Highly nanotwinned transition metal nitride film enabled by negative stacking fault energy

Nano-twinned structures offer significant potential on simultaneously enhancing hardness and toughness in materials. However, introducing high-density nanotwins into ceramics remains a formidable challenge. Here, we present a novel synthesis strategy for nano-twinned transition metal nitride thin films with negative stacking fault energy via magnetron sputter deposition under controlled growth conditions. By incorporating a hierarchical network of high-density twin boundaries into the film, we achieve a synergistic enhancement of hardness (43.8 ± 2.2 GPa) and fracture toughness (4.1 ± 0.1 MPa√m) compared to previously reported TiN/TaN superlattices. This study highlights the viability of nano-twinned architectures as a transformative approach for developing advanced superhard coatings and provides a scalable pathway for industrial applications.