Surface states induced photoluminescence from Mn2+ doped CdS nanoparticles

Manganese doped CdS nanoparticles were synthesized in basic aqueous solution by using mercapto acetate as capping reagents. The nanoparticles were characterized by HRTEM, EPR, photoluminescence and optical absorption measurements. Out of our expectation, doping of Mn2+ ions altered the recombination paths in CdS nanoparticles markedly. The surface stares facilitated PL from Mn2+ doped CdS nanoparticles is reported. A complete suppression of the emission from surface states at room temperature when doping with Mn2+ ions has been observed for the first time. (C) 2000 Elsevier Science Ltd. All rights reserved.

Optical properties of nanometer silicon prepared by silicon ion implanted into SiO2 layers

The samples of silicon nanocrystals (nc-Si) were prepared by Si ion implanted into SiO2 layers. Photoluminescence spectra were measured at room temperature and their dependence on thermal annealing was investigated. The experimental results show that PL peaks originate from the defects in SiO2 layers caused by ion implantation when the thermal annealing temperature is lower than 800 C. The PL peak from nc-Si was observed when the thermal annealing temperature was higher than 900 C, and PL intensity reached its maximum at the thermal annealing temperature of 1100 C. As the annealing temperature increases the red shift of PL peak from nc-Si shows the quantum size effect. The characterized Raman scattering peak of nc-Si was observed at the right angle scattering configuration for the first time. It provides further support for the PL measurements.

Role of surface defect states in visible luminescence from oxidized hydrogenated amorphous Si hydrogenated amorphous Ge multilayers

Nanocrystalline Ge embedded in amorphous silicon dioxide matrix was fabricated by oxidizing hydrogenated amorphous Si/hydrogenated amorphous Ge (a-Si:H/a-Ge:H) multilayers. The structures before and after oxidation were systematically investigated. The orange-green light emission was observed at room temperature and the luminescence peak was located at 2.2 eV. The size dependence in the photoluminescence peak energy was not observed and the luminescence intensity was increased gradually with oxidation time. The origin for this visible light emission is discussed. In contrast to the simple quantum effect model, the surface defect states of nanocrystalline Ge are believed to play an important role in radiative recombination process. (C) 1999 American Institute of Physics. [S0003-6951(99)02425-0].

Structure, fluorescence and stability of CdS nanoparticles prepared in air

CdS nanoparticies were prepared in air and their stability by air annealing was studied. A small change in crystal structure and particle size was observed by air annealing, but a rapid reduction in fluorescence was found. Through investigation, it is revealed that it is the surface change or reconstruction rather than the variation of the size or structure that decreases the fluorescence. The emission of the particles consists with two peaks which are dependent on the excitation energy. The two peaks are considered to be arisen from "two" different sizes of nanoparticles and may be explained in terms of selectively excited photoluminescence. Finally we discuss why the discrete state of nanoparticles are able to be resolved in the photoluminescence excitation spectrum, but could not be differentiated in the absorption spectrum.

A study of strong photoluminescence of SiOx : H films

We have examined photoluminescence (PL), IR absorption and Raman spectra of a series of hydrogenated amorphous silicon oxide (a-SiOx:H, (0 < x < 2)) films fabricated by plasma enhanced chemical vapor deposition (PECVD). Two strong luminescence bands were observed at room temperature, one is a broad envelope comprising a main peak around 670 nm and a shoulder at 835 nm, and the other, peaked around 850 nm; is found only after being annealed up to 1170 degrees C in N-2 environment. In conjunction with IR and Raman spectra, the origins of the two luminescent bands and their annealing behaviors are discussed on the basis of quantum confinement effects.

Quantum confinement effect in silicon quantum-well layers

The electronic states and optical transition properties of silicon quantum-well layers embedded by SiO2 layers are studied by the empirical pseudopotential homojunction model. The energy bands, wave functions, and the optical transition matrix elements are obtained for layers of thickness from 1 to 6 nm, and three oriented directions (001), (110), and (111). It is found that for Si layers in the (001) direction the energy gap is pseudodirect, for these in the (111) direction the energy gap is indirect, while for those in the (110) direction the energy gap is pseudodirect or indirect for a thickness smaller or larger than 3 nm, respectively. The optical transition matrix elements are smaller than that of diner transition, and increase with decreasing layer thickness. When the thickness of a layer is smaller than 2 nm, the Si QW layers have larger transition matrix elements. It is caused by mixing of bulk X states with the Gamma(1) state. The calculated results are compared with experimental results.

Mode analysis of photonic crystal polarization beam splitter and its application in integrated circuits design - art. no. 698437

In this work, the guided modes of a photonic crystal polarization beam splitter (PC-PBS) are studied. We demonstrate that the transmission of a low-loss photonic crystal 120 degrees waveguide bend integrated with the PBS will be influenced if the PBS is multi-moded. We propose a single-moded PC-PBS structure by introducing deformed structures, and it shows twice the enhancement of the transmission. This device with remarkable improvement of performance is promising in the use of photonic crystal integrated circuits design.

Optical properties and electrical bistability of CdS nanoparticles synthesized in dodecanethiol

We reported the synthesis of CdS semiconductor nanoparticles using a simple one-pot reaction by thermolysis of cadmium acetylacetonate in dodecanethiol. Optical measurements of the as-obtained CdS nanoparticles revealed that their optical properties were closely related to surface effects. Based upon the cocktail of poly (N-vinylcarbazole) (PVK) and CdS nanoparticles, a bistable device was fabricated by a simple solution processing technique. Such a device exhibited a remarkable electrical bistability, which was attributed to the electric field-assisted charge transfer between PVK and the CdS nanoparticles capped by dodecaethiol. The conduction mechanism changed from an injection-controlled current to a bulk-controlled one during switching from OFF-state to ON-state.

A kinetic model for nanocrystal morphology evolution

A kinetic model is developed with the goal of understanding and predicting the morphology evolution of nonocrystals in nonequilibrium growth conditions. The model is based on the assumption that under such conditions, different crystal planes have different kinetic parameters. This model focuses on the morphology-developing stage and is successfully related to the nucleation process and other crystal evolution mechanisms. It is believed to be a universal model and is applied to discuss the morphology evolution of CdSe nanocrystals, including the aspect ratio, injection I schemes, ligands effect and morphology distribution.

可生物隆解聚合物的辐射交联及其生物降解性的研究

近年来，塑料废弃物污染环境的问题日趋严重。对于环境的关心，已经使越来越多的科研人员对于研究环境友好化合物的发展产生了极大的兴趣。聚唬拍酸丁二醋(PBS)，商品名Bionolle，是通过二醇例如乙二醇和丁二醇与脂肪族二梭酸如琉拍酸和己二酸作为主要原料进行缩合反应得到的。日本昭和高分子与昭和电工共同于1993年11月建成年产3000吨的这类脂肪族聚醋系的生物降解塑料的生产装置。由于经济或加工工艺等原因限制了生物降解聚合物的应用和推广，经常是由于它们不良的耐热变形性。目前，脂肪族聚脂尚未能单独用作塑料制品，原因是它们的熔点大都低于100℃。在通常情况下，聚醋的熔点只有高于100℃，经过加工成型后，得到的塑料制品才具有使用价值。辐射交联技术是一种很好的用于提高聚合物某些性能的方法。本工作研究了聚琉拍酸丁二醋的辐射交联行为和它的热稳定行为、生物降解行为。同时，通过辐射手段使用另一种可生物降解聚合物聚。一己内酷（PCL）和纤维布制备了一种可重复节省资源、且对环境无害的复合材料。产得到了如下的结果：1)系统地研究了聚唬泊酸丁二酷的辐射交联行为，发现高分子量的聚唬泊酸丁二醋相比其它两种熔点高的聚琉伯酸丁二醋更易产生交联，在 熔点以上有利于聚唬T}酸丁二酷的交联。由于交联结构的产生，聚合物的力学性能降低。2）两步法辐照（预先在室温下交联，然后在100"C辐照），没有加入任何添加剂，得到了较高的凝胶含量，而且所得的样品不含有气泡。比同剂量下直接在室温辐照凝胶含量提高了20％，比在熔融状态下辐照凝胶含量提高了10%0两步法辐照所得的样品的耐热变形性有了很大的提3）在100℃加入10% PCL对PBS 1的交联有利于交联，而且力学性能没有太大的变化。在210kGy辐照下，比没有加入PCL之前，室温凝胶含量提高120/0，熔融状态（1001,C)提高了22%o（4）生物降解试验，系统地考察了聚唬拍酸丁二醋的结构、厚度、凝胶含量等对于酶降解性的影响，以及温度的影响。发现聚唬拍酸丁二酷（PBS1)很容易被酶所降解，即使有交联结构的存在。在土埋降解试验中通过样品在一定时间的失重率的研究，PBS 1能够被土壤里存在的微生物、细菌所侵蚀。(5）通过形态结构的研究，发现在酶降解中，酶首先侵蚀聚合物的非晶相，但同时也作用于聚合物的结晶相。(6)我们通过辐射技术制备了生物降解聚合物／纤维布复合材料，聚合物可生物降解，纤维布作为回收资源再利用。复合材料的机械性能既依赖于辐射产生的凝胶含量，而且与纤维布的体积分数也相关。本工作所采用的两步法辐射，没有添加任何添加剂得到了比其它辐射条件高的凝胶含量，交联样品有很好的耐热变形性和生物降解性。并且通过辐射方法制备了生物降解聚合物／纤维布复合材料。

可生物降解电纺丝超细纤维

电纺丝技术是一种用来制备超细纤维的方法，成本低廉、简单易行。近十年来，电纺丝技术在理论研究和实验参数研究等方面都取得了不小的进展。由电纺丝技术制备的超细纤维直径至少比传统的纺丝工艺低1-3个数量级，因此，在增强复合材料、过滤系统、防护衣、光学和电学器件及生物医药等方面都显示出巨大的应用潜力。尤其是在生物医药领域，电纺丝超细纤维可广泛用作组织工程支架、药物传输与控制释放的载体及创伤敷料等，这也是国际上的一个研究热点。但由于电纺丝过程的复杂性和实验参数的多样性，制备直径分布范围窄的纤维一直是电纺丝的难点之一，另外，以电纺丝超细纤维作为药物传输与释放的载体也是近两年才刚刚发展起来的，还不十分成熟，经常会存在药物的突释现象。针对以上问题，本论文以可生物降解高分子材料PLA、PLGA（80／20）和PCL进行电纺丝，系统地研究了溶剂体系、表面活性剂、鲜溶液流速、喷丝口直径及环境温度与空气流动速度等因素对电纺丝过程及纤维形貌和直径分布的影响，同时对电纺丝纤维的性质进行了分析。在此基础上，我们研究了PLLA和PCL电纺丝超细纤綷的酶降解行为，并实现了PLLA纤维对抗癌药紫杉醇和1. 以氯仿、氯仿/丙酮、1、2-二氯乙烷及氯仿/1,2-氯乙烷为溶剂体系，制备了PLA、PCL和PLGA（80／20）的电纺丝超细纤维。当氯仿与丙酮的体积比为1：1时为最佳溶剂体系，电纺丝过程和纤维形貌都得到较大的改善。阳离子表面活性剂节基三乙基氯化按（TBBAC）和阴离子表面活性剂十二烷基硫酸钠（SDS）的加入也可以显著改善电纺丝过程和纤维的直径分布，而非离子表面活性剂脂肪醇聚氧乙烯醚（AEO10）的改善程度较小。压力较大或喷丝口直径较粗时，则会由于溶液流量的增大而造成纤维的粘连。空气流速较大时，则纤维会由于空气的对流速度加快而发生缠绕和卷曲。2．PLLA、PCL和PLGA（80／20）超细纤维毡的孔隙率都较大，分别达到89％、68％和80％，因此，PLLA和PCL纤维的力学性能都远远低于膜。3．电纺丝过程会使纤维中的高分子链产生一定的排列和高度的取向，但由于纤维的固化速度很快，高分子链来不及进行规整排列而形成结晶，因此，DSC和WXAD的结果都显示，PCL纤维毡的结晶度要比相应的膜低。对于PLLA纤维毡来说，由于Tg在室温以上，在进行DSC测试的升温过程中，会由于分子链的运动而使结晶度升高。4．蛋白酶K在Tris-HCL缓冲液中略显正电性，因而阴离子表面活性剂对蛋白酶K会有一定的吸附作用，而阳离子表面活性剂对蛋白酶K在纤维表面的吸附则有一定的阻碍作用，因此，含有5wt％SDS的PLLA纤维的酶降解速率比含有swt％TEBAC的PLLA纤维稍快。虽然纤维中PLLA的分子链可能高度取向，但在整个降解过程中，PLLA纤维样品都处在非晶状态，没有明显的结晶行为。5．与PLLA纤维的降解情况恰好相反，由于脂肪酶PS在磷酸盐缓冲液（PBS）缓冲液中显示较强的负电性，因而阳离子表面活性剂TEBAC会对脂肪酶PS有吸附作用，从而含有5wt％TEBAC的PCL纤维降解速度较快，而阴离子表面活性剂SDS会对脂肪酶PS在纤维表面的吸附有阻碍作用，因此，降解反应在含有5wt％SDS的PCL纤维中几乎不能发生。DSC和WAXD的结果均显示，在降解过程中，含有5wt％TEBAC的PCL纤维的结晶度明显升高。这有两个可能原因：一是脂肪酶PS对PCL纤维的降解是优先发生在无定形区：二是因为降解实验是在37℃的条件下进行的，该温度在PCL的Tg之上和TC温度附近，因而，具有高度排列和取向的PCL纤维就会由于分子链的运动而产生结晶，造成结晶度的提局。6，在电纺丝溶液中加入利福平、紫杉醇和阿霉素等药物，同样会改善电纺丝过程，使纤维直径降低，分布变窄。7．SEM照片和药物控制释放实验均显示，药物模型利福平或抗癌药紫杉醇完全被包埋在PLLA纤维内部，同时，利福平一PLLA纤维和紫杉醇－PLLA纤维在含蛋白酶K的Tris-HCl缓冲液中的释放遵循零级动力学，完全没有突释现象。PLLA纤维的降解速度是药物释放的主导因素。这是在国际范围内首次取得这样的结果，从而使电纺丝超细纤维药物剂型的发展取得了本质上的进步。8．药物在溶剂体系中的溶解性及与高分子材料的相容性是影响药物能否被纤维成功包埋的直接因素，一般脂溶性药物易于被脂溶性的高分子纤维包埋。因此，水溶性的盐酸阿霉素难于被包埋在脂溶性的PLLA纤维内部，在纤维外面和表面存在大量盐酸阿霉素的颗粒。相应地，其药物释放行为存在明显的突释现象，这主要是由纤维外面和表面的盐酸阿霉素的溶解、扩散造成的。而经去盐酸化的阿霉素的脂溶性较好，因此，在PLLA纤维中的包埋及释放行为均得到明显的改善，可实现阿霉素的恒速释放，无突释行为。9．SEM照片显示，药物模型利福平被完全包埋在PLGA（80／20）纤维内部，利福平-PLGA（80／20）纤维在PBS中的释放速率是随着纤维中利福平含量的增加而增加的，利福平的含量越大，其释放速率越快。在释放前期，利福平的扩散起主导作用，而在释放后期，其释放行为则是利福平扩散和PLGA（80／20）降解的双重作用结果。适当增加利福平在纤维中的含量（30wt％），则可以获得恒速的释放行为。10．PBS中TEBAC或SDS浓度的增加会在一定程度上使利福平-PLGA（80／20）纤维的释放速率加快，这主要是由于表面活性剂会降低PBS的表面张力，增加水对PLGA（80／20）纤维的浸润能力，从而加快了利福平的扩散速度。

聚合物结晶过程及形态结构的研究

聚合物结晶过程是高分子科学中的一个重要研究方向。本论文在系统研究几种聚合物结晶过程及形态结构的基础上，通过寻求合适的解析聚合物结晶动力学参数的方法，为聚合物结晶动力学的表征和加工工艺设计提供科学依据。采用偏光显微镜（POM）研究了尼龙1212（Nylon 1212）、聚丁二酸丁二醇酷（PBS）及其与己二酸的共聚物（PBS／A）的等温结晶过程。发现碰撞前后球晶的生长速率不变，而在结晶后期球晶生长速率逐渐减慢。PBS／A环带球晶生长过程中球晶半径和结晶时间并非完全的线性关系，而是在直线两侧周期性地摆动。首次非常清晰地观察到PBS结晶后期弱区中新球晶的成核和生长。采用非等温方法在较低的降温速率下获得的聚合物球晶生长速率与等温方法得到的结果有可比性。在计算Nyton1212平衡热力学参数的基础上，采用L-H二次成核理论对N贝on1212的结晶行为进行分析，发现区域I→II和II-III转变分别发生在179Oc和159OC。随着结晶温度的降低，Nylon1212的结晶形态分别为轴状结构晶体、环带球晶和非环带球晶。广角X射线衍射（WAXD）研究表明，PBS和PBS／A具有相同的晶体结构。与PBS相比，PBS／A的结晶度和结晶速率下降。PBS和PBS／A均出现了区域n一Hl的转变，分别发生在％。C和75OC。随着结晶温度的降低，PBS和PBS／A的结晶形态分别为轴状结构晶体、非环带球晶和环带球晶。与PBS相比，PBS／A形成的环带球晶更规整。采用示差扫描量热法（DSC）研究了Nylon 1212、PBS、PBS／A和间规1，2聚丁二烯（st-1，2PB）的本体结晶动力学。发现采用序列一并列Avrami方程能较好地描述Nylon1212的等温结晶全过程。采用不同方法对st-1，2PB的非等温结晶动力学进行研究，发现由Jeziony方法和ozawa方法分析很难得到可靠的动力学参数，而根据莫志深等提出的新方法可较好地进行描述。采用Vyazovkin方法计算了Nylon 1212、st-1，2PB、PBS和PBS／A的非等温结晶活化能，均发现结晶活化能随相对结晶度的升高而升高。初步研究了结晶条件和扫描速率对Nylon 1212、st-1，2PB、PBs和PBs／A熔融行为的影响，并根据Hoffinan-Weeks方法求得了几种聚合物的平衡熔融温度。

1. 大鼠海马-前额叶回路在学习记忆中的作用2. 芬克罗酮改善恒河猴空间工作记忆的谷氨酸机制

一、大鼠海马-前额叶回路在学习记忆中的作用 解剖学研究证实大鼠和猴的海马结构（hippocampal formation, HF；本文‘海马 (hippocampus, Hip)’一词即指海马结构）和前额叶 (prefrontal cortex, PFC) 之间存在一条单向、同侧和单突触的神经回路，即海马-前额叶回路（Hip-PFC回路）。Hip和PFC均参与学习记忆等多种认知功能，PFC是工作记忆的关键脑区，而Hip是空间参考记忆的关键脑区。虽然人们已经对PFC和Hip进行了广泛深入的研究，但对Hip-PFC回路参与哪些认知功能还知之甚少。本研究的目的就是通过暂时阻断Hip-PFC回路，探讨其在学习和记忆中的作用。 在大鼠，Hip-PFC回路中的纤维主要从Hip腹部 (ventral hippocampus, VH)发出，投射到PFC的前边缘皮质(prelimbic cortex, PLC)、下边缘皮质 (infralimbic cortex, ILC) 和外侧前额叶 (lateral prefrontal cortex) 等亚区，其中PLC是Hip-PFC主要投射的区域。我们通过给动物安装慢性导管向脑内注射GABAA受体激动剂muscimol (MU) 阻断Hip-PFC回路。注射位点包括 ①双侧PLC，②双侧VH，③一侧VH和对侧PLC (VH-PLC)。我们首先观察了在PLC或VH局部注射MU对自由活动大鼠PLC和VH脑电功率的影响，并以此确定在行为实验中所用蝇蕈醇的剂量。然后采用T-迷宫空间交互延缓作业 (spatial delayed alternation task) 测试Hip-PFC回路被阻断的动物的空间工作记忆功能；采用被动回避作业 (passive avoidance task) 测试其情绪相关记忆的能力（训练前给药；24 h后重测试）；采用Morris水迷宫作业 (Morris water maze task) 测试其空间参考记忆的能力（每天训练前给药；训练期（3 d）结束24 h后重测试）。结果表明：在大鼠PLC或VH局部注射0.5 μg/0.25μl MU后30 min显著抑制VH 和PLC的脑电功率 (VH, p < 0.01; PLC, p < 0.05 vs. PBS/baseline)。注射MU (0.5 μg/0.25μl) 到 ①双侧PLC、②双侧VH、③VH-PLC均显著降低动物在空间交互延缓作业 (All p < 0.001, vs. PBS) 和空间Morris水迷宫作业中的成绩 (All p < 0.05, vs. PBS)，表明Hip-PFC回路在空间工作记忆（空间短时记忆）和在空间参考记忆（空间长时记忆）中均起重要作用。在空间交互延缓作业中，双侧PLC被抑制的大鼠的成绩显著低于双侧VH或VH-PLC被抑制的动物，说明PFC在空间工作记忆功能中占有主导地位。在被动回避作业中，双侧VH被抑制动物的回避反应的潜伏期显著短于对照动物 (p < 0.05 vs. PBS)，说明双侧VH被抑制动物的情绪记忆受损；而双侧PLC或VH-PLC被抑制的动物其回避反应的潜伏期与对照动物无显著差异 (PLC, p > 0.9; VH-PLC, p > 0.3 vs. PBS)，表明双侧PLC或VH-PLC被抑制的动物情绪记忆正常。被动回避作业的结果说明VH参与情绪记忆的形成，但Hip-PFC回路在情绪记忆形成中不起重要作用。 以上结果表明，大鼠Hip-PFC回路参与空间工作记忆和空间参考记忆而不是情绪记忆功能。情绪记忆的关键脑结构是杏仁复合体 (amygdala complex, AMC)，VH与AMC有密切的纤维联系。VH被抑制的大鼠情绪记忆受损，说明情绪记忆可能与AMC-Hip回路有关。情绪记忆与空间记忆（参考记忆和工作记忆）在解剖上的分离说明，对于不同类型的记忆来说，其在脑内的信息加工过程是并行的。神经回路内部的信息加工过程则是串行的，回路上任何一个结构的破坏均可导致回路功能的损伤。本研究的结果为学习记忆的“多重记忆系统”理论和记忆信息加工的串行并行机制提供了新的实验证据。 二、芬克罗酮改善成年恒河猴空间工作记忆的谷氨酸机制 芬克罗酮是中科院昆明植物所郝小江等合成的取代吡咯烷酮类化合物。中科院昆明动物所蔡景霞等发现芬克罗酮能改善东莨菪碱、育亨宾等导致的多种动物的不同类型的学习记忆障碍，提高老年动物的学习记忆能力，尤其是老年猴的空间工作记忆。已证实芬克罗酮为部分钙激动剂，可使脑缺血沙土鼠脑内升高的谷氨酸降低，而使正常的沙土鼠海马胞外谷氨酸释放增加。那么芬克罗酮能否提高正常动物的学习记忆，其对正常动物学习记忆的提高是否与其增加谷氨酸的释放有关？本研究采用空间延缓反应作业和谷氨酸NMDA受体拮抗剂MK-801在正常成年猴恒河猴上探讨了以上问题。 结果表明，口服芬克罗酮可显著提高成年猴的空间工作记忆，其量效曲线呈倒‘U’形，符合许多促智药的量效特点。0.25 mg/kg和0.5 mg/kg为芬克罗酮的最佳有效剂量 (p < 0.05 vs. 安慰剂)。肌注MK-801 (0.1 mg/kg) 显著降低成年猴的空间工作记忆 (p < 0.01 vs. 安慰剂)，而口服2.0 mg/kg和4.0 mg/kg的芬克罗酮则显著改善MK-801导致的工作记忆障碍 (p < 0.05 vs. MK-801)。芬克罗酮的所有测试剂量不影响猴在作业中的反应时 (p > 0.05 vs. 安慰剂)，表明芬克罗酮在该剂量范围不影响动物的运动能力。 本研究结果提示，芬克罗酮可能通钙激动作用促进谷氨酸的释放，在一定剂量范围内提高胞外谷氨酸水平，提高正常动物的空间工作记忆等认知功能。 关键词：芬克罗酮，恒河猴，空间工作记忆，空间延缓反应作业，谷氨酸，MK-801

Fabrication of Silicon-Based Template-Assisted Nanoelectrode Arrays and Ohmic Contact Properties Investigation

A convenient fabrication technology for large-area, highly-ordered nanoelectrode arrays on silicon substrate has been described here, using porous anodic alumina (PAA) as a template. The ultrathin PAA membranes were anodic oxidized utilizing a two-step anodization method, from Al film evaporated on substrate. The purposes for the use of two-step anodization were, first, improving the regularity of the porous structures, and second reducing the thickness of the membranes to 100 similar to 200 nm we desired. Then the nanoelectrode arrays were obtained by electroless depositing Ni-W alloy into the through pores of PAA membranes, making the alloy isolated by the insulating pore walls and contacting with the silicon substrates at the bottoms of pores. The Ni-W alloy was also electroless deposited at the back surface of silicon to form back electrode. Then ohmic contact properties between silicon and Ni-W alloy were investigated after rapid thermal annealing. Scanning electron microscopy (SEM) observations showed the structure characteristics, and the influence factors of fabrication effect were discussed. The current voltage (I-V) curves revealed the contact properties. After annealing in N-2 at 700 degrees C, good linear property was shown with contact resistance of 33 Omega, which confirmed ohmic contacts between silicon and electrodes. These results presented significant application potential of this technology in nanosize current-injection devices in optoelectronics, microelectronics and bio-medical fields.

Electronic structure of quantum spheres and quantum wires

The electronic structures of quantum spheres and quantum wires are studied in the framework of the effective-mass theory. The spin-orbital coupling (SOC) effect is taken into account. On the basis of the zero SOC limit and strong SOC limit the hole quantum energy levels as functions of SOC parameter lambda are obtained. There is a fan region in which the ground and low-lying excited states approach those in the strong SOC limit as lambda increases. Besides, some theoretical results on the corrugated superlattices (CSL) are given.