Experimental evidence for a wetting transition in liquid Ga-Pb alloys

The surface composition of Ga-rich Liquid in equilibrium with Ph-rich solid has been investigated between 508 K and the monotectic temperature (586 K) of the Ga-Pb system using Auger spectroscopy. A Ph-rich layer is shown to thicken up to 9 equivalent monolayers of Pb at the surface of the liquid as the temperature increases. The thickness of the surface layer diverges logarithmically as the composition of the liquid approaches the monotectic composition. This is the signature of the existence of complete wetting in the Ga-Pb system occurring in the metastable region of coexistence of the two liquids.