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Élaboration et caractérisation de films minces de cuprate de lanthane

Abstract : Lanthanum cuprate is an antiferromagnetique insulator that becomes superconducting when sufficiently oxidized. The aim of this study is to show the feasibility of the lanthanum cuprate thin film deposition by magnetron sputtering on low cost substrates. This work is developed around three points: the synthesis of the films, a study of their crystallization and the influence of the substrate nature on the films delamination. The synthesis aspect includes the presentation of the four different synthesis processes and a comparison of these processes in terms of reproducibility, chemical composition and thickness homogeneous zones. The process using a ceramic target was determined to have the larger homogeneous zone but does not allow obtaining stoichiometric films. The films structure after annealing in air has been determined by X-ray diffraction and Transmission Electronic Microscopy. This technique allowed us to demonstrate that the films mostly crystallize in a metastable tetragonal structure and in a lesser extend in orthorhombic structure. The effects of the chemical composition of the film, the substrate nature, and the annealing atmosphere on the films crystallization were studied. The use of steel as a substrate is promising way to the elaboration of La2CuO4 thin films. By using in situ microscope techniques, we showed that the thermal treatment induces defaults formation on the film surface. The natures of these defaults strongly depend on the substrate nature. To explain these results, the apparent thermal expansion coefficients of the films were calculated from x-ray diffraction analyses. These results allowed us to suggest a film delamination initiation model
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  • HAL Id : tel-01749389, version 1


Nolwenn Tranvouez. Élaboration et caractérisation de films minces de cuprate de lanthane. Autre. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0196⟩. ⟨tel-01749389⟩



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