Over the past 100 years, electrodeposition has matured to an important method with numerous industrial applications, up to processes in micro- and nanofabrication. Knowledge on electrochemical processes on the atomic scale is still limited, however. While for vapor deposition under vacuum conditions the evolution of the deposit morphology can nowadays be predicted with high precision, a similar predictive understanding of electrodeposition is missing so far. A key issue here is the electrochemical interface where this growth occurs. The structural complexity of this interface on the one hand makes understanding of the elemental processes in nucleation and growth difficult. On the other hand, it is just this complexity that allows to tune electrodeposition processes in ways that are not possible for deposition in vacuum and thus make them attractive for many applications.

In this talk, I will discuss current challenges in developing a true microscopic picture of electrodeposition processes, using examples from us and other groups. The focus will be on puzzling experimental observations and fundamental aspects that we do not yet understand and thus provide a rich field for future research. These include the mechanisms of elemental steps in electrochemical growth processes, such as ion transfer, intra- and interlayer surface diffusion, and the resulting development of the deposit morphology. Of particular interest is how these events are influenced by the electric field and electrolyte species in the electrochemical double layer, which is of key relevance for understanding the effects of overpotential and additives. A further challenge is to extend the insights obtained for electrodeposition of metals to the electrochemical growth of compound materials, such as oxides.