Volume 9, article 1

Structural and chemical properties of RF sputtered a-C/WOx bilayers

E. Ech-chamikh* , M. Azizan , F. Debbagh , A. Essafti and Y. Ijdiyaou

Amorphous carbon on tungsten oxide (a-C/WOx) bilayers were deposited, on glass and silicon substrates, by radio-frequency (RF) sputtering. The WOx layers are obtained from a pure tungsten target in a mixture of argon and oxygen while the a-C ones were obtained from a pure graphite target in a pure argon plasma. The structural and chemical properties of the a-C/WOx interface were investigated by Grazing Incidence X-Ray Diffraction (GIXRD), X-Ray Reflectometry (XRR) and Electron Dispersive Analysis of X-Ray (EDAX). The XRR spectra show that the a-C/WOx interface is strongly reactive, for high RF powers, with the formation of an inhomogeneous WOxCy total layer. The density of this layer is much smaller than the WOx one. For low RF powers, the a-C/WOx interface is also reactive and the total layer obtained is inhomogeneous in depth but the W atoms content in the top layer is relatively small. This result is also confirmed by the EDAX analyses. The GIXRD spectra show that the WOx layers are crystallized while there is no formation of crystallized tungsten carbides or oxycarbides.

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Keywords : Amorphous carbon, Tungsten oxide, Interface, Reflectometry, X-ray diffraction, EDAX, RF sputtering

Laboratoire de Physique du Solide et des Couches Minces, Faculté des Sciences Semlalia,
Université Cadi Ayyad, BP:2390, Marrakech 40000, Morocco.

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Volume 9, article 7 

The Role Of Cadmium Oxide Within The Thin Films Of The Buffer Cds Aimed At Solar Cells Based Upon CIGS Films Fabrication

D. Soubane^1,2, A. Ihlal¹  And G. Nouet²

High quality Cadmium Sulphide thin films were grown on directly heated substrates of commercial glass by means of Modified Chemical Bath Deposition. Structural and optical properties of the obtained films were achieved. The impact of heat treatment in air at 450°C for one hour reveals the apparition of nano films of Cadmium Oxide on the surface of these buffer layers, which decreases dramatically the optical performance of the annealed films of CdS.

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1Laboratoire Matériaux et Energies Renouvelables, Département de physique, Faculté des sciences B.P.8106 Hay dakhla, Agadir, Morocco.
2Structure des Interfaces et Fonctionnalité des Couches Minces, Bd Maréchal Juin, 14050 Caen, France.

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Volume 9, article 8 

Study of Driving Forces for Atomic Migration in Dilute Alloys

Aditya M. Vora

We present a pseudopotential calculation of the driving forces for atomic migration in the 156 dilute alloys of the 23 host of the different groups of the periodic table in the presence of electron currents. The forces on an atom arising from the applied electric field and from the electron scattering together comprise the driving force, causes a net current of atoms. A well recognized Ashcroft’s empty core (EMC) local model potential is used to investigate the driving forces for interstitial (F_INT), vacancy (F_VAC), substitutional (F_SUB) and nearest neighbour (F_NN) migration in dilute alloys. Five different types of the local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used to study the effect of the exchange and correlation on the aforesaid properties. The driving forces are calculated for interstitial, vacancy, substitutional and nearest neighbour migration in dilute alloys, and the results are found to compare qualitatively with most experimental data. The present study concludes that F_INT is larger than F_VAC. For some dilute alloys the electron scattering force is found in the opposite direction to the electron drift velocity. Present findings are compared with the other such data, which confirms the applicability of the model potential.

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Keywords: model potential, driving forces, atomic migrations, dilute alloys
PACS: 71.15.Dx, 66.30.Jt, 66.30.Qa

Parmeshwari 165, Vijaynagar Area, Hospital Road,
Bhuj–Kutch, 370 001, Gujarat, INDIA

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Volume 9, article 9 

Extension of Self Consistent RPA method to off-site Hubbard Model

S.Harir^1,*, M.Bennai^1,3, Y.Boughaleb^{1, 2,4}

We are interested in the possibility that a generalization of Self Consistent Random Phase Approximation (SCRPA) to the Extended Hubbard Model can lead us to accurate estimations of the ground state energy, for closed chains in one dimension with periodic boundary conditions: N=2 (two states problem). We have considered an extended Hubbard model including on-site and off-site interactions, we have compared the SCRPA with a Direct Analytical(DA) results for the ground state energy, and have shown that SCRPA solves the two states problem exactly for any value of U (on-site interaction energy), V₂ (off-site interaction energy with opposite spins) and (off-site interaction energy with same spins).

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Keywords: Extended Hubbard Model, SCRPA, ph-RPA
Pacs numbers: 71.10, -W.75.10.Jm, 72.15.Nj

1. Laboratoire de Physique de la Matière Condensée, Faculté des Sciences Ben M.Sik, Université Hassan II-Mohammedia Casablanca, Morocco.
2. LPMC, Faculté des Sciences d’ El Jadida, Université Chouaib Doukkali, Morocco.
3. Groupement National de Physique des Hautes Energies, LabUFR-PHE, Rabat, Morocco.
4. Hassan II Academy of Sciences and Technology, Morocco.

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Volume 9, article 10 

Numerical solutions of the Fokker Planck equation in the case of randomly oriented field acting on magnetic nanoparticles

A. Housni^a, S. Sayouri^a,*, A. Elmesbahi^a, K. Limame^a, A. Labzour^b

The resolution of the Fokker-Planck equation (PFE) for the probability density of an assembly of fine particles, based on previous calculations, is extended to the case where the direction of the applied field has a random orientation. Using the PFE, Coffey et al. [6] have proposed a method of calculating the relaxation time τ, assuming H directed at an arbitrary angle ψ to the easy axis (H = H(ψ, φ=0)). In this report we will extend these calculations to the case where H = H(ψ, φ).

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Keywords: Ferromagnetic relaxation; Ultrafine particles; Fokker Planck equation.
* Corresponding author: Email: ssayouri@yahoo.com

^a LPTA, Département de Physique, faculté des Sciences-DM B.P. 1796, Fès Atlas, Morocco.
^b LPS, Département de Physique, faculté des Sciences-DM B.P. 1796, Fès Atlas, Morocco.

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Volume 9, article 11

Study of the Dielectric Relation and the Doping Effect

on Conductivity in Lithium Tantalate

M. Aboubakar^a, F. Bennani^b,*

Ceramics Li_0.98-xTa_1.004-x/5Ni_xO₃ (LTN) samples have been prepared, for x{0;0.01;0.02;0.05;0.08;0.15;0.2}. Ac impedance measurements were carried out in the frequency range 1Hz-1MHz and from 300°C to 900°C. The influence of Ni doping on dc conductivity was depicted. Through the ac impedance, dielectric constant was deduced and two dielectric relaxations have been clearly identified at high temperature. The low frequency relaxation is attibuted to the space charges, and the high frequency one to ferroelectric dipoles. Systematic fits have been done using the Cole-Cole model. It’s appears for identified relaxations, that at the temperature close to Tc, the dispersion step Δ ε is maximum ; the relaxation time τ is thermally activated and also present an extremum at Tc. The influence of Ni doping on these relaxations, specially the relaxation of the space charges was examined

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Keywords: Impedance spectroscopy, dc conductivity, relaxation, space charge

^a Département de Physique, Faculté des Sciences, LGPE, BP 133 Kénitra, Morocco.
   e-mail : aboumahamoudou@yahoo.fr
^b Département de Physique, Faculté des Sciences, LPMC, BP 133 Kénitra, Morocco.
  e-mail : f_bennani@yahoo.fr
* Corresponding Author.

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Volume 9, article 12

Taguchi methodology for the optimization of n⁺pp⁺ type silicon solar
photovoltaic conversion efficiency.

A.Habbou, H.Chaffoui, B.Hartiti

This study deals with n+pp+ type crystalline silicon solar cells performances using the Taguchi method in its optimum.We; then, discuss physical parameters influence on efficiency solar cell, and also, we determine photovoltaic parameters of our structure by numeric simulation (PC1D). Most previous work has used relatively low wafer resistivities (0.1-0.5Ωcm). The modeling in this work showed that high efficiencies could also be achieved with 1.0 Ωcm in the p-region and the flexibility in front junction depth and back junction depth. Key words: Taguchi methodology, numeric simulation (PC1D), solar cells, silicon, wafer resistivities, n+pp+ structure, front junction depth, back junction depth, conversion efficiency.

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Laboratory of Material Physics and Applications of the Renewable Energies
FST of Mohammedia BP 146, 20630 Mohammedia, Morocco,
E-mail: habbouabder@yahoo.fr.

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Volume 9, article 13

Synthesis analysis of the free form curves and surfaces parametrical models

B. Danouj¹, M. Bennani², A. Tizzard ³, H. El omari⁴

Parametrical models have become an important mathematical tool for free form curves and surface description. they allow the use of state-of-the-art computers to do the various processing and analysis with respect to shape (calculation of the volume and surface area, vibration analysis, NC programs preparation, etc.). Without these models, the current product design and manufacturing would be difficult.
        The paper presents an analysis study for the most important parametrical models of free form curves and surfaces description (Ferguson, Coons, Bezier, B-Spline and rational models). Firstly, it emphasises external and mathematical properties of each model. Secondly, it gives the most interesting interfaces between models. Thus the process of complex surface design and manufacturing would be more efficient in view this analysis. Finally for validation, the study is ended by an application to the design of a car bonnet.

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Keywords: Complex surfaces; patch; connection; control shape.

1 Laboratoire de génie mécanique, F.S.T. de Settat, B.P. 577, Settat-Morocco.
2 Laboratoire de génie mécanique, E.N.S.E.T. de Rabat, B.P. 6207, Rabat- Morocco.
3 Product Design and Engineering, S.L.L.E, Middlesex University, London N14 4YZ, UK
4 Laboratoire d’Instrumentation et Analyse des Matériaux, F.S.T. de Settat. B.P. 577, Settat-Morocco.

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Volume 9, article 14

Phase diagrams of site diluted ferromagnetic semi infinite system

M. Hamedoun^a,*, R. Masrour^a, K. Bouslykhane^a, A. Hourmatallah^a,b and N. Benzakour^a

 The spin correlations functions of face-centered cubic semi-infinite system are investigated by using the high  temperature series expansions extrapolated with the Padé approximant method for Heisenberg, XY and Ising models. The magnetic phase diagrams t_c(n) versus the dilution x are obtained. The value obtained of the percolation threshold is. X_p≈0.2  The X_p is defined as the concentration at which t_c =0

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Keywords: Correlation functions; Semi-infinite film; Magnetic phase diagrams; Percolation threshold.

a Laboratoire de Physique du Solide, Université Sidi Mohammed Ben Abdellah, Faculté des sciences Dhar Mahraz, BP 1796, Fes, Morocco.
b Equipe de Physique du Solide, Ecole Normale Supérieure, BP 5206, Bensouda, Fes, Morocco.

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Volume 9, article 15

Study of quenched impurities effect on order-disorder phase transition by Monte-Carlo method

M. Noureddine¹, R.Nassif^1,2, K. Saadouni¹, Y.Boughaleb^1,*

We investigate the effect of quenched impurities on phase transition of layer particles. The study is done by means of Monte-Carlo technique on a fixed square lattice in the framework of the lattice gas model. The considered interactions are restricted to first neighboring particles and are of repulsive nature between diffusing particles. Attractive interactions between mobiles particles and impurities are considered. We focus on the behavior of the tracer diffusion coefficient, D*, and the mean square fluctuation of adsorbates particles number <( δN )² >/<N>. Our results show that the parameter controlling of phase transition are strongly influenced by the presence of the quenched impurities.

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Keywords: Monte Carlo, order-parameter, tracer diffusion coefficient

1 Laboratoire de physique de la matière condensée Faculté des sciences Ben M’sik, B.P. 7955, Casablanca, Morocco.
2 Laboratoire de physique de la matière condensée Faculté des sciences El Jadida, Morocco.
* Hassan II Academy of Sciences and Technology

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Volume 9, article 16

Residual Resistivity of Some Metallic Elements

Aditya M. Vora

In the present article, the residual resistivity of some metallic elements of the periodic table is reported on the basis of model potential formalism. Ashcroft’s well known empty core (EMC) model potential is explored first time with five different types of the local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al (F) and Sarkar et al (S) to investigate the effect of the exchange and correlation on the aforesaid properties. The comparisons of presently computed results are found in qualitative agreement with available theoretical and experimental findings. Present investigation of the residual resistivity is found to be quite sensitive to the selection of local field correction function and showing a significant variation with the change in the function.

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Keywords: Pseudopotential; residual resitivity; metallic elements

 PACS : 71.15. Dx., 71.55.Ak, 72.10-d.

Parmeshwari 165, Vijaynagar Area, Hospital Road, Bhuj – Kutch, 370 001, Gujarat, INDIA

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Volume 9, article 17

Biotic and abiotic interactions between the superficial and interstitial water
of a river to the Middle Atlas (Oued Tizguit).

Nezha Berrada¹, Khadija Essafi¹ & Nezha Aouad²

Biotic and abiotic interactions between the superficial and interstitial waters have been analysed on the level of the interfacing zone between a river (Tizguit oued) and its underflow. The interactions were the results of water, mineral nutrients, organic matter and live beings transfers. Biotic interactions estimated by the taxonomic richness of invertebrate interstitial and superficial communities permitted to describe a zone of interfacing characterized by a dominance of epigean taxa and the scarcity of hypogean individus, represented here by the only stygobionte species Pseudoniphargus sp. The physico-chemistry of water permits to determines its quality and detect a certain natural or artificial pollution. It allows to determine its origin and explain the variations of the biological function. The interstitial waters of the Oued are relatively cold, slightly alkalised, mineralised, and relatively similar to the superficial waters from which they originate. The dynamic of exchanges at the level of interfacing zone between the river and its underflow is a direct vertical type. Exchanges take place from the surface to interstitial middle. They drag in depth epigean fauna, washed P.O.M (Particulate organic matter) and the physico-chemical features of the superficial water.

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Keywords: Cadmium Sulphide, Copper Indium Di-Selenide, Electrodeposition, direct heated substrate chemical Bath deposition

1 Laboratory of Hydrobiology and General Ecology. Faculty Science Dhar El Mehraz B.P: 1796 Atlas – Fez
2 University Hassan II, Faculty Science Aïn Choq - Casablanca.

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Volume 9, article 18

Study of Driving Forces for Atomic Migration in Dilute Alloys

Aditya M. Vora

We present a pseudopotential calculation of the driving forces for atomic migration in the 156 dilute alloys of the 23 host of the different groups of the periodic table in the presence of electron currents. The forces on an atom arising from the applied electric field and from the electron scattering together comprise the driving force, causes a net current of atoms. A well recognized Ashcroft’s empty core (EMC) local model potential is used to investigate the driving forces for interstitial (FINT), vacancy (FVAC), substitutional (FSUB) and nearest neighbour (FNN) migration in dilute alloys. Five different types of the local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used to study the effect of the exchange and correlation on the aforesaid properties. The driving forces are calculated for interstitial, vacancy, substitutional and nearest neighbour migration in dilute alloys, and the results are found to compare qualitatively with most experimental data. The present study concludes that FINT is larger than FVAC. For some dilute alloys the electron scattering force is found in the opposite direction to the electron drift velocity. Present findings are compared with the other such data, which confirms the applicability of the model potential. Keywords: model potential, driving forces, atomic migrations, dilute alloys
PACS: 71.15.Dx, 66.30.Jt, 66.30.Qa

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Keywords: model potential, driving forces, atomic migrations, dilute alloys

 PACS : 71.15.Dx, 66.30.Jt, 66.30.Qa.

1 Parmeshwari 165, Vijaynagar Area, Hospital Road, Bhuj–Kutch, 370 001, Gujarat, INDIA

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Volume 9, article 19 

Random crystal-field effect on magnetic materials

L. Bahmad, A. Benyoussef, and A. El Kenz

 Using the mean field theory, we investigate the effect of the random crystal-field on both the spin-3/2 and spin-2 Blume-Capel models. Several new features are found including the apparence of new ordered phases at low temperature and consequently rich ground state phase diagrams. At finite temperature, new types of phase diagrams are found. Furthermore, we show that at low temperature, first-order transition lines are terminated by isolated critical points, between the ferromagnetic phases. We also discuss some interesting phenomena such as the existence of compensation and the existence of topologically different types of phase diagrams. The magnetic properties and phase diagrams of this model are presented. The obtained results confirm the existence of new ferri-magnetic phases and consequently the existence of new topologies for the different types of the phase diagrams. Indeed, these phase diagrams present rich varieties of phase transitions with first and second order phase transition lines. These lines are found to be linked by tri-critical points and terminated at isolated critical points. In the case of the spin-2 Blume-Capel model, the interesting finding to emerge consists in the appearance of a new phase, with magnetization (m=3/2), and consequently new types of phase diagrams, divided on topologies depending on the existence of the paramagnetic phase at temperature T=0 K. Finally, the thermal behaviour of the sub-lattices magnetizations, showed the presence of the compensation behaviours for negative values of the crystal-field.

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Laboratoire de Magnétisme et Physique des Hautes Energies Département de Physique, Faculté des Sciences Avenue Ibn Batouta, B.P 1014 Rabat Morocco.