Imaging three phases of Iodine on Ag (111) using low-temperature scanning tunneling microscopy

TL;DR

This study uses low-temperature STM to analyze iodine adsorption on Ag (111), revealing three distinct phases and novel local structural variations, including the first real-space observation of the 'triangular' phase.

Contribution

It provides detailed real-space characterization of iodine phases on Ag (111), including the first LT-STM observation of the 'triangular' phase and its local variations.

Findings

Identified three iodine phases on Ag (111) with increasing coverage.

First LT-STM observation of the 'triangular' phase.

Revealed local variations and adatom effects on surface reconstruction.

Abstract

We investigated the adsorption of iodine on silver (111) in ultra-high vacuum. Using low-temperature scanning tunneling microscopy (LT-STM) measurements we catalog the complex surface structures on the local scale. We identified three distinct phases with increasing iodine coverage which we tentatively associate with three phases previously reported in LEED experiments (sqrt(3)x sqrt(3)R30, "triangular", "hexagonal"). We used Fourier space and real space analysis to fully characterize each phase. While Fourier analysis most easily connects our measurements to previous LEED studies, the real space inspection reveals local variations in the superstructures of the "hexagonal" and "triangular" phase. The latter, observed here for the first time by LT-STM, stabilized by one or two adatoms sitting at the center of a rosette-like iodine reconstruction. The most stunning discovery is that variation in the adatom separation of the "triangular" phase reconstruct the Ag (111) surface lattice.