Visualization of grain boundary-mediated domain nucleation and growth in polycrystalline Pb(Zr52Ti48)O3 ferroelectric capacitor

Understanding the mechanisms of domain nucleation and growth in ferroelectric materials is essential for developing faster ferroelectric memory devices. In this work, we combine domain imaging using piezoresponse force microscopy (PFM) with a pulse switching method to investigate the origin and evolution of ferroelectric domain nucleation in polycrystalline Pb(Zr52Ti48)O3-based ferroelectric capacitors. PFM imaging revealed that domain reversal is highly dependent on the voltage sweep direction, with forward sweeps achieving complete polarization reversal within a wider voltage range when compared to reverse sweeps. Interestingly, domain nucleation predominantly occurs at grain boundaries, which not only serve as initiation sites but also restrict the expansion of switched domains, thereby impacting switching uniformity and kinetics. To further quantify the polarization-switching kinetics, we employed the pulse switching method and fitted the resulting data with the nucleation-limited switching (NLS) model. The extracted parameters, including the activation field of 8.35 MV/m, the intrinsic switching time of 0.40 μs, and the width of switching time distribution, support PFM results indicating that nucleation is the rate-limiting step in the switching process of these polycrystalline films. In addition, the distribution width of switching times narrowed with increasing electric field, showing enhanced uniformity in domain nucleation under higher field strengths. These findings emphasize the significance of grain boundary-mediated nucleation in polycrystalline PZT films and underscore the effectiveness of the NLS model for understanding and optimizing ferroelectric switching performance. This study paves the way for engineering grain boundaries and minimizing defect-related barriers to achieve more uniform and efficient domain switching in ferroelectric devices.