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A seemingly simple oxide with a rutile structure, RuO2, has been shown to possess several intriguing properties ranging from strain-stabilized superconductivity to a strong catalytic activity. Much interest has arisen surrounding the controlled synthesis of RuO2 films, but unfortunately, utilizing atomically controlled deposition techniques, such as molecular beam epitaxy (MBE), has been difficult due to the ultra-low vapor pressure and low oxidation potential of Ru. Here, we demonstrate the growth of epitaxial, single crystalline RuO2 films on different substrate orientations using the novel solid-source metal-organic (MO) MBE. This approach circumvents these issues by supplying Ru using a “pre-oxidized” solid MO precursor containing Ru. High-quality epitaxial RuO2 films with a bulk-like room-temperature resistivity of 55 μΩ cm were obtained at a substrate temperature as low as 300 °C. By combining x-ray diffraction, transmission electron microscopy, and electrical measurements, we discuss the effect of substrate temperature, orientation, film thickness, and strain on the structure and electrical properties of these films. Our results illustrating the use of a novel solid-source metal-organic MBE approach pave the way to the atomic-layer controlled synthesis of complex oxides of “stubborn” metals, which are not only difficult to evaporate but also hard to oxidize.
Bibliographical noteFunding Information:
This work was primarily supported by the U.S. Department of Energy through Grant No. DE-SC002021. The work also benefitted from the Norwegian Centennial Chair Program (NOCC) and the Vannevar Bush Faculty Fellowship. S.N. and A.K.M. acknowledge support from the Air Force Office of Scientific Research (AFOSR) through Grant Nos. FA9550-19-1-0245 and FA9550-21-1-0025 and partially through NSF Grant No. DMR-1741801. D.L. acknowledges support from the U.S. DOE through the University of Minnesota Center for Quantum Materials under Award No. DESC0016371. A.R., H.Y., and K.A.M. acknowledge support from the UMN MRSEC program under Award No. DMR-2011401. 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. The authors declare no competing interests.
© 2021 Author(s).
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- 2 Active
9/1/20 → 8/31/26
Project: Research project