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Synthèse de nanostructures d’oxyde de ruthénium par plasma micro-ondes en post-décharge à la pression atmosphérique

Abstract : Various ruthenium dioxide nanostructures were locally grown by the oxidation with an atmospheric pressure Ar-O2 microwave micro-afterglow of bulk ruthenium samples or thin films previously deposited by magnetron sputtering on silicon and silica. A special attention was paid to the distribution of the surface temperature of the sample which evolves typically between 530 K and 900 K. The use of plasma discharges allows a lowering of the temperature compared with the thermal oxidation conditions, given that molecular oxygen is excited or dissociated, which provides more reactive species such as singlet oxygen or atomic oxygen. According to the substrate used and the operating conditions, different nanostructures can be formed: lamellae separated by 20–50 nm, localized nano-sea urchins, high density of long nanowires and microcrystals. Nanostructures obtained were characterized by various techniques (electron microscopy, X-ray diffraction or secondary ion mass spectrometry). The grown RuO2 nanowires were determined to be generally single-crystalline with random crystallographic orientations. Very different growth mechanisms were observed and identified. Although it seems impossible to obtain uniformly distributed nanostructures on bulk ruthenium substrates, it is possible from substrates coated by a thin layer of ruthenium, which allows the formation of nanowire carpet. The possibility to localize the growth of nanowires by adding alkali salts has been studied. However, if the use of NaCl or KCl crystals locally enhances the nanowire density, they do not ensure systematically the growth of nanowires
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Duclair Kuete Saa. Synthèse de nanostructures d’oxyde de ruthénium par plasma micro-ondes en post-décharge à la pression atmosphérique. Autre. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0057⟩. ⟨tel-01751666⟩

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