Enhancement of remanent polarization in epitaxial BaTiO3/SrTiO3 superlattices with “asymmetric” structure

Enhancement of remanent polarization has been demonstrated in epitaxial “asymmetric” BaTiO3/SrTiO3 strained superlattices, in which the thickness ratio of BaTiO3 to SrTiO3 layers is changed at molecular layer order accuracy. The superlattices have been prepared on Nb-doped SrTiO3 (100) single-crystal substrates by a pulsed-laser deposition technique. The superlattice with a stacking periodicity of 15 unit cells BaTiO3/3 unit cells SrTiO3 shows the largest remanent polarization 2Pr of 46 μC/cm2, which is about three times that of the BaTiO3 single-phase film formed under the same condition. The increase in the remanent polarization is attributed both to the BaTiO3-rich structure and to the increase in lattice parameter c due to the mismatch of in-plane lattice parameters between BaTiO3 and SrTiO3.