Engineering Metal Oxidation Towards Epitaxial Growth of Complex Iridates

Oxides of the platinum group metals like Ir and Ru have received increasing attention due to the delicate interplay of electron correlations, crystal field and spin-orbit coupling energies. However, their low vapor pressures and oxidation potentials make the synthesis of their oxide thin films challenging in an ultra-high vacuum system such as Molecular Beam Epitaxy (MBE). We address these challenges using a novel solid-source metal-organic MBE approach [1,2] and epitaxial strain. We demonstrate atomically precise synthesis of binary and complex iridates. Combining detailed growth, x-ray diffraction, transmission and scanning electron microscopy, spectroscopy techniques, and DFT calculations, we demonstrate a vital role of epitaxial strain on Ir oxidation. We will present a detailed growth study, structural characterization and electrical transport in high quality, epitaxial IrO₂ and Sr₂IrO₄ films.

References:

[1] W. Nunn, S. Nair, H. Yun, A. K. Manjeshwar, A. Rajapitamahuni, D. Lee, K. A. Mkhoyan, and B. Jalan, "Solid source metal-organic molecular beam epitaxy of epitaxial RuO₂" APL Mater. 9, 091112 (2021) 

[2] W. Nunn, A. K. Manjeshwar, J. Yue, A. Rajapitamahuni, T. K. Truttmann and B. Jalan, "Novel synthesis approach for “stubborn” metals and metal oxides", Proc. Natl. Acad. Sciences 118, e2105713118 (2021)