Effect and mechanism of point charge defects on ferroelectric domain switching properties of HfO2-based ferroelectric thin film

A multiphase phase field model considering point charge defects is established to investigate the effect and microscopic mechanism of point charge defects on phase transition between the ferroelectric and monoclinic phase of the HfO2-based ferroelectric thin film. The results show that point defects induced domain wall pinning and transition between ferroelectric and monoclinic phase are the main causes of fatigue failure and wake-up effect of thin films. The increase of point charge defects causes pinning of ferroelectric domain walls, leading to the fatigue failure. More seriously, low-concentration defect dipole pairs can induce the transition from the ferroelectric phase to the monoclinic phase, which further aggravates the fatigue failure. The wake-up effect occurs in the partial diffusion stage of point defects, in which stage the volume fractions of both the monoclinic phase and frozen ferroelectric domains continue to decrease, resulting in the increase of the reversible ferroelectric domain. At the stage when the point charge defects finally diffuse to uniformity, the volume change trends of the monoclinic phase and frozen ferroelectric domains are opposite, but their change amounts are almost the same, thus wake-up effect does not continue to intensify.