Intrinsically switchable bulk acoustic wave resonators based on paraelectric films

The concept of the frequency switching in the composite bulk acoustic wave (BAW) resonators based on the thin films of the paraelectric-phase ferroelectrics is demonstrated experimentally for the first time. The composite BAW resonators based on the Ba0.25Sr0.75TiO3/SrRuO3/Ba0.25Sr0.75TiO3 multilayer structure are fabricated and characterized. It is shown that the resonance frequency of the BAW resonators can be switched more than two times (from 3.6 GHz to 7.7 GHz) by changing polarity of the 5 V dc bias voltage at the one of the ferroelectric layers. The composite BAW resonators performance is analyzed using the theory of the dc field induced piezoelectric effect in the paraelectric-phase ferroelectrics