Development of ferroelectric thin films and composite materials by sol-gel process

Abstract

Sol-gel processing provides an interesting alterative for the fabrication of ferroelectric thin films and composite materials which both are useful in various electronic applications. In this study , lead zirconate titanate (PZT) thin films with a Zr/Ti ratio of 52/48 were fabricated by spin-coating solutions of polymeric complex Pb, Zr, Ti-methoxyethoxide onto Pt-coated Si substrates. A technique of adding excess Pb in the solution was used in order to reduce an intermediate or second phase formation phase formation which usually became a problem for PZT film formation. This techmque led to a complete transformation of the intermediate phase to the desired perovskite phase. In addition, the exploration of annealing conditions was also considered. The sol-gel derived PZT films containing 10 mole% excess Pb showed good ferroelectric and dielectric properties at the annealing condition of 700℃, 30 minutes. The remnant polarization was 19.2 µc/cm² for 7 volts applied voltage. The coercive field was 46.4 kV/cm for films with thickness of 3,000 Å . The relative reasonable value of dielectric constant was 940. The good quality films could be due to the nearly complete crystallization to the single perovskite phase. The results from electrical properties corresponded to the uniform and dense microstructure which was observed by field-emission scanning electron microscope (FE-SEM). In the part of thick film, printable paste of sol-gel based composite can be produced by dispersing 75% by weight PZT powders in 0.88 M PZT sol-gel solution.