Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr2RuO4 films

Rashmi Choudhary; Zhaoyu Liu; Jiaqi Cai; Xiaodong Xu; Jiun Haw Chu; Bharat Jalan

doi:10.1063/5.0150893

Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr₂RuO₄ films

Rashmi Choudhary, Zhaoyu Liu, Jiaqi Cai, Xiaodong Xu, Jiun Haw Chu, Bharat Jalan

Research output: Contribution to journal › Article › peer-review

Abstract

Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a “dirty” solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)₃], can yield single-phase, epitaxial, and superconducting Sr₂RuO₄ films with the same ease and control as III-V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru⁴⁺ oxidation, the use of the Ru(acac)₃ precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials.

Original language	English (US)
Article number	061124
Journal	APL Materials
Volume	11
Issue number	6
DOIs	https://doi.org/10.1063/5.0150893
State	Published - Jun 1 2023

Bibliographical note

Funding Information:
This work was supported by the Air Force Office of Scientific Research (AFOSR) through Grant Nos. FA9550-21-1-0025 and FA9550-21-0460 and by the NSF through the MRSEC program under Award No. DMR-2011401. Film growth was performed using instrumentation funded by AFOSR DURIP Award No. FA9550-18-1-0294. The work at the University of Washington was supported by the NSF MRSEC at UW (Grant No. DMR-1719797) and the U.S. AFOSR under Grant No. FA9550-21-1-0068 (Transport measurements) and through AFOSR DURIP Award No. FA9550-20-1-0310 (Helium 3 cryostat). Parts of this work were carried out at the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC program under Award No. DMR-2011401. Substrate preparation was carried out at the Minnesota Nano Center, which is supported by the NSF through the National Nano Coordinated Infrastructure under Award No. ECCS-2025124.

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© 2023 Author(s).

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title = "Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr2RuO4 films",

abstract = "Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a “dirty” solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)3], can yield single-phase, epitaxial, and superconducting Sr2RuO4 films with the same ease and control as III-V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru4+ oxidation, the use of the Ru(acac)3 precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials.",

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note = "Funding Information: This work was supported by the Air Force Office of Scientific Research (AFOSR) through Grant Nos. FA9550-21-1-0025 and FA9550-21-0460 and by the NSF through the MRSEC program under Award No. DMR-2011401. Film growth was performed using instrumentation funded by AFOSR DURIP Award No. FA9550-18-1-0294. The work at the University of Washington was supported by the NSF MRSEC at UW (Grant No. DMR-1719797) and the U.S. AFOSR under Grant No. FA9550-21-1-0068 (Transport measurements) and through AFOSR DURIP Award No. FA9550-20-1-0310 (Helium 3 cryostat). Parts of this work were carried out at the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC program under Award No. DMR-2011401. Substrate preparation was carried out at the Minnesota Nano Center, which is supported by the NSF through the National Nano Coordinated Infrastructure under Award No. ECCS-2025124. Publisher Copyright: {\textcopyright} 2023 Author(s).",

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N2 - Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a “dirty” solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)3], can yield single-phase, epitaxial, and superconducting Sr2RuO4 films with the same ease and control as III-V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru4+ oxidation, the use of the Ru(acac)3 precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials.

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Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr₂RuO₄ films

Abstract

Bibliographical note

MRSEC Support

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IRG-1: Ionic Control of Materials

University of Minnesota Materials Research Science and Engineering Center (DMR-2011401)

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Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr2RuO4 films

Abstract

Bibliographical note

MRSEC Support

Publisher link

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Projects

IRG-1: Ionic Control of Materials

University of Minnesota Materials Research Science and Engineering Center (DMR-2011401)

Cite this

Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr₂RuO₄ films