The initial stages of silver fluorination: a scanning tunneling microscopy investigation

TL;DR

This study uses low-temperature scanning tunneling microscopy to investigate the initial stages of silver fluorination on Ag(100) and Ag(110) surfaces, revealing adsorbate species, their shapes, and adsorption sites.

Contribution

It provides detailed STM characterization of fluorine adsorption sites and topographies on silver surfaces during early fluorination stages.

Findings

On Ag(100), one adsorbate species shows bias-dependent shape changes.

On Ag(110), three distinct adsorbate topographies are observed.

Adsorbates occupy hollow, short-bridge, and top sites with specific abundances.

Abstract

We use low-temperature scanning tunneling microscopy (LT-STM) to characterize the early stages of silver fluorination. On Ag(100), we observe only one adsorbate species, which shows a bias-dependent STM topography. Notably, at negative bias voltages, $V_{\rm B}<0$, the apparent shape can be described as a round protrusion surrounded by a moat-like depression (sombrero). As the voltage increases, the apparent shape changes, eventually evolving into a round depression. From the STM images, we determine the adsorption site to be the hollow position. On Ag(110) we find adsorbates with three distinct STM topographies. One type exhibits the same shape change with $V_{\rm B}$ as observed on Ag(100), that is, from a sombrero shape to a round depression as the voltage changes from negative to positive values; the other two types are observed as round depressions regardless of $V_{\rm B}$. From the STM images, we find the three adsorbates to be sitting on the short-bridge, hollow and top position on the Ag(110) surface, with a relative abundance of 60\%, 35\% and 5\%.