Direct observation of Schottky-vacancy clusters and their mechanical response in MoN/TiN superlattice

A deeper understanding of vacancy-induced effects in ceramics may lead to optimized material design and mechanical properties. However, current research primarily focuses on the impact of vacancies on the intrinsic mechanical properties of materials, lacking direct experimental validation of their mechanical response behavior. In this study, we closely investigate the influence of Schottky-vacancy defects introduced during the deposition process on the mechanical behavior of MoN/TiN superlattice. In the as-deposited coating, Schottky vacancies are found to be distributed inside MoN as clusters. By coupling FIB with cross-sectional TEM observation, we further revealed Schottky vacancies evolution under loads at the atomic level and their significant impact on superlattice deformation. These Schottky vacancies promote superlattice intermixing and weaken the interface-strengthening effect. However, they are also beneficial to dislocation nucleation and increase the nitride plastic deformability. These findings provide a new perspective on the impact of point defects on the mechanical properties of ceramic materials.