Low-loss, tunable microwave capacitors using bismuth zinc niobate thin films

A new high dielectric constant material, bismuth zinc niobate that combines low dielectric losses with an electric-field dependent permittivity was implemented as the dielectric in MIM capacitors. Dielectric properties up to 20 GHz were evaluated by measuring the reflection coefficient with a vector network analyzer. The dielectric constant was around 180 and the quality factor remained greater than 100 up to 5 GHz for 64 μm² devices. No onset of a dielectric relaxation, as expected from bulk data, could be detected in the measured frequency range. The results show that BZN thin films have great potential for low loss, tunable microwave devices.