Couplage des techniques ellipsométriques et électrochimiques pour l'étude de la réactivité de métaux : application à la croissance de films de sulfate de plomb et d'heptanoate de cuivre

Abstract : aThe ellipsometry is a non destructive optical method for surface analysis. The aim of this work was to apply the ellipsometry to the analysis of the film growth by electrochemical techniques. After introducing the theoretical background of the ellispometry, a first technological stage was consisted to an adaptation of electrochemical and optical devices. The ellipsometry is an indirect technique of surface analysis, whose exploitation of results is based on the utilization of models. We have described the main models according to the state of analysed surface. In the first experimental part, the process of lead sulphate film formation on Pb electrode in 0.5M H2SO4 by imposed constant potential was investigated by in situ ellipsometric. The polishing quality of lead electrode surface was previously evaluated by spectroscopic ellispometric measurements. The results of the present work confirm that the passive film have a two-layer lead sulphate structure. The growth mechanism of the inner layer is explained by a nucleation and three dimensional growth model. The inner layer appears appears to be porous and Pb2+ ions diffuse through this semi-impermeable barrier. As consequence, an outer layer of larger crystals was observed. The second study was the inhibition of cooper in a desaerated sodium heptanoate solution by electro-oxidation. Rp measurements were carried out to compare inhibition efficiency using this original method with that based on other usual chemical oxidation methods. In situ spectroscopic and kinetic ellipsometric measurements was performed to study the copper passivation mechanism. The copper inhibition is attributed to the formation of a protective layer composed of a mixture of copper II heptanoate and copper hydroxide. The thickness of the passive film was evaluated at 14 nm. Two growth rates were observed during the passivation process and a model of a duplex layer was proposed
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Nicolas Stein. Couplage des techniques ellipsométriques et électrochimiques pour l'étude de la réactivité de métaux : application à la croissance de films de sulfate de plomb et d'heptanoate de cuivre. Autre. Université Paul Verlaine - Metz, 1997. Français. ⟨NNT : 1997METZ042S⟩. ⟨tel-01775914⟩

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