REFLECTION ELECTRON-MICROSCOPY OF COPPER ELECTROCRYSTALLIZATION ON PLATINUM

Monatomic steps on Pt single crystal surfaces have been directly imaged in a conventional electron microscope in reflection mode. With the reflection electron microscopy (REM) technique the surface topography of Pt single crystal spheres at the progressive stages of Cu electrocrystallization has been studied. Although the formation of Cu submonolayer superstructures on Pt(111) surfaces has not yet been detected, a layered Cu deposition of one monolayer or two and the Stranski-Krastanov type crystal growth, which is influenced by the surface steps, have been observed. Deposition of bulk Cu and subsequent stripping altered the Pt(111) surface, leaving traces of the Cu deposit geometry on the bare Pt surface after removal of Cu by anodic stripping. No such a surface change was visible during Cu adsorption-desorption cycles only in the underpotential region. The observed REM images have been discussed in terms of surface rearrangements during Cu electrocrystallization due to the formation of layered deposition and bulky island crystals.