Abstract: The strategy of nanolaminates has been shown to significantly optimize the electrical properties and reliability of fluorite HfO₂-ZrO₂ ferroelectric thin films. However, HfO₂-ZrO₂ nanolaminates typically exhibit low ferroelectric polarization, which severely limits their application in high-performance ferroelectric memory devices. In this work, strong and reliable ferroelectricity in equal thick ZrO₂/Hf_0.5Zr_0.5O₂ (ZO/HZO) nanobilayer films has been successfully achieved using post-deposition annealing (PDA) process. Compared to the HZO (15) solid solution film, the 2P_r (Double remanent polarization) value of ZO/HZO (7.5/7.5) nanobilayer film increases by 87 % to 68.6 µC/cm². The experimental results indicate that the pronounced ferroelectric phase transition is attributed to significant in-plane tensile stress within ZO/HZO nanobilayer films and surface energy effects caused by the decrease of grain size. Moreover, the nanobilayer structure also demonstrates superior scalability, with all the 6-21 nm thick ZO/HZO nanobilayer films possessing large 2P_r values above 56.0 µC/cm². In particular, the 6 nm thick ZO/HZO (3/3) nanobilayer film achieves a ultra-high remanent polarization (2P_r≈65.1 µC/cm²) while exhibiting excellent fatigue endurance (10¹⁰ cycles) and uniformity (Δ2P_r/2P_{r, max}<6.5 %). This study opens up the possibility of developing high-performance and reliable high-density ferroelectric memory devices.

Key words: Nanolaminates, ZrO₂/Hf_0.5Zr_0.5O₂ nanobilayer, Ferroelectricity, Scalability, Uniformity, Ultrathin ferroelectric material