Auger electron spectroscopy was used to study the diffusive spreading and adsorption of pure Bi, and Pb-11at%Bi, precursor films on Cu(111) surfaces; from droplets of the various materials. It was found that the Bi diffusion coefficient increased with Bi coverage. The Bi diffusion coefficient remained approximately constant in the intermediate-coverage range. This was assumed to be due to the formation of an ordered hexagonal Bi overlayer. In the case of Pb–Bi alloy spreading, the presence of Bi appreciably slowed the Pb diffusion kinetics. The kinetics of Bi spreading were also slower in the presence of Pb; but the effect was less marked. The equilibrium concentrations at the Pb-Bi drop surface, and in the surrounding precursor film, were both Bi-enriched.

Diffusion Kinetics of Bi and Pb–Bi Monolayer Precursing Films on Cu(111). J.Moon, P.Wynblatt, S.Garoff, R.Suter: Surface Science, 2004, 559[2-3], 149-57