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Etude STM in situ de la microstructure et de la croissance de films ultraminces d'alliages sur Au(111) synthétisés par co-dépôt

Abstract : The fact that, in ultrathin films a large part of the atoms are located at the two interfaces substrate-film and film-environment, induces specific film microstructures and thus interesting new properties different from those of the bulk materials. We studied the microstructure of electrochemically co-deposited binary alloys, composed of an element B and of Ni, where B is either Pd, Au or Ag. We also studied the deposition of B over a predeposited Ni monolayer. In addition we devised a method to maintain the Au(111) surface un-reconstructed during film deposition limiting the alloying process with the substrate. On this un-reconstructed Au(111) surface, we studied the deposition of Ni monolayer which microstructure is well documented on the Au(111) reconstructed surface. We then studied the microstructure of the codeposited alloys as a function of their composition and deposition speed. Furthermore, the B elements (Ag, Au, Pd) allow us to study the influence of the mixing enthalpy on the alloys' microstructure. We showed using in situ scanning tunnelling microscopy that all cases lead to a phase separation but with a specific phase separation length for each case. B = {Ag, Au, Pd} deposition over a Ni monolayer showed that Ni atoms undergo place exchange with B atoms in the Ni layer to form an alloy. Alloys are made out of two phases, one rich or pure in B atoms and the other rich or pure in Ni. Nevertheless, the morphology of those alloys is different than what is obtained with codeposition.
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Contributor : Florian Le Cadre <>
Submitted on : Friday, August 2, 2013 - 1:40:15 PM
Last modification on : Wednesday, March 27, 2019 - 4:18:02 PM
Long-term archiving on: : Sunday, November 3, 2013 - 1:10:11 PM

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Florian Le Cadre, Fouad Maroun, Philippe Allongue. Etude STM in situ de la microstructure et de la croissance de films ultraminces d'alliages sur Au(111) synthétisés par co-dépôt. Matériaux. Ecole Polytechnique X, 2013. Français. ⟨pastel-00850027⟩

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