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SYNTHÈSE DE NANOSTRUCTURES MÉTALLIQUES SOUS FAISCEAU D'IONS

Abstract : This work presents an original approach of the synthesis by ion implantation of buried nanostructures. This non-equilibrium thermodynamics synthesis includes two steps : the first is to control the formation of nanocavities in the semiconductor matrix, the second is to use the created free surfaces in order to favor the growth of silicide by trapping the point defects (vacancies, interstitials) associated to implantation or the implanted elements. The management of the first stage involves the control of the size distribution, density and location of nanocavities. This thesis presents a detailed study of the formation of nanocavities, through the variation of experimental parameters such as the implantation energy and temperature or the annealing time. The nucleation-growth mechanisms involved have been studied. A noticeable result of this first step get the point about the balance time dependence of the 2 mechanisms involved in the growth process of (nano)cavities. At the very beginning of the annealing the main mechanism occurring is a migration-coalescence including nanobulles and vacancy-helium complexes leading to the cavities formation. Then, related to the helium exodiffusion, an Ostwald ripening mechanim, progressively appeared between the nanocavities and cavities. The second step approach was made in the case of cobalt and nickel. In particular, we have shown that the nanocavities allow the epitaxial growth of CoSi2 nanoprecipitates during Co implantation at 650 ° C, while the classical synthesis of CoS2 precipitates coherent with the matrix of Si requires annealing at 1000 ° C. We discuss this result in the light of the nucleation-growth model associated with those disilicide metals, and propose an explanation related to the trapping of vacancies by nanocavities. Besides the technical implantation and characterization of ion beam, used in the sample synthesis, the main investigative technique used in this work is the conventional Transmission Electron Microscopy (TEM). The observations under bright field allowed to identify and quantify nanocavities formation while, from dark field observations, I was able to determine the nature of precipitates (coherent or semi-coherent interface growth with the matrix).
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Submitted on : Tuesday, October 12, 2010 - 10:53:05 PM
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My-Anh Nguyen. SYNTHÈSE DE NANOSTRUCTURES MÉTALLIQUES SOUS FAISCEAU D'IONS. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2009. Français. ⟨tel-00525840⟩

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