Abstract
The NdNiO3 (NNO) system has attracted a considerable amount of attention owing to the discovery of superconductivity in Nd0.8Sr0.2NiO2. In rare-earth nickelates, Ruddlesden–Popper (RP) faults play a significant role in functional properties, motivating our exploration of its microstructural characteristics and the electronic structure. Here, we employed aberration-corrected scanning transmission electron microscopy and spectroscopy to study a NdNiO3 film grown by layer-by-layer molecular beam epitaxy (MBE). We found RP faults with multiple configurations in high-angle annular dark-field images. Elemental intermixing occurs at the SrTiO3–NdNiO3 interface and in the RP fault regions. Quantitative analysis of the variation in lattice constants indicates that large strains exist around the substrate–film interface. We demonstrate that the Ni valence change around RP faults is related to a strain and structure variation. This work provides insights into the microstructure and electronic-structure modifications around RP faults in nickelates.
Highlights
The recent discovery of nickel-based superconductors has filled the gap in nickel-based oxide materials in superconducting systems [1–5]
The NdNiO3 film was grown on a SrTiO3 (001) single-crystal substrate at 630 ◦ C in an ozone–oxygen atmosphere with a pressure of 1.8 × 10−5 Torr in an atomic layer-by-layer fashion in a custom-made ozone-assisted molecular beam epitaxy (MBE) setup
According to the relationship that the atomic-column brightness is approximately proportional to Z1.7 (Z: atomic number), the sufficient contrast difference enables us to distinguish the atomic columns [27]
Summary
The recent discovery of nickel-based superconductors has filled the gap in nickel-based oxide materials in superconducting systems [1–5]. The infinite-layer phase NdNiO2 can only be synthesized from the precursor ABO3 perovskite structure by removing apical oxygen atoms from NiO6 octahedra through soft-chemistry topotactical reduction [6]. For stabilization of the superconducting phase, chemical doping with divalent Sr replacing trivalent Nd is crucial. Optimal doping with the highest superconducting transition temperature (around 15 K) has been found in Nd0.8 Sr0.2 NiO2 thin films [1]. During pulsed-laser deposition growth of Sr-doped thin NdNiO3 films, a strong tendency to form Ruddlesden–. The epitaxial strain from the substrate can induce the formation of RP faults [7,8]. These RP faults display an atomic structure, where the inclusion of an additional AO layer breaks the long-range order of the ABO3 perovskite phase [3,7–17]. RP structures are related to a variety of physical and chemical properties, e.g., electro-catalytic activities [11], microwave dielectric performance [18], magnetic properties [19], and ferroelectric properties [20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
