化学无序FeRh薄膜的外延应变自适应
Epitaxial strain adaption in chemically disordered FeRh thin films
摘要：
现代功能材料中的应变和应变适应机制对其性能至关重要。了解这些机制将推进材料性能工程的创新方法。本文研究了薄膜模型系统中应变自适应机制随外延应变的变化。化学无序的FeRh薄膜沉积在W-V缓冲层上，这允许预设的晶格常数的大的变化，例如外延边界条件。它示出通过高分辨率的X射线倒易空间图和透射电子显微镜，该系统的反应与倾斜机制的结构单元，以适应缓冲层的晶格常数。这种响应解释的密度泛函理论计算，这证明了一个充满活力的最低结构的失真的c/a =0.87。实验观察到的倾斜机制是由这种能量增益引起的，并允许系统保持在最有利的结构中。在一般情况下，它表明，使用外延模型异质结构组成的合金缓冲层的完全混溶的元素和感兴趣的功能材料允许研究应变自适应行为非常详细。这种方法使得即使很小的次级效应也可以观察到，例如本案例研究中确定的结构域的方向倾斜。
英文摘要：
Strain and strain adaption mechanisms in modern functional materials are of crucial importance for their performance. Understanding these mechanisms will advance innovative approaches for material properties engineering. Here we study the strain adaption mechanism in a thin film model system as function of epitaxial strain. Chemically disordered FeRh thin films are deposited on W-V buffer layers, which allow for large variation of the preset lattice constants, e.g. epitaxial boundary condition. It is shown by means of high resolution X-ray reciprocal space maps and transmission electron microscopy that the system reacts with a tilting mechanism of the structural units in order to adapt to the lattice constants of the buffer layer. This response explained by density functional theory calculations, which evidence an energetic minimum for structures with a distortion of c/a =0.87. The experimentally observed tilting mechanism is induced by this energy gain and allows the system to remain in the most favorable structure. In general, it is shown that the use of epitaxial model heterostructures consisting of alloy buffer layers of fully miscible elements and the functional material of interest allows to study strain adaption behaviors in great detail. This approach makes even small secondary effects observable, such as the directional tilting of the structural domains identified in the present case study.
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