title: Initiation and inhibition of dealloying of single crystalline Cu3Au (111) surfaces.
abstract: Dealloying is widely utilized but is a dangerous corrosion process as well. Here we report an atomistic picture of the initial stages of electrochemical dealloying of the model system Cu(3)Au (111). We illuminate the structural and chemical changes during the early stages of dissolution up to the critical potential, using a unique combination of advanced surface-analytical tools. Scanning tunneling microscopy images indicate an interlayer exchange of topmost surface atoms during initial dealloying, while scanning Auger-electron microscopy data clearly reveal that the surface is fully covered by a continuous Au-rich layer at an early stage. Initiating below this first layer a transformation from stacking-reversed toward substrate-oriented Au surface structures is observed close to the critical potential. We further use the observed structural transitions as a reference process to evaluate the mechanistic changes induced by a thiol-based model-inhibition layer applied to suppress surface diffusion. The initial ultrathin Au layer is stabilized with the intermediate island morphology completely suppressed, along an anodic shift of the breakdown potential. Thiol-modification induces a peculiar surface microstructure in the form of microcracks exhibiting a nanoporous core. On the basis of the presented atomic-scale observations, an interlayer exchange mechanism next to pure surface diffusion becomes obvious which may be controlling the layer thickness and its later change in orientation.
authors.affiliation: Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, D-40237 Düsseldorf, Germany.
authors.forename: Aparna
authors.initials: A
authors.lastname: Pareek
authors.forename: Sergiy
authors.initials: S
authors.lastname: Borodin
authors.forename: Asif
authors.initials: A
authors.lastname: Bashir
authors.forename: Genesis Ngwa
authors.initials: GN
authors.lastname: Ankah
authors.forename: Patrick
authors.initials: P
authors.lastname: Keil
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Eckstein
authors.forename: Michael
authors.initials: M
authors.lastname: Rohwerder
authors.forename: Martin
authors.initials: M
authors.lastname: Stratmann
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Gründer
authors.forename: Frank Uwe
authors.initials: FU
authors.lastname: Renner