Enhanced tunability and temperature-dependent dielectric characteristics at microwaves of K0.5Na0.5NbO3 thin films epitaxially grown on (100)MgO substrates

Barthélemy Aspe (1, 2) , Xavier Castel (2) , Valérie Demange (3, 1) , Damien Passerieux (4) , Marie-Amandine Pinault-Thaury (5) , François Jomard (5) , Stéphanie Députier (1) , Dominique Cros (4) , Valérie Madrangeas (4) , Valérie Bouquet (1) , Ronan Sauleau (2) , Maryline Guilloux-Viry (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 IETR - Institut d'Électronique et des Technologies du numéRique
3 ScanMAT - Synthèse Caractérisation Analyse de la Matière
4 XLIM - XLIM
5 GEMAC - Groupe d'Etude de la Matière Condensée

K0.5Na0.5NbO3 thin films were deposited by pulsed laser deposition on (100)MgO substrates for microwave device applications. A fine epitaxial growth of pure perovskite phase was evidenced by X-ray diffraction. Dielectric characterizations were performed from 1 to 40 GHz using coplanar microwave devices printed on the 500 nm-thick K0.5Na0.5NbO3 thin films. Dielectric permittivity εr = 355 and loss tangent tanδ = 0.35 at 10 GHz were retrieved without biasing. A comparison of the results with those retrieved from the resonant cavity method (to characterize as-deposited films) showed no deleterious influence neither from the device patterning nor the thin film-device interface. A frequency tunability up to 22% was measured under a moderate external DC bias electric field Ebias = 94 kV/cm. Temperature measurements from 20° to 240°C exhibited a permittivity increase up to εr = 975 coupled to a loss decrease tanδ = 0.25 at 10 GHz. According to such measurements, an orthorhombic-tetragonal phase transition was evidenced close to 220 °C with an increase of the frequency tunability up to 34%. Comparison of the properties of such films with those grown on R-plane sapphire substrates demonstrated the benefit brought by the epitaxial growth of K0.5Na0.5NbO3 films on (100) MgO.

Mots clés: KNN; ferroelectric; thin film; tunable device; microwave

Domaines: Matériaux; Micro et nanotechnologies/Microélectronique; Electromagnétisme

Barthélemy Aspe, Xavier Castel, Valérie Demange, Damien Passerieux, Marie-Amandine Pinault-Thaury, et al.. Enhanced tunability and temperature-dependent dielectric characteristics at microwaves of K0.5Na0.5NbO3 thin films epitaxially grown on (100)MgO substrates. Journal of Alloys and Compounds, 2021, 856, pp.158138. ⟨10.1016/j.jallcom.2020.158138⟩. ⟨hal-03059275⟩