Prestrain Guided Yield of Large Single‐Crystal Nickel Foils with High‐Index Facets

Single‐crystal metal foils with high‐index facets are currently being investigated owing to their potential application in the epitaxial growth of high‐quality van der Waals film materials, electrochemical catalysis, gas sensing, and other fields. However, the controllable synthesis of large single‐crystal metal foils with high‐index facets remains a great challenge because high‐index facets with high surface energy are not preferentially formed thermodynamically and kinetically. Herein, single‐crystal nickel foils with a series of high‐index facets are efficiently prepared by applying prestrain energy engineering technique, with the largest single‐crystal foil exceeding 5×8 cm2 in size. In terms of thermodynamics, the internal mechanism of prestrain regulation on the formation of high‐index facets is proposed. Molecular dynamics simulation is utilized to replicate and explain the phenomenon of multiple crystallographic orientations resulting from prestrain regulation. Additionally, large‐sized and high‐quality graphite films are successfully fabricated on single‐crystal Ni(012) foils. Compared to the polycrystalline nickel, the graphite/single‐crystal Ni(012) foil composites show more than five‐fold increase in thermal conductivity, thereby showing great potential applications in thermal management. This study hence presents a novel approach for the preparation of single‐crystal nickel foils with high‐index facets, which is beneficial for the epitaxial growth of certain two‐dimensional materials. Large single‐crystal nickel foils with high‐index facets, the largest one of which exceeds 5×8 cm2 in size, are successfully produced through prestrain energy engineering technique, in which the strain energy drives the single crystal conversion. High‐quality graphite films are synthesized on the single‐crystal Ni(012) foils, and the graphite/Ni(012) foil composites exhibit enhanced thermal conductivity compared to polycrystalline nickel foil.