Improved dielectric and electrical behaviour of low-temperature deposited (Ba_0.6Sr_0.4)TiO₃ films by thin SrTiO ₃ buffer layer

(Ba_0.6Sr_0.4)TiO₃ (BST) thin films were deposited at a low temperature of 420 °C using thin SrTiO₃ (STO) buffer layers on (1 0 0)LaNiO₃/Si substrates by radio frequency magnetron sputtering. BST thin films showed a pure perovskite phase and preferred (h 0 0) orientation. The effect of the SrTiO₃ layer thickness on crystallinity, dielectric and electrical properties of BST thin films was investigated. Compared with single BST films, the BST/STO multilayer thin films exhibited improved crystallinity when the STO layers were thicker than 10 nm. The dielectric constant clearly increased and the dielectric loss decreased with a 10 nm thick STO buffer layer. As a result, the figure of merit of films at a certain frequency reached the maximal value of 19.7 with the applied voltage of 6 V. In addition, the multilayer films exhibited a reduced leakage current density, which could be attributed to the improved crystallinity of the BST films by using the thin STO buffer layer.