Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba0.5Sr0.5TiO3 Films

Ba0.5Sr0.5TiO3 (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO3 (STO), and LaAlO3 (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of 80 mTorr temperature 720 °C. X-ray diffraction in situ reflection high-energy electron routinely ascertained the epitaxial quality (100)-oriented nanocrystalline films. The broadband microwave (1–40 GHz) dielectric properties measured using coplanar waveguide transmission line test structures. out-of-plane relative permittivity (ε⏊/) exhibited strong substrate-dependent (relaxation) dispersions with their attendant peaks loss tangent (tanδ), former dropping sharply from tens thousands to ~1000 10 GHz. Although homogeneous in-plane strain (ϵǁ), enhances ε⏊/ εMgOBST−0.5⏊/>εSTOBST−0.5⏊/>εLAOBST−0.5⏊/ lower frequencies, two crossover points 8.6 GHz 18 eventually change trend to: εSTOBST−0.5⏊/>εLAOBST−0.5⏊/>εMgOBST−0.5⏊/. are qualitatively interpreted (a) theoretically calculated (T)−(ϵǁ) phase diagram for domain BST-0.5 film, (b) predicted ϵǁ-dependent, anomaly that does not account frequency dependence, (c) literature reports intrinsic extrinsic microstructural effects, including defects-induced inhomogeneous gradients. From Vendik Zubko model, defect parameter metric, ξs, was estimated be 0.51 40 film STO.