Influence of the biasing scheme on the performance of Au/SrTiO3/LaAlO3 thin film conductor/ferroelectric tunable ring resonators

Abstract

The performance of gold/SrTiO3/LaAlO3 conductor/ferroelectric/dielectric sidecoupled, tunable ring resonators at Ku-band frequencies is presented. The tunability of these rings arises from the sensitivity of the relative dielectric constant (εr) of SrTiO3 to changes in temperature and dc electric fields (E). We observed that the change in εr which takes place by biasing the ring up to 450 V alters the effective dielectric constant (εeff) of the circuit resulting in a 3λ resonant frequency shift of nearly 12% at 77 K. By applying a separate dc bias between the microstrip line and the ring, one can optimize their coupling to obtain high Q bandstop resonators with δfn −1 = f0/Δf3dB as high as 12,000. The 3λ resonance was tuned from 15.75 to 17.41 GHz while keeping δfn −1 above 768 over this range. The relevance of these results for practical microwave components will be discussed.