Interplay of electronic structure and atomic ordering on surfaces: Momentum-resolved measurements of Cs atoms adsorbed on a Ag(111) substrate

TL;DR

This study uses momentum-resolved photoemission to show how adsorbates like Cs on Ag(111) surfaces modify surface states and influence atomic ordering, explaining previously puzzling superlattice structures.

Contribution

It provides experimental evidence linking adsorbate-induced surface potential changes to modifications in surface state properties and atomic ordering.

Findings

Surface state Fermi wave vector increases by ~100% at 0.03 ML Cs coverage.

Adsorbate-induced surface potential alterations significantly affect atomic ordering.

Results explain the small lattice constant observed in Cs/Ag(111) superlattices.

Abstract

Surface-state mediated interactions between adsorbates on surfaces can be exploited for the fabrication of self-organized nanostructures such as two-dimensional superlattices of adatoms. Using angle-resolved photoemission we provide experimental evidence that these interactions can be drastically modified by adsorbate-induced alterations in the surface potential barrier. This, in turn, will cause significant changes in the ordering of the adsorbates. For the studied case example of Cs adatoms on Ag(111) our momentum-resolved measurements reveal the surface state Fermi wave vector to be increased by as much as $\sim$100% for coverages around 0.03 ML. Our results unravel the origin for the hitherto puzzling and unexpectedly small lattice constant in the adatom superlattice observed for this system.