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New insights on the Cd UPD on Au(111)
Author(s) -
del Barrio M. C.,
García S. G.,
Mayer C. E.,
Salinas D. R.
Publication year - 2008
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.2664
Subject(s) - underpotential deposition , scanning tunneling microscope , alloy , chemistry , nucleation , diffusion , monolayer , crystallography , electrochemistry , polarization (electrochemistry) , surface diffusion , vacancy defect , analytical chemistry (journal) , materials science , electrode , nanotechnology , adsorption , cyclic voltammetry , thermodynamics , biochemistry , physics , organic chemistry , chromatography
The Cd underpotential deposition (UPD) process on Au(111) was analyzed by means of combined electrochemical measurements and in situ scanning tunneling microscopy (STM). In the underpotential range 300⩽Δ E (mV) ⩽400, 2D Cd islands are formed on the fcc regions of the Au(111)‐(√3 × 22) reconstructed surface without lifting the reconstruction. At lower underpotentials, the 2D Cd islands grow and, simultaneously, new 2D islands nucleate and coalesce with the previous ones forming a complete condensed Cd monolayer (ML). STM images and long time polarization experiments performed at Δ E = 70 mV demonstrate the formation of an AuCd surface alloy. At Δ E = 10 mV, the formation of the complete Cd ML is accompanied by a significant AuCd surface alloying and the kinetic results reveal two different solid‐state diffusion processes. The first one, with a diffusion coefficient D 1 = 4 × 10 −17 cm 2 s −1 , could be ascribed to the mutual diffusion of Au and Cd atoms through a highly distorted (vacancy‐rich) AuCd alloy layer. The second and faster diffusion process ( D 2 = 7 × 10 −16 cm 2 s −1 ) is associated with the appearance of an additional peak in the anodic stripping curves and could be attributed to the formation of another Cd z Au x alloy phase. Copyright © 2008 John Wiley & Sons, Ltd.