KxNa1−xNbO3 perovskite thin films grown by pulsed laser deposition on R-plane sapphire for tunable microwave devices

• Published in: Journal of materials science 2018-09, Vol.53 (18), p.13042-13052
• Main Authors: Aspe, B., Cissé, F., Castel, X., Demange, V., Députier, S., Ollivier, S., Bouquet, V., Joanny, L., Sauleau, R., Guilloux-Viry, M.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Electromagnetism; Electronic Materials; Engineering Sciences; Materials; Materials Science; Micro and nanotechnologies; Microelectronics; Polymer Sciences; Solid Mechanics
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-018-2593-9

K x Na 1− x NbO 3 thin films with x  = 0.5 and x  = 0.7 were deposited by pulsed laser deposition onto R-cut sapphire substrates to be suitable for microwave applications. The 500–800-nm-thick films present a preferential (100) orientation. The ω -scans show a weak mosaicity (full-width at half-maximum equal to 0.36° and 0.60° for x  = 0.5 and x  = 0.7, respectively). In addition to this texture, the in-plane ordering evidenced by X-ray diffraction φ -scan for the (100) orientation is in agreement with an epitaxial-like growth in spite of the high lattice mismatch between K x Na 1− x NbO 3 and sapphire. The dielectric characteristics and the frequency tunability at microwave frequencies were obtained from coplanar waveguide devices (transmission lines and stub resonators). For the K 0.5 Na 0.5 NbO 3 and K 0.7 Na 0.3 NbO 3 compositions, high dielectric permittivity ε r values of 360 and 250 and loss tangent tan δ values of 0.36 and 0.43 without biasing were retrieved from the transmission line measurements at 10 GHz, respectively. Frequency tunabilities of 15 and 12% have been assessed under 80 kV/cm biasing from stub resonator measurements for the K 0.5 Na 0.5 NbO 3 and K 0.7 Na 0.3 NbO 3 compositions, respectively. K 0.5 Na 0.5 NbO 3 composition is therefore a promising solution for miniaturized tunable devices at microwave frequencies.