Study of ferroelectric/dielectric multilayers for tunable stub resonator applications at microwaves

Tunable coplanar waveguide stub resonators deposited on various ferroelectric/dielectric heterostructures are studied in the 10-GHz band. A frequency tunability up to 45% is achieved under a moderate biasing field (Ebias < 100 kV/cm) when the resonator is printed on KTa0.5Nb0.5O3 (KTN) ferroelectric thin film alone: this comes from the large permittivity agility of the KTN material (r(KTN) varies from 700 to 200). Nevertheless this also leads to significant insertion loss due to the dielectric loss of the ferroelectric material itself (tanr(KTN)≈ 0.15-0.30 at 10 GHz). In this paper, an original route has been considered to reduce the device loss while keeping up a high frequency tunability. It consists in associating the KTN film with a dielectric film to elaborate ferroelectric/dielectric multilayers. The * Corresponding author. Tel.: +33 2 96 60 96 53; fax: +33 2 96 60 96 52. E-mail address: [email protected] (X. Castel).