Characterization Of PZT Thin Films Research Articles

Effect of cerium doping on the micro-structure and electrical properties of sol-gel derived Pb 1.05(Zr 0.53− δCe δTi 0.47)O 3 ( δ≤10 at.%) thin films

We have studied the effect of Ce on the phase formation behavior, surface morphology and electrical properties of sol-gel derived PZT thin films. Ce doping has been found to have a dramatic influence on the surface morphology and electrical characteristics of PZT thin films. Up to 1 at.% doping content Ce is found to improve the dielectric and ferroelectric properties and also optimal Ce doping is found to be effective in reducing the leakage current density and increasing the dielectric breakdown strength of PZT thin films. The fractional site occupancy of Ce ion has been predicted theoretically and the validity of the prediction has been investigated by XPS analysis. We have observed that Ce ions can exist both in +3 and +4 valence states. Up to 1 at.% content Ce predominantly enters into the A site with +3 valence state and acts as a donor dopant. The observed variation in microstructure and electrical properties have been discussed to be due to the fractional site occupancy of Ce ion either in A or B site, as a function of Ce doping content in PZT thin films.

Metallorganic Chemical Vapor Deposition of Pb ( Zr , Ti ) O 3 Films Using a Single Mixture of Metallorganic Precursors

and were used as metallorganic chemical vapor deposition (MOCVD) sources for (PZT) films. Thermal properties of PZT precursors and the stability of precursor solution were evaluated. A mixed solution of three precursors in tetrahydrofuran (THF) solvent showed a time-dependent degradation due to a ligand exchange reaction between and Growth characteristics of PZT thin films deposited on a substrate by MOCVD have been investigated. A direct liquid injection technique using a flash-vaporized metallorganic precursor solution was employed for the film deposition. The incorporation rates of constituent metals in the PZT film are strongly dependent on the substrate temperature and precursor molar ratios in the precursor solution. As the substrate temperature was increased, the incorporation rate of Pb and Ti increased and that of Zr remained constant. As the ratio of Zr/Ti in the PZT precursor solution was increased, decreased and increased. Pure perovskite films were obtained at temperatures between 470 and when a solution with an atomic ratio of was used. © 2001 The Electrochemical Society. All rights reserved.

Etch Behavior of Pb ( ZrXTi1 − X ) O 3 Films Using a TiO2 Hard Mask

Dry etching of lead zirconate titanate (PZT) thin film and Pt/PZT stack structure was investigated using a hard mask in an inductively coupled plasma (ICP). An annealed thin film was employed as an etch mask for PZT and Pt/PZT stack etching. Etch characteristics of PZT thin films were examined with etch chemistry in terms of the etch rate, the etch selectivity, and the etch profile. The etch selectivity of the PZT film to the mask was in the range of one to five at the etch conditions used in this study. It was found that the etch selectivity of the PZT film to the mask was strongly affected by the ratio of to concentration. An X-ray photoelectron spectroscopy study revealed that the gas played an important role in obtaining high selectivity of films. Finally, the pattern transfer of Pt/PZT stack structure with the submicrometer dimension was achieved using a hard mask. The sidewall angle of etched Pt/PZT stack was approximately without etch redeposition or residue. © 2001 The Electrochemical Society. All rights reserved.

Structural characterization of PZT thin films and related properties

This work is devoted to PZT thin films obtained by spin coating technique. The effect of temperature annealing on the morphology of thin films is studied by means of SEM, HREM and XRD. Thin films, originally amorphous, present after annealing a random orientation with regard to the substrate. Taking into account the poor adherence on the substrate, a new mechanism for fatigue involving the role of domain walls, is proposed.

Enhanced Fatigue and Data Retention Characteristics of Pb(Zr, Ti)O3 Thin Films by the Selectively Nucleated Lateral Crystallization Method

Fatigue and data retention characteristics of Pb(Zr, Ti)O3 (PZT) thin films by the selectively nucleated lateral crystallization (SNLC) method were investigated. By placing the top Pt electrode inside the grain and directly on the grain boundary, we measured and compared the electrical properties of PZT thin films based on the grain boundary. When there was no grain boundary underneath the top electrode, no loss in switched polarization up to 2×1011 cycles and no data loss after 30000 s of memory retention at room temperature with the Pt/PZT/Pt structure were observed. However, serious degradation of the fatigue and data retention characteristics of PZT thin films occurred when there was a grain boundary in the area studied. In this study, we show that when there is no grain boundary in the area measured, no degradation such as fatigue and retention occurs, thus the main source of degradation is the grain boundary in PZT thin films.

Introduction of Selectively Nucleated Lateral Crystallization of Lead Zirconate Titanate Thin Films for Fabrication of High-Performance Ferroelectric Random Access Memory

We found that large single grains of lead zirconate titanate (PZT) thin film of which grain size was as large as 40 µm in length could be fabricated by lateral crystallization from the seeds. The seeds were prepared on the Pt substrate in the form of crystallized PZT dots. The electrical characteristics of PZT thin films (Pt/PZT/Pt structure) obtained by selectively nucleated lateral crystallization (SNLC) were found to be superior to those of polycrystalline PZT thin films. PZT thin films obtained by SNLC showed a leakage current density of 8×10-8 A/cm2, a breakdown field of 1240 kV/cm, a saturation polarization of 42 µC/cm2, and a remanent polarization of 30 µC/cm2. No degradation of the electrical properties was observed even after 2×1011 cycles using 1 MHz square wave form at ±10 V. Retention test revealed no appreciable data loss after 30000 s of memory retention at room temperature.

Preparation and characterization of highly oriented Pb(Zr, Ti)O 3 thin films with seeding titanium layer deposited at low temperature by facing target sputtering

The highly oriented perovskite Pb(Zr, Ti)O 3 thin films with seeding titanium layer were deposited at low substrate temperature by facing target sputtering. The effects of substrate temperature and total gas pressure on the crystallographic characteristics of PZT thin films are investigated in this paper. The seeding mechanism of titanium layer is discussed. The 435°C-deposited sample showed ferroelectric properties with P r of 10.1 μC/cm 2 and P s of 11.6 μC/cm 2.

Pulsed laser deposition and characterization of PZT thin films

Pb(Zr 0.53Ti 0.47)O 3 (PZT) thin films were deposited on TiN coated Si substrates. PZT and TiN layers were grown by two subsequent laser ablation processes in oxygen and, respectively, nitrogen reactive atmosphere. Both deposition processes were conducted at quite low substrate temperature: 350°C for TiN and 375°C for PZT in the same experimental setup (Nd-YAG laser, λ=1.06 μm, energy/pulse 0.3 J, t FWHM=10 ns). The TiN electrode and PZT films were crystalline as revealed by XRD. The orientation of the PZT films was mainly (111) with about 30% component of (002) crystallographic phase. The high frequency optical vibrational modes of the ferroelectric PZT structure have been obtained from FTIR measurements. A mapping of the d 33 piezoelectric constant was obtained. Polarization hysteresis cycles of the samples were measured and high values of the remanent polarization and coercive electric field were obtained for all the samples.

Characterization of PZT thin films prepared by a modified sol–gel method

Lead zirconate titanate (PZT) thin films with thicknesses of around 5 μm were prepared by the deposition a sol slurry. This sol slurry consists of a PZT-sol on acetic acid basis and PZT powder. The sol serves as the dispersion agent of the powder. Both are identical in composition with molar ratio Zr/Ti of 0·53/0·47. Lead in excess of 5% was used in all samples. This coating conditions enhance the possibilities of film preparation.

Structural, dielectric and ferroelectric characterization of PZT thin films

In this work ferroelectric thin films of PZT were prepared by the oxide precursor method, deposited on Pt/Si substrate. Films of 0.5 mm average thickness were obtained. Electrical and ferroelectric characterization were carried out in these films. The measured value of the dielectric constant for films was 455. Ferroelectricity was confirmed by Capacitance-Voltage (C-V) characteristics and P-E hysteresis loops. Remanent polarization for films presented value around 5.0 µC/cm2 and a coercive field of 88.8 kV/cm.

Polarization, pyroelectric coefficient, and current-voltage characteristics of PZT thin films

Methods and results of experimental investigations of electro-physical properties of thin ferroelectric films are discussed.

Acceptor dopant effects on endurance of PZT thin films

The effect of acceptor (Na, Mg, Fe) and donor (Nb, Ta) dopants on the switching properties of Pb(Zr0.53Ti0. 47)O3 (PZT) thin films with Pt electrodes was investigated for broad dopant concentration ranges. The effect of dopants on endurance was found to be characteristic to type of doping (donor or acceptor) and independent of individual dopant element, microstructural features, or site of doping. All acceptor dopants studied were found to strongly improve the endurance characteristics of PZT thin films. Increasing the acceptor dopant concentration was found to shift the onset of polarization suppression (electrical fatigue) toward a higher number of switching cycles. It is proposed that the origin of endurance degradation in PZT thin films with Pt electrodes is the transition from p to n type stoichiometry with AC-switching, which leads to the formation of Ti3+ defects. Acceptor dopants shift the p to n transition to higher number of switching cycles, thus postponing the formation of Ti3+ defects, which results in improvement of endurance. It is shown, that PZT compositions (away from the morphotropic phase boundary) in which Ti3+ defects are less stable have better endurance characteristics. Guidelines for optimization of endurance characteristics of PZT thin films with Pt electrodes were developed.

Piezoelectric Characterisation of Ferroelectric PZT Thin Films Using an Improved Vibrating Beam Method

AbstractThis study proposes an improvement of the free vibrating beam method allowing characterization of the d31 coefficients of piezoelectric thin films. Preparation and piezoelectric characterization of PZT thin films are shown. An analytical model of the beam and the thin film is developed. Finite element modeling allows for definition of the validity conditions of the model. A numerical fitting of the model to the experimental values exhibits an excellent overlap. We obtain d31 values from 10 pC/N to 14 pC/N. Advantages of this method are shown compared to the first maximum voltage method.

Influence of Al 2O 3 diffusion barrier and PbTiO 3 seed layer on microstructural and ferroelectric characteristics of PZT thin films by sol-gel spin coating method

Sol-gel spun-casted Pb(Zr 0.52Ti 0.48)O 3 [PZT]thin film with Al 2O 3 buffer layer and PbTiO 3 seed layer was successfully prepared at a low temperature of 550°C. Al 2O 3 buffer layer, as a diffusion barrier between the silicon substrate and the Pt bottom electrode, suppressed interface reactions between the film and the substrate and prevented the interdiffusion of Pb and Si elements. PbTiO 3 seed layer between the Pt bottom electrode and the PZT thin film promoted the formation of perovskite phase at lower temperature due to the presence of ample nucleation sites. The microstructure of the PZT thin film is composed of homogeneous submicron grains. Dielectric constant and tan δ of the PZT thin film with the buffer and the seed layer were enhanced by 3–5 times in comparison to the PZT film without the buffer and the seed layer. Typical P-E hysteresis behavior was observed even at applied voltages as low as 5 V, manifesting greatly improved remanent polarization and coercive field. Fatigue characteristic, measured at 7 V, showed stable behavior. Degradation in polarization was found to be less than 5% at 10 8 cycles.

Poling Field Dependence of Ferroelectric Domains in Tetragonal Lead Zirconate Titanate Ceramics

The ferroelectric domain structures of tetragonal lead zirconate titanate (PZT) ceramics were evaluated by investigating the poling field (E) dependence of the planar coupling factor (k p) and the relative intensity of X-ray diffraction (002) peak, I002. Fifteen typical domain configurations were proposed. Furthermore, we selected the two patterns which make a domain configuration model with 90° and 180° domains. It was thought that the change in domain structure due to poling could be explained by calculating the change in area of domain for each axis. Therefore, the total number of domains oriented along the c axis was estimated from using the relationship between I002, k p, the normalized polarization and E. Using our domain configuration model, it was confirmed that there were two peaks corresponding to 90° domain rotation and one peak corresponding to 180° domain switching. After the 90° domain rotation occurred, the domains along the c axis were changed mainly by 180° switching. As a result, the degree of 90° domain rotation decreased and that of 180° domain switching increased. Our study on domain structures in bulk ceramics is useful for understanding the degradation characteristics of PZT thin films.

The Effects of Biaxial Stress on the Ferroelectric Characteristics of PZT Thin Films

ABSTRACTThe design and implementation of microelectromechanical (MEMS) systems requires a sound understanding of the influence of film stress on both the ferroelectric and piezoelectric characteristics of thin films to be used for sensing and/or actuation. Experiments were conducted in which thin film samples of sol-gel derived PZT were subjected to applied biaxial stresses from -139 to 142 MPa. Films were characterized at known stress states (derived from known values of residual stress and large deflection plate theory) in terms of their ferroelectric polarization (saturated and remnant), dielectric constants, coercive field strengths, and tan δ. Results obtained indicate that domain wall motion in thin films contributes much less to the observed response than is typical for bulk PZT materials. Alternative mechanisms are proposed in an attempt to explain the discrepancies.

Characterization of PZT thin films for micromotors

Piezoelectric membranes consisting of sputter deposited PbZr xTi 1−xO 3 (PZT) films on silicon diaphragms have been investigated for their resonance and piezoelectrical properties, in view of their application as stator of a micromotor. The behavior of resonance frequencies was studied as a function of membrane thickness and dc-bias, in order to derive the total stress in the films and the piezoelectric coupling constant (d 31≈40 pm/V). The latter was also derived from the quasi-static deflections.

Electrical properties of PZT thin films for memory application

Abstract The development of ferroelectric memory device requires improvements in electrical characteristics such as fatigue, retention, imprint and other properties. Fatigue properties of PZT thin films were improved by using Pt/IrO2 or Ir/IrO2 used as electrodes, we reported. This report presents a study of the retention and the imprint characteristics of PZT thin films on various electrodes. Pt/IrO2 and Ir/IrO2 layer structures were used as electrodes of the PZT capacitors. In the case of using an Ir/IrO2 electrode, the improvements in electrical properties from the measurements of the retention and the imprint characteristics.

Electrical Properties of Pb(Zr,Ti)O 3 Thin Film Capacitors on Pt and Ir Electrodes

Pb(ZrxTi1-x)O3 (PZT) thin films were prepared on Ir/IrO2 and Pt/IrO2 electrodes. We have already reported that fatigue properties of PZT thin films were improved by using these electrodes due to barrier effects of IrO2. In this present paper we describe a study of the imprint characteristics of PZT thin films on these electrodes. There is little difference in fatigue properties between the PZT films on Pt/IrO2 and Ir/IrO2. However, we find some difference in imprint characteristics between the PZT films on these electrodes. In the case of Ir/IrO2 electrode, improvements in the electrical properties are observed in the measurements of the imprint characteristics. Moreover, improvements in imprint characteristics were also obtained with good (111)-axis orientation of PZT films when PtxIr1-x/IrO2 electrodes were used.

Comparison of lead zirconate titanate thin films on ruthenium oxide and platinum electrodes

High-resolution and bright- and dark-field transmission electron microscopy are used to characterize and compare the interface structures and microstructure of PZT/RuO2/SiO2/Si and PZT/Pt/Ti/SiO2/Si ferroelectric thin films, with a view to understanding the improved fatigue characteristics of PZT thin films with RuO2 electrodes. The RuO2/PZT interface consists of a curved pseudoperiodic minimal surface. The interface is chemically sharp with virtually no intermixing of RuO2 and PZT, as evidenced by the atomic resolution images as well as energy dispersive x-ray analysis. A nanocrystalline pyrochlore phase Pb2ZrTiO7−x, x≠1, was found on the top surface of the PZT layer. The PZT/Pt/Ti/SiO2/Si thin film was well crystallized and showed sharp interfaces throughout. Possible reasons for the improved fatigue characteristics of PZT/RuO2/SiO2/Si thin films are discussed.