Surface development during electroless copper deposition

We report on the electroless copper deposition with formaldehyde as the reducing agent. The reaction occurs in highly alkaline solutions. Since copper ions are present as EDTA complexes, a catalyst is needed to facilitate copper ion reduction. Methanediolate anions, intermediates of the formaldehyde oxidation, act as such a catalyst. Furthermore, freshly deposited copper exhibits increased catalytic activity toward formaldehyde oxidation. Both effects lead to strong coupling between the anodic and cathodic partial processes. Such a feedback can lead to oscillatory behavior of the deposition reaction. In this work we use scanning tunneling microscopy to study the deposition rate with high spatial resolution. We could establish that the deposition rate fluctuates locally and with time.