Highly efficient electroplating of (220)-oriented nano-twinned copper in methanesulfonic copper baths

The formation of a high-density nanotwinned structure in copper deposits is presently acknowledged as a paramount goal for enhancing the material characteristics of copper. However, the conventional manufacturing processes often involve the incorporation of organic additives, resulting in consequential impurity effects and aging concerns. In this work, we introduce a high-rate approach to fabricate (220)-orientation nanotwinned copper foils in a concentrated methanesulfonate copper solution with mere amount of chloride ions as additives. This solution exhibits a plating capability of 60 A dm^-2 (ASD) in the direct current (DC) mode at ambient temperature, giving rise to the formation of numerous twin boundaries inside the copper deposits with average twin spacing meticulously controllable at 30 nm. Moreover, the extent of chloride ion coverage on the cathode surface is posited to be a pivotal determinant of nanotwin formation, particularly under the conditions of relatively high interfacial energy and good crystallinity. This key factor leads to the formation of a coordinated ion-complex through the chloride bridge mechanism, thereby boosting the amount of Cu⁺ intermediates to foster an improved surface conducive to twin formation. Moreover, the formation of a nanotwinned structure can reduce the internal residual stress inside the copper deposits through a stress relaxation mechanism. This innovative methodology not only promotes our understanding on the formation of nanotwinned copper foils but also furnishes a practical and controllable avenue for manufacturing (220)-oriented nanotwinned copper deposits.