Atmosphere-Engineered PbOx-Mediated Phase Evolution in PZT Thin Films for Enhanced Ferroelectric Performance

Lead zirconate titanate (PbZr1-xTixO3, PZT) thin films are widely used in ferroelectric devices, yet their performance is strongly limited by uncontrolled Pb-related species and oxygen-vacancy defects during crystallization. Here, we demonstrate that the annealing atmosphere governs a unified PbOx-mediated phase evolution mechanism that dictates phase transformation pathways and ferroelectric properties. Systematic comparisons under vacuum, nitrogen, and oxygen reveal that PbOx acts as a dynamic reservoir regulating the competition between pyrochlore stabilization and perovskite nucleation. Vacuum annealing induces severe Pb loss and residual pyrochlore phases, while nitrogen promotes PbOx accumulation but results in oxygen-deficient, defect-rich films. In contrast, oxygen annealing enables simultaneous oxygen-vacancy compensation and PbOx re-integration, leading to complete perovskite formation and enhanced crystallinity. Depth-dependent grazing-incidence X-ray diffraction further uncovers a dual-nucleation mechanism involving interface-driven columnar growth and PbOx-assisted surface nucleation, producing a layered microstructure. Consequently, oxygen-annealed films exhibit superior ferroelectric performance with a maximum polarization of 84.94 μC cm-2 and low coercive field (<40 kV cm-1). Excess oxygen, however, may induce PbO2 formation and secondary phase segregation, indicating the need for balanced atmosphere engineering. This work establishes a general framework for atmosphere-controlled crystallization in ferroelectric oxides via PbOx-mediated phase evolution.