Recently, strong interest have been paid to the development of tunable dielectric materials for microwave devices, such as tunable filters, voltage controlled oscillators, varactors, delay lines and phase shifters. Ba_1-xSr_xTiO₃ (BST) thin films are considered as one of the forerunner material systems for realization of such tunable components due to their high dielectric constant and dielectric tunability, reasonably low dielectric loss, and controllable Curie temperature by adjusting the barium-to-strontium ratio. A practical concern in a tunable microwave resonator is that its resonant frequency changes with the temperature because it strongly depends upon the dielectric constant of material, which, for example, is highly temperature dependent for BST films of fixed composition. To improve the temperature stability of the dielectric constant, and simultaneously enhance the dielectric tunability and lower the dielectric loss, a promising approach is to prepare BST-based multilayer structures with different Ba/Sr ratios.

In this work a set of BST60/40 and 40/60 BST multilayers separated by nano-size layer of TiO₂ were produced by pulsed laser (KrF) deposition technique  on a (111)Pt/TiO₂/SiO₂/Si substrate. The study of dielectric properties and the impedance spectroscopy analysis have been performed in the frequency window 10-10⁶ Hz and temperature range 10-150 ^oC. The study of processing – structure – property relationships has been performed and the results are presented.

Acknowledgement. The Authors (D.C. and A.L-C) acknowledge the support of Polish Ministry of Education and Science within a research project N507 098 31/2319 funded from the funds for science in 2006-2009.

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