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Item CONTROLE DES CENTRES F+ DANS LES COUCHES MINCES D’OXYDE DE ZINC(2000) DJELLOUL AbdelkaderIn this study, the interested was focused on the variation of the green luminescence in thin films of ZnO according to the prior processing in an atmosphere of hydrogen. The green luminescence is induced by the singly ionised oxygen vacancy in the form of centre F+. It is established that the concentration of the vacancies could be regularised in the limit of order two for temperatures less than 980 K. For temperatures over 980 K an other defect created in the layers of ZnO which is called interstitial zinc. Keywords: Thin Films, Photoluminescence, Green luminescence, F+ Centre.Item CONTROLE DES CENTRES F+ DANS LES COUCHES MINCES D’OXYDE DE ZINC(2000-11-06) abdelkader. DjelloulDans cette étude, l’importance a été donnée à la variation de la luminescence verte dans les couches minces d’oxyde de zinc (ZnO) en fonction du traitement ultérieur dans une atmosphère d’hydrogène. Le défaut responsable de la luminescence verte dans ZnO est la lacune oxygène (VO ) sous la forme de centres F+. Il est établi que la concentration des lacunes peut être régulée à la limite de l’ordre deux pour des températures ne dépassant pas 980 K. Au-delà de cette température, se crée un autre type de défaut dans les couches de ZnO, qui est le zinc interstitielItem nfluence of vanadium on structure, mechanical and tribological properties of CrN coatings(2003) L. AissaniThis work aims to show the characterisation of Cr–V–N coatings, with the varied amounts of Cr and V. CrN, VN and Cr–V–N coatings were deposited onto silicon and XC100 steel substrates by reactive radio frequency magnetron sputtering and characterised with X-ray diffraction, X-ray photoelectron spectroscopies, energy dispersive X-ray spectroscopy, scanning electron microscopy, nanoindentation, pin on disc tribological tests and scratch tests. The residual stress was calculated using the Stoney formula. Compared to the CrN system, the Cr–V–N films presented a rough surface based on pyramidal morphology. A hardness of 19?53 GPa and a friction coefficient of 0?55 were obtained for CrN; in contrast, Cr–V–N coatings presented a weak hardness of 6?23 GPa. In the case of wear against a 100Cr6 ball, the Cr–V–N films were completely removed from the substrate, even though the Cr–V–N coating presented a low friction coefficient (0?39). However, the VN film showed good tribological performance.Item Thermochemical and Green Luminescence Analysis of Zinc Oxide Thin Films Grown on Sapphire by Chemical Vapor Deposition(2003-07-21) bdelkader DJELLOULThis study has been carried out to detail an integral thermochemical analysis of the principal reaction in the production of zinc oxide (ZnO) thin films, including developing an analytical form of the equilibrium constant. Zinc oxide thin films prepared by chemical vapor deposition have been studied in terms of deposition time and substrate temperature. The growth of the single-crystal films present two regimes depending on the substrate temperature, with increasing constant growth rates at lower, and higher, temperature ranges, respectively. Growth rates above 6 µm·min−1 can be achieved at Ts = 880 K. The variation of the green luminescence intensities in ZnO single-crystal thin films according to the subsequent processing in hydrogen atmosphere have been studied. After annealing of each ZnO sample at different temperatures, the luminescence intensity is maximal for λ = 510 nm. It is established that the concentration of the oxygen vacancies could be controlled to within two orders of magnitude for temperatures less than 980 K. Beyond 980 K, defects of interstitial zinc is created in the ZnO filmsItem Thermochemical and Green Luminescence Analysis of Zinc Oxide Thin Films Grown on Sapphire by Chemical Vapor Deposition(2004) DJELLOUL AbdelkaderThis study has been carried out to detail an integral thermochemical analysis of the principal reaction in the production of zinc oxide (ZnO) thin films, including developing an analytical form of the equilibrium constant. Zinc oxide thin films prepared by chemical vapor deposition have been studied in terms of deposition time and substrate temperature. The growth of the single-crystal films present two regimes depending on the substrate temperature, with increasing constant growth rates at lower, and higher, temperature ranges, respectively. Growth rates above 6 um.min−1 can be achieved at Ts = 880 K. The variation of the green luminescence intensities in ZnO single-crystal thin films according to the subsequent processing in hydrogen atmosphere have been studied. After annealing of each ZnO sample at different temperatures, the luminescence intensity is maximal for 𝜆 = 510 nm. It is established that the concentration of the oxygen vacancies could be controlled to within two orders of magnitude for temperatures less than 980 K. Beyond 980 K, defects of interstitial zinc is created in the ZnO films. Key Words: Zinc oxide, chemical vapor deposition, thermochemical, activation energy, hydrogen annealing, green emission.Item PROPRIETES ELECTRIQUES DES COUCHES MINCES D’OXYDE DE ZINC(2004) DJELLOUL AbdelkaderWe have investigated the growth conditions on the electric properties of ZnO thin films. Samples were deposited on (1010) , (0001) and (1120) Al2O3 substrates by the chemical vapor transport technique. At room temperature, the carrier concentration and Hall mobility were in the range of 21016 – 8.41018 cm-3 and 140 – 160 cm2V-1s-1, respectively. Results of temperature dependent Hall mobility measurements indicate there are different transport mechanisms at high and low temperatures. Keywords: Thin films. Zinc oxide. Chemical vapor deposition. Hall MobilityItem PROPRIETES ELECTRIQUES DES COUCHES MINCES D’OXYDE DE ZINC(2004-01-14) A. DJELLOULWe have investigated the growth conditions on the electric properties of ZnO thin films. Samples were deposited on (1010) , (0001) and (1120) Al2O3 substrates by the chemical vapor transport technique. At room temperature, the carrier concentration and Hall mobility were in the range of 21016 – 8.41018 cm-3 and 140 – 160 cm2V-1s-1, respectively. Results of temperature dependent Hall mobility measurements indicate there are different transport mechanisms at high and low temperaturesItem Photoluminescence Characterization of Al/Al_2O_3/InP MIS Structures passivated by anodic oxidation ABDELHAKIM MAHDJOUB(2004-10-25) ABDELHAKIM MAHDJOUBMetal-insulator-semiconductor (MIS) structures were produced by electron beam evaporation of Al2O3 on InP. Polyphosphate thin films of thickness 100{150 ˚ A were used to passivate the interface InPnInsulator. Photoluminescence spectra are reported at low temperature at various stages of the realization process of the MIS-InP structure. Photoluminescence topography at ambient temperature made it possible to characterize the surface state after each technological stage. The interface degradation under the effect of repeated annealing is insignificant up to temperatures of 350 ◦C. Radiative major defects detected by photoluminescence spectrum with energy 0.95{1.15 eV attributed to the complexes impurities of phosphorus vacancies are substantially reduced by the presence of anodic oxide.Item Accurate numerical modelling the GaAs MESFET current-voltage characteristics(2004-12-16) N. MerabtineIn this paper, we present a computing model of the current-voltage (I-V) characteristics of a gallium arsenide Schottky barrier field effect transistor called GaAs MESFET. This physical model is based on the two-dimensional analysis of the Poisson equation in the active region under the gate. In this frame, we elaborated a simulation software based on analysis of expressions that we have previously set up [1-3], the obtained theoretical results are discussed and compared to the experimental onesItem Hydrogen bonding in creatininium nitrate Fadila Berrah, Hanane Lamraoui and Nourredine Benali-Cherif(2005-01-08) Hanane LamraouiIn the title compound, C4H8N3O+ NO3ÿ, creatininium cations and nitrate anions are linked to each other through strong hydrogen bonds, formed by all H atoms covalently bonded to the N atoms. Short contacts are also observed between the anions. This complex three-dimensional network of hydrogen bonds ensures the cohesion of the ionic structure.Item DL-Leucinium nitrate(2005-04-30) Hanane Lamraouihe crystal structure of dl-2-ammonium-4-methylvaleric acid nitrate (C6H14NO2+ NO3ÿ, dl-leucinium nitrate) can be described by considering two types of layers parallel to the bc plane: hydrophilic layers including the head of the leucinium residue (ammonium and carboxylic groups) with the nitrate anion, and hydrophobic layers including the tail of the leucinium residueItem An HMM-based mmodel for moving object detection(Asian journal of information technology, 2006) A.D Debilou; Aouragh SalimaA new probabilistic background-foreground model based on Hidden Markov Models (HMMs) is presented. The hidden states of the model enable discrimination between foreground and background. This method is composed of two phases: first, an ICE (Iterative Conditional Estimation) is introduced to learn the unknown HMM parameters. In the second stage, each pixel is classified with MPM (Maximum Posterior Marginal) classification algorithm. The potential and efficiency of the method have been proven through simulations under Matlab.Item An analytical proof of saturability of an optimized lower bound for N-body Hamiltonians for some mass configurations, with arbitrary N(KheirEddine Boudjemaa, 2006-05-03) KheirEddine BoudjemaaWe begin by deriving explicit formulae for the energy levels of a system of N harmonic oscillators for two special mass configurations but for arbitrary N. Under the same conditions, we can perform analytically all the calculational procedure leading to an optimized lower bound for the ground state energy of an N-body system. The lower bound obtained in this way proves to be identical to the exact result. It is the first time, to our knowledge, that an explicit analytical proof of saturability has been worked out.Item Optimized lower bounds for N-body Hamiltonians(KheirEddine Boudjemaa, 2006-05-23) KheirEddine BoudjemaaGeneralizing a method used previously for three-body, four-body and very recently for five-body systems, we derive a lower bound for the ground state energy of an N-body Hamiltonian, with arbitrary N. Because the expression of the lower bound obtained in this way depends on a number of parameters, we obtain in fact a family of lower bounds, a lower bound for each set of values of these parameters. The best of these is of course obtained by maximizing over these parameters and is correspondingly named optimized lower bound. The set of values of the parameters corresponding to the optimized lower bound satisfy a number of relations, named universal dynamical constraints, which result from the application of a dynamical principle and are independent of the particular form of the potential. For N = 3, 4, 5, they can be worked out in the most general case. For N = 6 up, they can be worked out only for particular mass configurations. Furthermore, the optimized lower bound proves to be saturated in the harmonic oscillator case.Item Methylanilinium nitrate(2007) Zina BoutobbaThe crystal structure of the title compound, C7H consists of anion–cation layers parallel to the (100) plane, generated by N—H O hydrogen bonds. 16 of the 22 atoms (the exceptions being two O and four H atoms) lie on a mirror plane.Item 2-Methylanilinium nitrate(2007) BOUSSEKINE HoudaItem Carboxyanilinium hydrogensulfate(2007-03-18) Amani DiremThe cohesion in the title structure (p-CPABS), C7H8NO2+- HSO4 , is assured by an intricate three-dimensional hydrogen-bonded network of types N—H O and O— H O involving anions, carboxyl and amino groups in addition to the ionic interactions.Item Hydrogen bonding in 4-carboxyanilinium dihydrogenphosphate(2007-03-27) Amani DiremThe crystal structure analysis of the title compound, C7H8NO2+H2PO4 , has revealed a three-dimensional hydrogen-bonded network structure, involving the dihydrogenphosphate anions, the carboxyl groups and the ammonium groups. The anions are held together via strong O—H O hydrogen bonds. In addition to the N—H O and O—H O interactions, involving all the H atoms covalently bonded to the anion, the nitrogen and the carboxyl group, the crystal structure is also stabilized by C—H O and C—H short contacts.Item Hydrogen bonding in 2-carboxyanilinium dihydrogenphosphate(2007-04-02) Fatima AlloucheThis work is part of our research on intermolecular inter- actions in hydrogen-bonded molecular and ionic crystals. In recent years investigations of hybrid materials have attracted a great deal of attention; in addition to their interesting structural topologies and potential application in the field of new materials science, such as ion-exchange, adsorption, molecular recognition, catalysis and magnetism, hybrid compounds have very interesting electrical, magnetic and optical properties (Kagan et al., 1999; Mazeaud et al., 2000; Ravikumar et al., 2002; Aakeroy et al., 1999; Siegel et al., 1998). The kind of hydrogen bonding in hybrid compounds is also present in the active sites of several biological systems.