Kinetical phase transition paths and phase stability in ferroelectric HfO2

Abstract

Novel ferroelectric HfO2 films have obtained great attention owing to their super advantages in electronic applications. However, the phase transition paths and ferroelectric phase stability in HfO2 still remain elusive, represented by several contradictions in theoretical and experimental results. Based on kinetical calculations on the premise of crystal axis mapping relationship rules, we systematically study the transition paths and illustrate the kinetical process in HfO2 film during the cooling process. We find two paths with the same low energy barriers from tetragonal phase transforming to orthorhombic phase. Their polarization axes are exactly orthogonal, predicting 90° domain formation at the beginning of stage of new nucleus formation. This might explain the existence of high-proportioned 90° domains in HfO2 films. Furthermore, the impact of Zr doping concentration on the stabilization of ferroelectric phase is investigated, revealing the mechanism for 50 % doping concentration as the best condition to induce ferroelectricity in HfO2.