In-situ STM studies of thallium underpotential deposition on Au(111) single-crystal electrode in acid solution

摘要

The structure of electrodeposited Tl adlayers on Au(111) in 0.1 M. HClO$-4$/ has been investigated using in-situ scanning tunneling microscopy method. Incommensurate, rotated hexagonal (RHCP) Tl adlayer was found, within a wide potential window, between Tl bulk deposition at $MIN@0.7 V and $MIN@0.4 V. This adlayer is closely packed with Tl interatomic distance of 3.4 $POM 0.2 angstroms, its rotation from the gold substrate axis is 6$+0$/ $POM 1$+0$/ and its coverage is 0.74. At slightly more positive potentials, between $MIN@0.45 V and $MIN@0.37 V, low coverage 2 $MUL 2 phase of Tl was found, coexisting together with RHCP monolayer. At the potential region between $MIN@0.35 V and 0.8 V both ordered Tl phases disappeared and instead the formation of considerable amount of pits at the surface has been observed.