Faiza Meriche
Université de JIJEL, Physic, Faculty Member
In this work, pure and Al-doped zinc oxide (AZO) thin films were grown on glass substrates by sol–gel spin coating method. Structural, morphological, optical and waveguiding properties are investigated for different Al concentration (0–4... more
In this work, pure and Al-doped zinc oxide (AZO) thin films were grown on glass substrates by sol–gel spin coating method. Structural, morphological, optical and waveguiding properties are investigated for different Al concentration (0–4 at. %). X-ray diffraction confirmed the hexagonal ZnO Wurtzite structure of the films with a high c-axis preferred orientation. The crystallite size decreased from 30 to 20 nm with increasing Al content. Atomic force microscopy showed that Al-doped ZnO films presented a smooth and uniform surface and their roughness values depend on dopant concentration.The AZO films showed a high optical transparency more than 95% in the visible region and the optical band gap increased by increasing Al content. The optical waveguiding characterization demonstrated that our films have planar waveguide structure. All the AZO films supported only a well-guided fundamental mode for both transverse electric and transverse magnetic polarizations. Both ordinary and extraordinary refractive indices are found to decrease with Al doping content. Best performing thin films have been obtained with 2 at. % of Al.
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La structuration des materiaux a l echelle micro et nano metrique constitue un domaine de recherche et developpement tres prometteur dont le succes permettra de realiser le saut technologique tant attendu dans le domaine de la photonique.... more
La structuration des materiaux a l echelle micro et nano metrique constitue un domaine de recherche et developpement tres prometteur dont le succes permettra de realiser le saut technologique tant attendu dans le domaine de la photonique. Du point de vue du materiau, l utilisation des dielectriques de type LiNbO3 ou encore TiO2 qui possedent des proprietes specifiques qui different de ceux des semi-conducteurs est de nature a elargir les performances des composants photoniques a mettre au point. De plus, l utilisation de ces materiaux sous forme de couches minces permet de s affranchir des contraintes et des limitations imposees par le cristal massif. Dans le cadre de ce travail, nous nous interessons a la realisation de -structures 1D et 2D par ablation laser nanoseconde dans des couches minces et monocristaux de niobate de lithium ainsi que des couches minces de TiO2. Les couches minces de LiNbO3 ont ete deposees par pulverisation cathodique rf magnetron sur saphir tandis que les ...
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Structural and magneto-electrical transport properties of double-layered La1.6-xPrxCa1.4-xBaxMn2O7 (x = 0.2 and 0.4) manganite compounds were studied. X-ray diffraction patterns refinement shows that the samples crystallize in a... more
Structural and magneto-electrical transport properties of double-layered La1.6-xPrxCa1.4-xBaxMn2O7 (x = 0.2 and 0.4) manganite compounds were studied. X-ray diffraction patterns refinement shows that the samples crystallize in a tetragonal I4/mmm structure, whereas a rhombohedral structure phase with R3-c\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R\stackrel{-}{3}c$$\end{document} space group is detected as a secondary phase. The electrical resistivity under 0 and 1 T exhibited a metal–insulator transition at TMI. It is found that the ρ(T) decreases with increasing Pr-Ba contents. Magnetoresistance (MR%) curves displayed a maximum value of ∼51.69% at 63 K for the x = 0.2 sample and decreases with increasing Pr-Ba concentrations to ∼33.44% at 64 K for x = 0.4 under 1 T. The obtained values of the temp...
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Structural, microstructural and magneto-transport properties of polycrystalline La0.5Sm0.2Ca0.3-x PbxMnO3 (x= 0, 0.05 and 0.10) samples, prepared by conventional solid state reaction, were studied. Refinement of the Powder X-ray... more
Structural, microstructural and magneto-transport properties of polycrystalline La0.5Sm0.2Ca0.3-x PbxMnO3 (x= 0, 0.05 and 0.10) samples, prepared by conventional solid state reaction, were studied. Refinement of the Powder X-ray diffractograms revealed that all the samples crystallize into orthorhombic structure with Pnma space group and the lattice parameters increase with increasing Pb content. The scanning electron microscope (SEM) micrographs show a granular character and the estimated grain sizes ranges between 10 μm and 20 μm. The experimental electrical resistivity and the magnetoresistance in the temperature range 20 K - 250 K under magnetic field of zero and 1 Ta, have been recorded using four probe technique. The resistivity curves without magnetic field, exhibit a ferromagnetic-metallic (FM) to paramagnetic-insulating (PI) transition at TMI=125 K, 91 K and 37 K for x=0, 0.05 and 0.10, respectively. The magnetoresistance reaches 58% for undoped sample and decrease with Pb ...
ABSTRACT
ABSTRACT Thin films of transparent titanium oxide (TiO2) are prepared by the sol–gel dip-coating technique. Structural and optical properties of TiO2 thin films are investigated for different annealing temperatures and different number of... more
ABSTRACT Thin films of transparent titanium oxide (TiO2) are prepared by the sol–gel dip-coating technique. Structural and optical properties of TiO2 thin films are investigated for different annealing temperatures and different number of coatings. X-ray diffraction (XRD) and Raman spectroscopy analysis show that the anatase crystalline phase appears beyond 350°C for the four layers TiO2 film. At higher temperatures and for thicker films, we observe in addition to anatase the formation of brookite and rutile phases. The grain size calculated from XRD patterns increases as the temperature of annealing and number of dipping increase, from 11.9 to 17.1nm for anatase and decreases as the number of dipping increases, from 24.2 to 10.2nm for brookite. Film thickness, refractive index, and porosity are found to vary with treatment temperature and the number of coating. The obtained films are transparent in the visible range and opaque in the UV region. Waveguiding properties are studied using m-lines spectroscopy. The best results indicate that our films are monomodes TE0 at 632.8nm with optical losses of 2dBcm−1.