A Investigation of the Dielectric and Hysteresis Properties of Plzt Ferroelectric and Multilayer Composite Thin Films.
The dielectric and hysteresis properties of ferroelectric and multilayer composite thin films were investigated. PLZT ferroelectrics were produced in bulk ceramic and thin film form from the same acetate precursor solutions in order to compare their electrical and physical properties. Bulk ceramics were hot pressed from chemically coprecipitated powders, and thin films were fabricated by spin and dip coating on Ag and Pt-coated Si substrates. Internal film stress from thermal expansion mismatch between films and substrates was found to contribute to differences in electrical properties and Curie temperatures between the thin film and bulk materials as were interface layer effects, grain size and mechanical clamping from the substrates. Rapid thermal processing (RTP) of PLZT thin films using an automated spin coat reactor was found to improve thin film dielectric and hysteresis properties as well as enhance perovskite phase formation, induce preferred (110) and (111) orientations, decrease grain size and increase microstructural uniformity. RTP films were compared with manually spin coated thin films with conventional furnace pyrolysis (CFP) in order to isolate the effects of heating rate from deposition technique. Heating rates of at least 70^circC per second were obtained by RTP versus 35^circC per second for CFP. The development of composite thin films further optimized PLZT thin film properties. Improved antiferroelectric -to-ferroelectric domain switching with decreased ferroelectric coercive field, increased induced polarization with decreased coercivity and polarization remanence for relaxor-type composites and increased hysteresis loop squareness for ferroelectric memory materials were among the advances compared with films of homogeneous PLZT composition. Experimental dielectric and hysteresis properties were described by a series capacitor model consisting of the linear and nonlinear properties of the individual composite components.
- Pub Date:
- January 1995
- Engineering: Materials Science; Engineering: Electronics and Electrical; Physics: Condensed Matter