Microwave properties of ferroelectric thin films

The microwave properties of ferroelectric thin films are being investigated. Interdigitated capacitors fabricated on ferroelectric thin films of Sr0.5Ba0.5TiO3 have been characterized at room temperature from 50 MHz to 20 GHz, The relative dielectric constant and dielectric loss tangent of the ferroelectric thin film are then extracted using a conformal-mapping based approach. For large dielectric constants the upper frequency limit for which the conformal-mapping technique is valid can be as low as 5 GHz. This information is being used to optimize the ferroelectric film deposition process for microwave device application. Results indicate that this technology will compare favorably with conventional varactors above a few GHz, and should be useful for tunable microwave circuits in some 300 K applications.