Topochemical Synthesis and Electronic Structure of High-Crystallinity Infinite-Layer Nickelates on an Orthorhombic Substrate.

Dong, Zhengang; Hadjimichael, Marios; Mundet, Bernat; Choi, Jaewon; Tam, Charles C; Garcia-Fernandez, Mirian; Agrestini, Stefano; Domínguez, Claribel et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Superconductivity in infinite-layer nickelates has stirred much research interest, to which questions regarding the nature of superconductivity remain elusive. A critical leap forward to address these intricate questions is through the growth of high-crystallinity infinite-layer nickelates, including the "parent" phase. Here, we report the synthesis of a high-quality thin-film nickelate, NdNiO<sub>2</sub>. This is achieved through the growth of a perovskite precursor phase (NdNiO<sub>3</sub>) of superior crystallinity on the NdGaO<sub>3</sub> substrate by off-axis RF magnetron sputtering and a low-temperature topochemical reduction using NaH. We observe a nonlinear Hall effect at low temperatures in this "non-doped" phase. We further study the electronic properties using advanced X-ray scattering and first-principles calculations. We observe spectroscopic indications of the enhanced two-dimensionality and a reduced hybridization of Nd 5<i>d</i> and Ni 3<i>d</i> orbitals. These findings unlock new pathways for preparing high-quality infinite-layer nickelates and provide new insights into the intrinsic features of these compounds.