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Crystalline Surface Phases of the Liquid Au-Si Eutectic Alloy

Oleg G. Shpyrko·Reinhard Streitel·Venkatachalapathy S. K. Balagurusamy·Alexei Yu. Grigoriev·Moshe Deutsch·Benjamin M. Ocko·Mati Meron·Binhua Lin·Peter S. Pershan
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Abstract

A two dimensional crystalline layer is found at the surface of the liquid eutectic Au$_{82}$Si$_{18}$ alloy above its melting point $T_M=359 ^{\circ}$C. Underlying this crystalline layer we find a layered structure, 6-7 atomic layers thick. This surface layer undergoes a first-order solid-solid phase transition occurring at $371 ^{\circ}$C. The crystalline phase observed for T$>$371 $^{\circ}$C is stable up to at least 430 $^{\circ}$C. Grazing Incidence X-ray Diffraction data at T$>$371 $^{\circ}$C imply lateral order comprising two coexisting phases of different oblique unit cells, in stark contrast with the single phase with a rectangular unit cell found for low-temperature crystalline phase $359 ^{\circ}$C$<T<371 ^{\circ}$C.

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Oleg G. Shpyrko, Reinhard Streitel, Venkatachalapathy S. K. Balagurusamy, Alexei Yu. Grigoriev, Moshe Deutsch, Benjamin M. Ocko, Mati Meron, Binhua Lin, Peter S. Pershan. 2007-09-15. Crystalline Surface Phases of the Liquid Au-Si Eutectic Alloy. https://doi.org/10.1103/physrevb.76.245436

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