Study of ferroelectric/dielectric multilayers for tunable stub resonator applications at microwaves Article - Février 2014

Yonathan Corredores, Arnaud Le Febvrier, Xavier Castel, Ronan Sauleau, Ratiba Benzerga, Stéphanie Députier, Maryline Guilloux-Viry, Ali Mekadmini, Noham Martin, Gérard Tanné

Yonathan Corredores, Arnaud Le Febvrier, Xavier Castel, Ronan Sauleau, Ratiba Benzerga, Stéphanie Députier, Maryline Guilloux-Viry, Ali Mekadmini, Noham Martin, Gérard Tanné, « Study of ferroelectric/dielectric multilayers for tunable stub resonator applications at microwaves  », Thin Solid Films, février 2014, pp. 109-113. ISSN 0040-6090

Abstract

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.

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