Phase transition in ferroelectric BaTiO3/SrTiO3 superlattice: Raman spectroscopy studies

BaTiO3/SrTiO3 superlattice has been grown on (001)MgO substrate by pulsed laser deposition. The unit cell parameters of BaTiO3 and SrTiO3 layers and modulation period have been determined using X-ray diffraction. It was found that BaTiO3 and SrTiO3 layers revealed the pseudo-tetragonal distortion with out-of-plane and in-plane polarization, respectively. Electrostatic interaction of the alternating layers leads to the polarization rotations and to the symmetry lowering of the superlattice to orthorhombic or monoclinic with partial depolarization of the Raman spectra. It was found that the phase transition to the paraelectric phase occurs at approximate to 480K.