Relative dielectric constant of epitaxial BaTiO3 thin films in the GHz frequency range

The relative dielectric constant of epitaxial ${\mathrm{BaTiO}}_3$ thin films deposited on MgO was determined over the frequency range from 0.05 to 40.05 GHz. Coplanar stripline waveguides were formed on the ${\mathrm{BaTiO}}_3$ films and the dielectric constant was determined by matching the reflection $({\mathrm{S}}_{11}\mathrm{-)}$ parameter by measurement with that by simulation. The dielectric constants were ∼2200 and ∼500 at <1 and 40 GHz, respectively. The frequency response of the dielectric constant is well described by a Curie–von Schweidler power law with an exponent of 0.29. The effective index of the coplanar stripline structure on the ${\mathrm{BaTiO}}_3$ film and MgO substrate was 3.6.