The imprint effect, a major reliability issue in ferroelectric memories, degrades the device by shifting the coercive field over time. This work reviews existing imprint models and introduces a phase-field model for polycrystalline thin films. The model identifies grain-boundary charge screening (GBCS) as a key bulk imprint mechanism. It demonstrates that the depolarization field near grain boundaries attracts trapped charges, which in turn suppress domain nucleation for reverse polarization switching. Furthermore, the model reveals that domain wall motion is essential for the GBCS mechanism to induce imprint in a thin film and can explain the widened hysteresis loop observed in experiments. These findings provide new insights into imprint physics and advance strategies for improving ferroelectric memory reliability.

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• Charge dynamics
• Grain boundaries
• Nucleation
• Ferroelectrics
• Polycrystalline materials
• Thin films