Superconducting Sr2RuO4 Thin Films without Out-of-Phase Boundaries by Higher-Order Ruddlesden-Popper Intergrowth

Jinkwon Kim; Junsik Mun; Carla M Palomares García; Bongju Kim; Robin S Perry; Yongcheol Jo; Hyunsik Im; Han Gyeol Lee; Eun Kyo Ko; Seo Hyoung Chang; Suk Bum Chung; Miyoung Kim; Jason W A Robinson; Shingo Yonezawa; Yoshiteru Maeno; Lingfei Wang; Tae Won Noh

doi:10.1021/acs.nanolett.0c04963

Superconducting Sr₂RuO₄ Thin Films without Out-of-Phase Boundaries by Higher-Order Ruddlesden-Popper Intergrowth

Nano Lett. 2021 May 26;21(10):4185-4192. doi: 10.1021/acs.nanolett.0c04963. Epub 2021 May 12.

Authors

Jinkwon Kim^{1

2}, Junsik Mun^{1

3}, Carla M Palomares García⁴, Bongju Kim^{1

2}, Robin S Perry^{5

6

7}, Yongcheol Jo⁸, Hyunsik Im⁹, Han Gyeol Lee^{1

2}, Eun Kyo Ko^{1

2}, Seo Hyoung Chang¹⁰, Suk Bum Chung^{11

12

13}, Miyoung Kim^{1

3}, Jason W A Robinson⁴, Shingo Yonezawa⁷, Yoshiteru Maeno⁷, Lingfei Wang^{1

2

14}, Tae Won Noh^{1

2}

Affiliations

¹ Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.
² Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea.
³ Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea.
⁴ Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
⁵ London Centre for Nanotechnology and UCL Centre for Materials Discovery, University College London, London WC1E 6BT, United Kingdom.
⁶ ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom.
⁷ Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
⁸ Quantum Functional Semiconductor Research Center (QSRC), Dongguk University, Seoul 04620, Republic of Korea.
⁹ Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea.
¹⁰ Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea.
¹¹ Department of Physics, University of Seoul, Seoul 02504, Republic of Korea.
¹² Natural Science Research Institute, University of Seoul, Seoul 02504, Republic of Korea.
¹³ School of Physics, Korea Institute for Advanced Study, Seoul 02455, Republic of Korea.
¹⁴ Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, China.

PMID: 33979525
DOI: 10.1021/acs.nanolett.0c04963

Abstract

Ruddlesden-Popper (RP) phases (A_n+1B_nO_3n+1, n = 1, 2,···) have attracted intensive research with diverse functionalities for device applications. However, the realization of a high-quality RP-phase film is hindered by the formation of out-of-phase boundaries (OPBs) that occur at terrace edges, originating from lattice mismatch in the c-axis direction with the A'B'O₃ (n = ∞) substrate. Here, using strontium ruthenate RP-phase Sr₂RuO₄ (n = 1) as a model system, an experimental approach for suppressing OPBs was developed. By tuning the growth parameters, the Sr₃Ru₂O₇ (n = 2) phase was formed in a controlled manner near the film-substrate interface. This higher-order RP-phase then blocked the subsequent formation of OPBs, resulting in nearly defect-free Sr₂RuO₄ layer at the upper region of the film. Consequently, the Sr₂RuO₄ thin films exhibited superconductivity up to 1.15 K, which is the highest among Sr₂RuO₄ films grown by pulsed laser deposition. This work paves the way for synthesizing pristine RP-phase heterostructures and exploring their unique physical properties.

Keywords: Ruddlesden−Popper phase; Sr2RuO4 thin films; out-of-phase boundary; pulsed laser deposition; unconventional superconductivity.