厚度效应对Pb(Zr0.53Ti0.47)O3薄膜微结构、铁电、介电性能的影响

用改进的溶胶-凝胶法在Pt(111)/Ti/SiO₂/Si(100)衬底上制备了不同厚度的高度(111)取向的Pb(Zr_0.53Ti_0.47)O₃薄膜.运用X射线衍射(XRD)和原子力显微镜(AFM)分析了薄膜的微结构,原子力显微镜表明厚度为0.3μm和0.56μm的PZT薄膜的晶粒尺寸和表面粗糙度分别为0.2～0.3μm、2～3μm和0.92nm、34nm.0.3μm和0.56μm PZT薄膜的剩余极化(Pr)和矫顽场(Ec)分别为32.2μC/²、79.9kV/cm, 27.7μC/cm²、54.4kV/cm;在频率100KHz时,薄膜的介电常数和介电损耗分别为539、0.066,821、0.029.     

The charge storage characteristics of PZT nanocrystal thin film

Lead zirconate titanate (PZT) films have been extensively investigated for many applications: the nonvolatile memory devices based on their remarkable ferroelectric properties, the microelectromechanical system (MEMS) based on their piezoelectricity as well in sensors as in actuators. In this paper, we inject charges into PZT thin films, and then the charge storage and transportation through PZT thin films were observed by electric force microscopy (EFM). Results were studied and charging mechanisms were proposed.     

Dynamics of space and polarization charges of ferroelectric thin films measured by atomic force microscopy

Retention behavior and local hysteresis characteristics in Pb(Zr(0.52)Ti(0.48))O(3) (PZT) thin films on Pt electrodes have been investigated by electrostatic force microscopy (EFM). A sol-gel method is used to synthesize PZT thin films and drying conditions are carefully explored over a wide range of temperature. Decay and retention mechanisms of single-poled and reverse-poled regions of the ferroelectric thin films are explained by space charge redistribution. Trapping behavior of space charges is dependent on the nature of interface between ferroelectric thin films and bottom electrodes. Local measurement of polarization-electric field curves by EFM shows inhomogeneous space charge entrapment.     

Development of RF magnetron sputtering method to fabricate PZT thin film actuator

PZT piezoelectric very thin films suitable for a microactuator have been deposited onto Invar alloy substrate using a high-temperature RF magnetron sputtering technique. PZT thin films must be deposited onto conductive substrate for a monomorph or a bimorph actuator. The chemical composition and the crystalline structure of these films were measured by ESCA and XRD, respectively. The chemical composition of PZT deposited stoichiometrically was almost the same as commercially-produced bulk PZT. Crystal planes (1 1 0) and (1 1 1) of PZT perovskite structure were observed in XRD analysis. When the substrate was heated to above 600 °C, SEM revealed only a very small number of pinholes on the surface. A thin (500 nm) film actuator has been characterized by measuring the piezoelectric property using a Laser Doppler Vibrograph. It was confirmed that the piezoelectric property has a linear relationship with the grain size, which also increased with the substrate temperature. The piezoelectric property of deposited PZT thin films showed a good agreement with a quoted value of bulk PZT, when the substrates were heated to 600 °C.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr_0.2Ti_0.8)O₃ (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (1 1 1)Pt/MgO(1 0 0) and c-axis preferred on the (1 0 0)Pt/MgO(1 0 0), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (111)Pt/MgO(100) and c-axis preferred on the (100)Pt/MgO(100), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

Investigations into local ferroelectric properties by atomic force microscopy

In this article, we describe nanometer scale characterization of piezoelectric thin films of Lead-Zirconate-Titanate (PZT). Using the electric field from a biased conducting atomic-force microscopy (AFM) tip, we show that it is possible to form and subsequently image ferroelectric domains. Using a sphere-plane model for the tip-sample system we calculate the distribution of electric potential, field and polarization charge, and find good agreement with the experimental values. We also discuss the effects of surface contaminants on domain formation.     

气浮沉积技术

气浮沉积法简称AD法,是一种新近开发的表面涂层制备方法,属于热喷涂技术范畴。AD法由低真空沉积室,喷咀,粉末雾化室,机械真空泵等组成。AD法具有沉积温度低(室温),沉积率高,涂层密度高,结合强度高等优点。AD法的一个突出的应用就是制备铁电薄膜陶瓷涂层,如PZT(Pb(Zr,Ti)O3)。AD法制备的PZT涂层成分均匀,且由于沉积中的液相烧结机理而致密化。退火处理可以很好地提高PZT涂层的铁电特性。载流气体种类对PZT涂层的结合强度没有明显影响。     

Design and fabrication of a micro PZT cantilever array actuator for applications in fluidic systems

In this article, a micro cantilever array actuated byPZT films is designed and fabricated for micro fluidic systems. The design features for maximizing tip deflections and minimizing fluid leakage are described. The governing equation of the composite PZT cantilever is derived and the actuating behavior predicted. The calculated value of the tip deflection was 15 μm at 5 V. The fabrication process from SIMOX (Separation by oxygen ion implantation) wafer is presented in detail with the PZT film deposition process. The PZT films are characterized by investigating the ferroelectric properties, dielectric constant, and dielectric loss. Tip deflections of 12 μm at 5 V are measured, which agreed well with the predicted value. The 18 μ1/s leakage rate of air was observed at a pressure difference of 1000 Pa. Micro cooler is introduced, and its possible application to micro compressor is discussed.     

Structural properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO₃ (SRO) metallic oxide electrodes on SrTiO₃ (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

Characterization of lead zirconate titanate--lanthanum ruthenate thin film structures prepared by chemical solution deposition

In this work, the results of compositional and microstructural analysis of lead zirconate titanate--lanthanum ruthenate thin film structures prepared by chemical solution deposition are discussed. The cross-section transmission electron microscope (TEM) micrographs of the La-Ru-O film deposited on a SiO2/Si substrate and annealed at 700 degrees C revealed RuO2 crystals embedded in a glassy silicate matrix. When the La-Ru-O film was deposited on a Pt/TiO2/SiO2/Si substrate, RuO2 and La4Ru6O19 crystallized after annealing at 700 degrees C. After firing at 550 degrees C randomly oriented lead zirconate titanate (PZT) thin films crystallized on the La-Ru-O/SiO2/Si substrate, while on La-Ru-O/Pt/TiO2/SiO2/Si substrates PZT thin films with (111) preferred orientation were obtained. No diffusion of the Ru atoms in the PZT film was found. Ferroelectric response of PZT thin films on these substrates is shown in comparison with the PZT film deposited directly on the Pt/TiO2/SiO2/Si substrate without a La-Ru-O layer.     

溶胶-凝胶法制备铁电薄膜的研究进展

溶胶-凝胶法是制备铁电薄膜的一种重要方法。综述了溶胶-凝胶法制备铁电薄膜的原理、工艺过程、特点,以及采用此方法制备出的某些材料的铁电性能。最后指出,溶胶-凝胶法制备铁电薄膜工艺仍需优化和改进,薄膜的质量亟待提高,以适应器件的要求。     

Note: Utilizing Pb(Zr(0.95)Ti(0.05))O(3) ferroelectric ceramics to scale down autonomous explosive-driven shock-wave ferroelectric generators

Further miniaturization of recently designed autonomous ferroelectric generators (FEGs) [S. I. Shkuratov, J. Baird, and E. F. Talantsev, Rev. Sci. Instrum. 82, 086107 (2011)], which are based on the effect of explosive-shock-wave depolarization of poled ferroelectrics is achieved. The key miniaturization factor was the utilization of high-energy density Pb(Zr(0.95)Ti(0.05))O(3) (PZT 95∕5) ferroelectric ceramics as energy-carrying elements of FEGs instead of the previously used Pb(Zr(0.52)Ti(0.48))O(3) (PZT 52∕48). A series of experiments demonstrated that FEGs based on smaller PZT 95∕5 ferroelectric elements are capable of producing the same output voltage as those based on PZT 52∕48 elements twice as large. It follows from the experimental results that the FEG output voltage is directly proportional to the thickness of PZT 95∕5 samples. A comparison of the operation of FEGs based on PZT 95∕5 and on PZT 52∕48 ferroelectrics is presented.     

Deposition and Nanotribological Characterization of Sub-100-nm Thick Protective Ti-Based Coatings for Miniature Applications

Ti-based protective thin films with thicknesses below 100 nm, intended for miniature applications were deposited using physical vapor deposition magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy were employed for the assessment of microstructure, morphology, film thickness, surface topography, and roughness. XRD pattern showed the formation of f.c.c TiN, TiCN, and TiC phases with different preferred orientations for films prepared in Ar/N₂, Ar/N₂ + C₂H₂, and Ar/C₂H₂ gas mixtures, respectively. Nanotribological performance was investigated using multipass nanoscratch technique at variable applied normal loads (100–400 μN). The nanoscale coefficient of friction was found to be in the 0.08–0.1 range, a sufficiently low value showing the potential of these films for miniature applications, such as microelectromechanical systems. The nanowear resistance at mean contact pressures in the range of 5–8.5 GPa for each sample was evaluated in terms of the average residual wear depth and an abrasive-dominated wear mechanism was found.     

Read/write mechanisms and data storage system using atomic force microscopy and MEMS technology

Information storage system that has a potentially ultrahigh storage density based on the principles of atomic force microscopy (AFM) has been developed. Micro-electro-mechanical systems (MEMS) technology plays a major role in integration and miniaturization of the standard AFM. Its potential application for ultrahigh storage density has been demonstrated by AFM with a piezoresponse mode to write and read information bits in ferroelectric Pb(Zr(x)Ti(1 - x))O3 films. With this technique, bits as small as 40 nm in diameter have been achieved, resulting in a data storage density of simply more than 200 Gb/in2. Retention loss phenomenon has also been observed and investigated by AFM in the piezoresponse mode. Finally, local piezoelectric measurements of PZT films by different processing technologies are discussed in detail.     

Patterned crack-free PZT thick films for micro-electromechanical system applications

The fabrication and structuring of multilayer-thick film piezoelectric (PZT-lead zirconate titanate) structures, using composite sol-gel techniques and wet etching is described. The composite sol-gel technique involves producing a PZT powder/sol composite slurry which when spun down, yields films a few micrometres thick. Repeated layering and infiltration has been used to produce PZT films between 10 and 40 μm thick. Due to the low firing temperature (<720°C), it has also been possible to produce PZT films with embedded thin (ca. 100 nm thick) metal electrodes. The PZT thick films have also been structured using a wet etching technique. Examples of features and cavities with lateral dimensions in the order of tens of micrometres are presented. The ability to fabricate and structure thick functional films with embedded metal electrode structures offers the possibility to create novel micro-device structures suitable for use in micro-electromechanical systems (MEMS).     

Research on oxidation wear mechanism of the cast steels

The uni-directional pin-on-disk wear tests were performed in elevated-temperature air at 400 °C for the Cr–Mo–V cast steels with different compositions. Morphology, composition and structure of worn surfaces, oxidation films and matrix were examined using SEM, EDS, XRD and TEM. The relations between oxidation wear rate and matrix were studied. The mechanism of wear was clarified. Under elevated-temperature air at 400 °C, typical oxidation wear was presented in the cast steels. Oxidation of worn surface and fatigue delamination of oxide film proceed alternatively during sliding. As there are not coarse second phases in steel, oxide film is main factor in determining wear rate, which conforms to Quinn's oxidation wear theory. In this case, delamination of oxide film was found to take place inside oxide film or at interface of matrix and oxide film. This is classified as mild oxidation wear with lower wear rate. As coarse second phases exist in steel, the wear rate is strongly dependant on microstructures of matrix. In this case, oxide film delaminates from the inside of matrix under oxide film. This is classified as severe wear with high wear rate.     

Characterization and mechanical/tribological properties of nano Au-TiO2 composite thin films prepared by a sol-gel process

Nano Au-TiO₂ composite thin films on Si(1 0 0) and glass substrates were successfully prepared with a facile sol-gel process followed by sintering. The morphology and mircostructure of the films were investigated via X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The Au particles, of diameter 14-22 nm depending on the sintering temperatures used, were found to be well dispersed in the TiO₂ matrix, with a small amount of the particles escaped from the film. The surfaces of the films were uniform, compact and crack-free. Hardness and elastic modulus of the films were measured by using the nanoindentation technique. Friction and wear properties were investigated by using a one-way reciprocating tribometer. It was found that the highest hardness and elastic modulus values were obtained for the films prepared with 500 °C sintering temperature. The films displayed superior antiwear and friction reduction performances in sliding against an AISI 52100 steel ball. With 5.0 mol% Au, the friction coefficient was only 0.09-0.10 and the wear life was more than 2000 sliding cycles. The friction coefficient and wear life decreased with increasing sliding speed and load. The failure mechanism of the Au-TiO₂ films was identified to be light scuffing and abrasion. Those films can be potentially applied as ultra-thin lubricating coatings.     

A comparison of the microstructure of silicon nitride-silicon carbide composites made with and without deoxidized starting material

Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si₃N₄) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si₃N₄ powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si₃N₄ transformed into α-Si₃N₄ in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si₃N₄ and β-Si₃N₄ phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.     

基于激光多普勒技术的PZT薄膜压电性能测试研究

应用基于激光多普勒技术的微小形变分析方法,并引入数字锁相技术,成功实现了PZT(Pb(Zr,Ti)O₃)铁电薄膜的压电性能测试。对商用压电陶瓷在小信号激励下的压电性能测试表明,数字锁相技术的引入能有效抑制系统噪声,并提高激光多普勒系统的位移检测分辨率,使其达到皮米量级。此外,研究了用溶胶-凝胶技术和溶胶-电雾化技术制备得到的PZT薄膜的电压-位移曲线和压电位移"蝴蝶线",实验结果表明:在5 V直流偏置下测得两种方法制备得到的PZT薄膜的d₃₃压电系数分别为218.7 pC/N和215.8 pC/N,相应的标准偏差分别为12.7和28.6。