Abstract 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 er = 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 er = 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.

中文翻译：

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在 (100) MgO 衬底上外延生长的 K0.5Na0.5NbO3 薄膜在微波下增强的可调性和温度相关的介电特性

摘要 K0.5Na0.5NbO3 薄膜是通过脉冲激光沉积在（100）MgO 衬底上用于微波器件应用的。X 射线衍射证明了纯钙钛矿相的精细外延生长。使用印刷在 500 nm 厚 K0.5Na0.5NbO3 薄膜上的共面微波器件在 1 至 40 GHz 范围内进行介电表征。介电常数 er = 355 和损耗角正切 tanδ = 0.35 在 10 GHz 时没有偏置。将结果与从谐振腔法（以表征沉积膜）中检索到的结果进行比较，表明无论是器件图案还是薄膜-器件界面都没有有害影响。在中等外部直流偏置电场 Ebias = 94 kV/cm 下测量了高达 22% 的频率可调性。从 20°C 到 240°C 的温度测量显示介电常数增加到 er = 975，同时在 10 GHz 下损耗降低 tanδ = 0.25。根据这样的测量，在接近 220°C 时证明了正交-四方相变，频率可调性增加了 34%。将此类薄膜的性能与在 R 面蓝宝石衬底上生长的薄膜进行比较，证明了在 (100) MgO 上外延生长 K0.5Na0.5NbO3 薄膜带来的好处。