Structure and properties of heteroepitaxial Pb(Zr_0.35Ti_0.65)O₃/SrRuO₃ multilayer thin films on SrTiO₃ (100) prepared by MOCVD and RF sputtering

Abstract

Epitaxial SrRuO₃ thin films were deposited on SrTiO₃ (100) substrates by RF sputtering for use as bottom electrodes and epitaxial buffer layers. On these conductive substrates, epitaxial Pb(Zr_0.35Ti_0.65)O₃ (PZT) thin films were deposited by metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD), transmission electron microscopy (TEM) and optical waveguiding were used to characterize the phase, refractive index, and film thickness of the deposited films. The epitaxial PZT films were c-axis oriented and contained -19.7% volume fraction of 90° domains. Ferroelectric hysteresis and dielectric measurements of epitaxial PZT ferroelectric capacitor structures formed using sputtered ITO top electrodes showed: a remanent polarization of 51.8 Ω/cm₂, a coercive field of 54.9 kV/cm, a dielectric constant of 410, a bipolar resistivity of ∼5.8x10⁹ Ω-cm at a field of 275 kV/cm, and a breakdown strength of >400 kV/cm. The cyclic fatigue behavior of the films showed a strong dependence on the choice of electrode materials and the fatiguing wave form. These data support the model that the fatigue mechanism in these films arises from the trapping of injected charge carriers and is predominately an electronic phenomenon.