Atomic-scale characterization of defects generation during fatigue in ferroelectric Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> films: vacancy generation and lattice dislocation
Yunzhe Zheng, Yonghui Zheng, Zhaomeng Gao, Jun‐Hui Yuan, Yan Cheng, Qilan Zhong, Tianjiao Xin, Yiwei Wang, Cheng Liu, Yaru Huang, Rong Huang, Xiangshui Miao, Kan‐Hao Xue, Hangbing Lyu
Abstract
For the first time, we directly observed the lattice dislocation and monoclinic (m-) phase formation in ferroelectric Hf <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (HZO) films during fatigue, through the spherical aberration (Cs)-corrected transmission electron microscopy (TEM) technique. The main observations are: 1. More oxygen vacancies (Vo) tend to be generated when the orthorhombic (o-) phase polar axis is close to the out-of-plane direction (parallel to the electrical field); 2. The o-phase with large grain size tends to fragment with lattice dislocation and m-phase formation by martensitic-like transformation; 3. At the interface of m-/o-structure, the Vo formation energies are lowered. This work provides fundamental understanding on the defect generation mechanism of HZO film at the atomic-level, laying a solid foundation to further optimization and commercialization of the ferroelectric HZO devices.