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Morphologie de surfaces vicinales de métaux purs et d’alliages : stabilité et rugosité. Expériences et modélisations

Abstract : For technological applications in relation to the use of surface properties, the understanding and control of roughness and instabilities phenomena for pure metal and alloy crystal surfaces is a prerequisite. For that purpose, three surfaces have been experimentally investigated: Cu(1,1,5), Cu83Pd17(1,1,5) and Cu3Au(1,1,11). The Cu(1,1,5) surface has been studied by variable temperature STM (Scanning Tunneling Microscopy) (300 K-365 K). For all the explored temperature range, the surface is stable and not rough. Comparison of experimental results with Monte Carlo simulations allowed us to determine the strength of the step-step A/L^2 elastic repulsion A=100 K and the formation energy of kinks at step edges Ek=1430 K. The determination of the roughening temperature for Cu(1,1,5) lead us to extend this result by calculating the phase diagram of vicinal surfaces in the parameter space (A, Ek and miscut). We have determine the complete (A>0, A<0) phase diagram of a system of interacting steps by the cylinder method (transfer matrix method with periodic limit conditions). As for alloys, the Cu83Pd17(1,1,5) surface has been studied by STM (300 K). This face exhibits a single step structure in contrast with the paired-step structure of the Cu83Pd17(1,1,11) surface and in agreement with a theoretical prediction. The Cu3Au(1,1,11) vicinal surface has been studied by variable temperature STM (300 K - 700 K) and by helium diffraction. We find that steps are paired below the critical temperature for chemical disordering TC (=663 K) while above TC, the surface shows a facetted single-step structure. These findings illustrate the varied manifestation of the influence of chemical order on surface morphology.
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Eric Le Goff. Morphologie de surfaces vicinales de métaux purs et d’alliages : stabilité et rugosité. Expériences et modélisations. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 1999. Français. ⟨tel-03006559⟩

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