PZT压电薄膜无阀微泵

介绍了一种基于PZT压电薄膜的无阀压电微泵.该微泵利用自制的压电圆型薄膜片作为驱动部件、聚二甲基硅氧烷(PDMS)作为泵膜.本文在对微豕制备工艺研究的基础上,对其性能进行了数值和实验研究.建立了基于扩张管/收缩管理论的无阀微泵的有限元模型.利用MFX-AN-SYS/CFX技术实现了对微泵的双向流固耦合分析.对微泵的锥形角、最小宽度、扩散管长度、泵腔高度进行数值计算,得到了优化参数.数值计算的结果与实际测量的数据进行了比较,验证了仿真的正确性.     

A rod-shaped vibro touch sensor using PZT thin film

We have fabricated a probe sensor. This sensor is for high precision coordinate measuring machines, surface roughness measuring tools, or scanning probe microscopes (SPM). This sensor consists of a rod vibrating in the axial direction. The longitudinal vibration was excited and also detected by PZT thin film. The PZT thin film was fabricated by a hydrothermal method. The hydrothermal method uses the reaction process in hot and high pressure aqueous solutions. We made a 27.8-mm long sensor. Its resonance frequency was 116 kHz. The sensitivity and resolution were evaluated by experiments. We succeeded in oscillating the rod and detecting the contact.     

PZT thin film preparation by pulsed DC magnetron sputtering

Pulsed DC magnetron sputtering was used in this study to prepare lead zirconate titanate (Pb(Zr_xTi_1−x)O₃, PZT) thin films. A single metallic target was used for the deposition onto a Pt/Ti/SiO₂/Si substrate and parameters such as: pulse frequency, duty cycle, O₂/Ar flow ratio controlled so as to analyze the effect of the parameters on thin film deposition rate, crystalline structure and morphology. After the deposition, the thin film was annealed in a rapid thermal annealing (RTA) furnace. The experimental results showed that, when the pulse frequency was in the range of 10 kHz-100 kHz, along with the lowering of frequency and the oxygen argon flow rate ratio, the deposition rate gradually increased and the formation of PZT thin film perovskite phase was enhanced; however, if the oxygen argon flow rate ratio was too high, it caused the PZT thin film to generate a pyrochlore phase. However, when the duty cycle was in the range of 95%-75%, the highest deposition rate and better perovskite phase could be obtained in the range of 75%-80%.     

Theoretical calculations and performance results of a PZT thin film actuator

High piezoelectric coupling coefficients of PZT-based material systems can be employed for actuator functions in micro-electro-mechanical systems (MEMS) offering displacements and forces which outperform standard solutions. This paper presents simulation, fabrication, and development results of a stress-compensated, PZT-coated cantilever concept in which a silicon bulk micromachining process is used in combination with a chemical solution deposition (CSD) technique. Due to an analytical approach and a finite element method (FEM) simulation for a tip displacement of 10 /spl mu/m, the actuator was designed with a cantilever length of 300 /spl mu/m to 1000 /spl mu/m. Special attention was given to the Zr/Ti ratio of the PZT thin films to obtain a high piezoelectric coefficient. For first characterizations X-ray diffraction (XRD), scanning electron microscopy (SEM), hysteresis-, current-voltage I(V)and capacitance-voltage C(V)-measurements were carried out.     

镧掺杂对PZT铁电薄膜漏电学特性的影响

研究了镧掺杂对PZT铁电性能和相结构的影响。研究表明镧掺杂增加了(110)和(200)峰的强度,减小了(111)峰的相对强度,导致矫顽场和极化强度的下降。研究了镧掺杂对漏电特性的影响,以及肖特基势垒电流模型。     

Ultrasonically assisted hydrothermal synthesis of polycrystalline PZT thin film on titanium substrate

Ultrasonically assisted hydrothermal synthesis of PZT thin films was performed using an ultrasonic transducer integrated into the lid of an autoclave. Direct ultrasonic irradiation of 23 W at 53 kHz was carried out during the hydrothermal synthesis at a reaction temperature of 140°C for 24 h. The resultant PZT thin film was characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The PZT thin film had fine nanoparticles of approximately 100 nm in diameter when the substrate was placed perpendicular to the plane of ultrasonic irradiation. The film exhibited predominantly (001) orientation when the substrate was placed parallel to the plane of ultrasonic irradiation.     

Fabrication and characterization of microcantilever integrated with PZT thin film sensor and actuator

The purpose is to find the potential application of PZT thin film for microsensor and microactuator. Pb(Zr_0.5Ti_0.5)O₃ thin film is deposited by sol-gel method. Piezoelectric microcantilever with two-segment top electrodes is fabricated using bulk micromachining techniques. Piezoelectricity of the deposited PZT thin film and sensing and actuation capability of the each segment of microcantilever is proved. Experiments are performed when one segment acts as an actuator or vibrator and another segment as force sensor. The results show that the proposed PZT thin film microcantilever can be used in force feedback and object manipulation simultaneously.     

Controlled wrinkling of a thin elastic film capping a liquid layer

We perform a linear analysis to examine electric-field-induced stability of a thin film that caps a liquid layer resting on a pre-stretched soft elastic layer glued onto a rigid substrate. Our study shows that the capping film is always unstable for nonvanishing applied voltage. The undulation wavelength of the film is initially quite large, but undergoes a sharp transition when the voltage is increased to a critical value. In this case, well aligned winkles with considerably smaller wavelength appear in the fashion parallel to the tensile direction of the soft elastic layer. The magnitude of the wavelength is tunable, thus providing a mechanism to control the wrinkling pattern of the capping film.     

Magnetically actuated peel test for thin films

Delamination along thin film interfaces is a prevalent failure mechanism in microelectronic, photonic, microelectromechanical systems, and other engineering applications. Current interfacial fracture test techniques specific to thin films are limited by either sophisticated mechanical fixturing, physical contact near the crack tip, or complicated stress fields. Moreover, these techniques are generally not suitable for investigating fatigue crack propagation under cyclical loading. Thus, a fixtureless and noncontact experimental test technique with potential for fatigue loading is proposed and implemented to study interfacial fracture toughness for thin film systems. The proposed test incorporates permanent magnets surface mounted onto micro-fabricated released thin film structures. An applied external magnetic field induces noncontact loading to initiate delamination along the interface between the thin film and underlying substrate. Characterization of the critical peel force and peel angle is accomplished through in situ deflection measurements, from which the fracture toughness can be inferred. The test method was used to obtain interfacial fracture strength of 0.8-1.9 J/m² for 1.5-1.7 μm electroplated copper on natively oxidized silicon substrates.     

Fracture analysis of a surface through-thickness crack in PZT thin film under a continuous laser irradiation

In this paper, the surface crack problem in PZT thin films under a continuous laser irradiation has been investigated by the superposition principle. Using commercial (FEM) software ANSYS 9.0, the piezoelectric fields near the crack tip were solved for surface crack in the finite PZT thin film. The SIFs for crack-tip fields were obtained by using the limited stress extrapolation technique (LSET) and then the energy release rates were calculated by the relation to the intensity factors. When the irradiation time and crack location were changed, the energy release rates G, G_I, and G_e for total, mechanical terms (mode I) and electric contribution were investigated. The results show that the mechanical opening mode I is the main mode for the surface crack under a continuous laser irradiation. However, electric mode IV has inhibiting effect on crack growth. At the beginning of laser irradiation, the surface tiny crack which is close to the centre of film will propagate more easily. During the laser irradiation, the crack which is far from the centre of film will propagate more easily.     

Interfacial crack propagation in a thin viscoelastic film bonded to an elastic substrate

Edge decohesion along the interface of a thin viscoelastic film bonded to an elastic substrate under tensile residual stresses is considered. The tensile residual stress in the film is replaced by a combination of edge loads, and an explicit relation of strain energy with respect to time is obtained through simple beam analysis. The strain energy function is discretized into time steps which are assumed to be very small so that the dissipation effects over the time steps can be neglected. The energy release rate is then calculated using a Griffith type energy balance. An analytical model is developed to predict the crack growth and its velocity. Extent of crack growth along the interface is prediced based on a fracture criteria. The analytical predictions are compared with results from a viscoelastic finite element analysis.     

Surface effects on delamination of a thin film bonded to an elastic substrate

The delamination of a circular thin film at micro/nanoscale is studied using the Kirchhoff plate theory incorporating surface effects in this paper. Bending of a clamped circular nanoplate subjected to a concentrated force at the center or a uniformly distributed force over a lateral surface is solved. The bending deflection is derived in closed form. The adhesion energy and its release rate for delamination are determined when surface effects are taken into account. The influences of surface residual stress and surface elasticity along with the film’s size on the energy release rate of debonding advance or interfacial adhesion of a thin film bonded to an elastic substrate are analyzed for applied loading or given displacements. Analytic results are compared with experimental data and satisfactory agreement is confirmed.     

Determination of the orthotropic elastic constants of thin PET film by an ultrasonic micro-spectrometer

The elastic constants of a thin polyethylene terephthalate (PET) film, whose thickness was 12 mum, were determined from the acoustic reflection coefficients. The reflection coefficients were measured by an ultrasonic micro-spectrometer (UMSM), and all of the elastic constants were obtained through the fitting of a theory to the dip points of the magnitude of the reflection constants where leaky Lamb waves were excited. As a result, the film was found to be an orthotropic material, and the observed elastic constants were consistent with those measured by tensile tests. Besides, the in-plane shear modulus was found to be much larger than the out-of-plane shear moduli. Then, the reflection coefficients were calculated using the obtained stiffness matrix. The calculated values reproduced not only the dip points but also the change in magnitude of measured reflection coefficients depending on the frequency and the incident angle. These agreements suggest that the stiffness matrix components were determined accurately.     

Effects of elastic anisotropy on the surface stability of thin film/substrate system

The surface stability of thin film/substrate system is an important problem both in the film synthesis and reliability of micro electrical and mechanical system (MEMS). In this work, the elastic anisotropy effect on surface stability of thin film/substrate system was considered. The theoretical analysis indicates that elastic anisotropic influence could play an important role in the surface stability of thin film/substrate system. And the anisotropy effect should be considered both in the thin film synthesis process and its service reliability. In addition, there exists an nondimensional parameter k for cubic crystalline thin film materials in evaluating the anisotropic effect. When k is larger than one unit, the surface stability will be weakened by anisotropic effect; vice versa. The method used in present work could be easy extended to multi-layered thin film/substrate system and help us to consider the elastic anisotropy effect.     

以Al2O3为过渡层脉冲激光法制备PZT铁电薄膜

为实现PZT铁电薄膜与半导体衬底的直接集成引入Al2O3为过渡层，首先用真空电子束蒸发法在Si(100)，多昌金刚石（111）衬底上生长约20nm厚的Al2O3过渡层，接着在上述衬底上采用脉冲激光淀积（PLD）法淀积PZT薄膜，衬底温度为350-550℃。X光电子能谱（XPS）测试表明，在高真空下，电子束蒸发Al2O3固态源能获得化学配比接近蒸发源的Al2O3薄膜。X射线衍射（XRD）测试说明，不论衬底是硅还是多晶金刚石，当衬底温度为550℃时，PZT在Al2O3过渡层上呈现（222）取向的焦绿石相结构，当衬底是金刚石时，通过如下工艺：（1）较低温度（350℃）淀积；（2）空气氛围650℃快速退火5min，可以在Al2O3过渡层上获得高度（101）取向的钙钛矿结构的铁电相PZT薄膜，最后AFM测试显示，在硅衬底上，PZT薄膜的表面均方根粗糙度为9.78nm；而在多晶金刚石衬底上，PZT薄膜的表面均方根粗糙度为17.2nm。     

Sol-gel独立前驱单体制备PZT铁电薄膜技术

采用醋酸铅、硝酸氧锆(硝酸锆)、钛酸丁酯独立稳定的前驱单体。sol—gel法旋转涂膜技术制备了PZT铁电薄膜。研究了水的添加量对溶胶形成的影响,比较了不同的溶胶浓度、膜层结构(PT／PZT／PT Sandwich)及热处理工艺条件对薄膜结构、铁电性能的影响。     

Surface morphology,elastic modulus and hardness of thin film cathodes for Li-ion rechargeable batteries

In this study, surface morphology, elastic modulus and hardness of two thin film cathode materials, namely layered structured LiNi_1/3Co_1/3Mn_1/3O₂ and spinel structured LiMn₂O₄, during the charge/discharge cycles, are measured by using Scanning Electron Microscopy, Atomic Force Microscopy and nanoindentation experiments. Furthermore, the effects of depth of discharge (DOD) and charging rate (current density) on the changes of elastic modulus and hardness of the spinel structured LiMn₂O₄ are also investigated. The results have shown that both elastic modulus and hardness of the thin film cathodes have been significantly affected by the charge/discharge cycles as well as the condition of the charge/discharge processes. These results suggest the importance of the mechanical properties of the cathode materials to the reliability and integrity of the cathode materials to be used for the Li-ion batteries. The possible mechanisms of the changes in mechanical properties are also discussed.     

Growth of perovskite PZT and PLZT thin films

This paper reports preliminary results on the fabrication of perovskite PZT and PLZT thin films using a sputtering technique. For glass, quartz and sapphire substrates, it was necessary to raise the substrate temperature above 550 ° C to achieve perovskite tetragonal structures of interest. Growth at temperatures below 550 ° C yielded a major pyrochlore structure phase. Excess of PbO in the target was also required to maintain stoichiometry in these films.