Layer-by-layer epitaxial growth of monoclinic SrIrO₃ thin films on (111)-oriented SrTiO₃ through interface engineering

When transition metal oxides is grown along (111) direction, a variety of intriguing phenomena is expected to arise. One of important system, SrIrO₃, crystallizes into monoclinic hexagonal-based 6M structure when grown on (111)-oriented perovskite SrTiO₃, and is expected to host novel topological states. However, the growth of high quality SrIrO₃ on (111)-oriented substrate is still a challenge. We report on high-quality layer-by-layer epitaxial growth of monoclinic SrIrO₃ on SrTiO₃(111) substrate by inserting the CaTiO₃ buffer layer. The scanning transmission electron microscopy image shows perfect epitaxial growth of monoclinic SrIrO₃. Reflection high-energy electron diffraction and low-energy electron diffraction patterns exhibit smooth film surface with reconstruction. Inserting CaTiO₃ buffer layer proves to be an effective way of interface engineering in realizing layer-by-layer growth by reducing the lattice mismatch. The study paves way for the future research on novel quantum states in monoclinic SrIrO₃ films and heterostructures.