Chi Yen-Ting, Van Vliet Krystyn J, Youssef Mostafa, Yildiz Bilge
Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Department of Mechanical Engineering, The American University in Cairo, AUC Avenue, P.O. Box 74, New Cairo, 11835, Egypt.
Adv Sci (Weinh). 2022 Feb;9(4):e2104476. doi: 10.1002/advs.202104476. Epub 2021 Dec 10.
Polarization of ionic and electronic defects in response to high electric fields plays an essential role in determining properties of materials in applications such as memristive devices. However, isolating the polarization response of individual defects has been challenging for both models and measurements. Here the authors quantify the nonlinear dielectric response of neutral oxygen vacancies, comprised of strongly localized electrons at an oxygen vacancy site, in perovskite oxides of the form ABO . Their approach implements a computationally efficient local Hubbard U correction in density functional theory simulations. These calculations indicate that the electric dipole moment of this defect is correlated positively with the lattice volume, which they varied by elastic strain and by A-site cation species. In addition, the dipole of the neutral oxygen vacancy under electric field increases with increasing reducibility of the B-site cation. The predicted relationship among point defect polarization, mechanical strain, and transition metal chemistry provides insights for the properties of memristive materials and devices under high electric fields.
在诸如忆阻器件等应用中，离子和电子缺陷在高电场作用下的极化对于确定材料的性能起着至关重要的作用。然而，分离单个缺陷的极化响应对于模型和测量来说一直具有挑战性。在此，作者们对中性氧空位的非线性介电响应进行了量化，这些中性氧空位由氧空位处强烈局域化的电子组成，存在于ABO形式的钙钛矿氧化物中。他们的方法在密度泛函理论模拟中实施了计算效率高的局域哈伯德U校正。这些计算表明，该缺陷的电偶极矩与晶格体积呈正相关，他们通过弹性应变和A位阳离子种类来改变晶格体积。此外，电场作用下中性氧空位的偶极矩随着B位阳离子还原性的增加而增大。所预测的点缺陷极化、机械应变和过渡金属化学之间的关系为高电场下忆阻材料和器件的性能提供了见解。
