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

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Title: Enhanced tunability and temperature-dependent dielectric characteristics at microwaves of K0.5Na0.5NbO3 thin films epitaxially grown on (100)MgO substrates.
Authors: Aspe, B.1,2 (AUTHOR) barthelemy.aspe@list.lu, Castel, X.1,2 (AUTHOR) xavier.castel@univ-rennes1.fr, Demange, V.1 (AUTHOR), Passerieux, D.3 (AUTHOR), Pinault-Thaury, M.A.4 (AUTHOR), Jomard, F.4 (AUTHOR), Députier, S.1 (AUTHOR), Cros, D.3 (AUTHOR), Madrangeas, V.3 (AUTHOR), Bouquet, V.1 (AUTHOR), Sauleau, R.2 (AUTHOR), Guilloux-Viry, M.1 (AUTHOR) maryline.guilloux-viry@univ-rennes1.fr
Source: Journal of Alloys & Compounds. Mar2021, Vol. 856, pN.PAG-N.PAG. 1p.
Subjects: Thin films, Epitaxy, Pulsed laser deposition, Microwave devices, Dielectrics, Magnesium oxide
Abstract: K 0.5 Na 0.5 NbO 3 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 K 0.5 Na 0.5 NbO 3 thin films. Dielectric permittivity ε r = 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 E bias = 94 kV/cm. Temperature measurements from 20° to 240°C exhibited a permittivity increase up to ε r = 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 K 0.5 Na 0.5 NbO 3 films on (100) MgO. ga1 • Epitaxial KNN perovskite thin films deposited by PLD on (100)MgO. • The structural characteristics of KNN thin films grown on (100)MgO benefit the frequency tunability of microwave devices. • Investigation of the dielectric characteristics from 20 °C to 240 °C shows the polymorphic phase transition of the KNN films. • The frequency tunability measured on a stub resonator at 180 °C emphasizes its enhancement near the PPT transition. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:K 0.5 Na 0.5 NbO 3 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 K 0.5 Na 0.5 NbO 3 thin films. Dielectric permittivity ε r = 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 E bias = 94 kV/cm. Temperature measurements from 20° to 240°C exhibited a permittivity increase up to ε r = 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 K 0.5 Na 0.5 NbO 3 films on (100) MgO. ga1 • Epitaxial KNN perovskite thin films deposited by PLD on (100)MgO. • The structural characteristics of KNN thin films grown on (100)MgO benefit the frequency tunability of microwave devices. • Investigation of the dielectric characteristics from 20 °C to 240 °C shows the polymorphic phase transition of the KNN films. • The frequency tunability measured on a stub resonator at 180 °C emphasizes its enhancement near the PPT transition. [ABSTRACT FROM AUTHOR]
ISSN:09258388
DOI:10.1016/j.jallcom.2020.158138