New research directions in tunable microwave dielectrics

Nano-structured Ba0.6Sr0.4TiO3 (FIST) thin-films are currently being investigated by our group for applications in tunable microwave devices and circuits. This work is performed in collaboration with Air Force Research Laboratory Materials Directorate. We have synthesized low microwave-loss nano-structured columnar BST thin-films using a self-directed process-controlled pulsed laser deposition system. The average grain size of the films was controllable from similar to20 nm to similar to150 nm without any clustering by increasing the oxygen ambient pressure from 38 mT to 150 mT. The films with lower average grain size have been found to be tunable and low loss up to 50 GHz. Precise grain size control has resulted in low loss tunable high-K dielectric for variety of applications. Two new research applications are pursued by our group. One is in the design and development of electromagnetic band gap structures (EBGs) and the other in the design and development of capacitive shunt switches for microwave applications.