The effects of Tl additions on a wetting-related adsorption transition in liquid Ga-Pb alloys

This paper reports the effects of Tl additions on Pb adsorption to the surf ace of liquid Ga-Pb alloys. Adsorption of Pb and Tl was measured by Auger e lectron spectroscopy, as a function of temperature, for six ternary alloys ranging in composition from Ga-3.33 x 10(-1) at.% Pb-1.65 x 10(-1) at.% Tl to Ga-1 x 10(-4) at.% Pb-5 x 10(-5) at.% Tl, all having a 2:1 ratio of Pb:T I. The temperature of the prewetting critical point in binary Ga-Pb alloys had previously been estimated to lie at about 240 K. The motivation for thi s work was to raise the temperature of the prewetting critical point by the addition of Tl. However, the results show that whereas Pb adsorption is en hanced by Tl additions, as expected from simple models, the estimated tempe rature of the prewetting critical point is lowered even further to about 21 5 K. (C) 2000 Elsevier Science B.V. All rights reserved.