Comparative studies of ferroelectric thin films for high frequency phase shifter applications

We have synthesized Pb0.3Sr0.7TiO3 (PST30) thin films on platinum and lanthanum aluminate substrates using chemical solution deposition technique. The films on platinum substrate were polycrystalline, whereas the film on LAO substrate was highly (100) oriented. These films were characterized for their structure, surface morphology, and dielectric properties. Dielectric measurements of the films on Pt were carried out using metal-insulator-metal(MIM) structure and that on LAO, using 50 finger inter-digitated electrodes. For high frequency (Ku band) measurements, eight element coupled phase shifters were deposited on the PST film on LAO and the characteristics were evaluated in terms of their phase shift and insertion losses. The figure of merit was found to be similar to 49 degrees/dB at 15.75 GHz, which is better than the one obtained for pure BST50 film (similar to 33 degrees/dB).