Large ferroelectric polarization and high dielectric constant in HfO2-based thin films via Hf0.5Zr0.5O2/ZrO2 nanobilayer engineering

Abstract

HfO₂-based ferroelectric films have been extensively explored and utilized in the field of non-volatile memory and electrical programmability. However, the trade-off between ferroelectric polarization and dielectric constant in HfO₂ has limited the overall performance improvement of devices in practical applications. Herein, a novel approach is proposed for the Hf_0.5Zr_0.5O₂/ZrO₂ (HZO/ZrO₂) nanobilayer engineering, which can effectively regulate the phase structure evolution of HfO₂ films to construct a suitable morphotropic phase boundary (MPB). The findings highlight that the top ZrO₂ layer can regularly promote the formation of either the ferroelectric o-phase or the antiferroelectric t-phase. An ideal MPB is successfully established in HZO/ZrO₂ (6/9 nm) nanobilayer film by carefully optimizing the HZO/ZrO₂ thickness ratio, which presents a high dielectric constant of 52.7 and a large 2P_r value of up to 72.3 μC/cm² without any wake-up operation. Moreover, the HZO/ZrO₂ nanobilayer thin films demonstrate faster polarization switching speed (1.09 μs) and better fatigue performance (10⁹ cycles) compared to the conventional HZO solid solution films. The relationship between ferroelectric and dielectric properties can be harmoniously balanced through the designation. The results indicate that the HZO/ZrO₂ nanobilayer engineering strategy is quite potential to pave the way for the development of next-generation memory technologies with superior performance and reliability.