Heteroepitaxy of perovskite-type oxides on oxygen-annealed SrTiO3(1 0 0) - Important factors for preparation of atomically flat oxide thin films

Thin him growth of perovskite-type oxides, CaTiO3 and La0.7Sr0.3MnO3 on atomically smooth SrTiO3(1 0 0) substrate has been studied by in-situ reflection high-energy electron diffraction (RHEED) and ex-situ atomic force microscope (AFM) in order to understand the key points to keep the surface flatness. It is found out that the termination of substrate surface by AO layer of perovskite structure (ABO(3)), i.e., CaO, SrO and BaO, is quite effective to prepare the atomically flat thin films. Among these top layers, the SrO termination gives the best result. CaTiO3 film on SrTiO3(1 0 0) can keep the atomically flat surface in spite of large lattice mismatch (similar to 2.3%), while La0.7Sr0.3MnO3 needs more strict lattice matching to keep the flat surface. Structure and orientation of SrO are analyzed by only in-situ RHEED observation as the first step of real-time growth control. Furthermore, the migration process of Sr supplied by laser ablation is studied by time-resolved measurement of RHEED intensity. The growth process of thin film by laser ablation method is discussed with this experiment.