Pb Zr 1 − x Ti x O 3 (PZT) is one preferred ferroelectric material being used in nonvolatile ferroelectric random access memory devices. The use of oxide electrodes like IrO2 or SrRuO3 (SRO) is necessary to suppress the serious loss of polarization due to bipolar voltage cycling. Although, there are a number of models under discussion, the origin of the fatigue phenomenon is still not completely understood. In this paper, the fatigue effect of ferroelectric Pb(Zr0.40,Ti0.60)O3 thin films has been studied in detail. To achieve a deeper understanding of the effect, several PZT samples with different electrode materials were investigated. After determining the dependence of the single fatigue parameters, a simulation approach was made to analyze the fatigue effect qualitatively. A sample with SRO electrodes was measured up to 1013cycles and no fatigue of the switchable polarization was observed.
Effects of the thermal treatment and the fabrication process of Pb͑Zr 0.3 Ti 0.7 ͒O 3 ͑PZT͒ thin films using chemical solution deposition on Pt/ TiO x electrode stacks were investigated using complementary analytical techniques including atomic force microscopy ͑AFM͒, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and grazing incidence x-ray reflectivity of synchrotron radiation. The surface and interface structures of the Pt/ TiO x electrode stacks with different thermal treatments, and the PZT/ Pt/ TiO x sample were examined. The propagation of Pt hillocks on the bare Pt/ TiO x electrode stacks upon the annealing was observed. AFM observations also revealed that the upper surface of the Pt bottom electrode under PZT thin film became rougher than that of the bare Pt electrode with the same thermal history. Global structural information including the density, surface or interface root-mean-square roughness, and thickness of each constituent layer in the samples were determined using x-ray reflectivity. A density decrease of the Pt layer upon the annealing or during the fabrication of PZT thin films was found from fitting the specular reflectivity, and further confirmed by the negative shift of the Yoneda peak of Pt in the diffuse reflectivity. The formation of Pt hillocks on the bare Pt electrodes was attributed to the compressive stress during the high-temperature annealing caused by the limited incorporation of Ti and O into the Pt layer. Roughening of the PZT/Pt interface was ascribed to the interaction between the compressive stress in Pt and the indentation by the PZT crystallization and grain growth during the annealing.
Ferroelectric thin film capacitors are promising candidates for non-volatile ferroelectric Random Access Memories (FeRAM's) as they exhibit a switchable polarization. There are three important failure-mechanisms influencing the performance of these capacitors and disturbing the long-term stability and reliability under operation conditions fatigue, retention, and imprint. The imprint effect of lead zirconate titanate (PZT) thin films was investigated in this paper. Establishing and maintaining a polarization state leads to a shift of the hysteresis loop on the voltage axis and also to a loss of polarization. The voltage shift as well as the loss of polarization can cause a failure of the ferroelectric memory cell (read and write failure). The experimental results obtained on PZT films are discussed in view of the predictions of imprint models proposed in the literature.
Abstract:Effects of thermal annealing on the structure of polycrystalline Pb(Zr 0.3 Ti 0.7 )O 3 (PZT) ferroelectric thin films prepared by chemical solution deposition (CSD) on Pt/TiO x electrode stacks were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and grazing incidence X-ray specular and diffuse reflectivity of synchrotron radiation. The stratified multilayered structure and element diffusions in the sample were characterized by TEM. Global statistical structural parameters including the density, surface or interface roughness and thickness of each layer in the samples were obtained from fitting the Xray specular reflectivity using a homogeneous stratified multilayer model of PZT/Pt/TiO x /SiO 2 .The results showed that the PZT surface and PZT/Pt interface roughness changed only slightly during thermal annealing in oxygen at 700°C. By contrast, the density increase of the PZT ceramic and density decrease of the Pt bottom electrode during annealing were observed. A high density value of the PZT ceramic film after the annealing was found up to 99.8% of the theoretical value of the corresponding bulk ceramics. The density changes of the PZT and Pt layers were further confirmed by X-ray diffuse reflectivity. The influences of the annealing treatment on the density changes of the PZT and Pt layers were attributed to the further densification of the PZT ceramic and incorporation of light elements such as Zr, Ti and O from Title and abstract page 2 the neighboring layers into the Pt layer respectively, as discussed in correlation with the TEM analyses.
The fatigue of the electromechanical properties of tetragonal PbZrx, Ti1−xO3 thin films is investigated. The decrease of electromechanical small-signal response is compared to the fatigue of the electric properties and examined in detail. Property fatigue is attributed mainly to switching-failure of the unit cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.