Enhancing remnant polarization in ferroelectric Hf0.5Zr0.5O2 thin films by oxygen-diffusive interlayers

Abstract

Ferroelectric phases in Hf_0.5Zr_0.5O₂ (HZO) films are stabilized by an appropriate concentration of oxygen vacancies, but an artificial heterostructure that controls oxygen vacancies at the interface needs to be developed to balance the beneficial and detrimental effects of oxygen vacancies. Here, we demonstrate that inserting oxygen-diffusive V₂O₅ interlayers at the electrode/HZO interface increases remnant polarization (P_r) and decreases coercive field (V_c), as well as improves the device reliability of HZO ferroelectric devices further. Interestingly, the fully woken-up V₂O₅ (6 nm)/HZO (9 nm) stack exhibited a maximum 2P_r of 77.07 µC cm⁻² from hysteresis loops and 64.42 µC cm⁻² from PUND, whose values are 48.27% and 41.99% higher than those of HZO without V₂O₅, respectively. Moreover, V₂O₅/HZO showed an excellent device-to-device variation of 2P_r with a standard deviation of 1.10 µC cm⁻². Atomic-scale characterization combined with synchrotron X-ray diffraction confirms that V₂O₅-triggered oxygen redistribution during wakeup cycles is likely to facilitate the conversion and alignment of the ferroelectric domain of HZO; our study will provide a new strategy of interface engineering between electrodes and ferroelectrics to further enhance remnant polarization and decrease the coercive field in hafnium-based ferroelectrics for emerging applications.