  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+1}Ir_{n}O_{3n+1}),
conventional PLD methods often result in mixed phases of Sr2IrO4 (n = 1),
Sr3Ir2O7 (n = 2), and SrIrO3 (n = infinity). 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-teminated 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.
