المقـــــــــــــــــــالات
Permanent URI for this collection
Browse
Browsing المقـــــــــــــــــــالات by Issue Date
Now showing 1 - 20 of 247
Results Per Page
Sort Options
Item Toy Model Of Spinfet Transistor(Oum-El-Bouaghi University, 2011) Boudine, A.; Benhizia, K.; Djebbari, N.The study of spin polarized transport in semiconductors is achieved by the transmission of current in semiconductor devices, our study focuses on spintronics or spin electronics in these devices. We chose the spinFET transistor or the transistor at`spin rotation’ as a better implementation because it is a type of HEMT transistor in which we replace the source and drain by ferromagnetic contacts. The source contact acts as a spin polarizer for electrons injected into the conduction channel of the transistor and the drain contact is a spin analyzer to those (spins) have reached the end of the canal. The drain current varies with orientations of the spin of electrons at the end of the canal and the magnetization of the drain contact. However, it is possible to control the current through the grid voltage. We have presented a simple toy model in the 1D channel formed in In0,53Ga0,47As a spin FET transistor.Item Electronic structure calculation of the GaAs/AlAs quantum dot superlattices(Oum-El-Bouaghi University, 2011) kanouni, F.; Brezini, A.; Sekkel, N.; Saidane, A.; Chalabi, D.; Mostefa, A.theoretical investigation of the electronic structure of GaAs/AlAs quantum dots tuperlattices is presented. We use the envelope function approximation in connection with Kronig-Penney model to calculate the conduction band structure of the cubic quantum dot crystal. . We show that, when quantum dots are separated by a finite barrier and positioned very close to each other so that there is a significant wave function overlap, the discrete energy levels split into three-dimensional minibands. We can control the electronic structure of this artificial quantum dot crystal by changing theirs technological parameters, the size of quantum dots, interdot distances, barrier height, and regimentation. This type of structure provides electronic and optical properties very important that are different to that of bulk and quantum well superlattices. The proposed engineering of three-dimensional minibands in quantum dot crystals allows one to fine-tune electronic and optical properties of such nanostructures.Item Numerical analysis of GaAs MESFETs OPFET(Oum-El-Bouaghi University, 2011) Hamma, I.; Saidi, Y.; Zaabat, M.; Azizi, C.A Tow dimensional numerical model of channel potential for GaAs MESFET (Metal semiconductor field effect transistor) doped uniformly .the model takes into acount the effects in channel region considering both the photoconductive effect and photovoltaic effect at the gate schottky . the 2-D potential distribution function in the active layer of the divice is solved numerically under dark and illumination condition.Item Treatment of commercial aluminum by Nd(Oum-El-Bouaghi University, 2011) Baziz, L.; Nouiri, A.In this work, two types of commercial aluminum alloys (industrial and recovered aluminum) are studied. The surface is irradiated by Nd: Yag laser (l = 532 nm, with a pulse duration of 15 ns and an energy of 50 mJ). The experimental results show that the hardness profile can be divided into three regions. The melted area is the hardest region, Then, the hardness decreases sharply in the interface region between the melted area and the heat-affected zone.Item Optical and structural study of plastic deformation of single crystals CdTe and CdZnTe(Oum-El-Bouaghi University, 2011) Harouni, S.; Guergouri, k.; Arabe, L.; Hamdellou, S.CdTe pure and alloyed with some isoelectronic impurities was found in front of more than twenty years as very promising in optoelectronics. The effectiveness of components based on these materials is strictly related to their quality. It is in this context that our work. The objective in this study is to see the effect of plastic deformation of crystals of CdTe and CdZnTe on crystallographic and optical properties. The investigation methods are X-rays as a means of crystallographic characterization, measurements of UV-Visible spectrophotometry, as means of optical characterization. The main results show that: the best crystal (CdZnTe) before deformation, which shows the highest dislocation density after deformation and increased optical gap, which decreases for CdTe. The effect of dislocations on the optical properties is characterized by a shift of the absorption edge relative to the undeformed state, due to the creation of acceptor centers, which are the neutral hole CdTe and Cd decreased concentration of Zn atoms substituting Cd atomsItem Investigation on chemical bath deposited CdS thin films(Oum-El-Bouaghi University, 2011) Moualkia, H.; Attaf, N.; Hadjeris, L.; Herissi, L.; Abdelmalek, N.n this work we report the structural, optical and electrical properties of CdS thin films prepared by chemical bath deposition (CBD) under the effect of solution temperatures. The XRD patterns show that the films have a hexagonal phase with a preferential (002) orientation. The structural parameters such as the grain size, dislocation density and strain are calculated for the films. The transmission spectra, recorded in the UV visible range reveal a high transmission coefficient (85%) in the obtained films. The optical gap values of 2-2, 4 eV are deduced from the UV-visible transmittance. The electrical characterizations show that the films deposited possess good optoelectronic properties.Item Elaboration and characterization of zinc oxide varistors(Oum-El-Bouaghi University, 2011) Bouchekhlal, A.; Beggah, Y.; Aida, M.S.ZnO-based varistors were fabricated by sintering zinc oxide micro crystals with several additives of metal Oxides. The effect of sintering temperature on varistor properties of (Bi, Co, Cr, Mn, Sb, Al)-doped ZnO ceramics was investigated in the range of 1280–1350 °C. The average grain size increased to 5.13 to 7.88 µm with the increase of sintering temperature. However, the nonlinear coefficient of this system was nearly constant in the range of sintering temperature. The highest breakdown voltage was 1143.4 v / cm for the varistor sintered at 1350 °C the sample C sintered exhibited the best electrical properties.Item Realization and study of ZnO thin films intended for optoelectronic applications(Oum-El-Bouaghi University, 2011) Herissi, L.; Hadjeris, L.; Moualkia, H.; Abdelmalek, N.; Hafdallah, A.; Attaf, N.; Aida, M. S.The objective of this study is the realization of zinc oxide (ZnO) thin films intended for optoelectronic applications. For this purpose, thin films were prepared by spray pyrolysis technique from zinc acetate solutions of different molarities (0.025 M, 0.05 M and 0.1 M) used as precursors on Si and glass substrates heated between 200 and 500 °C. The nozzle to substrate distance was varied between 20 and 30 cm. Structural, optical and electrical properties of the films have been studied. The results indicated that the films deposited were transparent in the visible region, well adherent to the substrates and presented surface roughness. All samples were polycrystalline in nature, having hexagonal würtzite type crystal structure. A (002) preferred orientation was observed at 450°C and a 0.025M molarity. The optical energy gap measured was about 3.3 eV. The refractive index values presented small variations with the deposition conditions and were located between 1.8 and 2.0. The electrical properties showed that the samples are natively n‑type semiconductor and the electrical conductivity at room temperature varied between 10-5 and 102 (Ω.cm)‑1.Item Study of the performance of ballistic carbone nanotube FETs(Oum-El-Bouaghi University, 2011) Rechem, Dj.; Benkara, S.; Lamamra, K.Using a two-dimensional (2-D) simulation, we study the impact of varying the nanotube diameter and gate oxide thickness on the performance of a ballistic nanoscale carbon nanotube field effect transistor (CNTFET). Our results show that the nanotube diameter influences the ION/IOFF current ratio; the drain induced barrier lowering (DIBL), the subthreshold slop as well as transconductance and drain conductance. We also show that these device characteristics are affected by the gate oxide thickness. Thus, nanotube diameter and gate oxide thickness must be carefully taken into account when designing robust logic circuits based on CNTFETs with potentially high parameter variability.Item Reflexion/ Transmission of a plane wave on a plane interface(Oum-El-Bouaghi University, 2011) Rahmi, F.; Aklouche, H.; Bedrici-Fraï, N.; Gatignol, Ph.; Potel, C.On a plane interface between two elastic half-space, P and SV waves propagating in the pare related by Snell's law and the law of continuity of displacement components and and constraints and on both sides of the interface. An incident wave P or wave SV generates two P or SV reflected waves and two transmitted waves P or SV. The four continuity equations are written in the form of a matrix multiplied by a vector transmission-reflection coefficient, defined for potential movement of the particles. For an planar boundary between fluids with different characteristic impedances, there is continuity of and on both sides of the interface and the shear in the medium must vanish at the interface (fluid media involving only perfect no viscosity, so that was normal stresses, not shear stress ). As soon as the angle of incidence exceeds a critical value of incidence, the wave for which the value of incidence is greater than becomes evanescent. The reflection-transmission coefficients become complex.Item Spin polarized transport in semiconductor(Oum-El-Bouaghi University, 2011) Boudine, A.; Benhizia, K.; Kalla, L.In this paper, we study two-dimensional spin polarized transport in semiconductors. Based on the some semiclassical considerations and taking account of the spin relaxation. We determined the relationship of the polarization as a function of time and the distance. And we have also established the relationship of the drain current in a 2D channel of a transistor called "spin-FET" where it was matter to highlight this type of transport. This study was crowned with a numerical study of the characteristics of spinFET 2D transistor depending on the external field and internal characteristics of the semiconductor.Item Nanopowders prepared by Solar Physical Vapor Deposition (SPVD)(Oum-El-Bouaghi University, 2011) Monty, Claude J. A.The Solar Physical Vapor Deposition (SPVD) is an original process to prepare nanopowders. This method has been developed in Odeillo-Font Romeu in France using solar reactors working under concentrated sunlight in 2kW solar furnaces. Various oxides, pure or containing other elements in addition, have been obtained. This paper focus on ZnO and TiO2. based oxides It is shown that the X-Rays Diffraction analysis allows a fine nanostructural characterisation of the nanophases present in these nanopowders. In many cases, HRTEM or SEM and XPS complement the XRD analysis. The properties such as Electrical, magnetic properties, photoreactivity, luminescence known on microstructured materials of the same composition are revisited on these nanopowders or on nanomaterials prepared from them and led in many cases to original behaviours.Item Substrate effect temperature on Cu2ZnSnS4 thin films deposited by ultrasonic technique(Oum-El-Bouaghi University, 2011) Daranfed, W.; Fassi, R.; Hafdallah, A.; Ynineb, F.; Attaf, N.; .Aida, M.S; Hadjeris, L.; Rinnert, H.; Bougdira, J.Cu2ZnSnS4 (CZTS) thin films are a potential candidate for absorber layer in thin film solar cells. CZTS films were deposited by spray ultrasonic technique. An aqueous solution composed of copper chloride, zinc acetate, tin chloride and thiourea like precursors is sprayed on heated glass substrates at various temperatures. The substrate temperature was changed from 280°C to 360°C in order to investigate its influence on CZTS films properties. The DRX analyses indicated that Cu2ZnSnS4 films have nanocrystalline structure with (112) preferential orientation and a crystalline size, ranged from 30 to 50 nm with increasing substrate temperature. The obtained films are composed of SnS, ZnO, ZnS and Cu2ZnSnS4 phases. The optical films characterization was carried by the measurement of UV-visible transmission. The optical gap was deduced from the absorption spectra. Broad emissions at around 1.27 eV was observed in the photoluminescence spectrum measured at 77 K.Item Photovoltaic applications of Light Beam Induced Current technique(Oum-El-Bouaghi University, 2011) Sayad, Y.; Kaminski, A.; Blanc, D.; Bazer-Bachi, B.; Lemiti, M.; Nouiri, A.Light or Laser beam induced current technique (LBIC) is conventionally used to measure minority charge carrier’s diffusion length LD by scanning a light spot away from collector (abrupt pn junction or Schottky contact). We show here the necessary precautions to be taken in order to apply this method on materials used in photovoltaics. We talk about SRLBIC or spectral response LBIC when this technique is combined with spectral reflectivity to allow determination of cells quantum efficiency. From internal quantum efficiency analysis, one deduces an effective carrier diffusion length, Leff, including bulk and surface recombinations. LBIC is, also, often used to reveal electrically active extended defects such as grain boundaries and dislocations, and to check passivation efficiency of fabricated cells.Item Low Copper Doped CdO Nanowires Grown by Sol-Gel Route(Oum-El-Bouaghi University, 2011) Benhaliliba, M.; Benouis, C. E.; Silver, A. TiburcioIn the current work, pure and copper doped cadmium oxide (Cd1-x Cux O, x=0, 0.02, 0.03) thin films are grown by sol-gel spin coating route. Optical transmittance is measured in UV, VIS and IR spectra; it is revealed that the copper improves the transmittance. The optical band gap increased with the doping. The room temperature electrical resistance was affected by copper doping. The AFM morphology reveals that pure CdO and Cu doped thin films are nanostructured.Item Influence Of Optical Kerr Nonlinearity On The Dynamic Behaviour Of Quantum Cascade Laser(Oum-El-Bouaghi University, 2012) Hamadou, A.; Thobel, Jean-luc; Lamari, S.The effect of optical Kerr nonlinearity on the dynamic behaviors of quantum cascade laser operating in the mid-infrared is theoretically studied. Our model is based on three-level rate equations including the dependence of the loss on photon number in the cavity. The optical stability domain that allows for the determination of current injection is investigated. The equation that allow for the determination of the delay time is derived within the premises of our model in the most general case. Furthermore, nonlinear effects influence significantly the dynamics of photons in cavity and electrons in the upper laser level.Item Morphological And Physico-chemical Characterization Of Mn-bi System Electrodeposited In A Mixed Sulfate-nitrate Bath(Oum-El-Bouaghi University, 2012) Boudinar, S.; Benbrahim, N.; Benfedda, B.; Kadri, A.n this paper, the electrodeposition kinetics of the Mn-Bi system in a mixed sulfate nitrate bath is reported. The plating bath is characterized by the presence of some additives like the boric acid and the ammonium sulfate. In this work, cyclic voltammetry is used to characterize reduction and dissolution potential of each element. The morphological and the chemical composition of the deposit were determined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The deposit has a heterogeneous appearance with different grain size, the energy dispersive spectroscopy (EDS) analysis reveals the presence of manganese and bismuth peaks with almost the same intensities.Item Investigation Of Impact Strength And Hardness Of Aluminum Based Sic Particle Reinforced Composites(Oum-El-Bouaghi University, 2012) Sundriyal, P.; Singh, V. K.Metal Matrix Composites have evoked a keen interest in recent times for potential applications in aerospace and automotive industries owing to their superior strength to weight ratio and high temperature resistance. Although several technical challenges exist with casting technology yet it can be used to overcome this problem. Achieving a uniform distribution of reinforcement within the matrix is one such challenge, which affects directly on the properties and quality of composite material. In the present study a modest attempt has been made to develop Aluminum based Silicon Carbide particulate. To achieve these objectives two step-mixing method of stir casting technique has been adopted and subsequent property analysis has been made. Aluminum 6063 series and Si-C (300 mesh) has been chosen as matrix and reinforcement material respectively. Experiments have been conducted by varying weight fraction of Si-C (7%, 14% and 21%), while keeping all other parameters constant. The results indicated that the ‘developed method’ is quite successful to obtain uniform dispersion of reinforcement in the matrix results obtained by microstructure test. An increasing trend of hardness and impact strength with increase in weight percentage of Si-C has been observed.Item Drimenin-rich Essential Oils From Hertia Cherifolia Growing In Algeria(Oum-El-Bouaghi University, 2012) Zellagui, A.; Gherraf, N.; Lahouel, M.The hydrodistilled oil from crushed dry leaves of Hertia cherifolia which is endemic to Algeria and Tunisia collected from Ain Fekroun (Oum el Bouaghi, Algeria) were analyzed by gas chromatography-mass spectrometry to afford 36 components accounting for 99.3% of the total oil. the major components were found to be: Drimenin (67.5%), 1,2-Di(2-pyridinyl)-1,2-ethanediol (11.2 %), globulol(1.7 %), Cycloheptane, 4-methylene-1-methyl-2-(2-methyl-1-propen-1-yl)-1-vinyl- (1.5 %).Item Identification Of The Tensile Properties Of Hybrid Composite Material By Artificial Neural Network(Oum-El-Bouaghi University, 2012) Singh, Vinay KumarComposite materials are made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure. In the present work a silica-styrene-butadiene rubber hybrid composite material is developed with 1 and 2 wt% of nano sized silica particle and 0.25 to 1.5 wt% of styrene-butadiene rubber mixed in resin. Nonlinear relation between mechanical properties and filler material have been obtained. An artificial neural network (ANN) model with one hidden layer and two neurons seems to be approximate for the prediction of mechanical characteristic from the various weight percentage of filler material. Neural networks trained with the back-propagation algorithm are applied to predict the future values of tensile data with different percentage of constitute material. The influencing indicators of constituent percentage of composite material and strain rate are taken into consideration. The design and implementation of a neural network forecasting system is described that has been developed to estimate mechanical properties with different combination of constituent of developed composite material. The performance of the networks is evaluated by comparing them to the experimental data. The comparison shows that neural networks perform the conventional techniques with regard to the prediction quality.