Fig. 2

Electrochemical deposition of Cu at lower growth rate. a Bright-field images extracted from Supplementary Movie M2. The electrolyte is the same as in Fig. 1, but with cycles of 75 nA for 10 s/zero current for 10 s applied repeatedly after an initial cleaning cycle of 15 s. Time t = 0 indicates the end of the initial cleaning cycle. An image is shown then and after every five current pulses. Each set of five pulses takes 100 s and there is a longer interval between each set that is not included in the indicated time. Scale bar 300 nm. b Interface position from movie frames, color coded by normal growth speed. Scale bar 200 nm. c Structural and electrical data as a function of time: growth height (black = average, red = maximum, and blue = minimum), relative length of the growth front, and potential. In the potential, the initial peak is associated with the electrode cleaning cycle; the gray bars indicate the intervals between groups of five current pulses. The average growth rate during the on-time is 1.3 nm s⁻¹, equivalent to current density 35 A m⁻². The staircase shape of the growth front position reflects the growth-pause cycles. Slow etching (more than 10 × slower) retracts the growth front slightly during times of zero current (Methods). d RMS roughness of the growth interface shown as a log–log plot with best-fitting straight lines and exponents. The off time is included to reflect that diffusive behavior is governed by the total time