Ordered Mesoporous Thin Film Ferroelectrics of Biaxially Textured Lead Zirconate Titanate (PZT) by Chemical Solution Deposition

摘要

Lead zirconate titanate (PZT) thin film nanostructures with a high degree of biaxial texturing and good ferroelectric properties have been prepared by facile chemical solution deposition on (001)-oriented STO:Nb and LSMO/STO:Nb substrates using a poly(ethylene-co-butylene)-block-poly(ethylene oxide) diblock copolymer as structure-directing agent. The samples were thoroughly characterized by electron microscopy, synchrotron-based grazing incidence small-angle X-ray scattering, X-ray diffraction (including $\theta$–2$\theta$, $\omega$, and $\psi$ scans), X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and by ferroelectric polarization switching and fatigue measurements. We show that (1) the cubic mesostructured films with 16 nm diameter pores can be crystallized to produce single phase perovskite PZT with retention of nanoscale order, (2) the sol–gel derived material has an in-plane texture of $\sim$1.9° and an out-of-plane texture of $\sim$1.5°, and (3) the top surface is Zr-rich (the composition in the interior of the films is closer to the targeted composition of $PbZr_{0.52}Ti_{0.48}O_{3}$). The coercive field and remanent polarization of approximately 100 nm-thick films derived from dynamic P–E experiments are $\sim$250 kV cm$^{–1}$ and $\sim$25 $\mu$C cm$^{–2}$ ($\sim$7 $\mu$C cm$^{–2}$ after subtracting the non-switching components). Despite the use of Au top electrodes, the nanocrystalline samples show reasonable fatigue performance. All these features render the mesoporous PZT thin films attractive, for example, for producing strain-coupled composite multiferroics.