Spatial Oxygen-Vacancy Engineering for Enhanced Ferroelectricity in Flexible Hf0.5Zr0.5O2 Devices

HfO2-based ferroelectrics are promising for scalable memories, neuromorphic systems, and flexible electronics, but their performance is governed by oxygen vacancies that affect phase stability, leakage, wake-up behavior, and domain switching. Existing strategies mainly focus on tuning the overall oxygen-vacancy concentration, making it difficult to balance polarization and stability, especially in flexible devices where the low thermal budget and mechanically compliant stack complicate vacancy distribution and interfacial reactions. Here, we develop a growth-compatible spatial oxygen-vacancy engineering strategy by adjusting oxidant exposure during Hf0.5Zr0.5O2 (HZO) film growth. This method regulates the bottom-interface, bulk, and top-interface oxygen environments without post-treatment. Depth-resolved defect analyses verify position-selective regulation of the oxygen environment and reveal the depth-dependent effects of oxygen vacancies. Reducing oxygen vacancies near the top interface improves reversible polarization switching, whereas excessive oxygen regulation in the bulk or bottom-interface region weakens the ferroelectric response. The top-enhanced device achieves the highest remanent polarization of 31.82 μC cm-2, 41.0% higher than that of the bottom-enhanced device, and exhibits the weakest wake-up effect and the smallest long-term fatigue degradation after 1010 cycles. This work reveals the influence and underlying mechanism of spatial oxygen-vacancy distribution on HZO ferroelectricity, providing a practical design principle for high-performance HfO2-based ferroelectric devices.