Développement par voie chimique à basse température de couches minces perovskite de titanates de baryum et de strontium

Abstract : The high-k character of ferroelectric materials allows their utilisation in electronic devices. The permittivity depends on intrinsic properties, film compactness, surface roughness, defects like oxygen vacancies in the case of a high temperature crystallization, etc. The present work aims to the development of dense and compact ferroelectric films at low temperatures. Two synthesis routes have been studied. The first is room temperature electrophoretic deposition of BaTiO3 and SrTiO3 nanoparticles, which were elaborated from inorganic precursors in an aqueous solution by a solvothermal route and stabilized in colloidal suspensions. X-Ray diffraction, SEM, TEM, IR and Raman spectroscopy, TGA / MS, density, and BET were employed in order to study composition and morphology of the nanoparticles as a function of the precursor nature and concentration and the thermal treatment. Photon correlation spectroscopy and zeta potential measurements allow determination of the nanoparticles sizes and the conditions for a stable colloidal solution. The second route is a low temperature solvothermal in-situ synthesis, directly from a titanium substrate. Dense and uniform BTO and STO films, slightly textured in the (001) direction, are obtained at temperatures below 200C̊. The study of the dielectric properties indicates the existence of the BaTiO3 tetragonal phase. Dielectric losses may be related to space charges located at the grain boundaries which give rise to diffusion currents at low frequencies. The synthesis route developed may open the way for new applications and may also be adapted to other transition metal oxides.
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Elsy Bacha. Développement par voie chimique à basse température de couches minces perovskite de titanates de baryum et de strontium. Physique [physics]. UNIVERSITE DE NANTES, 2010. Français. ⟨tel-01107433⟩

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