Ag adatoms on Si(111)5x2-Au surface

TL;DR

This study combines STM and DFT to analyze Ag adatoms on Si(111)5x2-Au, revealing disordered adatom arrangements and multiple nearly degenerate structural models, emphasizing the surface's electronic stabilization.

Contribution

It provides the first combined experimental and theoretical analysis of Ag adatoms on Si(111)5x2-Au, showing disordered adatom positions and multiple stable structural configurations.

Findings

Ag adatoms do not form ordered chains with 5x4 periodicity.

Multiple structurally similar models are nearly degenerate in energy.

Ag adatoms occupy various nonequivalent positions, indicating electronic stabilization.

Abstract

Using scanning tunneling microscopy together with the first-principles density functional theory calculations we study structural properties of the Si(111)5x2-Au surface covered by Ag adatoms. The STM topography data show that a submonolayer coverage of Ag does not lead to a well-ordered adatom chain structure with a periodicity 5x4, as it was observed for Si, Pb and In adatoms. Instead of that, we observe Ag adatoms located in different nonequivalent positions within the unit cell, which confirms the electronic nature of stabilization of the Si(111)5x2-Au surface. Moreover, the DFT calculations give five different structural models of the Si(111)5x2-Au/Ag surface. All the models are almost degenerate in energy, which further supports the above scenario.