不同转移法对碳纳米管场发射特性的影响

通过印刷法、喷涂法和电泳沉积法转移经过处理的碳纳米管(CNT)原料到ITO电极上,高温烧结制备CNT阴极阵列,并对CNT的表面形貌和场发射性能进行测试分析。结果表明,不同转移方法对CNT阴极场发射性能的影响不同,印刷法、喷涂法及电泳沉积法3种方法制备CNT阴极场发射的开启电场分别为2.21、1.62和1.85 V/μm;当电场为2.3 V/μm时,喷涂法制备的CNT阴极场发射性能最佳,电泳沉积法制备CNT阴极次之,印刷法制备的CNT阴极最差,并根据金属半导体理论分析其原因。     

表面形貌特殊的碳纳米管薄膜及其场发射增强

采用磁控共溅射法在Si片表面镀NiTi膜作为碳纳米管生长的催化剂,制备出表面形貌特殊的碳纳米管薄膜,如"丘状"和"星状"的表面微结构。通过扫描电子显微镜对碳纳米管薄膜的形貌进行表征,采用二极管形式测试了碳纳米管薄膜的场发射性能。实验结果表明,这两种碳纳米管薄膜都具有优异的场发射性能,10μA/cm~2时的开启电场分别仅为1.02 V/μm和1.15 V/μm,在外加电场为2.4 V/μm时的电流密度分别达到4.32 mA/cm~2和6.88 mA/cm~2。通过场发射FN的曲线计算得到的场发射增强因子分别为10113和6840。这两种碳纳米管薄膜优异的场发射性能与其表面的微结构有关。表面的粗糙结构增强了部分碳纳米管的局域电场,易于发射电子。     

电流法改善碳纳米管阴极场发射特性

针对丝网印刷碳纳米管阴极,提出电流法进行表面后处理,有效改善碳纳米管阴极场发射特性.利用扫描电子显微镜表征电流法处理前后CNTs阴极表面形貌变化,并对处理前后CNTs阴极进行场发射特性测试.结果表明,电流法处理后CNTs阴极表面残留有机物被破坏,开启电场从2.4 V/μm降低到1.6 V/μm,同样面积的薄膜(印制面积为1 cm×1 cm)在2.6 V/μm场强下的发射电流由30 μA提高到了800 μA,说明电流处理对于提高薄膜的场发射特性有明显作用.该方法在碳纳米管场发射显示器的制作中具有很好的实际应用价值.     

碳纳米管薄膜的电泳沉积及其场发射性能研究

利用电泳沉积法在铝片上制备了碳纳米管薄膜冷阴极。通过扫描电镜、Raman光谱观察分析了表面形貌和结构,并对场发射性能进行了测试。经过研磨处理的碳纳米管薄膜样品,开启电场为2V／μm,当电场强度为4V／μm时电流密度达到2600μA／cm^2,发光点密度大于10^4／cm^2。     

电解液法改善碳纳米管阴极场发射特性

针对丝网印刷碳纳米管(CNT)阴极,提出用电解液法进行表面后处理,有效改善碳纳米管阴极场发射特性.利用扫描电子显微镜表征电解液法处理前后CNT阴极表面形貌变化,并对处理前后CNT阴极进行场发射特性测试.结果表明,电解液法处理后有更多的CNT伸出有机浆料表面,开启电场从2.4 V/μm降低到1.4 V/μm,同样面积的薄膜(印制面积为1 cm×1 cm)在3.0 V/μm场强下的发射电流由100μA提高到了1 800μA,说明电解液处理对于提高薄膜的场发射特性有明显作用.该方法在碳纳米管场发射显示器的制作中具有很好的实际应用价值.     

碳纳米管薄膜的电泳沉积与场发射性能

采用电泳法在Si基片上沉积碳纳米管(CNTs)薄膜。研究了电泳极间距、电泳时间及电泳电压等对沉积的薄膜形貌结构与场发射性能的影响。SEM、高倍光学显微镜和场发射性能测试结果表明,保持阴阳极间距为2cm,在100V的直流电压下电泳2min所获得的CNTs薄膜均匀、连续、致密且具有最好的场发射性能,其开启电场强度仅为1.19V/μm,当外加电场强度为2.83V/μm时,所获得的最大发射电流密度可达14.23×10–3A/cm2。     

非晶碳和碳纳米管混合薄膜的场发射性能

利用微波等离子体化学气相沉积法在不锈钢衬底上直接合成非晶碳和碳纳米管混合薄膜.采用氢气和甲烷作为反应气体,流量分别为100和16sccm.沉积室内的压强为5.0kPa.利用场发射扫描电镜(SEM)和喇曼谱(Raman)对制备的薄膜的结构和形貌进行了分析.场发射实验在5×10-5Pa的真空下进行.实验结果表明:制备的非晶碳和碳纳米管混合薄膜开启电场较低,仅有0.9V/μm;在电场为3.7V/p.m时电流密度达到4.0mA/cm2,发射点密集,分布均匀.表明此种材料是一种优良的场发射冷阴极材料.     

非晶碳和碳纳米管混合薄膜的场发射性能

利用微波等离子体化学气相沉积法在不锈钢衬底上直接合成非晶碳和碳纳米管混合薄膜.采用氢气和甲烷作为反应气体,流量分别为100和16sccm.沉积室内的压强为5.0kPa.利用场发射扫描电镜(SEM)和喇曼谱(Raman)对制备的薄膜的结构和形貌进行了分析.场发射实验在5×10-5Pa的真空下进行.实验结果表明:制备的非晶碳和碳纳米管混合薄膜开启电场较低,仅有0.9V/μm;在电场为3.7V/p.m时电流密度达到4.0mA/cm2,发射点密集,分布均匀.表明此种材料是一种优良的场发射冷阴极材料.     

三色碳纳米管场发射灯的研制

报道了以粉末状碳纳米管为原料用丝网印刷法制备图形化的碳纳米管阴极的技术.采用热处理和氢等离子体表面处理方法提高了丝网印刷法制备的碳纳米管阴极的场发射性能,处理后阴极的阈值场强从4V/μm降到～1V/μm,场发射电流密度在4.5V/μm时达到了2.53mA/cm2,发射点密度从～103/cm2增加到～105/cm2.在此基础上,成功地设计和封装了三极管结构的三色高亮度碳纳米管场发射灯器件.     

三色碳纳米管场发射灯的研制

报道了以粉末状碳纳米管为原料用丝网印刷法制备图形化的碳纳米管阴极的技术.采用热处理和氢等离子体表面处理方法提高了丝网印刷法制备的碳纳米管阴极的场发射性能,处理后阴极的阈值场强从4V/μm降到～1V/μm,场发射电流密度在4.5V/μm时达到了2.53mA/cm2,发射点密度从～103/cm2增加到～105/cm2.在此基础上,成功地设计和封装了三极管结构的三色高亮度碳纳米管场发射灯器件.     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

光子晶体微腔发光二极管

光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。     

Comparative study of maximum power point tracking techniques for hybrid renewable energy system

The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES.     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC)。该方法有效简化了TAC电路结构,减小了TAC占用面积,显著提高了TOF的满量程范围(FSR)。采用0.18 μm标准CMOS工艺设计。集成TAC的单光子探测器像素单元的填充因子可达到26.8%。后仿真结果表明,该TAC在120 ns的FSR内具有230 ps的定时分辨率,微分非线性(DNL)低于0.05 LSB,积分非线性(INL)低于1.1 LSB。蒙特卡洛仿真表明,512个TAC像素间的不均匀性低于0.5 %。该TAC非常适用于高密度时间相关的单光子计数(TCSPC)探测器阵列。     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

超宽带脉冲信号的光学生成方法研究

近年来超宽带(UWB)通信技术迅猛发展,在测量、雷达技术、民用和军事无线通信中有着重要的应用,UWB-over-fiber技术已经成为目前研究的热点,其中就包括UWB脉冲信号的产生方法。区别于传统的电子学方法,光子学产生方法不受电子瓶颈制约,可以实现很高的带宽,并且具有抗电磁干扰、重量轻、结构紧凑的优点。通过对比国内外本领域研究成果,讨论及总结了以下三种原理的UWB脉冲信号的光学生成方法:1)相位调制-强度调制转换(PM-IM);2)半导体光放大器(SOA)的非线性效应;3)频谱塑形和色散所致频域-时域映射,然后对各种方案进行了对比分析。     

多孔硅发光机制的分析

从量子力学的基本理论出发讨论了量子限制效应，推导出多孔硅有效禁带宽度增量并用量子限制效应和表面态及其物质在发光中作用的理论解释了ＰＳ光致发光的实验现象。