Effects of Oxygen Adsorption on the Surface State of Epitaxial Silicene on Ag(111)

TL;DR

This study investigates how oxygen adsorption affects the surface states of epitaxial silicene on Ag(111), revealing decoupling of Si-Ag bonds and changes in electronic structure through experimental and theoretical methods.

Contribution

It provides new insights into the chemical reactivity and electronic structure evolution of silicene on Ag(111) during oxidation, combining STM, ARPES, XPS, and first-principles calculations.

Findings

Oxygen adsorption causes gradual decay of hybridized surface states.

XPS confirms decoupling of Si-Ag bonds after oxygen treatment.

Silicene's high chemical activity is linked to Si pz states.

Abstract

Epitaxial silicene, which is one single layer of silicon atoms packed in a honeycomb structure, demonstrates a strong interaction with the substrate that dramatically affects its electronic structure. The role of electronic coupling in the chemical reactivity between the silicene and the substrate is still unclear so far, which is of great importance for functionalization of silicene layers. Here, we report the reconstructions and hybridized electronic structures of epitaxial 4x4 silicene on Ag(111), which are revealed by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. The hybridization between Si and Ag results in a metallic surface state, which can gradually decay due to oxygen adsorption. X-ray photoemission spectroscopy confirms the decoupling of Si-Ag bonds after oxygen treatment as well as the relatively oxygen resistance of Ag(111) surface, in contrast to 4x4 silicene [with respect to Ag(111)]. First-principles calculations have confirmed the evolution of the electronic structure of silicene during oxidation. It has been verified experimentally and theoretically that the high chemical activity of 4x4 silicene is attributable to the Si pz state, while the Ag(111) substrate exhibits relatively inert chemical behavior.