Crecimiento de bismuto sobre sustratos semiconductores por electrodeposición (Electrodeposition of bismuth on semiconductor substrates)

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El bismuto (Bi) es un semimetal con propiedades electrónicas muy interesantes incluyendo una longitud de onda de Fermi grande que lo convierte en un potencial candidato para la observación de efectos cuánticos de tamaño (QSE) en nanoestructuras. Para poder observarlos es necesario obener películas ultra delgadas y de alta calidad sobre sustratos aislantes o semiconductores. En este trabajo presentamos un estudio del crecimiento de películas delgadas de Bi sobre sustratos semiconductores de GaAs, con diferentes orientaciones y dopados. Se muestra como, en condiciones de oscuridad, el potencial de crecimiento y la morfología de las películas depende fuertemente de la orientación. Voltametrías cíclicas y la morfología de las películas crecidas, estudiada con AFM, sugiere la presencia de una capa de hidrógeno adsorbida en la superficie del sustrato que dificulta la nucleación de la película, aumentando la rugosidad y disminuyendo el grado de compactación. Las muestras con mejores propiedades - baja rugosidad y mejor orientación - han sido obtenidas en los sustratos de GaAs de menor dopado. [ABSTRACT] Bismuth (Bi) is a semimetal with very interesting electronic properties including a long Fermi wavelength which make it a potential candidate for the observation of quantum size effects (QSE) in nanostructures. For this observation, high quality ultra-thin Bi films have to be grown on insulating or semiconducting substrates. In this work we present a study of the growth of Bi thin flms on GaAs semiconductor substrates, with different orientations and doping. We show that, under dark conditions, growth potential ando films morphology strongly depends on the orientation. Cyclic voltammetries and the morphology of the grown films, studied by AFM, suggest the presence of an adsorbed hydrogen layer on the substrate surface that hinders the nucleation of the film, increasing the roughness and decreasing the compactness. The samples with best properties - low roughness and better orientation - have been obtained in the lowest doped GaAs substrates.
Máster de Física Aplicada. Facultad de Ciencias Físicas. Curso 2011-2012
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