Nanoscale analysis of the interface structure and strain of the Bi2Sr2CaCu2O8+δ/LaAlO3 heterogeneous system

The interface structure and strain significantly affect the performance of superconducting films with heterogeneous structures. In this context, the interface structure and strain of the Bi2Sr2CaCu2O8+δ superconducting thin film fabricated using the sol-gel technique were investigated through aberration-corrected HAADF-STEM, EDX, and GPA. The results revealed that the interfacial atomic sequence was LaAlO3 (AlO2 terminated)-SrO-(Bi2212)n, where the -SrO- layer was the nucleation layer, and (Bi2212)n included the intergrowth phases of Bi2201, Bi2212, and Bi2223. The combined effect of the different lattice mismatch relaxation methods, such as lattice distortion and stacking fault, caused the final Bi2212 film to undergo an average in-plane compressive strain (εxx ∼ –0.4501 %) compared to bulk Bi2212. In addition, the in-plane compressive strain related to the structure of the Bi2212/LaAlO3 heterostructure was gradually released as the distance from the heterointerface increased.