RESUMO
Ferroelectric oxide films are attractive to design and fabricate reconfigurable and miniaturized planar devices operating at microwaves due to the large electric field dependence of their dielectric permittivity. In particular, KTa1-xNbxO3 (KTN) ferroelectric material presents a high tunability under moderate dc bias electric field. However, its intrinsic dielectric loss strongly contributes to the global loss of the related devices and limits their application areas at microwaves. In this paper, a twofold approach is investigated to reduce the device loss. The intrinsic loss of KTN is first reduced by doping the ferroelectric material with a low-loss dielectric material, namely, MgO. Second, the doped ferroelectric films are confined using an original laser microetching process. Both routes have been implemented here to provide a synergic effect on the total insertion loss of the microwave test device, namely, a coplanar waveguide stub resonator. The experimental data demonstrate a decrease of the intrinsic loss by a factor of ~2 and a decrease of the global loss by a factor of ~4 with a frequency tunability close to 10% at ~10 GHz under a moderate biasing (80 kV/cm).
RESUMO
In this study about the relationships between structural and microwave electrical properties of KTa(1-x)NbxO3 (KTN) ferroelectric materials, a KTN thin film was deposited on different substrates to investigate how KTN growth affects the microwave behavior. Interdigital capacitors and stubs were made on these films through a simple engraving process. Microwave measurements under a static electric field showed the importance of the substrate on the circuit behavior and, notably, on the tuning factor.
