In situ scanning tunneling microscopy of electrochemical oxidation of single crystal Au(100) surface in aqueous solution

Department of engineering science, Faculty of engineering, Tohoku University, Sendai 980, Japan.

Abstract

In situ electrochemical scanning tunneling microscopy (ESTM) was applied to gold surfaces (Au(100)) in an aqueous perchloric acid solution. Images observed on fully oxidized surfaces seemed to be similar to those in the double layer region. This indicated that oxide layers such as AuOH and AuO were uniformly formed on the surface. New islands of a height of ca. 0.15 nm were observed on partially oxidized surfaces, suggesting that the AuOH layer was formed by an island-growth mechanism. Pits and islands of monatomic height were simultaneously created by rather mild oxidation-reduction cycles. The surface diffusion of Au was also investigated.

Résumé

On a appliqué la microscopie à effet tunnel in-situ dans les conditions de l’électrochimie à des surfaces d’or Au(100) au contact de solutions aqueuses d’acide perchlorique. Les images observées, sur des surfaces complètement oxydées, paraissent semblables à celles obtenues dans la région de couche double. Ceci montre que les couches d’oxydes tels que AuOH et AuO se forment uniformément sur la surface. Observables sur des surfaces partiellement oxydées, des îlots d’une hauteur 0.15 nm apparaissent, suggérant que la couche AuOH est formée par un mécanisme de croissance par Ilots. Des cycles d’oxydation-réduction modérée créent simultanément des piqûres et des Ilots de hauteurs monoatomiques.