TEM study of SrIrO3 thin films with various thicknesses grown on (0 0 1) SrTiO3 substrates synthesized by pulsed laser deposition

The microstructure of SrIrO3 thin films with various thicknesses is characterized by transmission electron microscopy. We observed that the SrIrO3 thin films are formed in meta-stable orthorhombic structure and demonstrate the single-crystalline quality when the thickness is thinner than 30 nm; in contrast, SrIrO3 thin films with thickness thicker than 30 nm are composed of both meta-stable orthorhombic and stable monoclinic SrIrO3 phases, and show polycrystalline quality. The interfacial structure and crystalline domain structure of orthorhombic SrIrO3 thin films are characterized. The formation of meta-stable orthorhombic SrIrO3 thin films is discussed by strain between substrates and thin films on the basis of the Gibbs formation energy difference between monoclinic and orthorhombic SrIrO3 phases. Stabilization of meta-stable orthorhombic SrIrO3 with single crystalline quality provides an ideal system to elucidate the intrinsic physical property of SrIrO3.