Physique

Nombre total de résultats : 255
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Simulation des propriétés électriques d'une jonction à base de nitrure de gallium. Application au détecteur de rayonnement

Fayçal BOUZID (2018)
Thèse de doctorat

Le nitrure de gallium (GaN) est l'un des composés semi-conducteurs les plus intéressants, bien adaptés pour fonctionner dans n'importe quelle application dans laquelle la température ou le niveau de radiation pourrait endommager l'électronique conventionnelle. Récemment, la détection du rayonnement ultraviolet (UV) au moyen de dispositifs à base de GaN a suscité un grand intérêt dans de nombreux domaines importants, nécessitant des détecteurs à haute performance, à faible courant d'obscurité et à haute sensibilité. Dans ce travail, nous avons évalué, au moyen d'une étude de simulation en utilisant le simulateur de conception assistée par ordinateur (TCAD) Silvaco-Atlas, les caractéristiques électriques de deux types de photodétecteurs UV: le premier est un photodétecteur à barrière de Schottky (Pt / n-GaN) tandis que le deuxième est un photodétecteur "p+-n-n+" à base du composé ternaire Al0.17Ga0.83N. Les caractéristiques électriques densité de courant - tension et réponse spectrale monochromatique, sous différentes intensités de lumière UV en polarisation inverse et directe, ainsi que les effets de la température et les pièges sont présentées. Les résultats de simulations, ont montré que les densités de courants sous des tensions de polarisation inverse et dans l’obscurité, sont extrêmement faibles. Par contre, en illuminant les détecteurs par des rayons UV avec différentes intensités, nous avons montré que les densités de photo-courants augmentent de plusieurs ordres de grandeur, ce qui confirme l'utilité des structures étudiées pour la détection des rayons UV. D'autre part, on a constaté une réduction significative de la réponse spectrale des détecteurs étudiés, sous l'effet de la présence de certains niveaux de piégeage. Voir les détails

Mots clés : simulation, GaN, Photodétecteur, Ultraviolet, température, Réponse spectrale

Characterization of the Polylactic acid stretched uniaxial and annealed by Raman spectrometry and Differential scanning calorimetry

A. Bouamer, A. Younes, M. Zergoug, A. HAMOUDA  (2018)
Article de conférence

in this work, we have been interested in the characterization of the effect of heat treatment and mechanical treatment on the crystallinity of a polylactic acid (PLA) film by two techniques, DSC and Raman spectroscopy. the results obtained by the DSC for the stretched film shows the appearance of a broad peak of crystallization around 120 ° C, a rise in melting peak in a significant way, which shows that the uniaxial stretching has increased the crystallinity of the PLA, whereas for the annealed film appearance of a double melting peak. The results obtained by Raman spectroscopy show new peak appears at 922 cm−1 after stretching process, indicating crystallization process occurs. Voir les détails

Mots clés : Raman, DSC, PLA, crystallinity

Effet de la température sur les propriétés électriques d’une photopile

Fayçal BOUZID (2004)
Mémoire de magister

Le but principale de ce travail est d’étudier l’effet de la température sur la performance d'une cellule solaire à base de Silicium, à travers deux méthodes de caractérisation qui sont la caractéristique courant tension et la réponse spectrale. Dans cette optique, nous avons élaboré un logiciel « RS-Cellule.V2 » sous Visual Basic pour l’acquisition expérimentale et la modélisation numérique de la réponse spectrale, ainsi qu’un code de calcul « FIVT.1 » pour la modélisation de l’effet de la température sur la caractéristique courant tension selon les quatre modèles de la cellule.Les résultats obtenus montrent une amélioration de la réponse spectrale, notamment dans la région des longues longueurs d’ondes, avec l'accroissement de la température pour les deux types d’éclairements AM0 et AM1.5, ce qui traduit une augmentation du courant de court circuit.Ce résultat est confirmé lors de l’étude de l’effet de la température sur la caractéristique courant tension en utilisant les différents modèles. D'autre part, les résultats de simulation montrent la bonne approximation du fonctionnement réel de la cellule solaire par le modèle à deux diodes. L'emploi de la méthode de Marquardt-Levenberg pour extraire les paramètres de la cellule nous a donné de bons résultats en bon accord avec la littérature. Voir les détails

Mots clés : Cellule solaire, Silicium, Réponse spèctrale, Caractéristique I-V, température

Theoretical design and performance of InxGa1-xN single junction solar cell

Y.Marouf, L.Dehimi, F.Bouzid, F.Pezzimenti, F.G. Della Corte  (2018)
Publication

The insertion of optimized Window and a back surface field (BSF) layers on an InxGa1-xN p-n basic single junction (BSJ) solar cell is the chief reason behind the reduction of front and back recombination. In this context, this work is focused on the selection of the suitable parameters including the indium (In) content, thickness and doping concentration for the InxGa1-xN inserted layers, that gives the best photovoltaic performances. At this aim, numerical simulations were performed using the computational numerical modeling TCAD Silvaco-Atlas to design, optimize the InxGa1-xN BSJ and extract the above Window and BSF parameters that enhance the BSJ performances. A short circuit current density ?(J?_sc) of 26.15 mA⁄?cm?^2 , an open circuit voltage ?(V?_oc) value of 0.904 V and a fill factor (FF) value of 79.67 % are obtained under AM1.5G illumination, exhibiting a maximum conversion efficiency (η) of 19.62 %. Other parameters like the external quantum efficiency (EQE), electric field developed, the current density-voltage (J-V) and the power density-voltage (P-V) characteristics are also calculated and plotted for the designed solar cell. Voir les détails

Mots clés : InGaN, solar cell, BSF layer, Window layer, simulation, Silvaco

Oi and Cs Impurities Study on the Edge of Si-mc Ingot for Photovoltaic Applications

Fayssal Boufelghab, Y. CHETTATE, S. BELHOUSSE  (2016)
Publication

The objective of this work is determining the substitutional carbon ([Cs]) and interstitial oxygen ([Oi]) concentrations in the edge of the multicrystalline silicon ingot (mc-Si) for photovoltaic applications obtained by the heat exchanger method (HEM). Some calculations of [Cs] and [Oi] was obtain by the Fourier Transform InfraRed spectroscopy (FTIR). The results obtained for [Cs] give an increase of bottom-up of the ingot: 130 ppm to 150 ppm. The results obtained for the [Oi] give constant concentrations throughout the edge of the ingot with an author of concentration 325 ppm. Voir les détails

Mots clés : Crystallization, mc-Si, HEM, FTIR, [Cs], [Oi]

Ultrasonic device calibration for estimation of retained austenite in tool steel

Faci, Y, Abbas, a, Mebtouche, A.  (2005)
Publication

High percent of retained austenite in tool steel involve ill-fated effects as cracks. It is very important to control it. Ultrasonic device can be calibrated by using of ultrasonic velocities measurements. The variation of the velocities in tool steel as function of the rate of austinite is very small and require measurements with high accuracy. The calibration method is very simple and need neither mathematical methods nor simulations. Voir les détails

Mots clés : • Martensite, • Retained austenite, • Ultrasound longitudinal velocity, • Ultrasound transversal velocity

Performance analysis of a Pt/n-GaN Schottky barrier UV detector

F. Bouzid, L. Dehimi, F. Pezzimenti  (2017)
Publication

The electrical and optical characteristics of an n-type gallium nitride (GaN) based Schottky barrier ultraviolet (UV) detector, where a platinum (Pt) metal layer forms the anode contact, have been evaluated by means of detailed numerical simulations considering a wide range of incident light intensities. By modeling the GaN physical properties, the detector current density-voltage characteristics and spectral responsivity for different (forward and reverse) bias voltages and temperatures are presented, assuming incident optical power ranging from 0.001 to 1 Wcm-2. The effect of defect states in the GaN substrate is also investigated. The results show that, at room temperature and under reverse bias voltage of -300 V, the dark current density is in the limit of 2.18×10-19 Acm-2. On illumination by a 0.36-µm UV uniform beam with intensity of 1 Wcm-2, the photocurrent significantly increased to 2.33 Acm-2 and the detector spectral responsivity reached a maximum value of 0.2 AW-1 at zero-bias voltage. Deep acceptor trap states and high temperature strongly affected the spectral responsivity curve in the considered 0.2 µm to 0.4 µm UV spectral range. Voir les détails

Mots clés : Gallium nitride, Schottky barrier, ultraviolet detector, photocurrent, responsivity, Temperature

ELABORATION et CHARACTERISATION des COUCHES MINCES DES OYDES DE CUIVRES (CuO)

H. Serrar, A.BOUABELLOU, A.BOUHANK, Y.BELLAL, S.AMARA  (2017)
Article de conférence

Copper oxide thin films were deposited by a low-cost and simple spray pyrolysis technique on glass substrate at 485°C, The aqueous copper nitrate Cu(NO3)2,6H2O with the different concentrations (0.1 M , 0.3M) used as a source of copper. The structural, morphological, and optical properties of the CuO thin films were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-vis-spectrophotometer. The X-ray diffraction patterns confirm the presence of CuO phases with preferential orientation along (-111), (111). The optical direct gap energy for Copper oxide calculated from optical absorption measurement is 2.82 eV , which is quite comparable with the report value Voir les détails

Mots clés : Copper oxide, Spray pyrolysis, Thin films

Numerical simulations of the electrical transport characteristics of a Pt/n-GaN Schottky diode

Fayçal Bouzid, Fortunato Pezzimenti, Lakhdar Dehimi, Mohamed L. Megherbi, Francesco G. Della Corte  (2017)
Publication

In this paper, using a numerical simulator, we investigated the current-voltage characteristics of a Pt/n-GaN thin Schottky diode on the basis of the thermionic emission (TE) theory in the 300 to 500 K temperature range. During the simulations, the effect of different defect states within the n-GaN bulk with different densities and spatial locations is considered. The results show that the diode ideality factor and the threshold voltage decrease with increasing temperature, while at the same time, the zero-bias Schottky barrier height (Φb0) extracted from the forward current density-voltage (J-V) characteristics increases. The observed behaviors of the ideality factor and zero-bias barrier height are analyzed on the basis of spatial barrier height inhomogeneities at the Pt/GaN interface by assuming a Gaussian distribution (GD). The plot of apparent barrier height (Φb,App) as a function of q/2kT gives a straight line, where the mean zero-bias barrier height ( ) and the standard deviation (σ0) are 1.48 eV and 0.047 V, respectively. The plot of the modified activation energy against q/kT gives an almost the same value of and an effective Richardson constant A* of 28.22 Acm-2K-2, which is very close to the theoretical value for n-type GaN/Pt contacts. As expected, the presence of defect states with different trap energy levels has a noticeable impact on the device electrical characteristics. Voir les détails

Mots clés : Gallium nitride, Schottky barrier, diode, Temperature

FINITE ELEMENT MODELING OF GROUND MOVEMENT ON THE ROADCW16 SÉRAIDI -CHÉTAIBI (ANNABA, ALGERIA)

A. Saihia, L. Sayad, H. MERADI  (2017)
Publication

Grounds movements are considered a natural hazard, some of which have, over time, significant slow movements.Significance of these dynamic effects involves a risk which generates human and material damage. Policymakers musttake this issue into account in their permanent security organization program. Some landslides exhibit a function of time,significant slow movements. They are assigned to a behavior of clay materials mechanism caused by the variation ofgeotechnical properties. The effects of water seepage in wet periods generally linked to the viscous nature of claymaterials are causes primarily .They can also be related to the variation modeling parameters. The land slip site is locatedat the road CW16 Seraidi -Chétaibi, (Annaba, Algeria) area with an annual rainfall of more than 700mm. Analysis of theslope stability is carried out using several methods of deformation calculation of the natural ground state. In our case weuse a plastic Mohr Coulomb from supported models. The project proposes to examine the different causes using theexample of Cam Clay. The project will examine the different causes using the example of Cam Clay; elasticvisco plasticmodel with time (SSCM: Soft Soil Creep Model) set in a finite element program Plaxis. This technique can show us howdifferent behavioral assumptions can describe the slow movements of a slope. A comparison will be made with the MohrCoulomb (MC). Voir les détails

Mots clés : Mohr Coulomb, slip, numerical modeling, plaxis, cam clay, elasticvisco plastic model