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Etude de la stabilité des surfaces vicinales des métaux de transition à partir de leur structure électronique et vibrationnelle.

Faical Raouafi
Abstract : Study of the stability of vicinal surfaces in transition metals from their electronic and vibrational structures. This theoretical work is dedicated to the study of vicinal surfaces of Rh, Pd and Cu and, in particular, of their stability with respect to faceting. The manuscript includes three parts. It starts with the calculation of their surface energies, on a rigid lattice at 0K, using a tight-binding method with a basis set including s, p and d atomic valence orbitals. The energies of isolated steps are deduced from this calculation. They allow to determine the shape of adislands built by homoepitaxy on low-index surfaces, as well as step-step interactions which exhibit an oscillatory behavior. This behavior is strongly depending on the types of steps and surfaces. Kink energies are also computed by the same method. The electronic structure is briefly described. Then the vibrational properties of vicinal surfaces of Copper are studied using a semi-empirical potential which leads to good results for the relaxation of surfaces and describes correctly, in the harmonic approximation, their projected phonon band structure. It is thus possible to determine vibrational thermodynamical quantities, such as the root mean square displacement and the free energy. Finally, the stability of vicinal surfaces is discussed with semi-empirical potentials and with the calculation of electronic structure. It is shown that the stability can be inverted as a function of the potential range and that the atomic relaxation plays in favor of the stabilization of the surface but does not change qualitatively the results. Contrary to the semi-empirical potentials, electronic structure calculations open up the possibility of a large variety of behaviors, including a possible faceting of a vicinal surface into other vicinal surfaces. This phenomenon is due to electronic oscillatory step-step interactions. Finally, it is proven that the temperature has a minor effect on the stability of vicinal surfaces, at least up to room temperature.
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Submitted on : Monday, December 16, 2002 - 2:02:29 PM
Last modification on : Monday, December 16, 2002 - 2:02:29 PM
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  • HAL Id : tel-00002142, version 1

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Faical Raouafi. Etude de la stabilité des surfaces vicinales des métaux de transition à partir de leur structure électronique et vibrationnelle.. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00002142⟩

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