Investigation of the High Frequency Properties of BST Thin Films--A Comparison of Three Different Commonly Used Methods

Abstract

In this work three different commonly used high frequency measurement techniques for the determination of the electrical properties of BST thin films are compared. Two of the three setups determine the permittivity and the loss factor of planar sapphire capacitors by either measuring the reflection coefficient or the influence onto the resonance frequencies of two coupled microstrip resonators. The third setup utilizes the differential propagation constant of two identical coplanar wave guides (CPW) of different length to calculate the permittivity and the loss factor of the involved sapphire substrate.It is found that the latter method shows the best accuracy for the measurement of the permittivity and the loss factor of the sapphire substrates over a broad frequency range. Measurements of BST coated sapphire substrates are presented using this technique.