Buffer electrode layers tuned electrical properties, fatigue behavior and phase transition of KNN-based lead-free ferroelectric films

Abstract

This study investigates the impact of different conductive buffer electrode layers on the electrical properties, fatigue behavior and phase transition of epitaxial KNN-based ferroelectric films. Two types of buffer electrode layers, p-type La_0.67Ca_0.33MnO₃/La_0.67Ba_0.33MnO₃ and n-type LaNiO₃/Nb-SrTiO₃, are selected for analysis. The results demonstrate that the electrical properties and fatigue behavior of the KNN-based films are significantly influenced by the buffer electrode layers. Specifically, the KNN-based films buffered with p-type electrodes exhibit superior ferroelectric/dielectric properties and fatigue resistance compared to those buffered with n-type electrodes. The ferroelectric hysteresis loops of p-type electrode buffered KNN-based films demonstrate higher saturation, larger twice remnant polarization (2P_r) and higher dielectric constant (ε) (2P_r = 58.5/46.9 μC cm⁻² and ε = 1290/1003 for La_0.67Ca_0.33MnO₃/La_0.67Ba_0.33MnO₃-buffered KNNLT-M films) compared to the films grown on n-type electrodes (2P_r = 29.5/24.5 μC cm⁻² and ε = 802/668 for LaNiO₃/Nb-SrTiO₃-buffered KNNLT-M films). Moreover, the KNN-based films grown on p-type buffer electrode layers exhibit high fatigue resistance, maintaining consistent ferroelectric hysteresis loops even after 10⁸ bipolar switching cycles, while those on n-type buffer electrode layers experience dramatic fatigue after only 10⁶ cycles. Temperature-dependent dielectric analysis reveals that all studied KNN-based films exhibit relaxor ferroelectric behavior, with the p-type electrode buffered films exhibiting higher phase transition temperatures than the n-type electrode buffered films. These findings demonstrate that the conductive type of the buffer electrode layer can effectively tune the performance of KNN-based films, indicating the high application potential in lead-free electronic device.