X-ray reflectivity studies of atomic-level surface-segregation in a liquid eutectic alloy of AuSn

Abstract

X-ray reflectivity studies reveal atomic-level surface-segregation at the free surface of the eutectic ${\mathrm{Au}}_{71}{\mathrm{Sn}}_{29}$ 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.