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.     

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.     

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.     

Characterization of self-assembling isolated ferroelectric domains by scanning force microscopy

Lead zirconate titanate (PZT) thin films were prepared by a sol–gel process on platinized Si substrate. Their microstructure and surface morphology were characterized by XRD and Scanninn Force Microscopy. Phase transformation of the prepared PZT films from pyrochlore to ferroelectric was observed by XRD and PFM (piezoresponse force microscopy), respectively. Self-assembling nano-structured ferroelectric phases are fabricated by solution deposition technique followed by the controlling kinetics of the transformation. Complex structures of ferroelectric domains in the isolated ferroelectric phases were found in the furnace annealed PZT films in the temperature range of 400–500°C. Single ferroelectric domain structure in the isolated ferroelectric phases could be found in thinner PZT films and used to study the size effect of laterally confined ferroelectric domains.     

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.     

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.     

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).     

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.     

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。     

Imaging of ferroelectric thin films by X-ray photoemission electron microscopy (XPEEM)

We performed X-ray photoemission electron microscopy (XPEEM) measurements at the Nanospectroscopy Beamline of the synchrotron light source ELETTRA, Trieste, Italy, to demonstrate the principal possibility of imaging ferroelectric thin films by low-energy photoelectrons. Due to the insulating properties of ferroelectric films, severe surface charging was the major experimental challenge to overcome. This was achieved by grounding an array of gold inter-digital electrodes (with 5 microm blank intervals between them) deposited on top of the films. The images taken with BaTiO(3) films revealed 50-100 nm-sized holes (material discontinuities) on the surface, an observation confirmed by high-resolution scanning electron microscopy (HRSEM). Finer details, e.g. a granular structure, which has been resolved with HRSEM, could not be observed in the XPEEM images. Our measurements indicate that despite some residual charging, a 50 nm lateral resolution can be achieved in XPEEM measurements with ferroelectric films.     

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.     

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.     

BIMORPH-TYPE PIEZOELECTRIC THIN FILM BENDING ACTUATORS SYNTHESIZED BY HYDROTHERMAL METHOD

Lead zirconate titanium solid-solution (PZT) thin films with various thickness are synthe-sized on titanium substrates by repeated hydrothermal treatments. Young modulus, electric-field-in-duced displacement and the density of the PZT film are measured respectively. Bimorph- type bendingactuators are fabricated using these films. The model, which is used to analyze the driving ability ofbimorph-type bending actuators by hydrothermal method, is set up. It can be seen that the drivingability of bimorph-type bending actuators can be greatly improved by optimizing the thickness of PZTthin film and substrae from the theoretical analysis results. The measured values are expected to agreewith the theoretical values calculated by the above model.     

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

Coating of 0.65Pb(Mg(1/3)Nb(2/3))O(3)-0.35PbTiO(3) (PMN-PT) relaxor ferroelectrics by a sol-gel method is followed by growth of epitaxial SrRuO(3) (SRO) metallic oxide electrodes on SrTiO(3) (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.     

硅基PZT压电功能结构研究

PZT压电薄（厚）膜是制备MEMS传感元件和执行元件重要的功能材料,对近年PZT薄（厚）膜在MEMS领域的研究现状进行了分析,提出了一种新型的双杯PZT/Si膜片式功能结构;采用有限元方法对双杯PZT/Si膜片进行了结构优化,得到PZT和上、下硅杯的结构优化值为DPZT: D1:D2 =0.75:1.1:1;一阶模态谐振频率为13.2KHz;以氧化、双面光刻、各向异性刻蚀,以及PZT厚膜丝网印刷等工艺技术制作了双杯硅基PZT压电厚膜膜片,该膜片具有压电驱动功能。双杯PZT/Si膜片式功能结构的MEMS技术兼容性好,对芯片内其它元件或电路的影响小,适合作为MEMS片内执行元件的驱动机构。     

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。     

Electrical and electrochemical properties of the MEH–PPV and MEH–PPV doped calix[4]arene derivative layers for the detection of Cu and Na ions

A modified ITO electrode based on conducting polymer (MEH–PPV) matrix doped with the calix[4]arene molecules (β-ketoimine calix[4]arene) is deposited by spin coating. The carrier transport mechanism of the MEH–PPV and MEH–PPV:β-ketoiminecalix[4]arene films is investigated by using I–V characteristics measurements. The conduction mechanisms in these thin films are identified to be a space-charge-limited current (SCLC). The dielectric behavior of the MEH–PPV and the composite β-ketoimine calix[4]arene/MEH–PPV thin films are investigated by impedance spectroscopy (IS). The Cole–Cole plots are studied showing single semicircles and the solid interfaces are modeled by an equivalent circuit. The characteristics of chemical sensors based on MEH–PPV and MEH–PPV doped β-ketoimine calix[4]arene thin films for the detection of Cu²⁺ and Na⁺ ions are investigated by electrochemical impedance spectroscopy (EIS). The experimental impedance data of the modified electrodes are modeled by an equivalent circuit using the Z-View software. The inclusion of calixarene molecules into conducting polymer (MEH–PPV) exhibited considerable rise charge transfer resistance and improves sensing properties.     

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.     

PDDA/PSS分子沉积膜的摩擦学行为研究

以聚对苯乙烯磺酸钠为聚阴离子,聚二烯丙基二甲基胺盐酸盐为聚阳离子在基底上交替沉积制备分子沉积膜。用紫外-可见吸收光谱仪、接触角测量仪、原子力显微镜对所制备的有序薄膜进行了表征。用UMT-2摩擦仪考察了超薄膜的摩擦学行为,结果表明,所制备的超薄膜具有良好的减摩抗磨性能,薄膜的表面电荷及亲水、疏水性对其摩擦学行为有较大影响,负电荷表面、亲水性强的表面在较高湿度下,耐磨寿命较长。     

PZT薄膜驱动的全光纤相位调制器数学模型

提出了一种简单、高效的PZT压电陶瓷薄膜覆膜驱动的全光纤相位调制器数学模型,该模型计入了PZT压电陶瓷薄膜侧向压电常数d₃₁对相位调制效率的影响,结果表明,对于PZT压电陶瓷薄膜覆膜驱动的全光纤相位调制器,这种影响是不能忽略的,由侧向压电常数d₃₁引起的相位调制相当于由压电常数d₃₃引起的相位调制的15%。应用此模型计算了PZT压电陶瓷薄膜、内电极以及外电极的机械与压电性能等参数对于全光纤相位器的相位调制效率的影响。该模型可应用于全光纤相位调制器的设计与优化。