A Comparative Analysis of Asymmetric (BaTiO3) 1−xΛ/(BaZrO3)xΛ Superlattices via X-Ray Diffraction and Raman Spectroscopy

This work is aimed at studying asymmetric BaTiO31 − xΛ/BaZrO3xΛ ((BT) 1−xΛ/(BZ)xΛ) superlattices, grown by pulsed laser deposition onto (001) MgO substrates. The thicknesses of BT (ferroelectric) and BZ (paraelectric) layers were varied so that х ranged from 0 to 1 at a modulation period Λ of about 80 Å. The films were 400 nm thick. The out-of-plane lattice parameters of constituents were assessed using X-ray diffraction. The lattice dynamic peculiarities of superlattices were probed via Raman spectroscopy; special attention is paid to the analysis of E(1TO) and A1(2TO) ferroelectric soft modes. A comparative analysis of data acquired via both experimental techniques reveals the enhancement of stress between BT and BZ layers with a decrease in symmetry from the tetragonal to a monoclinic phase due to strains induced by the lattice parameter mismatch between the constituents.