Epitaxial stabilization of pulsed laser deposited Sr${}_{n+1}$Ir${}_n$O${}_{3n+1}$ thin films: entangled effect of growth dynamics and strain

The subtle balance of electronic correlations, crystal field splitting and spin–orbit coupling in layered Ir${}^{4+}$ oxides can give rise to novel electronic and magnetic phases. Experimental progress in this field relies on the synthesis of epitaxial films of these oxides. However, the growth of layered iridates with excellent structural quality is a great experimental challenge. Here we selectively grow high quality single–phase films of Sr${}_2$IrO${}_4$, Sr${}_3$Ir${}_2$O${}_7$, and SrIrO${}_3$ on various substrates from a single Sr${}_3$Ir${}_2$O${}_7$ target by tuning background oxygen pressure and epitaxial strain. We demonstrate a complex interplay between growth dynamics and strain during thin film deposition. Such interplay leads to the stabilization of different phases in films grown on different substrates under identical growth conditions, which cannot be explained by a simple kinetic model. We further investigate the thermoelectric properties of the three phases and propose that weak localization is responsible for the low temperature activated resistivity observed in SrIrO${}_3$ under compressive strain.