Aspects of the Synthesis of Thin Film Superconducting Infinite-Layer Nickelates

Kyuho Lee; Berit H. Goodge; Danfeng Li; Motoki Osada; Bai Yang Wang; Yi Cui; Lena F. Kourkoutis; Harold Y. Hwang

doi:10.1063/5.0005103

paper

Aspects of the Synthesis of Thin Film Superconducting Infinite-Layer Nickelates

arXiv:2002.07749 · doi:10.1063/5.0005103

Abstract

The recent observation of superconductivity in Nd $_{0.8}$ Sr $_{0.2}$ NiO $_{2}$ calls for further investigation and optimization of the synthesis of this metastable infinite-layer nickelate structure. Here, we present our current understanding of important aspects of the growth of the parent perovskite compound via pulsed laser deposition on SrTiO $_{3}$ (001) substrates, and the subsequent topotactic reduction. We find that to achieve single-crystalline, single-phase superconducting Nd $_{0.8}$ Sr $_{0.2}$ NiO $_{2}$ , it is essential that the precursor perovskite Nd $_{0.8}$ Sr $_{0.2}$ NiO $_{3}$ thin film is stabilized with high crystallinity and no impurity phases; in particular, a Ruddlesden-Popper-type secondary phase is often observed. We have further investigated the evolution of the soft-chemistry topotactic reduction conditions to realize full transformation to the infinite-layer structure with no film decomposition or formation of other phases. We find that capping the nickelate film with a subsequent SrTiO $_{3}$ layer provides an epitaxial template to the top region of the nickelate film, much like the substrate. Thus, for currently optimized growth conditions, we can stabilize superconducting single-phase Nd $_{0.8}$ Sr $_{0.2}$ NiO $_{2}$ (001) epitaxial thin films up to ~ 10 nm.

Aspects of the Synthesis of Thin Film Superconducting Infinite-Layer Nickelates

Abstract

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