Depth Profiling Square Planar Nickelates

Published

March 31, 2026

Author(s)

Purnima P. Balakrishnan, Maria Bambrick-Santoyo, Lin Chow, Dan Segedin, Mythili Surendran, Ranjan Patel, Paige Quarterman, Shinichiro N. Muramoto, Grace Pan, Zhaoyang Luo, Michael Fitzsimmons, Amanda Huon, Timothy Charlton, Christy Kinane, Andrew Caruana, Hui Wu, Charles Brooks, Qi Song, Hanjong Paik, Srimanta Middey, Jayakanth Ravichandran, A. Ariando, Julia A. Mundy, Alexander Grutter

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.

Citation

Physical Review Materials

Volume

10

Issue

3

Pub Type

Journals

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Keywords

superconductivity, magnetism, reflectometry, nickelate

Citation

Balakrishnan, P. , Bambrick-Santoyo, M. , Chow, L. , Segedin, D. , Surendran, M. , Patel, R. , Quarterman, P. , Muramoto, S. , Pan, G. , Luo, Z. , Fitzsimmons, M. , Huon, A. , Charlton, T. , Kinane, C. , Caruana, A. , Wu, H. , Brooks, C. , Song, Q. , Paik, H. , Middey, S. , Ravichandran, J. , Ariando, A. , Mundy, J. and Grutter, A. (2026), Depth Profiling Square Planar Nickelates, Physical Review Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960754 (Accessed October 14, 2026)

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