Kavli Affiliate: Darrell G. Schlom
| First 5 Authors: Anna Scheid, Tobias Heil, Y. Eren Suyolcu, Qi song, Niklas Enderlein
| Summary:
Delafossites, comprised of noble metal (A+) and strongly correlated sublayers
(BO2-), form natural superlattices with highly anisotropic properties. These
properties hold significant promise for various applications, but their
exploitation hinges on the successful growth of high-quality thin films on
suitable substrates. Unfortunately, the unique lattice geometry of delafossites
presents a significant challenge to thin-film fabrication. Different
delafossites grow differently, even when deposited on the same substrate,
ranging from successful epitaxy to complete growth suppression. These
variations often lack a clear correlation to obvious causes like lattice
mismatch. Unidentified stabilization mechanisms appear to enable growth in
certain cases, allowing these materials to form stable thin films or act as
buffer layers for subsequent delafossite growth. This study employs advanced
scanning transmission electron microscopy techniques to investigate the
nucleation mechanism underlying the stable growth of PdCoO2 films on Al2O3 and
LaAlO3 substrates, grown via molecular-beam epitaxy. Our findings reveal the
presence of a secondary phase within the substrate surface that stabilizes the
films. This mechanism deviates from the conventional understanding of strain
relief mechanisms at oxide heterostructure interfaces and differs significantly
from those observed for Cu-based delafossites.
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