Electric and ferroelectric properties of PZT/SBT multilayer films prepared by photochemical metal-organic deposition

The electric and ferroelectric properties of lead zirconate titanate and strontium bismuth tantalate multilayer films prepared using photosensitive starting precursors were characterized. The electric and ferroelectric properties were investigated by characterization of the effect of stacking order of four ferroelectric layers of PZT or SBT in the multilayer films of 4-PZT, PZT/2-SBT/PZT, SBT/2-PZT/SBT, and 4-SBT. The P_r value of the 4-SBT multilayer film was relatively small (6 μC/cm²) and a two times higher value (12 μC/cm²) was obtained with the SBT/2-PZT/SBT multilayer film. The films with SBT layers at the top and bottom showed improved leakage current and fatigue resistance compared to the films with PZT layers at the top and bottom. It was revealed that the defect dipole was reduced at the SBT/Pt interface due to a self-regulation layer such as (Bi₂O₂)²⁺ in the SBT film. Also, the bottom layer on the Pt substrate showed a significant influence on the growth orientation of the entire ferroelectric films.     

Fabrication and characterizations of a monolithic PZT microstage

This paper reports on the fabrication and characterizations of a monolithic Pb(ZrTi)O₃ (PZT) microstage with multi-degrees of freedom for high-precision positioning. The entire device is fabricated in a symmetrical arrangement from a PZT plate with a size of 15 × 15 × 0.8 mm³. Four actuation units with displacement amplification mechanisms are integrated in the structure. All the actuators can be driven individually which result in movements of a stage in different directions. The main fabrication steps include dicing, electroplating, lithography and laser machining. The performances of the displacement and the resonant frequencies of the microstage are simulated using a finite element method (FEM) with different dimensions. A prototype has been fabricated and evaluated. Comparisons between FEM simulation and experimental results are carried out.     

应用静电纺丝法制备PZT纳米纤维薄膜

提出应用静电纺丝法制备PZT纳米纤维薄膜。研究中配制PZT溶液后再进行静电纺丝,获得了PZT纳米纤维薄膜,并且通过调整纺丝时间和沉积次数来控制纳米纤维薄膜的厚度。运用SEM对获得的热处理前后的薄膜进行了观察对比,测量其平均直径约为200 nm;运用XRD对退火后的样品进行分析,测得样品的主要成分为Pb(Zr0.52Ti0.48)O3,证明所制备的正是PZT薄膜;运用AFM测得薄膜的表面粗糙度为1.034 nm,说明该纳米薄膜材料非常的均匀整齐。     

Preparation of ferroelectric ceramics in a film structure and their photovoltaic properties

This paper reports the formation of a new-layered film structure and the highly improved photovoltaic output of the lead lanthanum zirconate titanate (PLZT) employed. The new structural design is described using an upper top transparent indium tin oxide (ITO) electrode. The PLZT film structure exhibited V and μA output. The photovoltaic current of the PLZT film per unit width was more than 10² times larger than that of bulk PLZT, while the photovoltaic voltage per unit thickness in the layered film structure was almost the same as that in bulk ceramics and single crystals. These differences are due to the characteristics of the film structure and configuration of the electrode. The PLZT film also has the advantage of easily controllable parameters: film thickness, illuminated area, and illumination intensity. A simple model is used for the phenomenological explanation of the improved photovoltaic effect of the PLZT film.     

纳米银/石墨烯电化学传感器的制备及应用研究

以硝酸银和氧化石墨为原料,采用硼氢化钠还原法制备了纳米银/石墨烯纳米复合材料(Nano-Ag/ERGO),并采用紫外-可见吸收光谱法、X-射线粉末衍射法及红外光谱法进行表征.采用滴涂法制备了纳米银/石墨烯复合纳米材料修饰的玻碳电极(Nano-Ag/ERGO/GCE).研究了过氧化氢(H2O2)在制备的修饰电极上的电化学行为.结果表明:采用一步还原法制备石墨烯支持银纳米粒子,具有制备方法简单且纳米粒子粒径可控等优点,对H2O2的电还原具有极强的催化活性.研究成果在实际样品的H2O2快速检测中具有潜在的应用价值.     

Fabrication of TiN-based three-terminal nano mechanical relays using nanoimprint technology

This paper reports the fabrication of nanoscale mechanical relays using a nanoimprint technology, called contact-transfer and mask-embedded lithography. This cost effective method facilitates the fabrication of nanoscale metallic source electrodes in one easy step. For the design and simulation of relays, we developed a purpose-built system to measure the resonant frequency of TiN nano-structures to determine the mechanical properties of nanoscale thin films. The results presented a Young’s modulus of approximately 600 GPa and residual stress low enough to be disregarded in the proposed process. Finally, we succeeded in fabricating three-terminal nano-relays of various lengths, the operation of which was demonstrated by measuring the I–V curve of each device. Measured pull-in voltages were compared with those of the simulation results.     

Fabrication of high aspect ratio nano gratings using SR lithography

In this paper, the fabrication technique for high-aspect-ratio diffractive optical element (DOE) is introduced. The 500 nm-width and 1,000 nm-width line-and-space pattern has been successfully fabricated. It was fabricated by synchrotron radiation (SR) lithography for the application of nano gratings, and poly-methylmethacrylate (PMMA) was used as X-ray resist. The nanoscale grating with the aspect ratio of 4.4 and 2.2 was achieved. So far, there are a number of reported techniques for fabrication of DOEs yet the height of those gratings is not sufficient. Therefore, we have attempted to investigate the fabrication of high-aspect-ratio nano gratings by a high-resolution X-ray lithography using SR source at Ritsumeikan University, Japan. Nevertheless, the evaluation of various factors influencing the high-aspect-ratio structure fabricated by our recommended technique is discussed. So far the fabricating process, such as, proximity gap of exposure, the exposure dosage, and the development time have been optimized to fabricate the gratings.     

Microstructure and optical properties of nano Ag-ITO films

Nano Ag-ITO films with Ag volume fraction of 0.3%-1.0% were prepared by radio-frequency magnetron co-sputtering and analyzed by X-ray diffraction,scanning electron microscopy and ultraviolet-visible spectroscopy.Microstructure analysis shows that the films are composed of polycrystalline ITO matrix embedded with Ag nanoparticles with a mean size of 60-100 nm.Transmissivity spectra of Ag-ITO films indicate that the visible light transmissivity of the films decreases with increasing the Ag fraction.The transm...     

Fabrication of microneedle array using LIGA and hot embossing process

We demonstrate a novel fabrication technology of the microneedle array applied to painless drug delivery and minimal invasive blood extraction. The fabrication technology consists of a vertical deep X-ray exposure and a successive inclined deep X-ray exposure with a deep X-ray mask whose pattern has a hollow triangular array. The vertical exposure makes triangular column array with a needle conduit. With the successive inclined exposure, the column array shapes into the microneedle array without deep X-ray mask alignment. Changing the inclined angle and the gap between the mask and PMMA (PolyMethylMetaAcrylic) substrate, different types of microneedle array are fabricated in 750–1000 m shafts length, 15^o–20^o tapered tips angle, and 190–300 m bases area. The masks are designed to 400–600 m triangles length, 70–100 m conduits diameter, 25–60EA/5 mm² arrays density, and various tip shapes such as triangular, rounded, or arrow-like features. In the medical application, the fabricated PMMA microneedle array fulfills the structural requirements such as three-dimensional sharp tapered tip, HAR (High-Aspect-Ratio) shafts, small invasive surface area, and out-of-plane structure. In the skin test, the microneedle array penetrates back of the hand skin with minimum pain and without tip break and blood is drawn after puncturing the skin. Hot embossing process and mold fabrication process are also investigated with silicon and PDMS mold. The processed tetrahedral PMMA structures are fabricated into the microneedle array by the additional deep X-ray exposure. With these processes, the microneedle array can be utilized as the mold base for electroplating process.The author thanks the staff in 9 C LIGA beamline, Pohang Light Source (PLS), Korea for their assistance on the fabrication process.     

Ferroelectric properties of direct-patterned half-micron thick PZT film

Ferroelectric properties of direct-patterned PZT(PbZr_0.52Ti_0.48O₃) films with 460 μm × 460 μm size and 510 nm thick were analyzed for applying to micro-detecting devices. A photosensitive solution containing ortho-nitrobenzaldehyde was used for the preparation of direct-patterned PZT film. PZT solution was coated on Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrate for three times to obtain half-micron thick film and three times of direct-patterning process were repeated to define a pattern on multi-layer PZT film. Through intermediate and final anneal procedure of direct-patterned PZT film, any shrinkage along horizontal direction was not observed within this experimental condition, i.e., the size of the pattern was preserved after annealing, only a thickness reduction was observed after each annealing treatment. Ferroelectric properties of direct-patterned PZT film with 460 μm × 460 μm size and 510 nm thick were compared with those of un-patterned conventional PZT film and shown to be almost the same. Through this work, the high potentiality of direct-patternable PZT film for applying to micro-devices without the introduction of physical damages from dry-etching could be confirmed.     

阵列型微拓扑结构基底的制备及其对神经细胞电生物物理特性的影响

以紫外光光刻、硅蚀刻及软光刻技术制备了微柱阵列型细胞培养基底.实验发现,在4μm的结构高度下,当微柱特征尺寸大于或等于4 μm时,该法能制备结构规整清晰的聚二甲基硅氧烷微柱阵列型基底.特征尺寸为2μm的基底已经接近该法的极限加工能力,所加工的微柱阵列出现倒伏或缺失.采用一种简单的倾斜角法可以制备一种聚苯乙烯微球致密阵列...     

Energy states of vertically aligned quantum dot array with nonparabolic effective mass

The electronic properties of a three-dimensional quantum dot array model formed by vertically aligned quantum dots are investigated numerically. The governing equation of the model is the Schrödinger equation which is incorporated with a nonparabolic effective mass approximation that depends on the energy and position. Several interior eigenvalues must be identified from a large-scale high-order matrix polynomial. In this paper, we propose numerical schemes that are capable of simulating the quantum dot array model with up to 12 quantum dots on a personal computer. The numerical experiments also lead to novel findings in the electronic properties of the quantum dot array model.     

Fabrication of a ZnO piezoelectric micro cantilever with a high-aspect-ratio nano tip

This paper reports on a ZnO piezoelectric micro cantilever with a high-aspect-ratio (HAR) nano tip, which is proposed for a ferroelectric material based nano storage system. The system uses the interaction between the nano tip and a storage medium, and the HAR nano tip is needed to suppress undesirable effects caused by the small gap between the cantilever and the storage medium. The fabrication process for the cantilever with the HAR nano tip consists of three parts: the HAR nano tip formation, the cantilever fabrication, and the bonding/releasing process. The HAR nano tip is formed by the Si deep reactive ion etching for a long shaft and the anisotropic wet etching for a nano tip end. The cantilever is made up of 1 m-thick LPCVD poly-Si layer and 0.2 m-thick Si nitride layer, and has 0.5 m-thick ZnO actuation layer. A final releasing process is followed by an anodic bonding process. The fabricated HAR nano tip has 6 m side length, over 18 m height, and less than 15 nm tip radius, which is built on the 85 m-wide, 300 m-long, and 1.2 m-thick cantilever. The experimental results show a linear behavior with respect to input voltage of 1 to 5 V and the first resonance frequency at 17.9 kHz.     

Fabrication of bio/nano interfaces between biological cells and carbon nanotubes using dielectrophoresis

The authors have previously demonstrated the manipulation of bacteria and carbon nanotubes (CNTs) using dielectrophoresis (DEP) and its application for various types of biological and chemical sensors. This paper demonstrates simultaneous DEP handling of bacteria and CNTs, which are mixed and suspended in water. The CNTs were solubilized in water using microplasma-based treatment. When a microelectrode was energized with an ac voltage in the suspension of Escherichia coli (E. coli) cells and multi-walled CNTs (MWCNTs), both of them were simultaneously trapped in the microelectrode gap. Scanning electron microscopy (SEM) images revealed that E. coli cells were trapped on the surface or the tip of MWCNTs, where the electric field strength was intensified due to high aspect ratio of MWCNTs. As a result, bio/nano interfaces between bacteria and MWCNTs were automatically formed in a self-assembly manner. A potential application of the DEP-fabricated bio/nano interfaces is a drug delivery system (DDS), which is realized by transporting drug molecules from CNTs to cells across the cell membrane, which can be electroporated by the local high electric field formed on the CNT surface.     

Several properties of array languages

The languages generated by connected and disconnected array grammars are studied. We define substitutions of array languages, and we study closure properties of classes of array languages under substitutions. A characterization by means of substitutions for connected context-free array languages and a Kleene-like theorem for regular array languages are given.     

Fabrication of a high aspect ratio nanoporous array on silicon

In this study, a simple method for the fabrication of high aspect ratio silicon nanoporous arrays is developed. A N-type silicon wafer is used as the substrate material. A micro-scale pattern of the desired porous array is transferred to the front surface of the silicon wafer by photolithography after which the wafer is placed in a home-made fixture to efficiently expel the etching generated air and promptly hold the back-side illumination light. A halogen lamp is used as the light source for backside illumination to enhance the electron–hole pair generation. An anodization process is then carried out using a new etchant consisting of hydrofluoric acid and mixed EtOH and EMSO surfactant to effectively polish the pore surfaces and sharpen the tips of the etched pores. A nanochannel array with a nano-tip of 61.4?nm is obtained.     

Fabrication of strongly adherent platinum black coatings on microelectrodes array

Platinum black coating can effectively improve the performance of MEAs(microelectrodes array)in neural signal transduction,though its lack of adhesion strength and durability tampers its usage in long term experiments.Here a new method of composite electrodeposition provides highly adhesive platinum black coating that enables MEAs for a month’s long task and repeatable utilization.The new method was compared with present techniques on multiple aspects,e.g.actual surface area,surface morphology,interfacial impedance,durability and real application tests.Results show that the new composite coating provides greatly improved durability without compromising its performances.Neural cells were cultured on these MEAs for 40 days in vitro and spontaneous action potentials with high signal/noise ratio were recorded.Theoretical model and simulation provided preliminary understanding on the mechanism of this strengthened platinum black coating.     

Identification and pattern recognition analysis of Chinese liquors by doped nano ZnO gas sensor array

In this paper, ZnO nanoparticles were prepared by the renovated hybrid induction and laser heating. The sensitivities of gas sensors can be greatly improved by doping MnO₂, TiO₂ and Co₂O₃. Five different Chinese liquors, namely, Baiyunbian, Beijing Erguotou, Red Star Erguotou, Zhijiangdaqu and Jianliliangjiu, alcohol and diluted alcohol (forged liquor) were measured. Though the main ingredient is alcohol in liquors, Chinese liquors mainly differ from their flavour types, which rely on their trace components. Flavour type of liquors is a very important factor in Chinese liquor identification. Principal component analysis incorporating with discriminant analysis (PCA-DA), back-propagation artificial neural network (BP-ANN) and learning vector quantization (LVQ) were compared for their classification ability. The accuracy of PCA-DA, BP-ANN and LVQ in terms of predicting tested samples was 76.8, 71.4 and 89.3%, respectively. The LVQ is the most suitable pattern recognition algorithm in present experiment. This work shows the potential application of the gas sensor arrays for monitoring the quality of Chinese liquors.     

具有3D微纳结构PDMS阵列免疫传感芯片研制

介绍了一种简便快速加工微阵列免疫传感芯片的新方法。采用化学刻蚀技术加工具有μm级山脉状起伏和nm级表面粗糙度结构(简称为3D微纳表面)的玻璃阳模,以该阳模为模板浇注法制得表面具有3D微纳表面结构的PDMS基片,再借助于物理吸附,将抗体直接固定于该PDMS表面,形成具有3D微纳结构的PDMS微阵列免疫传感器。利用光学显微镜和原子力显微镜对玻璃阳模和PDMS基片表面形貌进行表征,研究了PDMS表面微纳结构化处理对抗体吸附能力的影响。结果表明:3D微纳结构的PDMS由于具有大的比表面积,能显著增强抗体的吸附能力。将研制所得的3D微纳表面结构的PDMS芯片用于微阵列荧光免疫分析,其灵敏度是平板PDMS的5倍。