(JNTM) مجلة التكنولوجيا الجديدة والمواد

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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.
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.
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.
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.
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.
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.
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.
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.
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 atoms
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.
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.
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.
Low Copper Doped CdO Nanowires Grown by Sol-Gel Route
(Oum-El-Bouaghi University, 2011) Benhaliliba, M.; Benouis, C. E.; Silver, A. Tiburcio
In 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.
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.
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.
Structural And Optical Properties Of Cdse Doped Kcl Single Crystal
(Oum-El-Bouaghi University, 2012) Bouhdjer, L.; Addala, S.; Chala, A.b.; Halimi, O.; Boudine, B.; Sebais, M.; Kara, S.
Undoped and doped KCl single crystals by CdSe nanocrystals (NCs) have been grown by Czochralski (CZ) method with pulling rates in the 8-10 mm/h range. The crystals thus obtained were cleaved into samples of required size. The structural investigation of these samples has been deduced from Ө-2Ө (XRD) and Raman spectroscopy. The nano-size of CdSe aggregates in KCl host determined from XRD measurements by using the Sheerer formula. The Raman spectroscopy presented the LO mode vibration relative of (Cd-Se) chemical liaison. Moreover, the results of the optical absorption and photoluminescence spectra confirmed the nano-size of CdSe aggregates were observed band absorption located at 622,5nm relative of electronic transition 1se-1s3/2 of CdSe, with a blue shift from the bulk gap of ΔEg=0,26eV (Eg (CdSe) bulk=1,73eV), while the photoluminescence showed a band situated at 643, 55 nm, with displacement Eg towards the short wavelength (blue shift), this bleu shift due to the nanometric size of CdSe aggregates.
Characterization Of The Fe90-xsi10crx (x=10, 15) Nanostructured Powders Prepared By Mechanical Alloying
(Oum-El-Bouaghi University, 2012) Bensebaa, Z.; Bouzabata, B.; Otmani, A.; Djekoun, A.; Grenèche, M.
In this study, structural and magnetic properties of nanocrystalline Fe80Si10Cr10 and Fe75Si10Cr15 powders produced by mechanical alloying (MA) have been investigated and examined by X-ray diffraction and 57Fe Mössbauer spectrometry. Mechanical alloying was carried out in a planetary high energy ball mill starting from pure elements of iron, silicon and chrome. After 15 h of milling, it is observed the formation of two bcc solid solutions α-Fe1 (Si, Cr) and α-Fe2 (Si, Cr) for the Fe80Si10Cr10 alloy. Their grain sizes decrease with milling time and attains 23 nm and 11 nm respectively. For the Fe75Si10Cr15 alloy the XRD shows the formation of the bcc and the cfc solid solution with a low concentration. The lattice parameter of the bcc solid solution increases with increasing time and chrome content. Mössbauer spectrum at room temperature of the Fe80Si10Cr10 alloy resulted in the formation of two contributions, ferromagnetic and paramagnetic with a low concentration of 4 %. Addition of Cr as in the case Fe75Si10Cr15 alloy increases the paramagnetic contribution with a relative concentration of 17.5 %.
Humidity Sensing And Electrical Properties Of Hmdso Plasma Thin Film
(Oum-El-Bouaghi University, 2012) Guermat, N.; Bellel, A.; Sahli, S.; Segui, Y.; Raynaud, P.
This paper reports the study of humidity-sensitive and electrical properties plasma polymerization of hexamethyldisiloxane (pp-HMDSO) thin film based sensors. The humidity sensitive film was deposited by glow discharge at low frequency power (19 KHz) in a capacitively coupled parallel plate plasma reactor. The sensor design comprises the intredigited electrodes and the absorbing layer. The sensor was calibrated in terms of impedance as a function of relative humidity, using a Frequency Response Analyzer. The signal frequency range was between 102 to 107 Hz with amplitude of 3V. Structural analysis of the sensitive layer was carried out by Fourier Transform Infrared spectroscopy (FTIR). Electrical properties, including capacity-humidity, hysteresis of the elaborated sensor were investigated. Interdigital electrodes and sensing layer were modeled using equivalent circuits to resolve the effects of adsorption and ion migration. The HMDSO films showed promising characteristics for humidity sensor development.
The Electrochemical Nucleation And Properties Of The Co-cu Alloys Thin Films Deposited On Fto Substrate
(Oum-El-Bouaghi University, 2012) Mentar, L.; Azizi, A.
In this study, the properties of Co-Cu alloys thin films prepared by the electrodeposition method from a sulfate bath under potentiostatic conditions on a fluorine-doped tin oxide (FTO)-coated conducting glass substrate have been investigated. The electrochemical characteristics of granular alloys were studied by using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. The structural behaviors of the deposits have been determined by X-ray diffraction (XRD) measurements. The magnetic properties were investigated by alternating gradient force magnetometer (AGFM) technique. The effect of deposition potential on the electrodeposition process, phase structure and magnetic behaviors has been studied. CV studies revealed that the potential of Co dissolution depends on experimental parameters such as presence of Cu ions and cathodic limit. X-ray diffraction patterns of the Co-Cu alloys thin films exhibit an fcc and hcp phases, with peaks quite close to those of the Co phase (fcc and hcp). Magnetic properties such as coercivity and saturation magnetization showed strong dependence on the crystallite size and consequently the deposition potentials.
Extraction Of Important Parameters Of A Silicon Diode Used As Particles Detector
(Oum-El-Bouaghi University, 2012) Saadoune, A.; Dehimi, L.; Sengouga, N.; Terghini, W.; Megherbi, M.L.
The Capacitance-Voltage characteristics (C-V) and the resistivity (ρ) of a p+nn+ silicon diode used as a particle detector is numerically simulated using the finite difference method. These characteristics permit to extract the important and useful parameters for the design of a detector diode used in a harsh environment and subjected to strong fluencies, such as the depletion voltage (Vdep), the effective concentration and the maximum resistivity, the reduction rate of the donors (c) and the introduction rate of defects (g). When this junction is subjected to strong radiations, physical defects which are created in the semiconductor lattice have undesirable effects and can degrade the performance of the detectors. These defects behave like deep levels and/or generation recombination (g-r) centres. The depletion voltage and the effective concentration were calculated by using C-V characteristic. The evolution of the effective density in function with the density of traps acceptor led as to find the redaction rate of the donors (c) and the introduction rate (β). The resistivity increases with increasing of the deep acceptor density to achieve the intrinsic resistivity (maximum).

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