Substrate Engineering for High‐Performance Ultrathin Copper Foils: Unveiling the Electronic‐Geometric Synergy of Low‐Range‐Order Ni‐W Alloys

ABSTRACT The precise regulation of microstructure and mechanical properties in ultrathin electrodeposited copper foils is critical for advanced interconnections yet remains constrained by the strength‐ductility trade‐off. While electrolyte additive engineering is common, the regulation mechanism of substrate intrinsic physicochemical properties remains elusive. Herein, a “substrate engineering” strategy is established by investigating copper nucleation thermodynamics and growth kinetics on low‐range‐order Ni‐W versus crystalline Ti substrates. Combined DFT calculations and multi‐scale characterizations reveal a unique electronic‐geometric synergistic effect of the low‐range‐order Ni‐W: its optimized work function alignment lowers the interfacial energy barrier for electron transfer, while the low‐range‐order structure provides abundant high‐activity sites. This mechanism reduces the nucleation barrier, inducing a transition from island‐like coarsening on Ti to high‐density instantaneous nucleation and uniform planar growth on Ni‐W. Consequently, the resulting foil exhibits a densely smooth surface ( S a = 0.11 µm), refined grain structure, and optimized (220) texture. These merits yield a significant strength‐ductility synergy, with tensile strength and elongation reaching 292.4 MPa and 2.88%, respectively. This work provides a theoretical basis for designing next‐generation high‐performance copper foils beyond traditional additive reliance.