Estimation of HTS electrodes properties for use in piezoelectric resonators

Abstract

The microwave (MW) impedance of piezoelectric (PE) resonators with high-temperature superconducting (HTS) and with metal electrodes operating at a longitudinal acoustic waves (AW) frequency of ~2 GHz was modeled using Mason’s and the acoustic transmission line models. The MW impedances of the electrodes were also included into the model and the modeling parameters were chosen so as to be close to those of AlN (PE part of the resonator) and of HTS YBCO, Ag, and Pt (electrodes). It was shown that the limiting Q-factor value due to electric losses in the electrodes (computed under the assumption of small losses in the PE) is very high (~6×105) if even very thin (20 nm) HTS electrodes are used in the resonator at 77 K. The limiting Q-factor value is several thousand in the case of using similar metal electrodes. Thus, the HTS YBCO electrodes can be considered as attractive alternatives for application in PE resonators at low temperatures as they are characterized by low MW losses and affect weakly the resonance frequency.