Near-Atomic-Scale Mapping of Electronic Phases in Rare Earth Nickelate Superlattices

• DOI: 10.1021/acs.nanolett.0c04538
• Publication Date: 2021-03-09T01:10:02Z
• Authors: Bernat Mundet; Claribel Domínguez; Jennifer Fowlie; Marta Gibert; Jean-Marc Triscone; Duncan T. L. Alex...
• Keywords: 3104 Condensed Matter Physics; superlattices; 1502 Bioengineering; 530 Physics; Mechanical Engineering; 2210 Mechanical Engineering; 1600 General Chemistry; Bioengineering; 10192 Physics Institute; General Chemistry; ddc:500.2; 02 engineering and technology; Condensed Matter Physics; 2500 General Materials Science; info:eu-repo/classification/ddc/500.2; nickelates; eels; phase mapping; General Materials Science; stem; 0210 nano-technology

Nanoscale mapping of the distinct electronic phases characterizing the metal-insulator transition displayed by most of the rare-earth nickelate compounds is fundamental for discovering the true nature of this transition and the possible couplings that are established at the interfaces of nickelate-based heterostructures. Here, we demonstrate that this can be accomplished by using scanning transmission electron microscopy in combination with electron energy-loss spectroscopy. By tracking how the O K and Ni L edge fine structures evolve across two different NdNiO3/SmNiO3 superlattices, displaying either one or two metal-insulator transitions depending on the individual layer thickness, we are able to determine the electronic state of each of the individual constituent materials. We further map the spatial configuration associated with their metallic/insulating regions, reaching unit cell spatial resolution. With this, we estimate the width of the metallic/insulating boundaries at the NdNiO3/SmNiO3 interfaces, which is measured to be on the order of four unit cells.