Optimization of ferroelectricity and endurance of hafnium zirconium oxide thin films by controlling element inhomogeneity

Ferroelectric thin films based on HfO₂ have garnered increasing attention worldwide, primarily due to their remarkable compatibility with silicon and scalability, in contrast to traditional perovskite-structured ferroelectric materials. Nonetheless, significant challenges remain in their widespread commercial utilization, particularly concerning their notable wake-up effect and limited endurance. To address these challenges, we propose a novel strategy involving the inhomogeneous distribution of Hf/Zr elements within thin films and explore its effects on the ferroelectricity and endurance of Hf_0.5Zr_0.5O₂ thin films. Through techniques such as grazing incidence X-ray diffraction, transmission electron microscopy, and piezoresponse force microscopy, we investigated the structural characteristics and domain switching behaviors of these materials. The experimental results indicate that the inhomogeneous distribution of Hf/Zr contributes to improving the frequency stability and endurance while maintaining a large remnant polarization in Hf_0.5Zr_0.5O₂ ferroelectric thin films. By adjusting the distribution of Zr/Hf within the Hf_0.5Zr_0.5O₂ thin films, significant enhancements in the remnant polarization (2P_r > 35 μC/cm²) and endurance (> 10⁹) along with a reduced coercive voltage can be achieved. Additionally, the fabricated ferroelectric thin films also exhibit high dielectric tunability (≥ 26%) under a low operating voltage of 2.5 V, whether in the wake-up state or not. This study offers a promising approach to optimize both the ferroelectricity and endurance of HfO₂-based thin films.