Wetting phenomena at the liquid-vapor interface of gallium-bismuth alloys studied by spectroscopic ellipsometry

Abstract

In order to study phase transitions at interfaces of liquid metallic alloys, spectroscopic ellipsometry was employed in the energy range 0.7 eV ≤ hv ≤ 3.2 eV. The complex dielectric function ε = ε1 + iε2 of binary gallium-bismuth alloys was measured at bismuth concentrations 0 ≤ xBi ≤ 0.28 and up to 621 K above the critical demixing temperature, 535 K. The character of the ε1-spectra undergoes a pronounced change from Ga-like to Bi-like behavior when the bismuth concentration in the liquid phase exceeds xBi = 0.085 which corresponds to the monotectic triple point. This change is interpreted as interfacial wetting of the gallium rich phase by a liquid bismuth rich phase.