Effect of Interlayer Thickness on Stress and Dielectric Properties of MgTiO3 Modified (Ba,Sr)TiO<sub>3</sub> Multilayer Thin Films

Abstract

Ba0.6Sr0.4TiO3 (BST)/MgTiO3 (MT)/ Ba0.6Sr0.4TiO3 multilayer thin films were deposited on LaNiO3 (100)/Pt/Ti/SiO2/Si (100) substrates by pulsed laser deposition. It was found that the film orientation and dielectric properties of BST/MT/BST multilayer thin films are strongly dependent on MT interlayer thickness. Pure BST thin film exhibits a (100) preferred orientation, while BST thin films with a MT interlayer exhibit a random orientation. Residual stress is relaxed dramatically due to a closer match of thermal expansion coefficients between the BST and MT interlayers. The largest figure of merit of 18.7 is achieved in the multilayer thin film with a 50-nm-thick MT interlayer, which exhibits a tunability of 30% and a lost tangent of 0.016. Dielectric constant and loss tangent decrease with increasing MT interlayer thickness due to a series dielectric dilution effect.