Effect of Stress on the Structure and Ferroelectric Properties of LaAlO₃/BaTiO₃ Superlattices

LaAlO3/BaTiO3 superlattices were prepared on (100) oriented SrTiO3 or Nb-doped SrTiO3 substrates by laser molecular beam epitaxy. The change of diffraction streaks observed in reflection high-energy electron diffraction during the growth of LaAlO3 and BaTiO3 illustrated the different epitaxial growth for LaAlO3 and BaTiO3. The X-ray diffraction spectra of the superlattices with different thickness of LaAlO3 and BaTiO3 layers within a period showed that the c-axis lattice constants changed with layer thickness due to the strain induced by lattice mismatch between LaAlO3 and BaTiO3. The remanent polarization of the superlattices increased with decreasing the thickness of BaTiO3 layers and increasing the thickness of LaTiO3 layers. This suggests that the remanent polarization is closely related with the lattice strain in the superlattices.