Resonant x-ray Scattering From the Surface of a Dilute Liquid Hg–Au Alloy

Abstract

We present the rst resonant x-ray re ectivity 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 re ectivity measurements near the Au L III 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.

Atomic-Scale Surface Demixing in a Eutectic Liquid BiSn Alloy

“…The case for new studies is strongly reinforced by the existence of a growing class of surface-induced ordering phenomena that have been observed in metallic liquids. In addition to the surface demixing reported here, these include layering [7,8,9,10,11], relaxation [11], segregation [2,3,4,30], wetting transitions [14,31], and surface freezing [32]. Finally, there is a basic unresolved question of whether the surfaces of liquid metals are fundamentally different from those of non-metallic liquids [33].…”

“…Liquid metals are ideal systems for studying Gibbs adsorption due to the nearly spherical shape of interacting particles, relative simplicity of the short-range interactions and the availability of bulk thermodynamic data for many binary alloys. While certain aspects of Gibbs theory can be tested through macroscopic measurements of surface tension or adsorption isotherms, very few direct measurements of the atomic-scale composition profiles of the liquid-vapor interface were reported [2,3,4]. In addition to fundamental questions related to surface thermodynamics of binary liquids, BiSn-based alloys have been widely studied as substitutes for Pb-based low-melting solders [5].…”

“…Over the last decade XR revealed the long-predicted surface-induced atomic layering at the liquid-vapor interface for a number of elemental liquid metals [7,8,9,10,11]. Resonant XR near an absorption edge resolved the density profile of each component in GaIn [2], HgAu [3] and BiIn [4] liquid binary alloys. The enhancement of the concentration of the low-surface-tension component was invariably found to be confined to the topmost surface monolayer, with subsequent layers having the composition of the bulk, in accord with the simplest, and widely used, interpretation of the Gibbs rule.…”

Pushing the Limits of Mercury Sensors with Gold Nanorods

“…The interaction between these two elements has been extensively studied by monitoring physical properties of Au upon Hg adsorption. Numerous gravimetric sensors exist based on the mass change when Hg adsorbs onto a gold-coated piezoelectric substrate. − Au films (∼10−40-nm thickness) have also been employed to monitor Hg upon changes in resistivity, − reflectivity, − and surface plasmon resonance (SPR) . We determine Hg upon wavelength changes in absorption spectra of Au nanorods.…”

“…Numerous gravimetric sensors exist based on the mass change when Hg adsorbs onto a gold-coated piezoelectric substrate. [17][18][19][20][21][22] Au films (∼10-40-nm thickness) have also been employed to monitor Hg upon changes in resistivity, [23][24][25] reflectivity, [26][27][28] and surface plasmon resonance (SPR). 29 We determine Hg upon wavelength changes in absorption spectra of Au nanorods.…”