Dielectric properties of BaTiO₃/SrTiO₃ ferroelectric thin film artificial lattice

Abstract

Dielectric behavior on BaTiO₃/SrTiO₃ artificial lattices has been investigated along with quantum mechanical simulation (first principles calculation). From the oxide artificial lattice approach, strain manipulation was performed to obtain a wide range of lattice deformation in the consisting BaTiO₃ and SrTiO₃ layers, which leads to two important consequences. First, we obtained enhanced dielectric constant and extremely large nonlinearity in the artificial lattices with very short stacking periods. Second, it is found that there exists a maximum dielectric constant in each BaTiO₃ lattice and SrTiO₃ lattice at a certain degree of lattice deformation. The first principles study successfully explains the dielectric behavior of strained BaTiO₃ and SrTiO₃ lattices, the existence of the maximum dielectric constant. The first principles study on BaTiO₃/SrTiO₃ artificial lattices with very short stacking periods also reveals that the artificial lattice undergoes phase transition between the tetragonal and monoclinic phases with a misfit lattice strain and exhibits an anomalous dielectric behavior at the phase boundary. Optical phonon behavior of the BaTiO₃/SrTiO₃ artificial lattice resembles that of strained SrTiO₃ lattice and optical phonon softening primarily derives the anomaly of the dielectric tensor at the phase boundary. The lattice deformation is a primary influencing factor to phonon and dielectric behaviors rather than interface layer effect in BaTiO₃/SrTiO₃ artificial lattice with very short stacking periods.