Li Linze, Cheng Xiaoxing, Blum Thomas, Huyan Huaixun, Zhang Yi, Heikes Colin, Yan Xingxu, Gadre Chaitanya, Aoki Toshihiro, Xu Mingjie, Xie Lin, Hong Zijian, Adamo Carolina, Schlom Darrell G, Chen Long-Qing, Pan Xiaoqing
Department of Chemical Engineering and Materials Science , University of California - Irvine , Irvine , California 92697 , United States.
Department of Materials Science and Engineering , Pennsylvania State University , University Park , Pennsylvania 16802 , United States.
Nano Lett. 2019 Oct 9;19(10):6812-6818. doi: 10.1021/acs.nanolett.9b01878. Epub 2019 Sep 19.
Ferroelectric heterostructures, with capability of storing data at ultrahigh densities, could act as the platform for next-generation memories. The development of new device paradigms has been hampered by the long-standing notion of inevitable ferroelectricity suppression under reduced dimensions. Despite recent experimental observation of stable polarized states in ferroelectric ultrathin films, the out-of-plane polarization components in these films are strongly attenuated compared to thicker films, implying a degradation of device performance in electronic miniaturization processes. Here, in a model system of BiFeO/LaSrMnO, we report observation of a dramatic out-of-plane polarization enhancement that occurs with decreasing film thickness. Our electron microscopy analysis coupled with phase-field simulations reveals a polarization-enhancement mechanism that is dominated by the accumulation of oxygen vacancies at interfacial layers. The results shed light on the interplay between polarization and defects in nanoscale ferroelectrics and suggest a route to enhance functionality in oxide devices.
铁电异质结构具有以超高密度存储数据的能力，可作为下一代存储器的平台。长期以来，人们认为在尺寸减小的情况下铁电性不可避免地会受到抑制，这阻碍了新器件范式的发展。尽管最近在铁电超薄膜中观察到了稳定的极化状态，但与较厚的薄膜相比，这些薄膜中的面外极化分量强烈衰减，这意味着在电子小型化过程中器件性能会下降。在此，在BiFeO/LaSrMnO的模型系统中，我们报告了随着薄膜厚度减小出现显著面外极化增强的观察结果。我们的电子显微镜分析与相场模拟相结合，揭示了一种由界面层处氧空位积累主导的极化增强机制。这些结果揭示了纳米级铁电体中极化与缺陷之间的相互作用，并提出了增强氧化物器件功能的途径。
