| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1665521 | Thin Solid Films | 2014 | 5 Pages |
•High tunability and significant global loss of resonator printed on KTa0.5Nb0.5O3 layer.•Resonator tunability decreases with the increase of the Bi1.5Zn0.9Nb1.5O7−δ (BZN) layer thickness.•Resonator global loss decreases with the increase of the BZN layer thickness.•The figures of merit of resonators are similar, with and without the BZN layer.
Tunable coplanar waveguide stub resonators deposited on various ferroelectric/dielectric heterostructures are studied in the 10-GHz band. A frequency tunability of 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 (εr(KTN) varies from ~ 700 to ~ 200). Nevertheless this also leads to significant insertion loss due to the dielectric loss of the ferroelectric material itself (tanδr(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 Bi1.5Zn0.9Nb1.5O7−δ (BZN) oxide material is selected here for two main reasons, namely its low dielectric loss (tanδr(BZN) ≈ 0.005–0.0075) and its moderate relative permittivity (εr(BZN) ≈ 95–125) at 12.5 GHz. The relevance of this approach is studied numerically and experimentally. We compare numerically two different heterostructures for which the ferroelectric film is grown on the dielectric film (KTN/BZN), or vice versa (BZN/KTN). A stub resonator printed on the most relevant heterostructure has been fabricated, and experimental data are discussed and compared to the numerical results.
