Field dependence of dielectric properties of (Pb,Sr)TiO3 thin films

(Pb,Sr)TiO3 (PST) thin films have been deposited on (111)Ir/SiO2/Si and <100>-oriented SrTiO3:La substrates by RF magnetron sputtering from a multi-target comprised of a SrTiO3 ceramics target, 4 PbO pellets and some pure Ti metal chips. The film sputtered on Ir/SiO2/Si was polycrystalline film, and showed a slender D-E hysteresis loop. The temperature dependence of dielectric constant showed a very broad peak at 60degreesC. The dielectric constant was 1250 at 500 kHz and the tunability by DC bias performed a high value of 50% (E=15kV/mm) at room temperature. The film grown on SrTiO3:La. substrate was epitaxial film, and drew a small asymmetrical D-E hysteresis loop. The dielectric constant dropped to 140. The tunability was 30% under bias from -0.8 to 0.8 V (20 kV/mm) at room temperature.