Dielectric properties of strained (Ba, Sr)TiO₃ thin films epitaxially grown on Si with thin yttria-stabilized zirconia buffer layer

We have grown epitaxial (Ba_0.5 , Sr_0.5)TiO₃ (BST) thin films on Si with very thin yttria-stabilized zirconia (YSZ) buffer layer. The thin YSZ buffer layer affects the stress state of the epitaxial BST layer as well as the growth behavior of the BST layer, i.e., the degree of epitaxy. The epitaxial BST films grown on Si are in two-dimensional tensile stress. We have found that the dielectric constant of the BST films increased with decreasing the lattice distortion in the state of tensile stress. The dielectric constant of the BST films reaches 1300 when the lattice distortion (surface normal lattice constant/in-plane lattice constant) is 0.993.