Misfit Strain Driven Phase Transformations in Epitaxial Barium Strontium Titanate Films

Abstract

AbstractWe develop phase diagrams for single domain epitaxial barium strontium titanate films on cubic substrates as a function of the misfit strain based on a Landau-Devonshire phenomenological model similar to the one developed by Pertsev et al. [Phys. Rev. Lett. 80, 1988 (1998)]. Unusual ferroelectric phases that are not possible in single crystals and bulk ceramics are demonstrated in epitaxially constrained BST films. The misfit strain is correlated with the film thickness quantitatively by taking into account the formation of misfit dislocations that relieve epitaxial stresses during deposition. Theoretical estimation of the dielectric constant of (001) Ba0.7Sr0.3TiO3 and Ba0.6Sr0.4TiO3 films grown on Si, MgO, LaAlO3, and SrTiO3 substrates as a function of film thickness is provided. It is shown that the selection of the substrate and the film thickness can be chosen as design parameters to manipulate the internal stress level in the film to achieve enhanced dielectric response.