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

Abstract

We investigated the adsorption of iodine on Ag (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 at various iodine coverage which we tentatively associate with three phases previously reported in LEED experiments ((3×3)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, appears to be 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 reflects the Ag (111) surface lattice.