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Probing Interfaces in Complex Oxide Heterostructures via 17O Solid State NMR Spectroscopy

preprint
submitted on 12.05.2020 and posted on 13.05.2020 by Michael Hope, Bowen Zhang, Bonan Zhu, David M. Halat, Judith L. MacManus-Driscoll, Clare P. Grey
The determination of the atomic-scale structure of a solid–solid interface is a major outstanding problem in the physical sciences, the structure controlling many properties including stability, ionic and electronic transport, magnetism, multiferroicity and superconductivity. NMR spectroscopy is sensitive to local structure but is not typically sufficiently sensitive or selective to observe solid–solid interfaces. In this work, CeO2–SrTiO3 vertically aligned nanocomposite (VAN) thin films are studied and, by combining selective isotopic enrichment with a lift-off technique to remove the substrate, the 17O NMR signal from single atomic layer interfaces can clearly be seen. The interfacial structure is solved by calculating the NMR parameters using density functional theory combined with random structure searching. By performing the isotopic enrichment at variable temperatures, the superior oxide-ion conductivity of the VAN films compared to the bulk materials is shown to arise in part from enhanced oxygen mobility at this interface; oxygen motion at the interface is further identified from 17O relaxometry experiments. These results highlight the information that can be obtained on interfacial structure and dynamics with solid-state NMR spectroscopy, in this and other nanostructured systems, our methodology being generally applicable to overcome sensitivity limitations in thin-film studies.

History

Email Address of Submitting Author

michael.hope@epfl.ch

Institution

University of Cambridge

Country

United Kingdom

ORCID For Submitting Author

0000-0002-4742-9336

Declaration of Conflict of Interest

None.

Exports