Abstract

CHANG, Wontae et al. (Ba,Sr)TiO₃ ferroelectric thin films for tunable microwave applications. Rev. mex. fis. [online]. 2004, vol.50, n.5, pp.501-505. ISSN 0035-001X.

The dielectric properties of ferroelectric thin films were investigated for tunable microwave applications. We have observed that epitaxially grown Ba_1-x Sr_x TiO₃ (BST, 0.4≤ X ≤1) films are distorted from the normal cubic symmetry of the corresponding bulk at room temperature. This structural distortion caused by film strain has a strong impact on the microwave dielectric properties. For compressive strain, the dielectric constant and tuning were decreased and the films showed high dielectric Q. However for tensional strain, the opposite effect was observed. This observation has been interpreted based on phenomenological thermodynamics and strain-induced polarization physics. Two experimental examples, strain-relieved films and strain-enabled films, are presented to show how film strain affects the tunable microwave properties.

Keywords : Ferroelectrics; thin films; tunable application; microwave.

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