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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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Semi-metallic SrIrO3 films using solid-source metal-organic molecular beam epitaxy
Perovskite SrIrO3 films and its heterostructures are very promising, yet less researched, avenues to explore interesting physics originating from the interplay between strong spin–orbit coupling and electron correlations. Elemental iridium is a commonly used source for molecular beam epitaxy (MBE) synthesis of SrIrO3 films. However, elemental iridium is extremely difficult to oxidize and evaporate while maintaining an ultra-high vacuum and a long mean free path. Here, we calculated a thermodynamic phase diagram to highlight these synthesis challenges for phase-pure SrIrO3 and other iridium-based oxides. We addressed these challenges using a novel solid-source metal-organic MBE approach that rests on the idea of modifying the metal-source chemistry. Phase-pure, single-crystalline, coherent, epitaxial (001)pc SrIrO3 films on (001) SrTiO3 substrate were grown. Films demonstrated semi-metallic behavior, Kondo scattering, and weak antilocalization. Our synthesis approach has the potential to facilitate research involving iridate heterostructures by enabling their atomically precise syntheses.
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- Award ID(s):
- 2011401
- PAR ID:
- 10594719
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- APL Materials
- Volume:
- 10
- Issue:
- 9
- ISSN:
- 2166-532X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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