外加电场制备CdS纳米线阵列、纳米带和纳米管

在外加电场的条件下利用物理热蒸发法成功制备出CdS纳米线阵列、纳米带和纳米管,纳米线阵列沿平行于电场方向生长。借助SEM、EDX和TEM以及XRD,研究了外加电场对CdS纳米线生长的影响。结果表明：外加电场大大促进了CdS纳米线定向排列生长;但是,低温区获得的CdS纳米带和纳米管没有任何方向性。     

基于AFM微加工技术制造微结构模板中纳米级高分子聚合物的自组装

介绍一种利用非对称聚合的三嵌段共聚物(SEBS(Styrene-Ethylene-Butylene-Styrene(SEBS))苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物)自组装特性制造大规模整齐排列纳米阵列的分层方法,该方法混合了自下而上/自上而下两种策略。通过AFM(原子力显微镜)获得的硅基上各式各样的微观结构被用来作为球形和高长径比圆柱形聚合物排列的模板。通过原子力显微镜微加工技术的引入,实现了多畴有序阵列的定向排列,并利用硅基的形貌来控制三嵌段共聚物的自组装过程。这种"图外延"的方法可以被应用在软硬混合的情况下,即凝聚态物质系统。此外,自上而下和自下而上方法的混合运用,是一种新颖的实现分子自组装和普遍采用的形态学约束相并行的有效办法,同时也是实现二者并行的基础及沟通桥梁。     

集成硅纳米线制造技术及其电学性质研究

采用传统MEMS工艺,利用精巧的结构设计和准确的工艺控制,制作出一种新型的、在芯片上可集成的、直径可控的硅纳米线,对其形貌和电学特性进行了初步测试和讨论.纳米线的直径达到50nm以下,长度为3～15μm,两端固支,底部悬空.电学测试结果表明,硅材料的表面活性很高,由于比表面积的增大,硅纳米线哌的电学特性受表面态的影响非常大.新鲜表面的硅纳米线与暴露在空气中一定时间的纳米线的I-V特性有着明显的不同.     

研究人员提出金属陶瓷超材料薄膜制备新方法

<正>中国科学院宁波材料技术与工程研究所提出了一种金属陶瓷超材料薄膜制备新方法,该方法采用传统的射频共溅射沉积工艺,辅以衬底偏压,制备了定向排布Ag金属纳米线/氧化铝陶瓷复合超材料薄膜,纳米线间距(轴心到轴心)进入sub-5 nm区间,阵列中纳米线平均直径约为3 nm;纳米线长径比可根据沉积时间来灵活调整;利用PVD     

基于氧化锌纳米线的硅谐振式加速度计

设计制作了一种基于氧化锌纳米线的谐振式硅加速度计,该加速度计的敏感单元为由氧化锌纳米线横跨金属微电极组成的谐振器。采用介电电泳的方法组装了氧化锌纳米线,并利用FIB沉积Pt将氧化锌纳米线固定在微结构上以确保结构的可靠性。在加速度的作用下,质量块引起的惯性力通过支撑梁对纳米线施加应力,因此,在谐振条件下,纳米线谐振频率的变化反映了加速度的大小。谐振式加速度计的准数字输出能解决多数MEMS器件输出微弱信号检测难的问题。实验结果表明,加速度计的灵敏度随着纳米线的厚度的减小而急剧增加,选择500 nm厚度的纳米线作为理论分析,加速度计的灵敏度可达2.5 kHz/g以上。     

基于直流-交变电场的单晶硅3D微纳结构制备方法研究

贵金属颗粒辅助化学腐蚀法在制备硅微纳线结构方面具有独特的作用。为了自动控制贵金属颗粒在单晶硅体内的运动方向,提高制备复杂3D硅微纳结构的可能性和结构品质,提出一种基于复合电场的单晶硅3D微纳结构制备方法。设计了直流-交变复合电场模型来研究贵金属颗粒辅助化学腐蚀法的机理,并分析了电场频率对单晶硅微纳结构的影响。设计了外电场控制模型及试验,讨论了电场强度和电场方向对腐蚀效率和腐蚀轨迹的作用规律。微结构观测结果验证了利用电场控制腐蚀加工过程的可行性,得到了优化的电场电流密度和电场频率工作区间,为制备3D硅微纳结构提供了新的试验思路和机理分析途径。     

残次烟支自动分拣装置结构设计

残次烟支自动分拣装置是一种应用于卷烟厂烟丝回收环节,代替人工分拣排列烟支的机械装置。文中在传统人工分拣排列烟支的基础上,研制出一种高速率、高稳定性、高可靠性的残次烟支自动分拣装置。该装置机械结构包括烟支供料模块、烟支定向传输模块以及烟支调头模块,依次完成对烟支的供料、传输、剔除和定向功能,从而解决了人工分拣排列枯燥无味、人员消耗大的缺点。     

油酸在机器润滑上的应用

润滑油在无特殊添加剂(如油性添加剂、极压添加剂等)的情况下,其粘度大小,是润滑溜在摩擦面上形成油膜厚薄的决定因素。在此情况下,油的润滑性能主要取决于粘度。而润滑油的粘度,对消耗在机器摩擦面上的功率损失、零件的磨损、机器起动的轻快和摩擦零件的温升等有很大影响。从润滑能力来看,最理想的润滑油应该是粘度低,且具有良好的润滑性。由于润滑油中的极性物质分子与金属表面按触时能发生静电吸引并产生垂直方向的定向排列,使极性分子牢固地吸附在金属表面,形成第一层极性分子层,其余极性分子也互相发生静电吸引而定向排列。与此同时,油中非极性的碳氢化合物(烃类)在电场作用下,也变成暂时极性分子,产生静电吸引和定向排列,从而形成油膜。这层油膜可达800～1000个单分子长度的     

切梗丝机来料烟梗定向排列喂料装置的研究

梗丝是烟丝中的重要组成部分,其结构特性是影响卷烟产品质量的重要因素。本文围绕滚刀式切梗丝机入口烟梗排列不规则进料问题进行研究,设计一种烟梗定向排列喂料装置,将烟梗以“长边横向”排列进行喂料切丝,达到改善所切梗丝结构的目的,进一步提高卷烟产品质量。     

一种新型液／液光波导的模拟研究

提出了一种新型单模液,液渐变型光波导模型。理论依据是非极性液体在高强度电场下的克尔效应。采用了多物理场耦合软件对微纳流体微管道模型进行分析．微纳流体管道和纳米线电极结构尺寸对电场强度影响表明,优化设计后的液体微管道可以实现光波导功能。     

用湿化学法在石英玻璃衬底上制备ZnO纳米线阵列

运用湿化学法在石英玻璃衬底上制备了ZnO纳米线阵列,用SEM、XRD和分光光度计对其形貌、晶体结构和发光性能进行了表征。结果表明:所制备的ZnO纳米线为六角纤锌矿结构,其直径为60～200nm,长度为0.1～3μm;ZnO纳米线的光致发光(PL)峰值为380nm,在波段为340～380nm时有很强的吸收峰,具有优越的紫外光响应特性;ZnO纳米线阵列具有高度取向性。     

Imaging and analysis of nanowires

We used vapor-liquid-solid (VLS) methods to synthesize discrete single-element semiconductor nanowires and multicomposition nanowire heterostructures, and then characterized their structure and composition using high-resolution electron microscopy (HRTEM) and analytical electron microscopy techniques. Imaging nanowires requires the modification of the established HRTEM imaging procedures for bulk material to take into consideration the effects of finite nanowire width and thickness. We show that high-resolution atomic structure images of nanowires less than 6 nm in thickness have lattice "streaking" due to the finite crystal lattice in two dimensions of the nanowire structure. Diffraction pattern analysis of nanowires must also consider the effects of a finite structure producing a large reciprocal space function, and we demonstrate that the classically forbidden 1/3 [422] reflections are present in the [111] zone axis orientation of silicon nanowires due to the finite thickness and lattice plane edge effects that allow incomplete diffracted beam cancellation. If the operating conditions are not carefully considered, we found that HRTEM image delocalization becomes apparent when employing a field emission transmission electron microscope (TEM) to image nanowires and such effects have been shown to produce images of the silicon lattice structure outside of the nanowire itself. We show that pseudo low-dose imaging methods are effective in reducing nanowire structure degradation caused by electron beam irradiation. We also show that scanning TEM (STEM) with energy dispersive X-ray microanalysis (EDS) is critical in the examination of multicomponent nanowire heterostructures.     

Note: Mechanical and electrical characterization of nanowires in scanning electron microscope

This note presents two experimental techniques for mechanical and electrical characterization of individual nanowires inside a scanning electron microscope (SEM). Tensile testing is realized by transferring a nanowire to a microelectromechanical systems device that stretches the nanowire and measures the elongations and tensile forces. The device consists of an electrostatic actuator and two capacitive sensors, capable of acquiring all measurement data (force and displacement) electronically without relying on electron microscopy imaging. For electrical characterization, four-point probe measurement of individual nanowires is performed automatically by controlling four nanomanipulators with SEM visual feedback. A feedforward controller is incorporated into the control system to improve the response time. This work represents advances in nanomaterial testing and automated nanomanipulation.     

GaAs纳米线阵列光阴极的制备及其特性研究

采用改进的Stber法合成直径为500nm的SiO_2纳米球,用旋涂法将所合成的SiO_2纳米球制作掩模版,采用纳米球刻蚀法制备GaAs纳米线阵列。利用扫描电子显微镜(SEM)、漫反射谱对其进行了表征分析,再对所制备出的GaAs纳米线阵列结构进行Cs-F交替激活实验,使其表面形成负电子亲和势光阴极,并对最终制备出的GaAs纳米线阵列光阴极样品进行量子效率测试,验证了GaAs纳米线阵列结构的量子效率比GaAs基片提高50%以上,从而证实了纳米线阵列结构的高光电转换效率。     

In situ electron backscattered diffraction of individual GaAs nanowires

We suggest and demonstrate that electron backscattered diffraction, a scanning electron microscope-based technique, can be used for non-destructive structural and morphological characterization of statistically significant number of nanowires in situ on their growth substrate. We obtain morphological, crystal phase, and crystal orientation information of individual GaAs nanowires in situ on the growth substrate GaAs(111) B. Our results, verified using transmission electron microscopy and selected area electron diffraction analyses of the same set of wires, indicate that most wires possess a wurtzite structure with a high density of thin structural defects aligned normal to the wire growth axis, while others grow defect-free with a zincblende structure. The demonstrated approach is general, applicable to other material systems, and is expected to provide important insights into the role of substrate structure on nanowire structure on nanowire crystallinity and growth orientation.     

空气中直接测量ZnO纳米线弹性模量的方法及其表层值研究

提出在大气环境中测量氧化锌纳米线共振频率的方法。通过自制平行微电极施加横置交变电场使纳米线振动,并利用原子力显微镜非接触模式使探针和纳米线顶端间距在分子力作用范围内,探针和纳米线在分子力作用下同步运动。又通过逐渐改变交变电场频率,使纳米线承受频率连续变化的激励作用。通过光电传感器识别探针的位置变化,从而可以通过判断光电传感器信号的激增来确定纳米线共振的发生,得到纳米线共振频率。根据共振频率和几何尺寸的对应关系,由欧拉伯努利梁理论得出氧化锌纳米线弹性模量的变化规律,发现其不等于氧化锌块状材料值且不是常量。由于纳米线尺寸为纳米级别,所以纳米线生长边界的张弛层厚度对纳米线整体性能影响较大。应用有限元多物理场耦合模拟,建立壳-核模型且考虑到在空气中振动的热黏阻尼对试验过程进行模拟,得到共振频率对应的壳部和整体模型弹性模量及其变化规律。     

Current and potential characterization on InAs nanowires by contact-mode atomic force microscopy and Kelvin probe force microscopy

We fabricated InAs nanowires on GaAs giant step structures, and studied their surfaces by two methods; one was current detection by contact-mode atomic force microscopy, and the other was surface potential measurement by Kelvin probe force microscopy (KFM). In the current detection method, the regions where the large current flowed were distributed along the step edges, and these regions agreed well with the expected distribution of InAs. This result confirms that the InAs nanowires were formed along the GaAs giant step edges. The KFM measurements showed that the potential value became more negative along each step edge, where the InAs nanowire was expected to be formed. The surface potential of the InAs nanowires is more negative than that of the surrounding GaAs, which may result from the electron accumulation in the InAs nanowires.     

Probing the local temperature by in situ electron microscopy on a heated Si3N4 membrane

We present a method allowing us to obtain localized heating that is compatible with high-temperature operation and real time scanning and transmission electron microscopy. Localized heating is induced by flowing current through tungsten nanowires deposited by focused ion-beam-induced deposition on a 50-nm-thick Si₃N₄ membrane. Based on the heat transport between the nanowire and the substrate, we applied an analytical model to obtain the temperature profile as a function of electrical power. In this model, the key parameter is the thermal resistance between the nanowire and the substrate that we determined experimentally by measuring electrical power and local temperature. The local temperature is measured by observing the evaporation of gold nanoparticle by electron microscopy. These in situ heating and temperature-probing capabilities are used to study the crystallization of the Si₃N₄ membrane and the growth of silicon nanowires.     

In situ study of electric field‐induced magnetization in multiferroic BiFeO3 nanowires

In this work, we have studied electric field‐induced magnetization effect of multiferroic BiFeO₃ (BFO) nanowires in situ using magnetic force microscopy (MFM). Changes in magnetic domain contrast have been observed in the MFM phase images under applied electric potential, which indicate local magnetoelectric (ME) coupling in the nanowires. The values of saturation and magnetization at different applied electric fields were evaluated. These results suggest that one‐dimensional multiferroic BFO nanowires are potential candidates for realizing multiferroic devices at nanoscale with unique functionalities. SCANNING 36:224–230, 2014. © 2013 Wiley Periodicals, Inc.