标题： BiFeO$_3$中偏振和手性偏振纹理的控制通过外延应变和界面化学 显示英文标题

标题： Control of polarization and polar chiral textures in BiFeO$_3$ by epitaxial strain and interfacial chemistry

摘要： 界面化学、静电效应和外延应变之间的平衡在稳定铁电薄膜中的极化方面起着关键作用。 在这里，我们将这些贡献在生长在带电表面终止的La$_{0.7}$Sr$_{0.3}$MnO$_3$(LSMO) 缓冲层的NdGaO$_3$(001) 基板上的BiFeO$_3$(BFO) 薄膜中进行竞争。 来自基板的大各向异性压缩应变促进了铁电畴的形成，尽管金属缓冲层的(La,Sr)O$^{0.7+}$终止预计会稳定一个均匀的垂直极化。 压电响应力显微镜和扫描透射电子显微镜显示，产生的纳米尺度畴结构通过在与LSMO施加的极化方向相反的区域形成类似萤石结构的Bi$_2$O$_2$表面层而得到稳定。 利用这种极化补偿机制，我们通过插入一个以Bi$_2$O$_2$末端的Aurivillius薄膜作为缓冲层，在高度应变的BFO薄膜中稳定了均匀的垂直极化。 此外，我们通过局部极化切换实验，在畴结构水平上揭示了BFO薄膜中同手性极化纹理的特征。 因此，我们的工作为控制氧化物铁电体中的极化方向和手性纹理提供了新的策略，为功能畴壁和基于畴的电子学开辟了道路。 显示英文摘要

摘要： The balance between interfacial chemistry, electrostatics, and epitaxial strain plays a crucial role in stabilizing polarization in ferroelectric thin films. Here, we bring these contributions into competition in BiFeO$_3$ (BFO) thin films grown on the charged-surface-terminated La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO)-buffered NdGaO$_3$ (001) substrates. The large anisotropic compressive strain from the substrate promotes the formation of ferroelectric domains despite the expected stabilization of a uniform out-of-plane polarization by the (La,Sr)O$^{0.7+}$ termination of the metallic buffer. Piezoresponse force microscopy and scanning transmission electron microscopy reveal that the resulting nanoscale domain architecture is stabilized by the deterministic formation of a fluorite-like Bi$_2$O$_2$ surface layer on regions polarized oppositely to the LSMO-imposed polarization orientation. Leveraging this polarization compensation mechanism, we stabilize a uniform out-of-plane polarization in our highly strained BFO films by inserting a Bi$_2$O$_2$-terminated Aurivillius film as a buffer layer. Additionally, we reveal signatures of homochiral polarization textures in our BFO films on the level of domain configurations using local polarization switching experiments. Our work thus brings new strategies for controlling polarization direction and chiral textures in oxide ferroelectrics, opening pathways for functional domain-wall and domain-based electronics.