Effect of Seed Layer Thickness on Texture and Electrical Properties of Sol−Gel Derived (Ba0.8Sr0.2)TiO3 Thin Films

Abstract

The perovskite phase nucleation and growth of Ba0.8Sr0.2TiO3 [BST(80/20)] films was restricted to the bottom interface by the use of a Ba0.8Sr0.2TiO3 [BST(80/20)] sol−gel seed layer of optimized thickness. As a result (h00) preferred orientation, BST thin films on Pt/Ti/SiO2/Si with enhanced electric properties were prepared by sol−gel at considerably low temperatures (700 °C). The effect of sol−gel seed layers and their thickness on the structure/microstructure and electric properties of BST sol−gel derived films was evaluated in this study. 400-nm-thick BST films with a 30-nm-thick seed layer showed a maximized (h00) preferred orientation growth with a grain size of 120 nm. The dielectric constant varied from 300 to 830 at 1 kHz and from 230 to 580 at 1 MHz for films without a seed layer and with a 30-nm-thick seed layer, respectively. In addition the tunability of the dielectric constant was improved to ∼37% at 150 kV/cm, compared with that without seed layer. The remanant polarization and leakage current of BST films with an optimal seed layer were 1.6 μC/cm2 with a coercive field of 30 kV/cm and 8.0 × 10-7 A/cm2 up to an applied electric field of 167.5 kV/cm, respectively. The electrical performance of these BST films is discussed in relation to the effect of the seed layer thickness on the texture and microstructure of the films.