Influence of the tip on electrode processes and on morphologies studied by in situ STM: Cu/Au

A smooth surface that may be amorphous was formed on a working electrode of polycrystalline gold by sweeping the potential. In an electrolyte of 0.01 M copper sulphate and 0.01 M sulphuric acid the morphology of the gold surface and of copper deposits were followed by in situ STM. Gold surfaces which had previously been subjected to many cycles of potentiostatic bulk copper electrodeposition exhibited a characteristic granular structure. On top of the granular structure the smooth gold surface was built up by surface diffusion, except underneath the tip, which shows that in situ STM only probes the surface locally. The action of the tip creates a cavity in the surface. From simultaneous recordings of current-voltage diagrams and of in situ STM images it is suggested that both surfaces' structural transformations and gas evolution contribute to the total charge passed. The potential of the electrode process depends linearly on the tip potential and it was found that the electrode process observed by in situ STM can be related to features of the current-voltage diagrams and of cyclic voltammograms only when the tip potential is zero.