Critical Thickness and Long-Term Ambient Stability in Superconducting LaPr<sub>2</sub>Ni<sub>2</sub>O<sub>7</sub> Films.
basic_science · Level V
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- Record sourced from PubMed, PMID 41090438.
- Also identified by DOI 10.1002/adma.202510394.
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Abstract
The recent observation of ambient-pressure superconductivity in compressively strained (La,Pr)<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> 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<sub>2</sub>Ni<sub>2</sub>O<sub>7</sub> 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<sub>c</sub>) of 44 K. No systematic correlation between T<sub>c</sub> and film thickness is identified. Angle-dependent T<sub>c</sub> measurements under external magnetic fields and vortex anisotropy analysis indicate 2D superconductivity in all samples. Structural and transport measurements show that superconductivity in LaPr<sub>2</sub>Ni<sub>2</sub>O<sub>7</sub> is confined to within 10 nm of the interface, while thicker films develop a protective (La,Pr)<sub>4</sub>Ni<sub>3</sub>O<sub>10</sub> 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.