is parallel with the LaAlO 3 (001) surface, but the iron unit cell is rotated of 45° around the growth direction compared with the substrate one (<100>Fe // <110> LaAlO 3). This configuration minimizes the elastic strain of the Fe which grow with the Volmer-Weber mode.

Journal of Crystal Growth, 2014

Fe deposits were performed on LaAlO 3 (001) by molecular beam epitaxy at different substrate temp... more Fe deposits were performed on LaAlO 3 (001) by molecular beam epitaxy at different substrate temperatures. Chemical and structural characterizations were carried out in-situ, by X-ray photoelectron spectroscopy (XPS), reflection high-energy electron diffraction (RHEED), Xray photoelectron diffraction (XPD), and ex-situ by high-resolution transmission electron microscopy (HRTEM). This temperature dependence study indicates that the growth of Fe is epitaxial in a tight temperature window around 500°C with a single epitaxial relationship, where the Fe and LaAlO 3 (001) lattices are brought into coincidence by a 45° rotation around the common [001] axis. This typical configuration via Fe-O bonds formation at the interface allows a minimization of the elastic strain inside Fe islands which follow a Volmer-Weber growth mode. Beyond a given thickness, and in agreement with the strain relaxation, Fe islands exhibit (001) facets, leading to islands coalescence and a possible iron 2D layer formation.