铁电/介电PbTiO $_3$ / SrTiO $_3$超晶格纳米结构中的畴取向
Domain alignment within ferroelectric/dielectric PbTiO$_3$/SrTiO$_3$ superlattice nanostructures
摘要：
光刻限定的PbTiO 3/SrTiO 3铁电/介电异质外延超晶格纳米结构内的铁电畴图案强烈地受结构的边缘的影响。同步辐射X射线纳米束衍射表明，自发形成的180°铁电条纹域表现出这样的超晶格采用的配置在矩形纳米结构中，域壁与长图案化的边缘对齐。来自纳米畴的X射线漫散射强度的角分布表明畴在相对于边缘约20°的角度范围内对齐。基于时间依赖的朗道-金兹伯格-德文郡模型的计算研究表明，由于释放的横向机械约束，从降低的体积和电致伸缩贡献的系统的自由能的结果的首选方向的对齐。这种出乎意料的对准似乎是固有的，而不是由图案化工艺引起的变形或缺陷的结果。我们的工作展示了异质外延超晶格的纳米结构化和图案化如何允许创建和控制可能看起来违反直觉的铁电结构的途径。
英文摘要：
The ferroelectric domain pattern within lithographically defined PbTiO3/SrTiO3 ferroelectric/dielectric heteroepitaxial superlattice nanostructures is strongly influenced by the edges of the structures. Synchrotron x-ray nanobeam diffraction reveals that the spontaneously formed 180° ferroelectric stripe domains exhibited by such superlattices adopt a configuration in rectangular nanostructures in which domain walls are aligned with long patterned edges. The angular distribution of x-ray diffuse scattering intensity from nanodomains indicates that domains are aligned within an angular range of approximately 20° with respect to the edges. Computational studies based on a time-dependent Landau-Ginzburg-Devonshire model show that the preferred direction of the alignment results from lowering of the bulk and electrostrictive contributions to the free energy of the system due to the release of the lateral mechanical constraint. This unexpected alignment appears to be intrinsic and not a result of distortions or defects caused by the patterning process. Our work demonstrates how nanostructuring and patterning of heteroepitaxial superlattices allow for pathways to create and control ferroelectric structures that may appear counterintuitive.
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