Abstract
Superconducting nickelate thin films with the layered square-planar structure are synthesized via the topotactic reduction of a more oxygen rich perovskite or Ruddlesden-Popper (RP) phase due to the instability of the target Ni1+δ valence. The topotactic reduction induces a dramatic structural transformation, which yields high defect densities in the resulting film and has introduced uncertainty regarding film uniformity, particularly as it relates to the calculation of physical parameters based on estimates of superconducting volume fraction. Here we use neutron reflectometry (NR) and secondary ion mass spectrometry (SIMS) to obtain a sub-nm resolved understanding of the structural depth profile across a wide range of layered square-planar nickelates. While the as-grown parent compounds are bulklike and of very high quality, the depth profiles of reduced films are generally nonuniform and indicative of partial amorphization. We identify careful selection of substrate and reduction conditions as promising directions toward mitigating amorphization and improving uniformity.
| Original language | English |
|---|---|
| Article number | 034801 |
| Journal | Physical Review Materials |
| Volume | 10 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 1 2026 |
Funding
M.B.-S., D.F.S., G.A.P., and J.A.M. acknowledge support from the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Award No. DE-SC0021925. J.A.M. acknowledges support from NSF Grant No. DMR-2323971. L.E.C., Z.L., and A.A. acknowledge support from the Ministry of Education (MOE), Singapore, under its Tier-2 Academic Research Fund (AcRF), Grant No. MOE-T2EP50123-0013, the MOE Tier-3 Grant (MOE-MOET32023-0003) ‘Quantum Geometric Advantage’, and the SUSTech-NUS Joint Research Program. J.R. and M.S. acknowledge support from an ARO MURI program with Award No. W911NF-21-1-0327, and the National Science Foundation of the U.S. under Grant No. DMR-2122071. R.K.P. and S.M. acknowledge funding support from a SERB (ANRF) Core Research grant: No. CRG/2022/001906 and I.R.H.P.A Grant No. IPA/2020/000034. Materials growth was supported in part by PARADIM under NSF Cooperative Agreement No. DMR-2039380. M.B.-S., D.F.S., G.A.P., and J.A.M. acknowledge support from the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Award No. DE-SC0021925. J.A.M. acknowledges support from NSF Grant No. DMR-2323971. L.E.C., Z.L., and A.A. acknowledge support from the Ministry of Education (MOE), Singapore, under its Tier-2 Academic Research Fund (AcRF), Grant No. MOE-T2EP50123-0013, the MOE Tier-3 Grant (MOE-MOET32023-0003) ‘Quantum Geometric Advantage’, and the SUSTech-NUS Joint Research Program. J.R. and M.S. acknowledge support from an ARO MURI program with Award No. W911NF-21-1-0327, and the National Science Foundation of the U.S. under Grant No. DMR-2122071. R.K.P. and S.M. acknowledge funding support from a SERB (ANRF) Core Research grant: No. CRG/2022/001906 and I.R.H.P.A Grant No. IPA/2020/000034. Materials growth was supported in part by PARADIM under NSF Cooperative Agreement No. DMR-2039380.P.P.B. and P.Q. received funding from the NRC RAP. G.A.P. acknowledges additional support from the Paul and Daisy Soros Fellowship for New Americans. D.F.S. and G.A.P. acknowledge support from the NSF Graduate Research Fellowship Grant No. DGE-1745303. M.B.S. acknowledges support from the NSF Graduate Research Fellowship Grant No. DGE-2141064.We would like to thank the ISIS neutron and Muon Source for the provision of beamtime RB2320137. The data is available at the following [67]. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to Magnetism Reflectometer (BL4A) on Proposal No. IPTS-29514.Access to CANDOR was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. Research was performed in part at the NIST Center for Nanoscale Science and Technology. Certain commercial equipment, instruments, software, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identifications are not intended to imply recommendation or endorsement by NIST, nor it is intended to imply that the materials or equipment identified are necessarily the best available for the purpose. Unless otherwise noted, NIST work was funded solely by the U.S. Government. Access to CANDOR was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. Research was performed in part at the NIST Center for Nanoscale Science and Technology. Certain commercial equipment, instruments, software, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identifications are not intended to imply recommendation or endorsement by NIST, nor it is intended to imply that the materials or equipment identified are necessarily the best available for the purpose. Unless otherwise noted, NIST work was funded solely by the U.S. Government. P.P.B. and P.Q. received funding from the NRC RAP. G.A.P. acknowledges additional support from the Paul and Daisy Soros Fellowship for New Americans. D.F.S. and G.A.P. acknowledge support from the NSF Graduate Research Fellowship Grant No. DGE-1745303. M.B.S. acknowledges support from the NSF Graduate Research Fellowship Grant No. DGE-2141064.
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