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Développement d'un nouveau système d'implantation ionique en immersion plasma et analyses des processus de nitruration

Abstract : The objective of this work was twofold, the development of a new high temperature plasma based ionic implantation system and the analysis of the nitridation mechanisms. As regards the nitridation of steels, we showed that treatments at floating potential at temperatures as low as 300 °C could be realized in the reactor URANOS with diffusion lengths of several hundred microns. For low alloys steels diffusion performed at 380 °C, improve significantly the mechanical properties of the surface by increasing the micro hardness by a factor 3 and the limit of the fatigue strength up to 30 %, after 4 hours treatment. In the case of stainless steels, very hard layers (5 times the hardness of the substrate) of expanded austenite are formed in surface. The hydrogen role in the plasma, was to reduce the oxide layer on the substrate, but also to accelerate the nitrogen diffusion in the metal. The second objective of this thesis was the development of a new high temperature plasma based ionic implantation. At low temperature, implantation of nitrogen on steels leads to the formation of a hard layers on the surface. The implantation of nitrogen on aluminium alloys reveals the growth between 180-500 °C, of an aluminium nitride (AlN) film. The great originality of this reactor is to enable implantation at high temperature (300-1000 °C). We thus could show that at 900 °C, implantation of titanium alloys, leads to a thick film growth of TiN and Ti2N and beyond to formation of diffusion zone on more than 60 µm. Nitrogen implantation on monocrystalline Silicon shows that a transparent film, of silicon nitride, was able to grow thanks to a transport combining thermal action and ionic implantation. In this case and for high fluence, the layer thickness reaches 40 nanometers and the film presents the stochiometry of the Si3N4 nitride. This result is perfectly impossible to obtained by other nitriding techniques, as for example, nitride growth is limited in this cases to a thickness less than 5 nm.
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Submitted on : Thursday, October 23, 2003 - 5:46:07 PM
Last modification on : Friday, January 31, 2020 - 1:36:26 AM
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Laurent Marot. Développement d'un nouveau système d'implantation ionique en immersion plasma et analyses des processus de nitruration. Matière Condensée [cond-mat]. Université de Poitiers, 2001. Français. ⟨tel-00003632⟩

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