X-ray Reflectivity Studies of Atomic-level Surface-segregation in a Liquid Eutectic Alloy of AuSn

TL;DR

This study uses X-ray reflectivity to analyze atomic-level surface segregation in a liquid AuSn alloy, revealing layered surface composition that challenges existing theoretical models regarding surface tension.

Contribution

It provides detailed atomic-scale surface composition profiles of AuSn alloy, highlighting discrepancies with current surface segregation theories.

Findings

Surface segregation extends up to three atomic layers.

Top layer is nearly pure Sn, second layer is nearly pure Au.

Measured surface tension cannot be fully explained by existing theories.

Abstract

X-ray reflectivity studies reveal atomic-level surface-segregation at the free surface of the eutectic Au71Sn29 liquid alloy. The surface-segregation extends up to three layers, in which the top layer is almost a pure monolayer of Sn, the second layer is almost a pure monolayer of Au and the third layer appears to be slightly enhanced in Au. Although the surface-segregation concentration profiles can be qualitatively accounted for by the theories of Defay-Prigogine and Strohl-King, they cannot satisfactorily account for the measured surface tension. PACS numbers: 61.20.-p, 61.10.-i, 68.03.-g