WETTING PHENOMENA AT THE LIQUID-VAPOR INTERFACE OF GALLIUM-BISMUTH ALLOYS STUDIED BY SPECTROSCOPIC ELLIPSOMETRY

In order to study phase transitions at interfaces of liquid metallic a lloys, spectroscopic ellipsometry was employed in the energy range 0.7 eV less than or equal to h nu less than or equal to 3.2 eV. The compl ex dielectric function epsilon = epsilon(1) + i epsilon(2) of binary g allium-bismuth alloys was measured at bismuth concentrations 0 less th an or equal to x(Bi) less than or equal to 0.28 and up to 621 K above the critical demixing temperature, 535 K. The character of the epsilon (1)-spectra undergoes a pronounced change from Ga-like to Bi-like beha vior when the bismuth concentration in the liquid phase exceeds x(Bi) = 0.085 which corresponds to the monotectic triple point. This change is interpreted as interfacial wetting of the gallium rich phase by a l iquid bismuth rich phase.