Electrodeposited FeCoNiCu High Entropy Alloy Thin Films and Nanowires*

High-entropy alloys (HEAs) have emerged as an exciting platform for explorations of new materials phases and novel functionalities. These alloys are typically formed using bulk synthesis or physical vapor deposition techniques. We have investigated the synthesis of FeCoNiCu high-entropy alloys by electrochemical deposition under ambient conditions. One major challenge is that it is nontrivial to find a common set of electrodeposition conditions to allow simultaneous deposition of the alloys with designed compositions. We have succeeded in realizing near equiatomic ratio FeCoNiCu thin films. Electrodeposition conditions, including potential, electrolyte composition, electrolyte pH, etc., have been optimized to yield continuous films with a metallic finish. X-ray diffraction has yielded a single-phase BCC structure. Magnetic properties of such films are comparable to those made by magnetron sputtering. Additionally, the synthesis approach has allowed the fabrication of HEA nanowires, which have been used as building blocks to construct nanoporous metallic foams. Such electrodeposited HEA nanostructures not only offer a new arena to explore the vast parameter space of HEAs, but also present opportunities for studies of their functionalities.