多岛微电极中纳米线介电组装机理研究

为了探究多岛微电极中纳米线的介电组装机理，基于单岛微电极和双岛微电极分别设计了纳米线介电组装实验，并建立了相应的微电极组装数值模型，分析了电场分布、介电泳力、交流电热流对介电组装的影响及合力作用下纳米线的电动力学行为.双岛微电极的电场分布具有更强的奇异性，对纳米线介电组装更有利；在电场频率超过反转频率后，双岛微电极中电热流的流动方向开始发生反向，中间微间隙区域上方出现的对流旋涡能够将纳米线输送至微间隙组装区域，进一步阐明纳米线的组装行为是介电泳力与电热流共同作用形成的.     

椭球粒子受光诱导介电泳的数值模型

基于分子动力学提出了一种光诱导介电泳控制椭球粒子运动的数值模型.研究了光电芯片中椭球粒子承受的光诱导介电泳和斯托克斯阻力,采用Runge-Kutta方法计算不同长宽比粒子的自转速度.采用COM SOL有限元计算电场,借助Velocity-Verlet算法模拟了粒子受介电泳的运动轨迹.仿真结果表明,粒子长宽比越大,转速越快;在28,30μm位置处的椭球粒子,受正介电泳力向光斑运动,且沿着电场强度梯度方向行进,最高速度可达到312μm/s.以上仿真的转动速度和运动轨迹都与实验保持了较好的一致性.     

碳纳米管介电电泳排布仿真研究

建立碳纳米管介电电泳排布的数学模型,利用有限元方法模拟电场分布对介电电泳力大小和方向的影响,结果表明碳纳米管最终的沉积位置以及排布方向受电场方向及梯度的控制,已沉积碳纳米管影响局部电场分布导致与其他碳纳米管产生排斥作用,因此通过改变电场分布可以有效控制介电电泳力的方向与大小,实现碳纳米管的规律排布.     

碳纳米管的手性对发射电流的影响

建立了SWCNT的发射电流与外加电场之间的关系式，分析了SWCNT的手性结构对发射特性的影响．数值计算的结果表明，在电场相同、管径相近的情况下，发射电流从大到小依次为锯齿型(金属性)、扶手椅型、手性(金属性)、手性(半导体性)和锯齿型(半导体性)管．     

基于光诱导介电泳技术的粒子分离研究

首先介绍了光诱导技术和介电泳技术的基础理论,并以此分析了光诱导介电泳的工作原理;其次,利用COMSOL Multiphysics软件建立仿真模型,对3种不同尺寸的圆环光斑产生的电场和介电泳力进行仿真,以验证光诱导介电泳技术分离粒子的可行性,同时为实验提供参考数据;最后,进行实验操作,验证利用光诱导介电泳技术分离粒子的正确性,并通过光诱导介电泳技术实现对粒子的高效无损的分离操作。     

介电粒子所受DEP力模型及相关参数分析

本文应用经典电磁场理论给出介电粒子在非均匀电场中的受力模型,在均匀电场和感应电场叠加原理的基础上,推导出了介电粒子在非均匀电场中的受力公式,进而推出在随时间呈正弦变化的电场和有损耗的媒介中粒子的受力公式．本文结论对运用介电泳理论实现粒子的定位、捕捉、输送、分类等操作具有重要意义．     

金原子在单壁碳纳米管中的结构理论研究

利用密度泛函理论方法研究了单个金原子填充于单壁碳纳米管(n,0)SWCNT(n=5–10)中的几何结构以及Au原子与不同横截面积的SWCNT的相互作用能.结果发现,在直径较小的(n,0)SWCNT(n=5–13)中,Au原子被束缚于纳米管的中心线上,随着横截面积的增加(n=11–13),Au原子将偏离纳米管的中心线.另外,随着纳米管横截面积的增加,Au原子与SWCNT的相互作用能随之增加,Au原子与(9,0)SWCNT的相互作用相对较强,然后随着SWCNT横截面积的进一步增加,曲率变小,Au与SWCNT的相互作用也随之变弱.结果表明(9,0)SWCNT可以被用作连续填充的对象构建SWCNT/一维线性单原子金属链纳米复合材料.     

集成阵列叉指电极介电泳芯片仿真与实验研究

分析了介电泳芯片中粒子所受的介电泳力的影响因素,采用Comsol软件建立阵列叉指电极介电泳芯片的数学模型。通过设置边界条件,对电极的电场进行仿真并对电极的尺寸参数进行优化。为了对仿真结果进行验证,采用MEMS工艺,在ITO玻璃表面制备出叉指电极结构,并与PDMS微流通道键合之后制备出完整的介电泳芯片。采用酵母菌为实验对象,分别对交流电压以及交流电压频率对介电泳的富集效率的影响进行研究。富集效率随电极施加的电压的增大而增大;但增加到一定的程度,富集效率保持不变。改变交流信号的频率,可以改变介电泳的类型。通过调整交流信号的频率,实现了酵母菌的正负介电泳富集。酵母菌在电导率为1μS/cm的悬浮溶液中,存在两个临界频率,分别为40 k Hz、15 MHz。当交流电压的频率为2 MHz时,酵母菌细胞的富集效率最高。     

介电泳操控不同基团修饰多壁碳纳米管气体传感器对SO_2的气敏性能

利用介电泳法在铬-银-金微电极上制备了本征多壁碳纳米管(MWNTs)气体传感器及不同基团修饰多壁碳纳米管(MWNTs-x,x:NH2,OH,COOH)气体传感器,考察了MWNTs和MWNTs-x在非均匀电场中的介电响应行为,将8 V,2 MHz的电泳参数确定为多壁碳纳米管气体传感器的制备条件;在介电泳力作用下MWNTs和MWNTs-x的颗粒均被捕获到电极尖端,发生了正介电泳(p-DEP).室温下研究了制备的气体传感器对不同浓度二氧化硫(SO2)的气敏性能,研究发现传感器对SO2的响应时间、恢复时间和灵敏度随SO2气体浓度的增加而增大,不同基团修饰MWNTs气体传感器对SO2的灵敏度较本征MWNTs传感器的灵敏度显著提高,氨基修饰MWNTs(MWNTs-NH2)气体传感器的灵敏度最高,为本征MWNTs气体传感器的17–23倍,碳管与SO2间的毛细力、表面张力、氢键、化学键等相互作用为影响传感器气敏性能的因素.     

多间隙串行纳米电极系统内粒子的介电行为

为了探究金属纳米粒子在多导电元件微电路修复上的应用,分析纳米粒子介电串行组装过程中的运动趋势,基于一种多间隙纳米电极系统,研究处于非均匀电场内的纳米粒子的介电串行组装行为。首先,进行了导电岛微电极系统的粒子介电组装实验,发现组装获得的熔融态纳米粒子线能够增强电路的导电能力。然后,针对双间隙与多间隙串行纳米电极系统进行了介电串行组装对比实验,发现随着系统内导电元件数量的增加,纳米间隙均存在体组装现象,实现了多间隙串行纳米电极系统内的导电元件连接。最后,通过电场分布及介电组装过程中纳米粒子所受介电泳力、交流电热流以及二者合力的仿真分析发现：在频率为150 kHz的条件下,相比纳米间隙外部,间隙内部的介电泳力及交流电热流流速平均值更高;而且,在多间隙串行纳米电极系统任意间隙内均会出现纳米流体泵现象,且不受间隙数量的影响。纳米流体泵现象表明,处于非均匀电场内的金属纳米粒子在介电串行组装过程中具有体组装与面组装的趋势,此类组装趋势能够直接影响纳米粒子线的生成质量。     

Di-electrophoresis assembly and fabrication of SWCNT field-effect transistor

In the process of fabricating nano electrical device or system based on single-walled carbon nanotube （SWCNT）, the controllable assembly and fabrication of SWCNT field-effect transistor （SWCNT FET） is a key issue. SWCNT FET is the most basic and important component in nano electronics. After microelectrode chip of back-gate FET is designed and fabricated, di-electrophoresis technology is adopted to realize the controllable alignment and assembly of SWCNTs, based on dispersing SWCNT by sodium dodecyl sulphate （SDS） facilitated ultra-sonication technique and removing impurities by centrifugal technique. The experiments of SWCNTs assembly demonstrate that SWCNTs are aligned and assembled uniformly at the microelectrodes gap with the alignment density nearly proportional to di-electrophoresis duration and solution concentration. After the processes of rinsing, drying and improving, metallic SWCNTs among the assembled SWCNTs are burned out and residual SDS is removed, and perfect field-effect performance of SWCNT FET is eventually obtained.     

Dielectrophoretic assembly of carbon nanotubes and stability analysis

Nanoscale dimensions and remarkable properties of carbon nanotubes make them promising building blocks for nanoelectronics.One requirement is the need to manipulate single or multiple carbon nanotubes to bridge electronic conductors.In this paper,multi-walled carbon nanotubes with a variety of sizes are assembled onto electrodes using alternative current electric felds by dielectrophoresis.The effect of the dielectrophoretic parameters and the nanotube size as well as the length uniformity on the assembly is experimentally investigated.Current–voltage characteristics of assembled carbon nanotubes are measured.The experimental results showed that both the dielectrophoretic parameters and length uniformity of carbon nanotubes have an infuence on the stability of assembly results.Choosing uniform carbon nanotubes with an appropriate length and suffcient stiffness,which are more controllable by dielectrophoresis,is necessary for an assembly of a small number of carbon nanotubes.     

碳纳米管阴极场致发射的电场数值模拟

利用Visual FORTRAN语言，对碳纳米管阴极的外电势分布和电场强度分布进行了数值模拟．采用非等间距的网格划分对碳纳米管尖端附近进行细致的划分处理，并利用等参有限元方法进行了模拟计算．分析了碳纳米管尖端局部电场强度的增强效应和相邻碳纳米管之间的电场屏蔽现象．讨论了碳纳米管电场强度随管间距变化的关系以及碳纳米管尖端电场强度随半径变化的关系。     

Indium phosphide nanowires as building blocks for nanoscale electronic and optoelectronic devices

Nanowires and nanotubes carry charge and excitons efficiently, and are therefore potentially ideal building blocks for nanoscale electronics and optoelectronics. Carbon nanotubes have already been exploited in devices such as field-effect and single-electron transistors, but the practical utility of nanotube components for building electronic circuits is limited, as it is not yet possible to selectively grow semiconducting or metallic nanotubes. Here we report the assembly of functional nanoscale devices from indium phosphide nanowires, the electrical properties of which are controlled by selective doping. Gate-voltage-dependent transport measurements demonstrate that the nanowires can be predictably synthesized as either n- or p-type. These doped nanowires function as nanoscale field-effect transistors, and can be assembled into crossed-wire p-n junctions that exhibit rectifying behaviour. Significantly, the p-n junctions emit light strongly and are perhaps the smallest light-emitting diodes that have yet been made. Finally, we show that electric-field-directed assembly can be used to create highly integrated device arrays from nanowire building blocks.     

碳纳米管阵列储氢的物理吸附特性

采用巨正则蒙特卡罗方法,在室温、100大气压下对以方阵和三角方式排列的碳纳米管阵列的物理吸附储氢进行计算机模拟,发现氢分子可被吸附于碳纳米管阵列的管内和管外,管外的储氢密度普遍高于管内,方阵阵列优于三角阵列,并给出了相应的理论解释。     

High-performance doping-free carbon-nanotube-based CMOS devices and integrated circuits

Ballistic n-type carbon nanotube (CNT)-based field-effect transistors (FETs) have been fabricated by contacting semiconducting single-walled CNTs (SWCNTs) using Sc or Y. The n-type CNT FETs were pushed to their performance limits through further optimizing their gate structure and insulator. The CNT FETs outperformed n-type Si metal-oxide-semiconductor (MOS) FETs with the same gate length and displayed better downscaling behavior than the Si MOS FETs. Together with the demonstration of ballistic p-type CNT FETs using Pd contacts, this technological advance is a step toward the doping-free fabrication of CNT-based ballistic complementary metal-oxide-semiconductor (CMOS) devices and integrated circuits. Taking full advantage of the perfectly symmetric band structure of the semiconductor SWCNT, a perfect SWCNT-based CMOS inverter was demonstrated, which had a voltage gain of over 160. Two adjacent n- and p-type FETs fabricated on the same SWCNT with a self-aligned top-gate realized high field mobility simultaneously for electrons (3000 cm² V^?1 s^?1) and holes (3300 cm² V^?1 s^?1). The CNT FETs also had excellent potential for high-frequency applications, such as a high-performance frequency doubler.     

Ge/Si nanowire heterostructures as high-performance field-effect transistors

Semiconducting carbon nanotubes and nanowires are potential alternatives to planar metal-oxide-semiconductor field-effect transistors (MOSFETs) owing, for example, to their unique electronic structure and reduced carrier scattering caused by one-dimensional quantum confinement effects. Studies have demonstrated long carrier mean free paths at room temperature in both carbon nanotubes and Ge/Si core/shell nanowires. In the case of carbon nanotube FETs, devices have been fabricated that work close to the ballistic limit. Applications of high-performance carbon nanotube FETs have been hindered, however, by difficulties in producing uniform semiconducting nanotubes, a factor not limiting nanowires, which have been prepared with reproducible electronic properties in high yield as required for large-scale integrated systems. Yet whether nanowire field-effect transistors (NWFETs) can indeed outperform their planar counterparts is still unclear. Here we report studies on Ge/Si core/shell nanowire heterostructures configured as FETs using high-kappa dielectrics in a top-gate geometry. The clean one-dimensional hole-gas in the Ge/Si nanowire heterostructures and enhanced gate coupling with high-kappa dielectrics give high-performance FETs values of the scaled transconductance (3.3 mS microm(-1)) and on-current (2.1 mA microm(-1)) that are three to four times greater than state-of-the-art MOSFETs and are the highest obtained on NWFETs. Furthermore, comparison of the intrinsic switching delay, tau = CV/I, which represents a key metric for device applications, shows that the performance of Ge/Si NWFETs is comparable to similar length carbon nanotube FETs and substantially exceeds the length-dependent scaling of planar silicon MOSFETs.     

多参数耦合作用输流纳米管的振动分析

基于非局部Euler-Bernoulli梁模型,考虑外加纵向磁场及Pasternak弹性基体,应用哈密顿原理建立了纵向磁场作用下嵌入弹性基体中的简支输流单层碳纳米管(SWCNT)系统振动微分方程及其边界条件。应用微分变换法(DTM)求解上述微分方程,着重研究磁场强度、Pasternak弹性基体的弹性参数与剪切参数以及纳米管小尺度系数对系统临界失稳流速的影响及各参数耦合作用时参数间的相互影响。数值计算结果表明:磁场强度与弹性基体增强系统刚度,提高系统稳定性,但二者耦合作用时对系统刚度的影响表现出“此长彼消”的特点。小尺度效应降低系统刚度,相比磁场对刚度的影响,磁场的影响更为显著。小尺度效应与弹性基体的相互影响则表现出较为复杂的特点。     

二维、三维模型碳纳米管场发射场强计算的比较研究

在计算碳纳米管场发射显示器中电场强度时,为了提高计算效率,许多资料将三维空间的场发射简化为二维模型进行计算,为了比较分析使用二维模型和三维模型计算结果的差异,建立了二维模型单根碳纳米管、三维模型单根碳纳米管和单碳纳米墙3个模型,应用Ansoft Maxwell有限元数值仿真软件进行了仿真,计算结果表明:二维碳纳米管场发射模型的仿真结果代表的三维空间实际情况为碳纳米墙场发射,而不是真正的三维空间碳纳米管场发射。对于单根碳纳米管,用二维模型计算的碳纳米管尖端电场强度仅为三维空间碳纳米管尖端电场强度的1／4。