Effect of Adsorbed Iodine on the Dissolution and Deposition Reactions of Ag(100):  Studies by In Situ STM

Abstract

In situ scanning tunneling microscopy has been employed to determine the structure of iodine adlayers formed on Ag(100) and to evaluate the role of such adlayers in the dissolution and deposition reactions of the substrate in perchloric acid. In the double-layer potential region, iodine was found to possess a c(2 × 2) structure; this structure was unaffected by anodic dissolution of the Ag substrate. On both bare and I-pretreated Ag(100) surfaces, the anodic dissolution of Ag occurred exclusively at step-edges in a layer-by-layer mechanism. However, whereas jagged monatomic step lines were found on the I-free surface, relatively smooth (straight) step lines existed along the direction of iodine atomic rows ({100}) on the Ag(100)-I surface. Etching rates on Ag(100)-I were dependent on the direction of the step-edges, which suggests that the adlayer near such edges plays a crucial role in the dissolution reaction. The deposition of Ag on Ag(100)-I was also found to occur preferentially at step-edges aligned along a particular direction. A model is proposed to explain the anisotropic dissolution and deposition.

Structural transitions of chemisorbed iodine on Cu()

“…Calculations have shown that halide adlayers on (1 0 0) metal surfaces tend to form commensurate structures, mainly c(2 · 2), reflecting the higher substrate corrugation potential [14], even if it means overcoming the strong iodine-iodine repulsive interaction due to a smaller NNS below the van der Waals diameter (4.3 Å ). Well known examples are Pt [15], Pd [16], Ag [17].…”

Atomically Controlled Electrochemical Deposition and Dissolution of Noble Metals

“…In this section, the discussion will be concentrated on the anisotropic layer-by-layer dissolution behavior of noble metal electrodes, palladium and gold, catalyzed by an adlayer of adsorbate on the substrate. Similar anisotropic anodic dissolution processes catalyzed by the ordered adsorbed layer have also been observed on S-Ni(100), [106] I-Ni (111), [107] IAg(100) [108] and Cl-Cu(hkl) [109][110][111][112] as well as Cl-Au(hkl) [29][30][31], which will be discussed in the next section in detail.…”

Kinetic Model for Oxide Film Passivation in Aluminum Etch Tunnels

“…The presence of such a layer during dissolution is consistent with recent STM studies of other systems. [13][14][15][16][17][18][19][20][21] Acknowledgments Support for this work was provided by KDK Corporation and by St. Jude Medical. Aluminum foils were provided by KDK Corporation.…”

“…Itaya and co-workers found ordered adsorbed layers of I on Pd, Ag, and Ni, as well as S on Ni, during dissolution processes. [13][14][15][16] Interestingly, the presence of the I layer on Pd and the S layer on Ni suppressed oxide passivation of these surfaces. Suggs and Bard, Vogt et al, and Wan and Itaya all observed ordered chloride layers on Cu which remained on the surface during dissolution.…”