用六维团簇模型和定量会聚束电子衍射优化i-AlPdMn准晶的结构因子

基于二十面体AlPdMn准晶的六维团簇模型,用定量会聚束电子衍射法优化了二十面体AlPdMn准晶的8个独立的强反射结构因子。将优化得到的结构因子替换X射线衍射实验得到的结构因子,并与其它的X射线衍射实验得到的结构因子相结合,用Fourier合成的方法得到二十面体AlPdMn准晶的电荷密度分布和差值电荷密度分布。所得差值电荷密度表明,当Al原子的最近邻原子为Mn时,Al原子失去较多的电子,Mn原子得到电子,说明发生了Al的外层电子向Mn原子转移,Mn显示负的化合价。这一结果与他人的理论计算结果相符。     

ZnS∶Mn纳米晶的制备及磁光性能研究

采用水热法制备了Mn掺杂的ZnS纳米晶,通过X线衍射(XRD)谱、扫描电子显微镜(SEM)、磁性曲线、光致发光谱对其微结构、表面形貌、磁学及光学性能进行了探究。结果表明,ZnS∶Mn纳米晶为球形闪锌矿结构,晶体颗粒大小均匀,平均粒径为20nm。在外加磁场的作用下,ZnS∶Mn纳米晶的磁化强度随着Mn掺杂浓度增加而增加。当掺杂x(Mn)=2%(摩尔分数)时,ZnS∶Mn纳米晶发射光谱的强度最强;当x(Mn)=10%时,离子间相互碰撞引发了浓度猝灭效应及高浓度Mn引入的大量缺陷,使光致发光谱的强度减小。     

AlCoNi十次准晶与金属铜间扩散机制分析

本文利用扫描电镜和透射电镜分析了粉末冶金法制备的Al72Co20 Ni8十次准晶颗粒与Cu基体之间的扩散行为与反应机制.研究发现700℃下,Cu原子沿两个方向扩散进入准晶颗粒,一是沿着准晶晶粒的晶界,二是垂直于准晶周期轴方向扩散进入其晶粒内部.Al72 Co20 Ni8准晶由于Al原子向外扩散先转变为片层状Al(Co,...     

急冷AlNi合金中的十次准晶与晶体相

准晶态的研究是近年来开展起来的。准晶是具有准平移周期序及非晶体学对称点群的一类固态相,被认为是介于晶态与非晶态之间的一种物质状态。按其准周期维数可分为三维、二维、一维准晶。十次准晶为二维准晶,即具有十次旋转对称点群及沿此对称轴的平移周期序。本文就AlNi系急冷合金中的准晶及其晶体相作了研究。样品通过锤淬技术将合金从液态高速冷却至固态而得到,所选合金成份如表l。AlNi系准晶为二维十次准晶,其特点是十次轴周期为0.4nm,这是所发现的十次准晶中最小的情况,被认为是十次准晶中最基本的周期单元,见图l(a)(b)(c)。研究表明,Al_3Ni接近Al—Ni系准晶的最佳成份,随着Ni含量的减少,准晶晶粒小大与数量都递减,直至Al_6Ni时,无准晶存在。实验证实了少量Si对于准晶的形成有影响,Al_6Ni中加入20％Si代替Al时,观察到了一种周期为1.6nm的十次准晶;加     

少量Ni添加对Al-Rh准晶系微结构的影响

自从发现具有十次对称性的二维准晶以来，十次对称二元合金系准晶由于成分简单成为研究准晶的热点。铝基准晶是准晶系中比较丰富的一族，其中Al-TM系（TM代表过渡族金属，如Mn、Pd、Co、Rh）准晶是一类典型的代表。最早发现Al-Mn二十面体准晶即是铝基准晶。Hiraga曾经报道了Al-Pd系统中存在的1．6nm周期的十次对称准晶及存在正交结构的大单胞晶体的准晶近似相。与Al-Pd结构及原子序数相似的Al-Rh合金系统的有关报道却比较少。Ma等曾报道了Al-Rh中存在周期为1．6nm的十次对称准晶，并研究了这种准晶的热稳定性能，指出它不是一种稳定的准晶。限于当时的电镜设备，有关Al-Rh二元准晶的微观结构报道的也不尽详细。Grushko等后来详细报道了Al-Ni-Rh三元合金系中存在的周期为0．4nm的十次对称准晶。另外还有报道认为微量Si的掺入促进准晶形成更为完美的结构。     

BaTiO3超细微粒精细结构的研究

超细微粒指直径小于0.1μm的颗粒。当颗粒的直径小到数十纳米时,每个微粒包含的原子总数很小,表面原子数占原子总数的比例较大,表面活性增加,微粒的外形可以通过微粒内部层错面与孪晶面的产生与消失而改变,成为“准固态”。超细微粒的熔点低于大块同种材料的熔点,颗粒的其他物理化学性能也与大块材料有很大的不同。近年来,超细微粒的研究与开发已形成物理学,化学与材料科学的一个新领域。     

碳辅助法制备Mn_3O_4纳米颗粒北大核心

以脱脂棉为碳源,氯化锰为前驱物,采用碳辅助法制备了粒径约为65 nm的Mn3O4纳米颗粒。通过透射电镜（TEM）和高倍透射电镜（HRTEM）对制备样品的形貌、粒径及晶面的结构特性进行了分析;通过X射线衍射（XRD）表征,分别对不同煅烧温度（400-600℃）下样品的物相、晶粒度进行了研究,表明500℃为Mn3O4纳米颗粒的最佳制备温度;X射线光电子能谱（XPS）表征表明制备的Mn3O4表面存在碳元素,N2吸附-脱附曲线测试结果表明Mn3O4纳米颗粒具有较大的比表面积。另外,通过紫外-可见光（UV-vis）吸收表征表明,在一定的波长范围内该Mn3O4纳米颗粒的可见光吸收能力明显增强,有利于提升其光解水制氢能力。     

具有膺八次旋转对称性电子衍射谱的45°微孪晶

在急冷Cr—Ni—Si合金中,一种具有膺八次对称性的45°孪晶(及微孪晶)被首次发现。此结构的电子衍射谱与在同一成份合金中发现的8次准晶在某些方面有些相似,尤其此两种结构共生时,仅从电子衍射谱(图1)上很难区分。高分辨技术使此两种结构很容易区分,既使微孪品的尺寸只有2—4nm,高分辨象仍然能清晰地显示出β—Mn结构的45°旋转畴,见图2。而八次准晶的高分辨象与这种45°微孪晶有根本的区别。这种45°孪晶通常在晶界处发生重迭而产生二次衍射。当李晶尺寸减小时重迭加重并渗杂进尺寸效应使电子衍射谱斑点模糊,如图la所示。虽然此时衍射谱的周期性已不再显现,但与8     

修正T矩阵公式及半空间随机球粒媒质的电磁波多散射

本文将“两外空间”概念与普通Ｔ矩阵公式相结合,提出了修正Ｔ矩阵公式,作为应用实例,本文用修正Ｔ矩阵理论研究了半空间随机球粒媒质的电磁波多散射,在Ｆｏｌｄｙ近似下得到了确定媒质有效波散的一个超越方程,低频时的数值结果表明：修正Ｔ矩阵方法当颗粒稀疏分时是可行的,当颗粒致密分布时,尚需采用引入颗粒对分布函数的准晶近似。     

急冷Mn—Si—Al中八次准晶中的反相畴界的观察

自从在急冷的Cr-Ni-Si合金中首次发现八次对称准晶后,在急冷的Mn-Si-Al合金中也观察到了八次准晶,且后者准晶颗粒比前者大,因此可以通过衍衬方法来研究Mn-Si-Al合金中准晶相的缺陷。图A是当电子束平行于八次轴方向入射时得到的八次对称衍射谱的四分之一部份,对该谱的衍射点逐个进行暗场成象分析,结果发现衍射斑点可以分为四类(a.b.c.d)。在a类点的暗场象中看不见黑线似的反相畴界衬度,如图B和图C所示。在b类点成象的暗场象中能看到图D所示的黑线似的反相畴界的衬度,c类点的暗场象则给出图E示的反相畴界衬度。我们从图D和图E可看出,b类点的畴界衬度在c     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.