The effect of SiO2, Pt, and Pt∕Au templates on the microstructure and permittivity of BaxSr1−xTiO3 films

Ba 0.25 Sr 0.75 Ti O 3 (BSTO) and SrTiO3 (STO) ferroelectric thin films were grown on templates of SiO2∕Si, Pt∕TiO2∕SiO2∕Si, and Pt∕Au∕Pt∕TiO2∕SiO2∕Si using pulsed laser deposition. The microstructure and surface morphology of the multilayer stacks were studied using x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The microstructural analysis shows that the ferroelectric films are polycrystalline textured with a columnar structure where the grain size is 50–100nm. The BSTO films deposited at 800°C on an amorphous SiO2∕Si template reveal a textured structure with a dominant (110) orientation, which is explained by a dominant growth of BSTO (110) grains due to the lower surface energy of the (110) phase. The STO and BSTO films deposited at 650°C on the Pt∕TiO2∕SiO2∕Si and Pt∕Au∕Pt∕TiO2∕SiO2∕Si templates, respectively, reveal a structure with a dominant (111) orientation, which is explained by the dominant growth of BSTO (STO) (111) grains imposed by the underlying Pt (111) texture. In all cases the ferroelectric films are subject to compressive in-plane strain which is different for different grain orientations. Strain modified permittivities of ferroelectric films grown on different templates are calculated from first principles for different orientations and compared with measured results. The correlations between grain orientations, grain sizes, grain boundaries, strain, and dielectric permittivity of ferroelectric films on different templates are discussed.