Colossal grain growth yields single-crystal metal foils by contact-free annealing

Single-crystal metals have unique properties due to the absence of grain boundaries and strong anisotropy. Commercial single-crystal metals are usually synthesized by bulk crystal growth or by deposition of thin films onto substrates, and they are expensive and small. We prepare extremely large single-crystal metal foils by ‘contact-free annealing’ from commercial polycrystalline foils. The colossal grain growth (up to 32 cm2) is achieved by minimizing contact stresses, resulting in a preferred in-plane and out-of-plane crystal orientation, and is driven by surface energy minimization during the rotation of the crystal lattice followed by ‘consumption’ of neighboring grains. Industrial scale production of single-crystal metal foils is possible from this discovery. (c) 2017 The Authors, Some rights reserved