Abstract With the increasing research on heterojunctions, it is gradually been realized that interface structure and strain have a huge impact on film properties. However, the research on Bi-based superconducting heterojunctions is still lacking and needs to be explored at the atomic-scale. In this article, the interface structure, element diffusion, and lattice mismatch relaxation of the Bi2Sr2CaCu2O8+δ(Bi-2212)/SrTiO3 heterojunction have been investigated by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (Cs-HAADF STEM), energy-dispersive X-ray spectroscopy (EDX), and geometric phase analysis (GPA). The experiment results reveal the interfacial atomic sequence as SrTiO3(TiO2-terminated)-SrO-Cu/TiO2-Ca-BiO-(Bi-2212)n, where the SrO layer is the nucleation layer and Ti atoms diffuse into the CuO2 layer. The Bi-2212/SrTiO3 heterointerface is found to be semi-coherent and accompanied by the non-ideally periodic arrangement of stand-off misfit dislocations. Moreover, lattice distortion and stacking fault have also been revealed to release part of the in-plane lattice mismatch. Through the combined effect of the above several lattice mismatch relaxation methods, the final Bi-2212 film experiences an average in-plane tensile strain (exx ∼ +0.414%) compared with bulk Bi-2212.

中文翻译：

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Bi2Sr2CaCu2O8+δ/SrTiO3异质结界面结构和晶格失配弛豫的原子尺度分析

摘要 随着对异质结研究的不断深入，人们逐渐认识到界面结构和应变对薄膜性能的影响巨大。然而，Bi基超导异质结的研究仍然缺乏，需要在原子尺度上进行探索。在本文中，Bi2Sr2CaCu2O8+δ(Bi-2212)/SrTiO3 异质结的界面结构、元素扩散和晶格失配弛豫已通过像差校正的高角度环形暗场扫描透射电子显微镜 (Cs-HAADF) 进行了研究。 STEM)、能量色散 X 射线光谱 (EDX) 和几何相分析 (GPA)。实验结果揭示了界面原子序列为 SrTiO3(TiO2-terminated)-SrO-Cu/TiO2-Ca-BiO-(Bi-2212)n，其中 SrO 层是成核层，Ti 原子扩散到 CuO2 层中。发现 Bi-2212/SrTiO3 异质界面是半相干的，并伴随着非理想的间隔错配位错的周期性排列。此外，还发现晶格畸变和堆垛层错可以释放部分面内晶格失配。通过上述几种晶格失配弛豫方法的综合作用，与块体 Bi-2212 相比，最终的 Bi-2212 薄膜经历了平均面内拉伸应变（exx ∼ +0.414%）。