Pulse gas alignment and AFM manipulation of single-wall carbon nanotube

In the fabrication process of nanoelectronic device arrays based on single-wall carbon nanotube （SWCNT）, oriented alignment of SWCNTs and property modification of metallic SWCNTs in the array are the key problems to be solved. Pulse gas alignment with substrate downward tilt is proposed to realize the controllable alignment of SWCNTs. Experimental results demonstrate that 84% SWCNTs are aligned in -15°- 15° angular to the pulse gas direction. A modified nanomanipulation technology based on atomic force microscope （AFM） is utilized to perform various kinds of SWCNT manipulation, such as SWCNT separation from the ＂Y＂ CNT, catalyst removal from the SWCNT end, continual nano buckles fabrication on SWCNT and even stretching to break, which provides a feasible way to modify the size, shape and the electrical property of SWCNTs.     

面向SWCNT-FET制造的介电泳装配技术

针对单壁碳纳米管(SWCNT)场效应晶体管(FET)制造过程中面临的SWCNT装配问题,采用介电泳技术实现SWCNT在微电极上的有效装配.对SWCNT在非均匀电场中所受到的介电泳力进行了相关理论分析,利用COMSOL多物理场耦合软件模拟了介电泳驱动电场,并做了大量装配实验,获得了高效装配SWCNT所需的实验参数.AFM扫描观测及电特性测试验证了这种方法的有效性,同时也为其他一维纳米材料纳电子器件的装配制造提供了借鉴.     

Organic Field-effect Transistors Based on Tetrathiafulvalene Derivatives

1 Restults Tetrathiafulvalene (TTF) and its derivatives have been extensively investigated in the field of organic conductors and superconductors since 1973. Recently, their application in organic field-effect transistors (OFETs) has attracted considerable attention. So far, on the one hand, the fabrication techniques of the TTF-based FETs have been primarily limited to high vacuum evaporation, which is a relatively expensive process. On the other hand, low FET performances, such as the low on/off ratio...     

含单空位的(10,10)碳纳米管的振动性质和拉曼谱

运用Brenner经验势计算了碳原子间力常数和具体的振动模式,在此基础上利用经验键极化模型计算了含有单空位的(10,10)碳管的非共振拉曼谱.计算结果表明,单空位造成的局域模式所对应的拉曼峰位于完整碳管的G带之外,因此,在实验上可以用这一特性来探测碳管中的单空位.同时,当单空位浓度较小时,碳管的管径几乎不发生变化,仅仅是在拉曼谱中R带上劈裂出一些新的峰,这一现象主要源自于空位带来的对称性破缺.     

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。     

场效应纳电子晶体管的构造和电学特性测量

研究了场效应纳电子晶体管构造过程中金属电极的结构设计,源-漏电极高度、SiO₂绝缘层厚度以及金属电极选材等因素对器件性能有关键的影响。在此基础上测量了单壁碳纳米管束的场效应行为,构造成功基于单壁碳纳米管束的场效应晶体管。     

基于可控Cd掺杂In2O3纳米线的电学特性研究

文章利用化学气相沉积法合成了不同摩尔比的Cd掺杂的In2O3纳米线,制备了基于单根In2O3纳米线的底栅场效应晶体管,并研究了其电输运特性。结果表明,相对未掺杂的In2O3纳米线,In2O3∶Cd纳米线的电导率有1～2个数量级变化,载流子迁移率高达58.1cm2/(V.s),载流子浓度高达3.7×1018 cm-3。可控Cd掺杂In2O3纳米线将在纳米光电子器件方面有着广泛的应用前景。     

Graphene-based ambipolar electronics for radio frequency applications

Graphene is considered as a promising material to construct field-effect transistors (FETs) for high frequency electronic applications due to its unique structure and properties,mainly including extremely high carrier mobility and saturation velocity,the ultimate thinnest body and stability.Through continuously scaling down the gate length and optimizing the structure,the cut-off frequency of graphene FET (GFET) was rapidly increased and up to about 300 GHz,and further improvements are also expected.Because of the lack of an intrinsic band gap,the GFETs present typical ambipolar transfer characteristic without off state,which means GFETs are suitable for analog electronics rather than digital applications.Taking advantage of the ambipolar characteristic,GFET is demonstrated as an excellent building block for ambipolar electronic circuits,and has been used in applications such as highperformance frequency doublers,radio frequency mixers,digital modulators,and phase detectors.     

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.     

水与扶手椅型SWCNT复合环境下α-Ala分子的手性转变机理

采用组合量子化学ONIOM方法,基于氨基作为氢迁移桥梁,考察单壁碳纳米管(SWCNT)与水复合环境下α-丙氨酸分子(α-Ala)的手性转变机理.结果表明:基于氨基作为氢迁移桥梁的手性转变反应有a和b两个通道,其中通道a最具优势;水与扶手椅型SWCNT复合环境对氢迁移反应具有较好的催化作用;在SWCNT(8,8)的限域环境下,3个水分子构成的链使主反应通道的决速步骤能垒从裸反应的266.1kJ/mol降至117.8kJ/mol.表明SWCNT(8,8)与水构成的复合环境可作为实现α-Ala手性转变的理想纳米反应器,生命体内α-Ala分子可在类似的纳米环境实现旋光异构.     

Top-gated graphene field-effect transistors on SiC substrates

We report on a demonstration of top-gated graphene field-effect transistors(FETs) fabricated on epitaxial SiC substrate.Composite stacks,benzocyclobutene and atomic layer deposition Al2O3,are used as the gate dielectrics to maintain intrinsic carrier mobility of graphene.All graphene FETs exhibit n-type transistor characteristics and the drain current is nearly linear dependence on gate and drain voltages.Despite a low field-effect mobility of 40 cm2/(V s),a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency of 1.5 GHz were obtained for the graphene devices with a gate length of 1 μm.     

Freestanding single-walled carbon nanotube bundle networks: Fabrication, properties and composites

As a type of thin film, two dimensional (2D) reticulate architectures built of freestanding single-walled carbon nanotube (SWCNT) bundles are suitable for scalable integration into devices and nanocomposites for many applications. The superior properties of these films, such as optical transparency, unique electrical properties and mechanical flexibility, result not only from the outstanding properties of individual SWCNTs but also from the collective behavior of the individual tubes, with additional properties arising from the tube-tube interactions. In this review, the synthesis, structure and fundamental properties, such as conductivity, transparency, optical nonlinearity and mechanical performance, of ??freestanding SWCNT bundle network?? thin films and nanocomposites, as well as their application as supercapacitors are highlighted. Some long-standing problems and topics warranting further investigation in the near future are addressed.     

基于热阻拓扑关系的高频电源金氧半场效晶体管的散热设计及仿真

研究了高频电源中金氧半场效晶体管（MOSFET）的散热设计问题,分析了MOSFET的热性能参数,建立了单个和耦合器件散热的热阻拓扑模型,推导出各接触面的温度公式,由此得到工程中选取散热器的切实依据,并用于实际高频电源中耦合MOSFET的散热处理.同时,采用计算流体动力学分析软件ICEPAK对所选散热器按工况进行仿真验证.结果表明,该热阻拓扑模型可满足工程设计的要求.     

微孔-大孔双孔结构β沸石材料的构筑规律

以聚苯乙烯小球（PS）为模板，纳米沸石为基元构件，采用受限空间和吸附沉降自组装法，在密堆积的聚苯乙烯小球间隙里组装纳米β沸石，高温焙烧除去PS模板后得到具有微孔－大孔双孔结构的β沸石多级孔材料。并考察了几何因素、化学因素以及浓度因素在受限空间自组装法中对制备规整有序大孔材料的影响。     

用于射频泄漏抑制的相位共轭电路设计

针对方向回溯天线中射频泄漏对相位共轭性能及波束指向性能影响的问题,提出了基于平衡结构的二次混频相位共轭结构,实现射频泄漏抑制。分析了传统相位共轭(phase-conjugating,PON)阵列中射频-中频(radio frequency-intermediate frequency,RF-IF)隔离度对相位共轭性能影响;并针对传统PON阵列射频泄漏抑制较差的问题,设计了基于平衡结构的阻性场效应管(field effect transistor,FET)混频电路来提高射频泄漏抑制指标和相位共轭性能;进一步设计了平衡型的二次混频相位共轭结构,利用跟踪锁相环和同相正交(in-phase/quadrature,IQ)调制结构促进RF-IF隔离。仿真结果表明,本文设计的平衡型二次混频相位共轭电路射频泄漏的抑制高于40 dB,且具有在射频输入功率低至-80 d Bm时,保持约4 dBm的稳定共轭信号输出。     

绝缘栅场效应管工作原理的统一表述

关于绝缘栅场效应管的工作原理,现行教材有几种不同的讲解,观点各不相同。结构示意图和特性曲线画法不同。但是,对同一类的场效应管而言,结构示意图和特性曲线只能有一种表述形式是正确的。从场效应管的基本结构出发,用新观点、新方法说明其基本工作原理,击穿的位置,击穿的原因。提出工作原理结构示意图的统一表述方法应当是在源衬、漏衬PN结之间是正负离子对应的耗尽层,在反型层与衬底之间是单一离子层（它不应该与耗尽层混同）。漏极特性曲线的统一表述规律是截止状态时的漏源击穿电压|BV‘DS|是各个不同VGS时,击穿电压的最大值。     

GaAsFET 4GHz电调振荡器的设计与制作

比较了共源、共栅、共漏3种电路,并组合场效应管外延,设计出采用反沟道接法的共漏电路。分析了FET场效应管的特征频率、最大输出功率、单向功率增益和最大振荡频率等主要特性参数。通过制作和调试,完成的GaAsFET振荡器达到频带输出功率>100 mW,频率 4~4.3 GHz的设计性能要求。所设计的电调振荡器误差小,性能稳定,具有良好的实际应用价值。     

硼掺杂对(2,2)单壁碳纳米管电子结构影响研究

基于密度泛函理论下的第一性原理,计算了不同Ｂ掺杂浓度的SWCNT的几何形状结构、杂质的形成能、能带结构和态密度（DFT）,研究了Ｂ掺杂对（2,2）单壁碳纳米管（SWCNT）电子结构的影响．Ｂ杂质的引入使SWCNT的管径增大,杂质的形成能为负值,表明（2,2）SWCNT进行掺Ｂ的过程为放热反应,Ｂ原子以替位形式掺入碳纳米管中是可行的．掺杂Ｂ后,SWCNT的费米能级向价带迁移,使（2,2）SWCNT转变为ｎ型半导体．     

石墨烯场效应晶体管的光响应特性研究

采用电子束曝光和剥离工艺制备石墨烯场效应晶体管, 并研究其光电响应特性。结果表明, 当激光光斑(波长为633 nm)照射在金属电极边缘的石墨烯沟道时, 可测得明显的光电流。背栅电压能够有效调制光电响应, 可以改变光电流的大小和方向。在背栅调控下, 光电流出现饱和现象, 石墨烯晶体管的光响应度最大达到46.5 μA /W,可用于构建基于石墨烯的新型光探测器。     

低电压并五苯薄膜场效应晶体管

利用全蒸镀法, 以并五苯作为有源层, 聚甲基丙烯酸甲 酯（PMMA）作为绝缘层, 制备了全有机薄膜场效应晶体管（TFT）. 测试结果表明, 器件具有较低的工作电压和较高的场效应迁移率. 对工作机理进行了探讨.