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La matière dense et tiède (WDM) est un régime caractérisé par une densité proche du solide pour une température avoisinant celle de Fermi. Pour étudier cet état de la matière, dans cette thèse, une expérience d'interférométrie dans le domaine des fréquences est mise en place afin de mesurer la phase et la réflectivité - dans les deux directions de polarisation S et P - d'une onde sonde en réflexion sur un échantillon chauffé de manière très brève par une impulsion laser ultra-courte (sub-100fs). Il est alors porté dans un état hors-équilibre. Une méthode basée sur les mesures de réflectivité est mise en place pour contrôler la forme de l'interface entre le vide et la matière chauffée. Pour des fluences laser de l'ordre de 1 J/cm2, l'hydrodynamique d'un échantillon chauffé est étudiée par la mesure du déplacement de la surface et comparée au code hydrodynamique à deux températures ESTHER. Ensuite, la fonction diélectrique à 800 nm et 400 nm est déduite des mesures expérimentales et certaines quantités en sont extraites comme la densité électronique, la température électronique et les fréquences de collision en régime WDM. Elles sont par la suite comparées avec des modèles couramment utilisés. / The Warm Dense Matter (WDM) regime is characterised by a density close to the solid density and an electron temperature close to the Fermi temperature. In this work, the nonequilibrium Warm Dense Matter is studied during the solid to liquid phase transition induced by an ultra short laser interacting with a solid. A 30 femtoseconds time resolution pump-probe experiment (FDI) is set up, yielding to the measurement of the heated sample complex reflectivity for both S and P polarisation.We have determined a criterion based on the measured reflectivities, which permits to control the interface shape of the probed matter. For pump laser fluences around 1 J/cm2, the hydrodynamics of the heated matter is studied and experimental results are compared to the two-temperatures code ESTHER. Furthermore, the evolution of the dielectric function at 800 nm and 400 nm is inferred from our measurements on a sub-picosecond time-scale. Within the Drude-Lorentz model for the conduction electrons, the dielectric function yields information such as ionisation state, electronic temperature and electron collision frequency.

Made available in DSpace on 2016-12-08T15:56:18Z (GMT). No. of bitstreams: 1 Luiz Antonio Alves.pdf: 4887074 bytes, checksum: 2921556dad24ae9311fe651e5a0ccdcf (MD5) Previous issue date: 2014-07-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Titanium nitride (TiN) films with niobium (Nb) addition (TiN[Nb], 0,01 < Nb/Ti < 0,15) were obtained by sputter deposition in a triode magnetron sputtering system from a mosaic target of titanium with niobium inserts at the erosion zone. The effects of Nb/Ti in surface morphology were analyzed by atomic force and confocal microscopy measurements. The reflectivities of the films with niobium incorporation are in agreement with the Drude-Lorentz model. The constants obtained by the fitting show an increase in plasma frequency and relaxation time with increased Nb/Ti ratio, indicating an increase in the number of charge carriers. The color parameters according CIELab system show an increase in L*, a* and b* coordinates. The visual analysis indicates an increased red tone when compared with pure TiN film in agreement with the increased absolute values of a* coordinates. / Filmes de nitreto de titânio com adição de nióbio ((TiN[Nb], 0,01 < Nb/Ti < 0,15) foram depositados pelo processo de pulverização catódica utilizando um sistema Triodo Magnetron Sputtering. A pulverização catódica de Titânio e Nióbio foi feita a partir de um alvo de titânio com insertos de nióbio dispostos na região de erosão. Foram analisados os efeitos da razão Nb/Ti na morfologia superficial do filme através de microscopia de força atômica e confocal. As medidas de refletividade dos filmes de TiN[Nb] obedecem perfeitamente o modelo de Drude-Lorentz. As constantes obtidas pelo modelo de Drude-Lorentz mostram um aumento nos valores da frequência de plasma e tempo de relaxação com o aumento na razão Nb/Ti, indicando que a presença de nióbio aumenta o número de portadores de carga. Os parâmetros de cor segundo o sistema CIELab mostram um aumento nas coordenadas L*, a* e b*. A análise visual das amostras mostra uma tonalidade avermelhada, quando comparadas com o filme contendo somente TiN, em concordância com o aumento absoluto nas coordenadas a*.