Inducing new phases in thick films via vertical lattice strain is one of the critical advantages of vertically aligned nanocomposites (VANs). In SrTiO₃ (STO), the ground state is ferroelastic, and the ferroelectricity in STO is suppressed by the orthorhombic transition. Here, we explore whether vertical lattice strain in three-dimensional VANs can be used to induce new ferroelectric phases in SrTiO₃:MgO (STO:MgO) VAN thin films. The STO:MgO system incorporates ordered, vertically aligned MgO nanopillars into a STO film matrix. Strong lattice coupling between STO and MgO imposes a large lattice strain in the STO film. We have investigated ferroelectricity in the STO phase, existing up to room temperature, using piezoresponse force microscopy, phase field simulation and second harmonic generation. We also serendipitously discovered the formation of metastable TiO nanocores in MgO nanopillars embedded in the STO film matrix. Our results emphasize the design of new phases via vertical epitaxial strain in VAN thin films.

中文翻译：

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通过纳米复合方法在SrTiO3中感应出铁电相。

通过垂直晶格应变在厚膜中诱导新相是垂直排列的纳米复合材料（VANs）的关键优势之一。在SrTiO ₃（STO）中，基态是铁弹性的，并且STO中的铁电受到正交晶系跃迁的抑制。在这里，我们探讨三维VAN中的垂直晶格应变是否可用于在SrTiO _3中诱导新的铁电相：MgO（STO：MgO）VAN薄膜。STO：MgO系统将有序的垂直排列的MgO纳米柱整合到STO薄膜基质中。STO和MgO之间的强晶格耦合会在STO膜中产生较大的晶格应变。我们使用压电响应力显微镜，相场模拟和二次谐波生成技术研究了存在于室温下的STO相中的铁电。我们还偶然发现了嵌入STO薄膜基质中的MgO纳米柱中亚稳TiO纳米核的形成。我们的结果强调了通过VAN薄膜中的垂直外延应变设计新相的方法。