Characterization of Ferroelectric Ba0.6Sr0.4TiO3 Thin Films on Different Substrates for Reconfigurable Microwave Application

This paper addresses the characterization of Ba0.6Sr0.4TiO3 dielectric properties on different dielectric substrates using three different components. First, for low frequencies, metal-insulator-metal (MIM) capacitors are used to determine the BST dielectric constant, loss tangent and tunability for different biasing voltages from 0-30 V showing a tunability range of 66%. For microwave frequency ranges, coplanar waveguides (CPW), and interdigital capacitors (IDCs) are investigated on silicon, R-plane sapphire (Al2O3) and magnesium oxide (MgO) substrates. CPW is used to determine the complex propagation constant, while IDCs are used to determine the BST voltage tunability from 0-55 V over 1-20 GHz. Sapphire and MgO introduce low loss tangent values of 0.03, while sapphire gives better tunability (20% at 18 GHz) than MgO (8.3% at 18 GHz).