近日，德国马普微结构与物理研究所Stuart S. P.Parkin教授课题组研究了钙铁石钴酸锶薄膜中应变驱动外延纳米结构的形成。相关成果已于2023年3月13日在国际学术期刊《美国科学院院刊》上发表。

该课题组通过基质诱导的各向异性应变，实现了外延BM-SCO纳米结构的形成和控制。当钙钛矿基质具有(110)取向且允许压缩应变时，会产生BM-SCO纳米条，而(111)取向的基质则会形成BM-SCO纳米岛。研究人员还发现，基质诱导的各向异性应变与晶体结构域的取向相结合，决定了纳米结构的形状和表面，而其大小可以通过应变度进行调节。此外，纳米结构可以通过离子液体门控在反铁磁性BM-SCO和铁磁性P-SCO之间转换。因此，这项研究为设计易于控制结构和物理性质的外延纳米结构提供了新思路。

据了解，纳米结构材料可以展现出独特的物理性质，并因其新功能而备受关注。外延生长是一种很有前途的合成具有所需结构和结晶度的纳米结构的方法。其中，SrCoO_x是一种特别有趣的材料，因其氧浓度的不同而在反铁磁绝缘钙铁石SrCoO_2.5 (BM-SCO)相和铁磁金属钙钛矿SrCoO_3-δ (P-SCO)相之间存在一种拓扑相变。

附：英文原文

Title: Strain-driven formation of epitaxial nanostructures in brownmillerite strontium cobaltite thin films

Author: Han, Hyeon, Deniz, Hakan, Parkin, Stuart S. P.

Issue&Volume: 2023-3-13

Abstract: Nanostructured materials can display unique physical properties and are of particular interest for their new functionalities. Epitaxial growth is a promising approach for the controlled synthesis of nanostructures with desired structures and crystallinity. SrCoO_x is a particularly intriguing material owing to a topotactic phase transition between an antiferromagnetic insulating brownmillerite SrCoO_2.5 (BM-SCO) phase and a ferromagnetic metallic perovskite SrCoO_3-δ (P-SCO) phase depending on the oxygen concentration. Here, we present the formation and control of epitaxial BM-SCO nanostructures by substrate-induced anisotropic strain. Perovskite substrates with a (110)-orientation and which allow for compressive strain result in the creation of BM-SCO nanobars, while (111)-oriented substrates give rise to the formation of BM-SCO nanoislands. We have found that substrate-induced anisotropic strain coupled with the orientation of crystalline domains determines the shape and facet of the nanostructures, while their size can be tuned by the degree of strain. Moreover, the nanostructures can be transformed between antiferromagnetic BM-SCO and ferromagnetic P-SCO via ionic liquid gating. Thus, this study provides insights into the design of epitaxial nanostructures whose structure and physical properties can be readily controlled.

DOI: 10.1073/pnas.2221651120

Source: https://www.pnas.org/doi/10.1073/pnas.2221651120