Enhanced Dielectric Properties in SrTiO3/BaTiO3 Strained Superlattice Structures Prepared by Atomic-Layer Metalorganic Chemical Vapor Deposition

We describe the investigation of epitaxial SrTiO3/BaTiO3 strained superlattice films prepared by an atomic-layer metalorganic chemical vapor deposition (ALMOCVD) method. Transmission electron microscopy (TEM) observation shows that the multilayered structure is globally uniform and that the interfaces formed between the different layers are of low roughness. X-ray diffraction (XRD) analysis reveals a series of satellite peaks on both sides of the zero-order peak, a characteristic feature of the superlattice structure. Careful analysis of XRD and HRTEM images suggests that the tetragonality in the superlattice films is enhanced; this is presumably due to strain caused by heteroepitaxial growth. Dielectric constants of the superlattice films increase with decreasing period of the superlattice structure. An equivalent oxide thickness of 0.8 nm is obtained. These results demonstrate that the ferroelectricity of SrTiO3/BaTiO3 superlattice films can be controlled artificially by fixing the period of the superlattice.