Proton-irradiated Pb(Zr0.52Ti0.48)O3 thick films for flexible non-volatile memory applications

We investigated the ferroelectricity in proton-irradiated flexible Pb(Zr_0.52Ti_0.48)O₃ (PZT) thick films and their non-volatile memory characteristics. The Ni-Cr metal foil substrate allowed high-quality polycrystalline PZT films with flexible functionality to be fabricated using conventional sol-gel and high-temperature annealing methods. The 10-MeV proton-irradiated PZT film exhibited an almost square polarization?electric field hysteresis curve with saturated (P_s) and remnant (P_r) polarizations of 18.9 and 17.0 μC/cm², respectively; which are slightly lower than as-grown PZT with P_s = 28.7 μC/cm² and P_r = 24.3 μC/cm². The P_r did not decrease even after 1000 cycles of continuous bending and unbending at a bending radius of 2.14 mm and decreased slightly to ～80% of its initial value after 10⁵ s. Although the P_r decreased to ～55% after 10¹⁰ cycles, the electric polarization remained switchable under positive and negative electric fields. These characteristics suggest that the flexible PZT films could be utilized in non-volatile memory device applications in environments with high doses of proton irradiation, such as those in aeronautics and nuclear power plants.     

Excimer laser-induced transformation in laser ablated Pb(Zr0.52Ti0.48)O3 amorphous thin films

Pb(Zr_0.52Ti_0.48)O₃ (PZT) amorphous thin films were deposited on Si substrates at room temperature and 573?K by pulsed laser deposition. The as-deposited films were subsequently annealed at various laser power densities using a KrF pulsed excimer laser irradiation to induce the phase transformation from amorphous to ferroelectric perovskite structure. Structural analysis shows the possibility of transformation from pyrochlore to perovskite transformation when irradiated above a laser power density of 1.4?MW/cm², which is in agreement with the thermal simulation. The surface quality of the PZT films deposited on 573?K is remarkably superior to that deposited at room temperature due to the enhanced thin structure and composition homogeneity. Almost all the pyrochlore phase transformed into perovskite structure after annealing at 2.8?MW/cm² for 120?s for both PZT films deposited at room temperature and 573?K, respectively. P-E hysteresis measurement of the laser-treated PZT shows relatively low remnant polarization P _r of about 1.2?μC/cm².     

Fatigue-free Pb(Zr0.52Ti0.48)O3 thin films on indium tin oxide coated substrates by a sol-gel process

Fatigue-free Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric thin films were successfully prepared on indium tin oxide (ITO) coated glass substrates using the sol-gel method combined with a rapid thermal annealing process (RTA). The films post-annealed at a temperature of 700 °C for 2 min by RTA process formed (110)-oriented Pb(Zr_0.52Ti_0.48)O₃ thin films with pure perovskite structure, and had a good morphology as well. The good ferroelectricity of the prepared PZT films was confirmed by P–E hysteresis loop measurements. Fatigue characteristics showed stable behavior. Degradation in polarization was not found while the repeating cycles were up to 10¹¹, and a low leakage current density of 10⁻⁸ A/cm² was also obtained from the highly fatigue-resisted PZT thin films on ITO/glass substrates. Received: 19 October 1998 / Accepted: 29 March 1999 / Published online: 26 May 1999     

不同衬底上Pb(Zr0.52Ti0.48)O3择优取向铁电薄膜的制备和研究

通过MOD法在Si(100)和Pt(111)/Ti/SiO2/Si基片上制备出LaNiO3 (LNO)薄膜.再通过修正的Sol-gel法,在Pt(111)/Ti/SiO2/Si,LNO/Si(100)和LNO/Pt/Ti/SiO2/Si三种衬底上制备出具有择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜.经XRD分析表明,LNO薄膜具有(100)择优取向的类钙钛矿结构;PZT薄膜均具有钙钛矿结构,且在Pt(111)/Ti/SiO2/Si衬底上的薄膜以(110)择优取向,在LNO/Pt/Ti/SiO2/Si和LNO/Si(100)衬底上的薄膜以(100)择优取向.经场发射SEM分析和介电、铁电性能测试表明,在LNO/Si和LNO/Pt/Ti/SiO2/Si衬底上的PZT薄膜的平均粒径、介电常数以及剩余极化强度均比以Pt/Ti/SiO2/Si为衬底的薄膜大.     

Pulsed laser deposition of Pb(Zr0.52Ti0.48)O3 thin film on cobalt ferrite nano-seed layered Pt(111)/Si substrate: effect of oxygen pressure

The effect of oxygen pressure during pulsed laser deposition of Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films on CoFe₂O₄ nano-seed layered Pt(111)/Si substrate was investigated. The PZT film deposited at oxygen pressure lower than 25 mTorr is identified as both perovskite and pyrochlore phases and the films deposited at high oxygen pressure (50-100 mTorr) show the single-phase perovskite PZT that has a perfect (111)-orientation. In addition, the film deposited at P_O2 of 50 mTorr has a uniform surface morphology, whereas the film deposited at P_O2 of 100 mTorr has a non-uniform surface morphology and more incompacted columnar cross-section microstructure. The polarization of film deposited at 100 mTorr is higher than that deposited at 50 mTorr, but shift of the hysteresis loop along the electrical field axis in the film deposited at P_O2 of 100 mTorr is larger than that of the film deposited at P_O2 of 50 mTorr.     

In situ hot-stage transmission electron microscopy of Pb(Zr0.52Ti0.48)O3

The domain structure of Pb(Zr_0.52Ti_0.48)O₃ before and after hot-stage experiment has been studied. The influence of maximum temperature, heating and cooling rate on the domain configuration of Pb(Zr_{1? x} , Ti _x )O₃ with x = 0.40, 0.45, 0.48 and 0.55 was analysed. A reliable basis for further hot-stage experiments of Pb(Zr_1?x, Ti_x)O₃ has been established. The investigations revealed a temperature dependent appearance and disappearance of nano- and microdomains. The appearance of microdomains in the nano scale range during cooling, denoted as domain miniaturisation, and the time dependent recovering of the former domain structure, revealed that under specific experimental conditions the domain configuration is reversible.     

In-situ X-ray microdiffraction analysis of local strain-field across the interface in a Pb(Zr0.52Ti0.48)O3/Ni0.8Zn0.2Fe2O4/Pb(Zr0.52Ti0.48)O3 tri-layered structure

We have performed a synchrotron X-ray microdiffraction to investigate the variation of the local strain-field across the interface in Pb(Zr_0.52Ti_0.48)O₃/Ni_0.8Zn_0.2Fe₂O₄/Pb(Zr_0.52Ti_0.48)O₃ (PZT–NZFO–PZT) tri-layered structure. In this study, we show that the in-plane lattice parameters of the NZFO lattice depend strongly on the piezoelectric strain of the PZT layer. This result explains that an electric-field-induced piezoelectric strain from the PZT layer is effectively transferred to the NZFO layer. Furthermore, the local strain persists within 20 μm away from the interface, inducing changes of magnetic responses via the inverse magnetostrictive effect.     

Pb(Zr0.3Ti0.7)O3铁电薄膜激光感生电压效应

采用脉冲激光沉积(PLD)技术在LaSrAlTaO₃(LSATO),LaAlO₃(LAO)和SrTiO₃(STO)的单晶倾斜衬底上成功制备了Pb(Zr_0.3Ti_0.7)O₃(PZT)薄膜,在三种倾斜衬底上生长的PZT薄膜中都首次发现了LIV效应.对PZT/LSATO薄膜在a,c轴两种不同取向择优生长下的LIV效应做了研究,发现在薄膜c轴取向择优生长 关键词： 激光感生电压效应 铁电薄膜 薄膜生长取向 原子层热电堆     

Effect of electric-field-assisted thermal treatment on the strain and ferroelectric properties of (100)-oriented ferroelectric Pb(Zr0.52Ti0.48)O3 thin films

Ferroelectric Pb(Zr_0.52Ti_0.48)O₃ thin films were deposited on the Pt/Ti/SiO₂/Si substrate by a sol-gel method. As a direct electric field was applied on the films during thermal treatment, strain behavior and ferroelectric properties have been investigated. X-ray diffraction patterns show that great tensile strain exists nearby the interface of the 250 nm thin film while thermal treatment assisted with direct electric field can obviously relax it. The analysis of hysteresis loops indicates that the remnant polarization increases with the thermal treatment time. These results suggest that electric-field-assisted thermal treatment is an effective way to reduce films' tensile strain through the local plastic deformation in Pt layer and enhance the remnant polarization.     

Low temperature crystallization behavior of multi-walled carbon nanotubes/Pb(Zr0.52Ti0.48)O3 nanocomposite thin films through annealing in various atmosphere and duration control

We report a successful fabrication of 300 nm thick carbon nanotubes and Pb(Zr_0.52Ti_0.48)O₃ (CNT–PZT) nanocomposite thin films with annealing temperature as low as 500 °C in H₂/N₂ atmosphere. Realizing the thickness of CNT–PZT nanocomposite thin films down to few hundred nanometers is one way to reduce the operating voltage of its application to micro- or nano-electromechanical system. The field emission scanning electron microscopic and atomic microscopic analysis revealed that the nanocomposite thin films annealed in H₂/N₂ atmosphere exhibits the most favorable surface morphology with adequate perovskite (111) reflection of PZT based on X-ray diffraction analysis. The measured dielectric constant and loss tangent of the nanocomposite thin films show that the annealing duration of 30 min promotes the optimum dielectric properties of the nanocomposite thin films. Our observations suggest that the annealing atmosphere and duration are important parameters in controlling the crystallization behavior hence the dielectric properties of the nanocomposite thin films, which can be readily applicable to other nanocomposite thin films.     

(111)择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜的制备及研究

选用不同浓度的Pb(Zr0.52Ti0.48)O3溶胶,用Sol-gel法在Pt/Ti/SiO2/Si基片上沉积一层厚度不同的Pb(Zr0.52Ti0.48)O3(PZT52)过渡层,经400℃烘烤、550℃退火等程序后,再用Sol-gel法在PZT52过渡层上沉积Pb(Zr0.52Ti0.48)O3薄膜.XRD分析表明,有PZT52过渡层的Pb(Zr0.52Ti0.48)O3薄膜具有(111)择优取向的钙钛矿结构,且随着过渡层厚度的增加,Pb(Zr0.52Ti0.48)O3薄膜的(111)择优取向程度越高.SEM分析表明,当PZT52过渡层的厚度达到14nm以上,Pb(Zr0.52Ti0.48)O3薄膜结晶程度得到明显改善,平均晶粒尺寸大大增加.介电、铁电性能测试表明,与没有过渡层的Pb(Zr0.52Ti0.48)O3薄膜相比,有PZT52过渡层的Pb(Zr0.52Ti0.48)O3薄膜具有较大的介电常数和剩余极化强度,而介电损耗则较小.     

Dielectric and impedance properties of Bi(Zn2/3V1/3)O3 electronic material

A polycrystalline vanadium doped lead free dielectric material of Bi(Zn_2/3V_1/3)O₃ (BZV) has been prepared using a standard high-temperature solid state reaction technique. Its temperature and frequency dependent capacitive, conductive and resistive characteristics are outlined though experimental investigation. The formation of single phase compound of BZV material with orthorhombic crystal symmetry is identified through X-ray diffraction data analysis, and the homogeneous distribution of grains are realized through scanning electron micrograph. The acquaintance of frequency–temperature dependent electrical parameters with the obtained micrograph provides the experimental evidence of contributions of grain as well as grain boundary in its capacitive and resistive characteristics. The negative temperature coefficient of resistance behaviour of the material is revealed from impedance characteristic, and non-Debye type relaxation has been realized from the Nyquist plot. The charge carriers of this electronic compound have both long & short range order that has been validated from the complex modulus and impedance analysis. The prepared electronic material substantiate some important dielectric features which props up the material as promising component for electronic devices.     

Growth and characterization of (001)-oriented Pb(Zr0.52Ti0.48)O3/LaNiO3/LaAlO3 heterostructures prepared by pulsed laser deposition

Completely (001)-oriented ferroelectric Pb(Zr_0.52Ti_0.48)O₃/LaNiO₃ heterostructures on single-crystal LaAlO₃(001) substrates have been successfully grown by pulsed laser deposition. X-ray-diffraction analyses (–2 scan, scan and scan) indicate that good out-of-plane orientation and in-plane alignment have been obtained with the epitaxial relationship of PZT(001)//LNO(001)//LAO(001) and PZT001//LNO001//LAO001. Scanning electron and atomic force microscopic images reveal very smooth LNO surfaces with roughness of about 0.4–0.6 nm. Based on a microstructural study of the LNO and PZT films, a layer-by-layer growth mode for the LNO growth is proposed, while island growth is dominant for the PZT films. Secondary ion mass spectroscopy analyses show that no distinct interdiffusion can be found between the PZT and LNO layers. P–E hysteresis loop measurements of the PZT films with LNO as bottom electrodes and Au as top electrodes were carried out at an applied voltage of 5 V. The best remanent polarization P_r and coercive field E_c were found to be 28 C/cm² and 74.5 kV/cm, respectively. PACS 81.15.Fg; 68.55.Jk; 77.22.Ej; 77.84.Bw; 68.65.Ac     

Uniaxial pressure influence on dielectric properties of Pb(Zr0.99Ti0.01)O3 single crystals

The effect of uniaxial pressure (0–1000 bars) applied parallel to AC electric field on dielectric properties of Pb(Zr_0.99Ti_0.01)O₃ single crystals has been investigated. It was found that uniaxial pressure significantly influences these properties. With increasing pressure: (i) peak ?(T) decreases, becomes diffuse and shifts to higher temperature, (ii) the thermal hysteresis is reduced, (iii) the hump in ?(T) profile connected with antiferroelectric–intermediate phase transition vanishes, and (iv) the local anomaly in ?(T) profile connected with polar microregions existence above T_m is protruded and slightly shifts towards higher temperature. It was concluded, that applied uniaxial pressure or increasing Ti-ions content in lead zirconate titanate system induces similar effects. The results were discussed in terms of domain switching under pressure.     

Tetragonal distortion and the domain structure of thin Pb(Zr,Ti)O3/MgO(100) films

3 /MgO(100) films was studied in synchrotron X-ray scattering experiments. In the thin epitaxial films, the tetragonal distortion of the ferroelectric phase and the transition temperature were significantly reduced. In sharp contrast to the reported mixture of the a-type and the c-type domains in thicker films, the 250-Å-thick film was purely composed of the c-type domains in the tetragonal phase. We attribute the suppression of the transition to the substrate effect, which prefers the c-type domains near the interface, and reduces the tetragonal distortion to minimize the strain energy caused by the lattice mismatch. Received: 1 November 1997/Accepted: 5 January 1998     

不同衬底上Pb(Zr0.52Ti0.48)O3择优取向铁电薄膜的制备和研究

通过MOD法在Si(100)和Pt(111)/Ti/SiO₂/Si基片上制备出LaNiO₃ ( LNO)薄膜.再通过修 正的Sol-gel法，在Pt(111)/Ti/SiO₂/Si,LNO/Si(100)和LNO/Pt/Ti/SiO_{2< /sub>/Si三种衬底上 制备出具有择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜. 经XRD分析表明，L NO薄膜具有(100)择优取向的类钙钛矿结构；PZT薄膜均具有钙钛矿结构，且在Pt(111)/Ti/S iO2/Si衬底上的薄膜以(110)择优取向，在LNO/Pt/Ti/SiO2/Si和LN O/Si(100)衬底上的 薄膜以(100)择优取向.经场发射SEM分析和介电、铁电性能测试表明，在LNO/Si和LNO/Pt/Ti /SiO2/Si衬底上的PZT薄膜的平均粒径、介电常数以及剩余极化强度均比以Pt/T i/SiO2/Si为衬底的薄膜大. 关键词： 3}薄膜')" href="#">LaNiO₃薄膜 PZT铁电薄膜 择优取向 剩余极化强度     

Superdomain structure and high conductivity at the vertices in the (111)-oriented epitaxial tetragonal Pb(Zr,Ti)O3 thin film

Recently, in ferroelectric materials, there have been many experimental efforts to find out more intriguing topological objects and their functionalities, such as conduction property. Here we investigated ferroelectric domain structures and related topological defects in the (111)-oriented epitaxial tetragonal PbZr_0.35Ti_0.65O₃ thin film. Systematic piezoresponse force microscopy measurements revealed that the field-induced polarization switching can form thermodynamically stable superdomain structures composed of nano-sized stripe subdomains. Within such superdomain structures, we observed the exotic equilateral triangular in-plane flux-closure domains composed of three stripe domain bundles with 120/120/120 degrees of separation. The conductive-atomic force microscopy measurements under vacuum showed that some vertices have significantly higher conductivity compared to other surrounding regions. This work highlights electric field-driven polarization switching and unique crystallographic symmetry (here, three-fold rotational symmetry) can generate exotic ferroelectric domain structures and functional topological defects, such as conductive vertices.     

Nonlinearity in inverse and transverse piezoelectric properties of Pb(Zr0.52Ti0.48)O3 film actuators under AC and DC applied voltages

The motion of domain walls is a crucial factor in piezoelectric properties and is usually related to the irreversible and hysteretic behaviors. Herein, we report on the investigation of inverse and transverse piezoelectric coefficients of capacitor-based and microcantilever-based Pb(Zr_0.52Ti_0.48)O₃ films with a change in the DC bias and the AC applied voltage. A large inverse piezoelectric strain coefficient of about 350 p.m./V, and a low strain hysteresis of about 7.1%, are achieved in the film capacitors under a low applied voltage of 2 V (20 kV/cm) which can benefit the actuators for motion control in high-precision systems. The field-dependences of the transverse piezoelectric coefficients, obtained from four-point bending and microcantilever displacement, are in good agreement with each other. The results also reveal that the irreversible domain-wall motion is attributed to the nonlinearity in the field-dependent piezoelectric strain and cantilever displacement.     

单磁场驱动的Tb1-xDyxFe2-y/Pb(Zr,Ti)O3三层膜磁电效应

研究了Tb1-xDyxFe2-y(TDF)与锆钛酸铅(PZT)三层膜样品的制备和在单一直流磁场驱动下的磁电(ME)效应.在该系列三层膜样品中测量到了巨大的ME耦合效应.所得实验结果与同种样品在两磁场驱动下的ME效应完全不同.这可能预示了某些新的物理内容.该技术可简化ME效应在某些实际应用中的复杂度.