Direct observation of ferroelectric field effect and vacancy-controlled screening at the BiFeO3/LaxSr1-xMnO3 interface
Direct observation of ferroelectric field effect and vacancy-controlled screening at the BiFeO3/LaxSr1-xMnO3 interface
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DOI：
10.1038/nmat4058
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发表时间：
2014-11-01
期刊：
影响因子：
41.2
通讯作者：
Borisevich, Albina Y.
中科院分区：
文献类型：
--
作者：
Kim, Young-Min;Morozovska, Anna;Borisevich, Albina Y.
基于界面的磁电器件的发展需要理解极化介导的电子现象和原子极化屏蔽机制。在这项工作中，LSMO/BFO界面上的一个单一的晶胞水平上进行了研究，通过结合直接序参量映射扫描透射电子显微镜和电子能量损失谱。我们证明了一个意想不到的类似于5%的晶格膨胀与负极化电荷的区域，与并发的Mn价态和氧K-边强度的变化异常减少。我们解释这种行为的直接证据筛选的氧空位。空位主要聚集在BFO的第二原子层，反映了组分之间离子电导率的差异。这种从界面的空位排斥导致尾到尾域壁的形成。同时，实现了对正极化电荷的纯电子屏蔽，晶格和电子性质的变化微不足道。这些结果强调了在确定氧化物界面的功能特性的电化学现象的非平凡的作用。此外，这些行为表明，空位动力学和排斥在确定氧化物多层膜中的界面功能中起着重要作用，为潜在电子器件中的新功能提供了明确的含义。
The development of interface-based magnetoelectric devices necessitates an understanding of polarization-mediated electronic phenomena and atomistic polarization screening mechanisms. In this work, the LSMO/BFO interface is studied on a single unit-cell level through a combination of direct order parameter mapping by scanning transmission electron microscopy and electron energy-loss spectroscopy. We demonstrate an unexpected similar to 5% lattice expansion for regions with negative polarization charge, with a concurrent anomalous decrease of the Mn valence and change in oxygen K-edge intensity. We interpret this behaviour as direct evidence for screening by oxygen vacancies. The vacancies are predominantly accumulated at the second atomic layer of BFO, reflecting the difference of ionic conductivity between the components. This vacancy exclusion from the interface leads to the formation of a tail-to-tail domain wall. At the same time, purely electronic screening is realized for positive polarization charge, with insignificant changes in lattice and electronic properties. These results underline the non-trivial role of electrochemical phenomena in determining the functional properties of oxide interfaces. Furthermore, these behaviours suggest that vacancy dynamics and exclusion play major roles in determining interface functionality in oxide multilayers, providing clear implications for novel functionalities in potential electronic devices.