Dielectric properties of BaTiO3/SrTiO3 ferroelectric thin film artificial lattice

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. (c) 2006 American Institute of Physics.