RHEED investigations of copper deposition on gold in the underpotential region

Abstract

The underpotential deposition of a Cu monolayer on single crystal gold electrodes of (111) and (100) orientation is investigated by cyclic voltammetry and, after removal of the electrode from the electrochemical cell and subsequent transfer into a vacuum chamber, by reflected high energy electron diffraction (RHEED). It is found, that underpotential deposition of about 2/3 of a Cu monolayer causes a (√3 ×√3) R30 superstructure to appear in RHEED. After stripping, a faint superstructure of the same type is still visible in the RHEED pattern. Deposition and stripping of bulk Cu also rearranges the Au electrode surface in a characteristic way producing an additional (2 × 2) superstructure. No such structure is seen when the electrode potential is cycled only in the double layer charging region of Au and in the oxygen adsorption region. The observed RHEED patterns are discussed in terms of surface rearrangements during Cu deposition due to the formation of ordered surface and bulk alloys.