Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by kinetic control

We report on the selective fabrication of high-quality Sr₂IrO₄ and SrIrO₃ epitaxial thin films from a single Sr₂IrO₄ target by pulsed laser deposition. We discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films and triggers the stablization of different Ruddlesden-Popper (RP) phases. Resonnant X-ray abosprtion spectra taken at Ir L-edge and O K-edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structures of both compounds. These results offer a new approach to the synthesis of ultra-thin films of RP series of iridates and can be extended to other compelx oxides with layered structure.