Characterization of the Property Degradation of PZT Thin Films with Thickness

Abstract

The property degradation of lead zirconate titanate (PZT) thin films with thickness was investigated. PZT thin films were fabricated under the optimum established conditions. PZT thin films with a thickness of less than 30 nm did not show the perovskite phase. When considering the thickness of the reacted layer between the PZT thin film and the Pt bottom electrode of about 10 nm in thickness, a thickness of 30 nm was considerable compared to the critical thickness (18 nm) over which PZT shows ferroelectricity. The degree of (001) orientation increased as the thickness increased due to the competition between the effect of the surface energy and that of the lattice mismatch with Pt(111). The degradation of the ferroelectricity with increasing PZT thickness was investigated. PZT thin films with a thickness of less than 30 nm did not show ferroelectric properties. The remnant polarization decreased and the coercive field increased as the PZT thickness decreased. We speculate that the increase in the residual stress and the decrease in the grain size with decreasing film thickness were the major factors in the decrease in the remnant polarization while the increase in the contribution of the low dielectric layer between the PZT and the bottom electrode contributed most to the increase in the coercive field. The leaky behavior of PZT thin films with thicknesses of less than 30 nm appeared to be due to the existence of metallic Pb at the PZT grain boundary, as observed by X-ray photoelectron spectroscopy.