Nanodomain patterns in ultra-tetragonal lead titanate (PbTiO3)
Nanodomain patterns in ultra-tetragonal lead titanate (PbTiO3)
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DOI：
10.1063/5.0007148
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发表时间：
2020-05
影响因子：
4
通讯作者：
Amit Kumar;J. Guy;Linxing Zhang;Jun Chen;J. Gregg;J. Scott
中科院分区：
文献类型：
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作者：
Amit Kumar;J. Guy;Linxing Zhang;Jun Chen;J. Gregg;J. Scott
最近，报道了发现超四方PbTiO 3薄膜[Zhang et al.，Science，361，494（2018）]，其中可切换的面外极化被认为几乎是任何先前已知的铁电体的两倍。为了更多地了解这个系统，并探索可能有助于这些显着的功能特性的功能，我们已经映射了偏振微结构的纳米级使用压电响应力显微镜（PFM）（扫描尺寸小于700 nm）。我们的研究揭示了一个非常精细的尺度图案，每个域的大小通常为20-50 nm，所有这些都表现出面外和面内偏振分量。平面矢量PFM极化图显示强带电的四重畴壁结（顶点）的象限晶格畴阵列。铁电体中四重顶点的存在是罕见的，但可以通过“Ashkin-Teller”模型来解释，其中非常大的界面晶格失配应变和局部电场起作用。这种超四方铁电体系统被预期包含直接的c轴面外180°畴，但相反地显示出极其丰富的纳米级畴平铺图案;这些不寻常的纳米畴可能在促进先前报道的极高可切换极化值方面很重要。
Very recently, the discovery of ultra-tetragonal PbTiO3 thin films was reported [Zhang et al., Science, 361, 494 (2018)], in which the switchable out-of-plane polarization was seen to be almost twice that of any previously known ferroelectric. To understand more about this system and to explore features that might contribute to these remarkable functional properties, we have mapped the polarization microstructure on the nanoscale using piezoresponse force microscopy (PFM) (scan sizes less than 700 nm). Our study reveals an extremely fine-scale pattern, with individual domains typically 20–50 nm in size, all of which exhibit both out-of-plane and in-plane polarization components. In-plane vector PFM polarization maps show strongly charged quadrant-lattice domain arrays with fourfold domain wall junctions (vertices). The existence of fourfold vertices in ferroelectrics is rare but can be explained via the “Ashkin-Teller” model, in which very large interfacial lattice mismatch strains and local electric fields play a role. This ultra-tetragonal ferroelectric system was expected to contain straightforward c-axis out-of-plane 180° domains, but instead shows an extremely rich nanoscale domain tiling pattern; these unusual nanodomains may be important in facilitating the extremely high switchable polarization values previously reported.