Selective growth of epitaxial Sr₂IrO₄ by controlling plume dimensions in pulsed laser deposition

We report that epitaxial Sr₂IrO₄ thin-films can be selectively grown using pulsed laser deposition (PLD). Due to the competition between the Ruddlesden-Popper phases of strontium iridates (Sr_n+1Ir_nO_3n+1), conventional PLD methods often result in mixed phases of Sr₂IrO₄ (n = 1), Sr₃Ir₂O₇ (n = 2), and SrIrO₃ (n = ∞). We have discovered that reduced PLD plume dimensions and slow deposition rates are the key for stabilizing pure Sr₂IrO₄ phase thin-films, identified by real-time in-situ monitoring of their optical spectra. The slow film deposition results in a thermodynamically stable TiO₂\\SrO\IrO₂\SrO\SrO configuration at an interface rather than TiO₂\\SrO\SrO\IrO₂\SrO between a TiO₂-terminated SrTiO₃ substrate and a Sr₂IrO₄ thin film, which is consistent with other layered oxides grown by molecular beam epitaxy. Our approach provides an effective method for using PLD to achieve pure phase thin-films of layered materials that are susceptible to several energetically competing phases.