Antiferroelectric–ferroelectric phase transition of HfO2 and its influencing factors

Abstract

Ferroelectric films based on hafnium oxide (HfO₂) are promising materials for the next generation non-volatile memory and logic devices. However, the anti-ferroelectric (AFE) phase with the Pbca space group dominates the ferroelectric (FE) phase in as-grown specimens, which suppresses switchable polarization. Unraveling the wake-up mechanism from AFE to FE, as well as its influencing factors, is crucial for the fabrication and application of HfO₂ ferroelectrics. In this study, the nudged elastic band method was employed to simulate the AFE–FE phase transition in HfO₂ and to study the effects of lattice strain, electron/hole doping, and yttrium/tantalum doping. Our findings indicate that the energy barrier of the phase transition with oxygen atoms through (T) the Hf atomic planes is 34% lower than that with oxygen atoms not through (N) the Hf atomic planes. In addition, in contrast to the N-pathway, the T-pathway phase transition was almost immune to strain. Y doping can lower the energy barrier for the N-pathway phase transition, whereas Ta doping does not facilitate the phase transition. In addition, high temperatures were found to promote the AFE–FE phase transition. These results significantly contribute to our understanding of the wake-up effects of HfO₂-based ferroelectrics.