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Anisotropic polarization-induced conductance at a ferroelectric–insulator interface
Nature Nanotechnology ( IF 38.3 ) Pub Date : 2018-09-24 , DOI: 10.1038/s41565-018-0259-z
Yi Zhang , Haidong Lu , Lin Xie , Xingxu Yan , Tula R. Paudel , Jeongwoo Kim , Xiaoxing Cheng , Hui Wang , Colin Heikes , Linze Li , Mingjie Xu , Darrell G. Schlom , Long-Qing Chen , Ruqian Wu , Evgeny Y. Tsymbal , Alexei Gruverman , Xiaoqing Pan

Coupling between different degrees of freedom, that is, charge, spin, orbital and lattice, is responsible for emergent phenomena in complex oxide heterostrutures1,2. One example is the formation of a two-dimensional electron gas (2DEG) at the polar/non-polar LaAlO3/SrTiO3 (LAO/STO)3,4,5,6,7 interface. This is caused by the polar discontinuity and counteracts the electrostatic potential build-up across the LAO film3. The ferroelectric polarization at a ferroelectric/insulator interface can also give rise to a polar discontinuity8,9,10. Depending on the polarization orientation, either electrons or holes are transferred to the interface, to form either a 2DEG or two-dimensional hole gas (2DHG)11,12,13. While recent first-principles modelling predicts the formation of 2DEGs at the ferroelectric/insulator interfaces9,10,12,13,14, experimental evidence of a ferroelectrically induced interfacial 2DEG remains elusive. Here, we report the emergence of strongly anisotropic polarization-induced conductivity at a ferroelectric/insulator interface, which shows a strong dependence on the polarization orientation. By probing the local conductance and ferroelectric polarization over a cross-section of a BiFeO3–TbScO3 (BFO/TSO) (001) heterostructure, we demonstrate that this interface is conducting along the 109° domain stripes in BFO, whereas it is insulating in the direction perpendicular to these domain stripes. Electron energy-loss spectroscopy and theoretical modelling suggest that the anisotropy of the interfacial conduction is caused by an alternating polarization associated with the ferroelectric domains, producing either electron or hole doping of the BFO/TSO interface.



中文翻译:

铁电绝缘体界面上的各向异性极化感应电导

不同自由度之间的耦合,即电荷,自旋,轨道和晶格,是复杂氧化物异质结构1,2中出现现象的原因。一个示例是在极性/非极性LaAlO 3 / SrTiO 3(LAO / STO)3,4,5,6,7界面处形成二维电子气(2DEG)。这是由于极性不连续引起的,并且抵消了横跨LAO膜3的静电势的累积。铁电/绝缘体界面处的铁电极化也会引起极性不连续8,9,10。取决于极化方向,电子或空穴被转移到界面,以形成2DEG或二维空穴气体(2DHG)11,12,13。尽管最近的第一原理建模预测了在铁电/绝缘子界面9,10,12,13,14处会形成2DEG,但铁电诱导的界面2DEG的实验证据仍然难以捉摸。在这里,我们报告了在铁电/绝缘体界面处出现强各向异性极化诱导的电导率,这表明对极化方向的依赖性很大。通过探测本地电导和铁电极在的的BiFeO的横截面3 -TbScO 3(BFO / TSO)(001)异质结构,我们证明此界面沿BFO中的109°畴带导电,而在垂直于这些畴带的方向上是绝缘的。电子能量损失谱和理论模型表明,界面传导的各向异性是由与铁电畴相关的交替极化引起的,从而产生了BFO / TSO界面的电子或空穴掺杂。

更新日期:2018-12-10
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