Resonant X-Ray Scattering from the Surface of a Dilute Hg-Au Alloy

TL;DR

This study uses resonant x-ray reflectivity to analyze the surface structure of a dilute Hg-Au alloy, revealing limited gold segregation and providing new insights into its surface phase behavior.

Contribution

First application of resonant x-ray reflectivity to a liquid metal surface, clarifying gold distribution at the Hg-Au alloy surface.

Findings

Gold concentration at the surface is no more than 30at%.

Pure gold layers do not segregate at the alloy surface.

Surface exhibits a low-density phase with temperature dependence.

Abstract

We present the first resonant x-ray reflectivity measurements from a liquid surface. The surface structure of the liquid Hg-Au alloy system just beyond the solubility limit of 0.14at% Au in Hg had previously been shown to exhibit a unique surface phase characterized by a low-density surface region with a complicated temperature dependence. In this paper we present reflectivity measurements near the Au LIII edge, for 0.2at% Au in Hg at room temperature. The data are consistent with a concentration of Au in the surface region that can be no larger than about 30at%. These results rule out previous suggestions that pure Au layers segregate at the alloy surface.