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Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 21: Phase transitions

O 21.1: Talk

Tuesday, March 28, 2006, 11:15–11:30, WIL C207

Inplane order observed at the liquid surface of eutectic AuSi above bulk melting temperature — •Reinhard Streitel1, Venkat Balagurusamy1, Peter Pershan1, Oleg Shpyrko2, and Alexei Grigoriev31Harvard University, Cambridge, MA — 2Center for Nanoscale Materials, Argonne National Lab, IL — 3University of Wisconsin-Madison, WI

The liquid surface of eutectic AuSi shows inplane order above bulk melting temperature (T=361 Celsius). Similar behaviour was not observed in any other binary alloy to date. In comparison to other Au based alloys AuSi shows anomalous, enhanced specular X-ray reflectivity (qz = 1.0 − 2.5 Å) indicating a pronounced surface layering. GID measurements at different temperatures show reversible structural changes at the surface about 12 Celsius above bulk melting temperature. For low temperatures (above Tmelt and below Tmelt + 12 Celsius) GID measurements indicate a powder like 2D inplane structure of the eutectic surface. At higher temperatures (380 Celsius) GID measurements indicate a structural change. At T=430 Celsius no stable phase is present. The inplane correlation length estimated from the FWHM for the low temperature phase is about 200nm.

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