Cheng Yan, Gao Zhaomeng, Ye Kun Hee, Park Hyeon Woo, Zheng Yonghui, Zheng Yunzhe, Gao Jianfeng, Park Min Hyuk, Choi Jung-Hae, Xue Kan-Hao, Hwang Cheol Seong, Lyu Hangbing
Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, 500 Dongchuan Road, 200241, Shanghai, China.
Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, No. 3 Bei-tu-cheng West Road, Chaoyang District, 100029, Beijing, China.
Nat Commun. 2022 Feb 3;13(1):645. doi: 10.1038/s41467-022-28236-5.
Atomic-resolution Cs-corrected scanning transmission electron microscopy revealed local shifting of two oxygen positions (O and O) within the unit cells of a ferroelectric (HfZr)O thin film. A reversible transition between the polar Pbc2 and antipolar Pbca phases, where the crystal structures of the 180° domain wall of the Pbc2 phase and the unit cell structure of the Pbca phase were identical, was induced by applying appropriate cycling voltages. The critical field strength that determined whether the film would be woken up or fatigued was ~0.8 MV/cm, above or below which wake-up or fatigue was observed, respectively. Repeated cycling with sufficiently high voltages led to development of the interfacial nonpolar P4/nmc phase, which induced fatigue through the depolarizing field effect. The fatigued film could be rejuvenated by applying a slightly higher voltage, indicating that these transitions were reversible. These mechanisms are radically different from those of conventional ferroelectrics.
原子分辨率的Cs校正扫描透射电子显微镜揭示了铁电（HfZr）O薄膜晶胞内两个氧位置（O和O）的局部移动。通过施加适当的循环电压，诱导了极性Pbc2相和反极性Pbca相之间的可逆转变，其中Pbc2相180°畴壁的晶体结构与Pbca相的晶胞结构相同。决定薄膜是被唤醒还是疲劳的临界场强约为0.8 MV/cm，分别高于或低于该场强时观察到唤醒或疲劳。用足够高的电压重复循环导致界面非极性P4/nmc相的形成，该相通过去极化场效应引起疲劳。通过施加稍高的电压可以使疲劳的薄膜恢复活力，表明这些转变是可逆的。这些机制与传统铁电体的机制截然不同。
