  Composition-dependent structural and polar properties of epitaxial
short-period CaTiO_3/SrTiO_3/BaTiO_3 superlattices grown on a SrTiO_3 substrate
are investigated with first-principles density-functional theory computational
techniques. Polarization enhancement with respect to bulk tetragonal BaTiO_3 is
found for two- and three-component superlattices with a BaTiO_3 concentration
of more than 30%. Individual BaTiO_3 layer thickness is identified as an
important factor governing the polarization improvement. In addition, the
degree of inversion-symmetry breaking in three-component superlattices can be
controlled by varying the thicknesses of the component layers. The flexibility
allowed within this large family of structures makes them highly suitable for
various applications in modern nano-electro-mechanical devices.
