Semi-metallic SrIrO₃ films using solid-source metal-organic molecular beam epitaxy

SrIrO₃ and its heterostructures show many interesting properties such as topological Hall effect and persistent metallicity in ultrathin films. Molecular beam epitaxy (MBE) is one of the commonly used methods for making high quality thin films because of its precise control on stoichiometry and defect density. However, MBE synthesis of iridium based thin films is extremely challenging due to high temperature (>2000°C) required to evaporate iridium and high oxygen pressure required to oxidize the iridium metal precursor. In this talk, we illustrate these synthesis challenges using a thermodynamics of the MBE phase diagram. We demonstrate our novel synthesis method that utilizes iridium precursor chemistry to solve these issues. We grew 35 nm thick (001)_pseudo-cubic SrIrO₃ films on (001) SrTiO₃ substrate at 650°C substrate temperature using co-deposition of Sr, iridium acetylacetonate, and oxygen plasma. Reflection high-energy electron diffraction confirms our films are epitaxial with (1x2) surface reconstruction. High-resolution X-ray diffraction scans indicate our films are single-crystalline and show Laue oscillations. Reciprocal space map reveals the films are fully strained to the substrate. Using electrical transport measurements, we show that the films are semi-metallic from 300 K to 1.8 K and exhibit Kondo-like resistivity behavior. Magnetotransport studies reveal positive magnetoresistance and weak antilocalization [1].