Electrical and optical characterization of wet chemically derived lead zirconate titanate thin films.

Abstract

The present investigation is concerned with the preparation and characterization of sol-gel derived lead zircon ate titanate (PZT) powders and films. Particular emphasis is placed on the synthesis, processing and characterization of thin films. The chemistry employed involves the use of alkoxides of Ti/Zr and lead acetate trihydrate. PZT gels were prepared and characterized insights gained were used as the basis for the synthesis and characterization of thin films. A model was also proposed to augment further understanding of the PZT capacitors obtained. PZT thin films were successfully prepared on various substrates such as platinized Si wafers and Corning 7059 glass. Numerous electrical and optical characterizations were performed, namely dielectric constant and loss, hysteresis loop, switching, fatigue, aging, leakage currents, refractive index, UV transmission spectroscopy, second harmonic generation (SHG) and waveguide loss. These electrical and optical properties are discussed in conjunction with film microstructure and phase assemblage. Very high quality films were obtained (e.g., dielectric constant as high as 3000 at 1kHz, and fatigue-free beyond 10⁸ cycles and optical loss as low as 1.1 dB/em). Aging of these films can be kept as low as l%/decade. It was found that the domains play an important role in determining the dielectric properties. A model of the Pt-PZT-Pt capacitor was successfully developed based on totally depleted back-to-back Schottky barriers and the model predictions agree extremely well with measured device characteristics. This model also explains the different dielectric behaviours of FE films compared to those of bulk ceramics. By tailoring the chemistry and controlling the post-deposition processing conditions and hence microstructures, the properties (both electrical and optical) of the PZT films can be effectively engineered.