Scanning probe microscope analysis of microstructures in optically variable devices

The fine-scale features of optically variable devices (OVDs) fabricated in resist by electron beam lithography have been examined using scanning probe microscopy (SPM). These features have included patterns of gratings, micro-text and geometrical images. Scanning probe microscopy has provided information on the groove angle, depth of profile and spatial frequency of the features as determined by the details of processing of the image. The OVD patterns formed in EBR-9 and X-AR-P 7400 resists exhibited a more rounded profile with a lower side-wall angle than in ZEP-7000 and PMMA resists.     

材料变形过程中的原位电子背散射衍射(in-situ EBSD)分析

本文介绍一套既具备电子背散射衍射（EBSD）,又具备应力加载功能的分析测试方法,简称原位EBSD。采用该系统能实现对拉伸、压缩、弯曲及剪切变形过程中材料的微观组织演变进行原位跟踪观察;可以分析材料在变形过程中的组织演变过程,获得组织演变的连续性信息,从而对研究材料变形过程中的机理及物理本质提供有力的实验依据。本文还以原位压缩过程中纯镁的微观组织演变的测试与分析为例,说明原位EBSD系统使用方法。     

Resonant tunneling in graphene microstructures

We present results for the resonant electronic transmission through graphene-based single and double barriers as a function of the incident wave vector, the widths and heights of the barriers, and the separation between them. Resonant features in the transmission result from resonant electron states in the wells or hole states in the barriers and strongly influence the ballistic conductance of the structures.     

Geometric effects of scattering in microstructures

Transfer Matrix techniques are used to study elastic scattering by point defects embedded in quasi-one-dimensional microstructures. This makes possible an exact analysis of phenomena that arise from breaking of transverse translation invariance. The dependence of transmission probability on scatterer position is studied for parallel transport in quantum wells and for perpendicular transport across single and double barrier structures. It is found that in laterally confined structures, delta-function and other extremely sharp models of a single defect lead to sharp resonances when such defects are well isolated. Such features are associated with multiple reflections between the lateral confining potential and the defect potential. In single-barrier structures with a single nearby defect, an approximate scaling behavior is found that relates transmission for defects at different distances to that at a fixed distance with different energy scales. In double-barrier resonant tunneling diodes (DBRTDs), the position of the transmission peak is affected primarily by defects within the quantum well region. The height of the transmission peak is very sensitive to the positions of defects within that region, acting essentially as a probe of the resonance wave function. Defects in front of a DBRTD also affect the valley current by modifying the longitudinal component of the incident momentum.     

Bi3.15Nd0.85Ti3O12微米薄片的熔盐合成与显微结构分析

以水热合成的 Bi3.15Nd0.85Ti3O12(BNdT)纳米颗粒为原料,用熔盐法合成了 BNdT 微米薄片,用 X 射线衍射和透射电镜研究了微米薄片的显微结构,讨论了片状结构的生长机理,并分析了微米薄片的紫外-可见光吸收性能。结果表明：合成的微米薄片是单晶的层状钙钛矿型结构,横向尺寸为 0.2~2.0 μm,光学带隙为 3.12 eV;随反应温度的升高和反应时间的延长,BNdT 微米片横向尺寸逐渐增大;随熔盐含量增加,晶粒尺寸几乎无变化;BNdT晶体结构的大各向异性使其容易形成片状结构。     

纳米固体Al微观结构的高分辨电镜研究

纳米晶体材料因表现出了常规材料许多不具备的性能,尤其是优于常规晶体的性能,而倍受人们的普遍关注[1]。如冷变形致密化纳米晶Al的屈服强度和断裂强度分别是同质粗晶Al的12倍和5倍[2]。纳米晶体材料的晶粒尺寸很小,界面占有很高的体积百分比,因此,晶界对纳米材料性能的影响将会很大。本项研究主要通过高分辨电镜观察纳米固体Al的微观结构特征,以期从微观结构方面获得与其性能有关的信息。鉴于此,重点对其中的晶界结构和晶内的缺陷进行了比较详细的高分辨电镜观察。纳米固体Al是采用等离子蒸发凝聚冷压成块后,在620℃退火40min,再进行冷变…     

便携式全方位微变监测雷达系统精度分析

微变监测雷达能够对观测区域进行全天时、全天候、非接触式、大面积、亚毫米级精度的形变位移监测,其监测精度分析是进行形变分析和精确预警的关键科学问题。本文采用便携式全方位微变监测雷达系统进行了精度研究和测试分析,首先推导了便携式全方位微变监测雷达的一维和二维信号模型,并对影响微变监测雷达监测精度的因素进行了分析;其次,设计一维形变监测实验,采用角反射器等强反射体作为观测目标,并将光学棱镜与角反射器刚性连接,通过雷达监测结果与全站仪监测结果的对比,对一维形变监测精度进行分析;最后,以分布式角反射器模拟观测场景,分析微变监测雷达的二维形变监测精度。一维、二维形变监测实验结果表明,监测结果与实际位移一致性较好,设计的参考角反测量均值在0.1mm之内,且系统形变监测精度可达亚毫米级,能够实现高精度的微变形监测应用。      

Technological processes and modeling of opto-electro-mechanical microstructures

Micromachining is a promising technology for the development of microsensor applications, based on integrated optics circuits. This paper presents technological processes for fabrication of an opto-electro-mechanical microstructure. Optical waveguides were integrated with photodiodes and three-dimensional structures (cantilevers) on a silicon substrate. We performed different analyses for reducing the induced tensile stress in the mechanical parts. We estimated the stress using ANSYS modeling.     

Inhomogeneously heated electron transport in MIS microstructures

It is demonstrated that in home-junction conducting metal-insulator-semiconductor (MIS) microstructures qualitatively new electron transport phenomena occur and involve an absolute negative resistance of hot electrons and a cold electron thermal bottleneck. These are due to the simultaneous existence of two physical factors: (i) high non-equilibrium electron state and (ii) its abrupt spatial inhomo-geneity. Taking as a basis the effects predicted, electron devices of two types (passive and active) are suggested.     

Deformation analysis to detect and quantify active lesions inthree-dimensional medical image sequences

Evaluating precisely the temporal variations of lesion volumes is very important for at least three types of practical applications: pharmaceutical trials, decision making for drug treatment or surgery, and patient follow-up. In this paper we present a volumetric analysis technique, combining precise rigid registration of three-dimensional (3-D) (volumetric) medical images, nonrigid deformation computation, and flow-field analysis. Our analysis technique has two outcomes: the detection of evolving lesions and the quantitative measurement of volume variations. The originality of our approach is that no precise segmentation of the lesion is needed but the approximative designation of a region of interest (ROI) which can be automated. We distinguish between tissue transformation (image intensity changes without deformation) and expansion or contraction effects reflecting a change of mass within the tissue. A real lesion is generally the combination of both effects. The method is tested with synthesized volumetric image sequences and applied, in a first attempt to quantify in vivo a mass effect, to the analysis of a real patient case with multiple sclerosis (MS).     

Adhesion of arbitrary-shaped thin-film microstructures

We develop, implement in a finite element environment, and experimentally validate an approach to model adhesion of a class of arbitrary-shaped thin-film microstructures commonly used in microsystems technology. The modeling approach adopts principles of three-dimensional linear elastic fracture mechanics and extends them to thin-film plate-like microstructures. A companion experimental effort is carried out to measure adhesion energy of polysilicon microcantilevers using interferometry, and then to study the adhesion behavior of a suite of circular and square plates. The finite element approach is validated by comparison with relevant analytical results. It is then applied to the circular and square plate microstructures and good agreement between measurements and predictions is obtained.     

Mapping of two-photon luminescence amplification in zinc-oxide microstructures

The mapping of two-photon excited luminescence in aggregations of free-standing zinc oxide microrods has been carried out at room temperature. Two-photon luminescence spectra in the excitonic region for individual microrods have been recorded. The luminescence intensity exhibits a power-law dependence on the optical pump power with the exponent n > 2. This fact, along with the existence of a threshold power above which the dependence in the exciton region deviates from a quadratic one, indicates the onset of light amplification in individual ZnO microrods and the conditions preceding laser oscillation.     

改性氧化铝陶瓷的抗弯强度和显微结构

用油酸对Al2O3粉末进行表面改性,研究了表面改性工艺对陶瓷致密性、抗弯强度及显微结构的影响。对改性机理进行了探讨。结果表明:改性粉末在1600℃保温2h制备的Al2O3陶瓷,相对密度达到98.9%,抗弯强度达393MPa。利用油酸与粉末表面羟基反应形成非极性有机表层结构,消除粉末间的硬团聚,降低压制过程中的内摩擦力,从而改善坯体的均匀性和致密性,提高陶瓷的抗弯强度。     

Cathodoluminescence of p-n-p microstructures in CuInSe2 crystals

Microstructures in p-CuInSe₂ single crystals tailored by the strong electric field have been studied using the method of local (d⩽1 μm) cathodoluminescence (CL). The shortest-wavelength radiation (ℏω=1.023 eV) has been observed from the n-type layer and longer-wavelength radiation (ℏω=1.006 eV)—from the p-type regions. An analysis of the cathodoluminescence spectra has allowed us to attribute the experimental features to optical transitions associated with donor and acceptor levels of V _Cu, V _Se, and Cu_i point defects in the crystal. Test measurements of EBIC, the C–V characteristics, and the DLT spectra confirm the cathodoluminescence data and reveal additional features of the p-n-p microstructures. Fiz. Tekh. Poluprovodn. 31, 114–119 (January 1997)     

Improved p- and n-type thin-film microstructures for thermoelectricity

Improved microstructures based on thin-films of n-type bismuth telluride (Bi_{2Te3) and p-type antimony telluride (Sb2Te3) to convert temperature differences in electricity are presented. The microstructures are obtained by thin-film deposition, applying the co-evaporation method to the bismuth/antimony and telluride materials. Measurements demonstrated the superior thermoelectric features of the obtained films when compared with the most recent thermoelectric thin-film deposition. Measurements show that the deposited films present thermoelectric properties comparable to those reported for the same materials in bulk form, as is the case of the materials used in conventional macro-scale Peltier modules. The absolute values of the Seebeck coefficient are in the range 150?250 μVK^-1 and the in-plane electrical resistivity is in the 7-15 μΩm range. Measurements for the Bi2Te3 and Sb2Te3 films also show figures of merit at room temperatures of 0.84 and 0.5, and power factors of 4.87 and 2.81 mWK^-2 m^-1, respectively. These microstructures are used for the fabrication of thermoelectric microgenerators to supply stand-alone microsystems with power consumption that ranges from cents of μW to a few mW.}     

Hooge fluctuation parameter of semiconductor microstructures

The Hooge 1/f fluctuation parameter α_H of a mesoscopic n-GaAs filament is studied experimentally and compared with that derived from the quantum model. The minimum value of the Hooge parameter α_H was 2×10^-6 and 1×10 ^-8 at room temperature and 60 K, respectively. The temperature dependence of α_H below 100 K and the electric field dependence at 77 K are favorably compared with those obtained for the impurity scattering fluctuation of the quantum 1/f noise theory     

Waveguide microcavity based on photonic microstructures

A waveguide based microcavity exhibiting a quality factor Q/spl ap/2500 has been realized by incorporating a /spl lambda//4 phase shift into a 1-D photonic microstructure. The microstructure has an overall length of 3 /spl mu/m, consists of a deeply etched grating with very narrow (75 nm) air-gaps and exhibits a third-order stop band in the 800-900 nm wavelength regime. A comparison between measurement and simulation suggests that there is a thin (approximately 18 nm) skin of oxidized material at the etched semiconductor-air interfaces.     

燃料电池技术采用硅微结构

针对甲醇燃料电池的不足，燃料电池开发商Neah Power Systems公司（位于美国华盛顿州Bothell）研制的一种硅电极架构改进了基于PEM的传统器件所采用的聚合物隔膜，该技术制成了一种由排满催化剂分子的5μm细孔所组成的蜂房结构，从而形成了一个约400μm深的3D构造，而相比之下，传统的燃料电池隔膜厚度则达10μm。     

放电等离子体烧结镍的形变组织研究

利用放电等离子体烧结(SPS)技术制备了粗晶(13μm)和细晶(2μm)两种镍样品.EBSD分析表明,两种烧结样都没有织构,且它们的晶粒都为完全再结晶组织.对此烧结样进行单轴压缩,研究晶粒尺寸对形变中微观组织演变的影响.在样品坐标系中,用每个像素点相对于平均取向的旋转轴来构图,结果显示在一些大晶粒中有扩展的平直界面.滑...