Theory of Adsorption and Surfactant Effect of Sb on Ag (111)

TL;DR

This study uses first-principles calculations to explore how Sb adsorbs on Ag (111) surfaces and how it influences Ag atom mobility, leading to surfactant effects that promote layer formation.

Contribution

It reveals the preferred substitutional adsorption of Sb and its role in reducing Ag adatom mobility, explaining the surfactant effect observed experimentally.

Findings

Sb forms a segregating surface alloy layer on Ag (111)

Sb adsorption reduces Ag adatom mobility

Results explain the surfactant effect of Sb in layer formation

Abstract

We present first-principles studies of the adsorption of Sb and Ag on clean and Sb-covered Ag (111). For Sb, the {\it substitutional} adsorption site is found to be greatly favored with respect to on-surface fcc sites and to subsurface sites, so that a segregating surface alloy layer is formed. Adsorbed silver adatoms are more strongly bound on clean Ag(111) than on Sb-covered Ag. We propose that the experimentally reported surfactant effect of Sb is due to Sb adsorbates reducing the Ag adatom mobility. This gives rise to a high density of Ag islands which coalesce into regular layers.