Millimeter-scale freestanding superconducting infinite-layer nickelate membranes

Kavli Affiliate: David A. Muller

| First 5 Authors: Yonghun Lee, Xin Wei, Yijun Yu, Lopa Bhatt, Kyuho Lee

| Summary:

Progress in the study of infinite-layer nickelates has always been highly
linked to materials advances. In particular, the recent development of
superconductivity via hole-doping was predicated on the controlled synthesis of
Ni in a very high oxidation state, and subsequent topotactic reduction to a
very low oxidation state, currently limited to epitaxial thin films. Here we
demonstrate a process to combine these steps with a heterostructure which
includes an epitaxial soluble buffer layer, enabling the release of
freestanding membranes of (Nd,Sr)NiO2 encapsulated in SrTiO3, which serves as a
protective layer. The membranes have comparable structural and electronic
properties to that of optimized thin films, and range in lateral dimensions
from millimeters to ~100 micron fragments, depending on the degree of strain
released with respect to the initial substrate. The changes in the
superconducting transition temperature associated with membrane release are
quite similar to those reported for substrate and pressure variations,
suggestive of a common underlying mechanism. These membranes structures should
provide a versatile platform for a range of experimental studies and devices
free from substrate constraints.

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