Origin and mitigation of the imprint effect in hafnia-based ferroelectrics

The potential of hafnia-based ferroelectric materials for Ferroelectric Random Access Memory (FeRAM) applications is limited by the imprint effect, which compromises readout reliability. Here, we systematically investigate the asymmetric imprint behavior in W/Hf_0.5Zr_0.5O₂/W ferroelectric capacitors, demonstrating that the imprint direction correlates directly with the ferroelectric polarization state. Notably, a pre-pulse of specific polarity can temporarily suppress the imprint effect. Combined experimental and theoretical analyses reveal that the directional segregation of oxygen vacancies (V_O) at the electrode/ferroelectric interface, coupled with their dynamic charge trapping and detrapping processes, constitutes the core mechanism driving the imprint phenomenon. These processes modulate the built-in electric field, resulting in a shift of the coercive voltage. Building on these findings, we propose an oxygen vacancy segregation-charge trapping model that accounts for critical observations, including the dependence of imprint direction on polarization history and its reversible modulation by pre-pulses. Leveraging this model, we introduce three practical strategies for imprint recovery: charge compensation, oxygen vacancy redistribution, and the design of a bidirectional alternating polarization circuit architecture. Experimental results confirm that these approaches markedly enhance the device's resilience to imprinting, offering innovative pathways to address the reliability challenges of hafnia-based FeRAM.