“…In contrast to these measurements, atomicscale studies of copper in Cl-containing electrolytes up to now were limited to the double layer potential regime or growth at very low deposition rates [5,6,8,9], where Cu (001) grows exclusively via a step-flow mechanism. How the atomic-scale growth proceeds under conditions resembling those during industrial electroplating is currently unclear.We recently demonstrated for the case of Au homoepitaxial deposition and dissolution that in situ SXRD allows studying very fast electrochemical growth, up to 20 monolayers (ML) per second [10,11], i.e., close to technologically relevant rates. For diffusion-limited Au deposition from a Cl-containing electrolyte on unreconstructed Au (001), these studies revealed a pronounced dependence of the growth behavior on the deposition potential.…”