New Synthesis Approach for “Stubborn” Metals and Metal Oxides

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Importance

Atomic-precision complex oxides containing “stubborn” elements, such as ruthenium, iridium and platinum, hold great promise as design quantum materials for the exploration of new electronic, magnetic, superconducting and topological phases in due to their strong spin-orbit interaction. This study shows a method to synthesize such materials by removing the major synthesis bottleneck of low vapor pressure and oxidation difficulty. This study serves as a “proof of concept” allowing us 1) to cultivate Pt, RuO2, and SrRuO3 thin films by providing Pt and Ru precursors at 65 to 100 ° C in a low temperature effusion cell, unlike the several thousand degrees Celsius required with electron beam evaporators; 2) reveal a resistivity at room temperature similar to the volume; and 3) ultimately providing pathways for creating atomically precise quantum structures.

Abstract

Advances in physical vapor deposition techniques have led to a myriad of quantum materials and technological breakthroughs, affecting all areas of nanoscience and nanotechnology that rely on innovation in synthesis. Despite this, one area that remains difficult is the synthesis of thin films of complex metal oxides with atomic precision and heterostructures containing “stubborn” elements that are not only easy to evaporate / sublimate, but also difficult to oxidize. . Here, we report a simple but atomically controlled synthetic approach that fills this gap. Using platinum and ruthenium as examples, we show that the low vapor pressure and the difficulty in oxidizing a “stubborn” element can be solved by using a solid organometallic compound with a significantly higher vapor pressure and with the additional advantages of being in a preoxidized state with excellent thermal and air stability. We demonstrate the synthesis of high quality monocrystalline, epitaxial and RuO Pt2 films, resulting in a record residual resistivity ratio (= 27) in Pt films and low residual resistivity, ∼6 μΩcm, in RuO2 movie theater. We demonstrate further, using SrRuO3 as an example, the viability of this approach for more complex materials with the same ease and control that have been largely responsible for the success of molecular beam epitaxy of III-V semiconductors. Our approach is a major advance in the synthetic science of “stubborn” materials, which has sparked great interest in materials science and the condensed matter physics community.

Footnotes

  • Author contributions: research designed by WN, AKM and BJ; WN, AKM, JY, AR, and TKT searched; WN, AKM, JY, AR, TKT and BJ analyzed the data; BJ conceived the idea with WN; and WN, AKM, JY and BJ wrote the article.

  • The authors declare no competing interests.

  • This article is a direct PNAS submission.

  • This article contains additional information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2105713118/-/DCSupplemental.

Data availability

All study data is included in the article and / or SI Annex.


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