Effect of N2-flow on nitrogen vacancies, leakage, and polarization switching in sputtered ferroelectric AlScN films

Nitrogen vacancy (VN) defects in AlScN films play a critical yet underexplored role in determining leakage and polarization switching dynamics. In this work, we systematically investigate the effect of N2 flow on modulating VN defects and establish correlations between these defects and key electrical properties. Through combined microscopic and macroscopic characterizations, we demonstrate that increasing N2 flow effectively enhances the in-plane tensile stress and suppresses VN defect formation, while preserving the desired wurtzite structure and Sc composition. The resulting reduction in defects improves insulating properties by limiting Poole–Frenkel emission through VN-related centers. Electrically, a higher N2 flow increases the coercive field without degrading the remanent polarization. Furthermore, frequency-dependent positive-up-negative-down analysis reveals that polarization switching follows the nucleation-limited switching model, wherein VN defects serve as nucleation sites that lower the switching energy barrier. The combination of reduced leakage paths and strengthened metal-nitrogen bonding contributes to the substantially enhanced endurance of AlScN films grown under nitrogen-rich conditions. This work establishes a clear linkage among processing, defect physics, and electrical performance, offering practical insights into the optimization of AlScN films for advanced memory platforms.