Critical Thickness and Long‐Term Ambient Stability in Superconducting LaPr <sub>2</sub> Ni <sub>2</sub> O <sub>7</sub> Films
Yuexin Shi, Chenyao Song, Yingze Jia, Yanzhi Wang, Qi Li, Ye Chen, Yue Yang, Junchi Fu, Ming Qin, Dongsheng Song, Zhen Chen, Huiqiu Yuan, Yanwu Xie, Meng Zhang
Abstract
Abstract The recent observation of ambient‐pressure superconductivity in compressively strained (La,Pr) 3 Ni 2 O 7 films marks a significant advance in nickelate superconductivity research. However, their fabrication remains challenging, with reported thickness limited to <6.6 nm and pronounced ambient degradation. In this study, LaPr 2 Ni 2 O 7 films with nominal thicknesses ranging from 3.5 to 23.5 nm are fabricated. Superconductivity is observed in all samples, with a maximum onset transition temperature ( T c ) of 44 K. No systematic correlation between T c and film thickness is identified. Angle‐dependent T c measurements under external magnetic fields and vortex anisotropy analysis indicate 2D superconductivity in all samples. Structural and transport measurements show that superconductivity in LaPr 2 Ni 2 O 7 is confined to within 10 nm of the interface, while thicker films develop a protective (La,Pr) 4 Ni 3 O 10 surface layer that enhances stability. Ex situ amorphous oxide capping layers further suppress superconducting degradation, yielding 10‐fold stability enhancement in ultrathin films (3 ≈ 4 nm) and prolonging stability from 30 to more than 100 days in thicker films.