Underpotentially deposited thallium on silver (111) byin situsurface x-ray scattering

Abstract

Using in situ surface x-ray scattering, we have investigated the atomic structure, the stability, and the dependence of the structure on electrode potential for electrochemically deposited Tl monolayers and bilayers on Ag(111). The layers were formed by underpotential deposition (UPD) at electrode potentials positive of the reversible potential for bulk Tl deposition. At potentials between -475 and -680 mV (versus Ag/AgCl), the Tl deposit forms an incommensurate, hexagonal two-dimensional (2D) monolayer that is compressed relative to bulk Tl by 1.4–3.0 % and rotated from the Ag [011¯] direction by Ω=4°–5°. The structure of the monolayer does not change over at least 24 h (the longest we waited). From diffraction scans of the Tl Bragg rods, we find that the in-plane and vertical root-mean-square displacement amplitudes are 0.36±0.1 and 0.46±0.1 Å, respectively.