Electrical and Mechanical Properties of PZT Films

Abstract

ABSTRACTPZT is a well known ferroelectric material which has been investigated in thin film form for memory, electro-optical and actuator applications. The electrical and electro-mechanical properties of thin PZT films deposited by opposed target RF-sputtering and laser ablation were determined. The targets were sintered and one of them had a composition near the morphotropic phase boundary (48% Ti and 52% Zr) while the other one was on the tetragonal side of the phase diagram with 60% Ti and 40% Zr. Both types had 25% excess lead. The thin films were deposited on a number of substrates (MgO, CaF2, Al2O3 and Spinel. Platinum electrodes were e-beam evaporated on Si/SiO2 as well as on the above single crystal materials). We have measured the relative dielectric constant ε, the polarization P and the electrical field to mechanical strain conversion factor d33. The values which were obtained are compatible with bulk materials but an annealing step at 575°C in oxygen is necessary after deposition. The values before anneal are often significantly lower and we have attributed the reduction to interface layers between the electrodes and the perovskite film or a surface layer on the grains. The d33 coefficients were determined by an interferometric technique which directly detects the surface displacement of the electrode dot.