Copper‐Based Crystalline‐Metallic Glass Composite Thin Films: A Novel Material with Enhanced Strength and Thermally Stable Nanotwins

ABSTRACT Nanotwinned crystalline‐glass composite thin films achieve enhanced performance by effectively utilizing the complementary properties of both phases. Combinatorial sputtering emerges as a powerful tool to discover new materials with targeted properties. In this study, by co‐sputtering Cu, Ti, and Re, Cu‐rich crystalline‐metallic glass composites with high strength and thermal stability are fabricated. They exhibit a unique columnar microstructure with alternating inclined Cu‐rich crystalline phase and Cu‐rich metallic glass. Inside the crystalline columns are abundant nanotwins with a twin spacing of around 5 nm, and the amorphous column has a thickness of around 20 nm. At room temperature, this bamboo‐like structure deforms in a rather homogenous manner due to the co‐deformation of the crystalline phase and a thin layer of metallic glass. It manifests a high yield strength ∼2.3 GPa, which still retains and even slightly increases (2.7 GPa) after heat treatment up to 550°C. The lasting high strength predominantly results from the thermal stability of nanograins and nanotwins, whose growth is thermodynamically unfavorable compared with structural relaxation in metallic glass columns, enabling their application as high‐performance coatings in cutting tools, microelectronics, aero‐space, energy systems, medical devices, and advanced optical technologies.