Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 21: Phase transitions

O 21.1: Vortrag

Dienstag, 28. März 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 Grigoriev³ — ¹Harvard 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 (q_z = 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 T_melt and below T_melt + 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.