Enriquez Erik, Li Qian, Bowlan Pamela, Lu Ping, Zhang Bruce, Li Leigang, Wang Haiyan, Taylor Antoinette J, Yarotski Dmitry, Prasankumar Rohit P, Kalinin Sergei V, Jia Quanxi, Chen Aiping
Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Nanoscale. 2020 Sep 21;12(35):18193-18199. doi: 10.1039/d0nr03460f. Epub 2020 Aug 28.
Inducing new phases in thick films via vertical lattice strain is one of the critical advantages of vertically aligned nanocomposites (VANs). In SrTiO (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 SrTiO: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.
通过垂直晶格应变在厚膜中诱导新相是垂直排列纳米复合材料（VANs）的关键优势之一。在SrTiO（STO）中，基态是铁弹性的，并且STO中的铁电性被正交转变所抑制。在此，我们探究三维VANs中的垂直晶格应变是否可用于在SrTiO:MgO（STO:MgO）VAN薄膜中诱导新的铁电相。STO:MgO体系将有序的、垂直排列的MgO纳米柱并入STO薄膜基质中。STO和MgO之间的强晶格耦合在STO薄膜中施加了较大的晶格应变。我们使用压电力显微镜、相场模拟和二次谐波产生研究了直至室温存在的STO相中的铁电性。我们还意外地发现了嵌入STO薄膜基质中的MgO纳米柱中形成了亚稳TiO纳米核。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。
