Antiphase Boundaries Constitute Fast Cation Diffusion Paths in SrTiO3 Memristive Devices
Antiphase Boundaries Constitute Fast Cation Diffusion Paths in SrTiO3 Memristive Devices
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DOI：
10.1002/adfm.202004118
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发表时间：
2020-09-16
影响因子：
19
通讯作者：
Dittmann, Regina
中科院分区：
文献类型：
--
作者：
Heisig, Thomas;Kler, Joe;Dittmann, Regina
基于过渡金属氧化物的金属-绝缘体-金属结构中的电阻切换依赖于在纳米尺度上施加的电场下离子的可逆漂移。在这样的结构中，导电细丝的形成被认为是由电场驱动的氧阴离子迁移引起的，而阳离子亚晶格通常被认为是无活性的。开关过程的这种简单的机械图是不完整的，因为氧阴离子和金属阳离子两者先前已被识别为在装置操作下的移动的物种。在这里，光谱显微镜技术结合原子模拟，以阐明扩散和漂移过程中发生的电阻开关模型材料SrTiO（3）。结果表明，外延SrTiO（3）器件中的导电细丝是不均匀的，但表现出复杂的微观结构。具体而言，灯丝由导电的富Ti 3+区域和绝缘的富Sr岛组成。透射电子显微镜表明，富锶岛出现以上Ruddlesden-Popper型反相界。这些扩展的缺陷的作用被澄清的分子静态和分子动力学模拟，这表明，Ruddlesden-Popper反相边界构成的钙钛矿结构中的Sr阳离子的扩散快速路径。
Resistive switching in transition metal oxide-based metal-insulator-metal structures relies on the reversible drift of ions under an applied electric field on the nanoscale. In such structures, the formation of conductive filaments is believed to be induced by the electric-field driven migration of oxygen anions, while the cation sublattice is often considered to be inactive. This simple mechanistic picture of the switching process is incomplete as both oxygen anions and metal cations have been previously identified as mobile species under device operation. Here, spectromicroscopic techniques combined with atomistic simulations to elucidate the diffusion and drift processes that take place in the resistive switching model material SrTiO(3)are used. It is demonstrated that the conductive filament in epitaxial SrTiO(3)devices is not homogenous but exhibits a complex microstructure. Specifically, the filament consists of a conductive Ti3+-rich region and insulating Sr-rich islands. Transmission electron microscopy shows that the Sr-rich islands emerge above Ruddlesden-Popper type antiphase boundaries. The role of these extended defects is clarified by molecular static and molecular dynamic simulations, which reveal that the Ruddlesden-Popper antiphase boundaries constitute diffusion fast-paths for Sr cations in the perovskites structure.