Downscaling magnetic field gradients for structured copper magnetoelectrodeposition on the micrometer scale

• Shape control of Cu electrodeposits is achieved by tailoring magnetic micro-templates • The deposition potential is identified as a control parameter to enhance structuring • The potential-dependence of the concentration gradient affects ∇ → × F → ∇B • Deposit thickness and morphology are tunable by potential and magnetic field gradient Electrochemical deposition in magnetic field gradients is a promising method to synthesize structured deposits by exploiting the magnetic field gradient force. Typically, magnetic field gradient templates with dimensions in the millimeter range are used, but a downscaling is desirable from fundamental and application points of view. In the present study, pulse reverse plating of copper is performed in combination with four successively downscaled magnetic field gradient templates, which consist of three iron wires with diameters of 1 mm, 500 µm, 250 µm, and 125 µm. Structuring is demonstrated for all four templates, upon downscaling the Fe diameter within the templates. The deposited copper structures closely resemble the calculated profile of the magnetic field gradient term B ∇ B . The application of more negative deposition potentials leads to improved structuring. Based on the analysis of the current transients, this effect is explained by the action of the curl of the magnetic field gradient force, which profits from the faster development of a steep Cu 2+ concentration gradient due to the earlier transfer from a charge-transfer-controlled to a diffusion-limited deposition mode. Significant differences in morphology, ranging from needle-like growth to smooth deposits, are obtained, which vary with the magnetic field gradient profile and the deposition voltage. The results demonstrate that the combination of tailored magnetic field gradient templates and optimized electrochemical parameters offers an advanced route to control the shape and morphology of structured Cu deposits at the micrometer scale, with potential applications in microelectronics and catalysis.