Microwave properties of SrTiO3/SrRuO3/CeO2/YSZ heterostructure on low-resistivity silicon

Properties of thin film SrTiO3/SrRuO3/CeO2/YSZ heterostructures on low-resistivity (25 Ωcm) Si substrates are studied at microwave frequencies. Heterostructures are grown by laser ablation at different conditions and characterized by XRD. Coplanar capacitors with 2 μm gap are formed by a lift-off process of the Au/Ti electrodes deposited by e-beam evaporation on the surface of heterostructures. Microwave properties of the capacitors are measured at room temperature in the range of 1–50 GHz as a function of electric field. The measured tunability of the capacitors is in the range of 10–20%. The loss in capacitors is caused mainly by the Si substrate with maximum value around the dielectric relaxation frequency 6 GHz. The intrinsic loss tangent (0.08 at 50 GHz) of capacitors is calculated from equivalent circuit model by removing the substrate loss.