Piezoresistive Sensors Based on Carbon Nanotube Films

Piezoresistive effect of carbon nanotube films was investigated by a three-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The experimental results showed that the carbon nanotubes have a striking piezoresistive effect. The relative resistance was changed from 0 to 10.5 X 10-2 and 3.25 X 10-2 for doped and undoped films respectively at room temperature when the microstrain under stress from 0 to 500. The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220 and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35 ℃. The origin of the resistance changes in the films may be attributed to a strain-induced change in the band gap for the doped tubes and the defects for the undoped tubes.     

Investigation into the InAs/GaAs quantum dot material epitaxially grown on silicon for O band lasers

InAs/GaAs quantum dot(QD)lasers were grown on silicon substrates using a thin Ge buffer and three-step growth method in the molecular beam epitaxy(MBE)system.In addition,strained superlattices were used to prevent threading disloca-tions from propagating to the active region of the laser.The as-grown material quality was characterized by the transmission electron microscope,scanning electron microscope,X-ray diffraction,atomic force microscope,and photoluminescence spectro-scopy.The results show that a high-quality GaAs buffer with few dislocations was obtained by the growth scheme we de-veloped.A broad-area edge-emitting laser was also fabricated.The O-band laser exhibited a threshold current density of 540 A/cm² at room temperature under continuous wave conditions.This work demonstrates the potential of large-scale and low-cost manufacturing of the O-band InAs/GaAs quantum dot lasers on silicon substrates.     

Disordered wall arrays by photo-assisted electrochemical etching in n-type silicon

The fabrication of ordered, high aspect-ratio microstructures in silicon by use of photo-assisted electrochemical etching is an important technology, where voltage and current density are significant factors. In this paper, disordered walls appear in 5-inch n-type silicon wafers when a large current density is used. Based on the theory of space charge region, these disordered walls are caused by the contradiction between the protection from dissolution by a high applied voltage and the dissolution by a high current density. To verify this point, wall arrays were fabricated at different applied voltages and current densities. Moreover, the critical voltage was kept constant and different current densities were applied to obtain conditions for avoiding disordered walls and achieving uniform wall arrays. Finally, a wall array with a period of 5.6μm and a depth of 55μm was achieved at an applied voltage of 3 V and a monotonically increasing current density ranging from 22.9 to 24.5 mA/cm².     

Influence of the initial transient state of plasma and hydrogen pre-treatment on the interface properties of a silicon heterojunction fabricated by PECVD

Amorphous/crystalline silicon heterojunctions(a-Si:H/c-Si SHJ) were prepared by plasma-enhanced chemical vapor deposition(PECVD).The influence of the initial transient state of the plasma and the hydrogen pre-treatment on the interfacial properties of the heteroj unctions was studied.Experimental results indicate that: (1) The instability of plasma in the initial stage will damage the surface of c-Si.Using a shutter to shield the substrate for 100 s from the starting discharge can prevent the influence of the instable plasma process on the Si surface and also the interface between a-Si and c-Si.(2) The effect of hydrogen pre-treatment on interfacial passivation is constrained by the extent of hydrogen plasma bombardment and the optimal time for hydrogen pre-treatment is about 60 s.     

Nano-photonic crystal formation on highly-doped n-type silicon

We present a novel electrochemical technique for the fabrication of nano-photonic crystal structures. Based on a specially designed electrolyte, porous silicon(PSi) layers with different porosities are possible to be produced on highly-doped n-type silicon substrate by varying the applied current density which determines the size and the morphology of pores. By applying an alternative current density modulation during anodization, porous silicon photonic crystals are obtained using HF-containing electrolyte without oxidizing components. The current burst model(CBM) is employed to interpret the mechanism of the formation of the macropore porous silicon.     

接触面陷阱密度对a-InSnZnO薄膜晶体管器件电气性能的影响研究

We reported the influence of interface trap density（Nt） on the electrical properties of amorphous InSnZnO based thin-film transistors,which were fabricated at different direct-current（DC） magnetron sputtering powers.The device with the smallest N_t of 5.68×10¹¹ cm^-2 and low resistivity of 1.21×10^-3Ω·cm exhibited a turn-on voltage(V_ON) of-3.60 V,a sub-threshold swing（S.S） of 0.16 V/dec and an on-off ratio(I_ON/I_OFF) of⁸ x 108.With increasing N_t,the V_ON,S.S and I_ON/I_OFF were suppressed to-9.40 V,0.24 V/dec and 2.59×10⁸,respectively.The V_TH shift under negative gate bias stress has also been estimated to investigate the electrical stability of the devices.The result showed that the reduction in N_t contributes to an improvement in the electrical properties and stability.     

Composite structure of ZnO films coated with reduced graphene oxide: structural,electrical and electrochemical properties

ZnO films coated with reduced graphene oxide (RGO-ZnO) were prepared by a simple chemical approach.The graphene oxide (GO) films transferred onto ZnO films by spin coating were reduced to RGO films by two steps (exposed to hydrazine vapor for 12 h and annealed at 600 ℃).The crystal structures,electrical and photoluminescence properties of RGO-ZnO films on quartz substrates were systematically studied.The SEM images illustrated that RGO layers have successfully been coated on the ZnO films very tightly.The PL properties of RGO-ZnO were studied.PL spectra show two sharp peaks at 390 nm and a broad visible emission around 490 nm.The resistivity of RGO-ZnO films was measured by a Hall measurement system,RGO as nanofiller considerably decrease the resistivity of ZnO films.An electrode was fabricated,using RGO-ZnO films deposited on Si substrate as active materials,for super capacitor application.By comparison of different results,we conclude that the RGO-ZnO composite material couples possess the properties of super capacitor.     

Physical Effects of Mechanical Processes on Bi-2223 Tapes

The effects of intermediate mechanical deformation （IMD） and bending processing on Bi-2223 tapes were studied. Bi-2223 tapes were manufactured by powder-in-tube process with an IMD. Normal rolling （NR）, pressing （P） and sandwich rolling （SR） with different reduction rate were used in the IMD. And there were an optimum reduction rate existing for the three MID techniques, at which critical current reached maximum. Critical current densities Jc of Bi-2223 crystals were measured with an applied magnetic field B respectively parallel to ab face and c axis. Relations of Jc dependences of reduction rate and superconducting materials density D were respectively studied and showed a Gaussian distribution law. Maximum pinning force density Fmax and irreversible magnetic field Birr were introduced to describe the effects of mechanical processing. Analysis of experimental results showed that Jcs Fmax and Birr were linear dependence on D. Obviously, increasing D was a vital way to enhance Jc Bending experiments were performed for SR tapes sheathed by Ag and Ag/Sb and Ag/Mg alloy, respectively. Silver alloy sheathed tapes showed better bending properties than pure silver sheathed one. Therefore, silver alloy sheathed, optimum reduction rate of IMD, and increasing D for Bi-2223 tapes＇ applications were important technical strategies to enhance their mechanical, electrical, and magnetic properties.     

TiO2 Thin Film UV Detectors Deposited by DC Reactive Magnetron Sputtering

CrystallineTiO2 thin films were prepared by DC reactive magnetron sputtering on indium--tin oxide(ITO) thin film deposited on quartz substrate, the photoconductive UV detector on TiO2 thin films was based on a sandwich structure of C/TiOz/ITO. The measurement of the I—V characteristics for these devices shows good ohmic contact. The photoresponse of TiO2 thin films was analyzed at different bias voltage. The detector shows a good photoresponse with a rise time of 2 s and a fall time of 40 s, the photocurrent is linearly increased with the bias voltage.     

Electrical and γ-ray energy spectrum response properties of PbI2 crystal grown by physical vapor transport

Lead iodide single crystal was grown by physical vapor transport method.Two radiation detectors with different configurations were fabricated from the as-grown crystal.The electrical and y-ray response properties at room temperature of the both detectors were investigated.It is found that the dark resistivity of the detectors are respectively 3×10¹⁰Ω·cm for bias electric field parallel to crystal c-axis（E//c） and 2×10⁸Ω·cm for perpendicular to crystal c-axis（E⊥c）.The energy spectrum response measurement shows that both detectors were sensitive to ²⁴¹ Am 59.5 keVγ-rays,and achieved a good energy resolution of 16.8%for the E⊥c-axis configuration detector with a full width at half maximum of 9.996 keV.     

非同相口径场瞬态辐射的计算

利用电磁脉冲的口径瞬态辐射场计算公式,针对圆形口径的线性相移、平方律相移等非同相口径场情况,计算了辐射高斯脉冲时的能量方向图、半能量波瓣宽度、面积利用系数等参数.计算表明,对于圆形口径非同相口径场,最大辐射场的方向为口径面法线方向,同时能量方向图关于口径面法线方向对称;随着口径的增大,波瓣变窄,无副瓣;随着平方律相移的滞后参数的增加,波瓣变宽,主瓣不分裂.     

两种自适应杂波抑制技术的比较：AMTI及ADPCA技术性能的分析和比较

本文在讨论机载雷达地面杂波回波的基础上，分析了ＡＭＴＩ和ＡＤＰＣＡ系统的性能。对这两个系统从原理上，并利用计算机模拟结果及实验结果进行了比较。本文将有助于工程实现。     

近红外光谱技术在水果品质无损检测中应用的研究与现状

简单概述了我国水果产业的发展现状,着重阐述了国内外利用近红外光谱技术进行水果品质无损检测的最新研究进展,分析了当今研究中存在的问题,并对利用近红外光谱技术进行水果检测的前景进行了展望,提出了一些建议。     

水的光学特性对水下光学成像质量影响的分析

水的光学特性对光学成像质量有着重要的影响,水对光的吸收、散射作用可造成光在水介质传播中的衰减,本文就水的光学特性及其对水下光学成像质量的影响进行了分析,以为成像系统在水下的应用提供基础的理论依据。     

星载差分吸收光谱仪转动部件测试系统设计

基于星载差分吸收光谱仪转动部件控制需求,设计了星载光谱仪转动部件的测试系统。采用微动开关复位加定步的电机运动方式实现电机的精确定位。采用脉冲调制（PWM）的方式实现驱动电流的精细调节。并搭建平台对系统进行重复性测试,实验结果表明,测试系统具有较高的可靠性和稳定性,能够满足光谱仪的精确定位要求,使电机在工作寿命内按计划完成定标工作。     

电子技术基础实验课程混合式教学设计

近年来,在线学习掀起了一场席卷全球的教育革命,MOOC/SPOC、翻转课堂、混合式教学对高等教育带来了前所未有的冲击。电子技术基础实验课程地位特殊,传统教学方式已无法满足创新性人才培养的需要,文章从其教学特点出发,提出了“线上教学+自主实验+翻转课堂”的混合式教学模式,同时还阐述了与此密切相关的集约化线上教学资源平台、智能化翻转教学环境以及多元化过程性考核评价机制三个重要环节。经研究发现,学生的课堂主动参与度、自主学习能力、创新思维能力、动手实践能力以及教师的教学创造力得到全面提升。教学环境支持课堂互动和全周期教学行为数据采集,体现了教学过程的信息化、教学实施的精准化和教学评价的客观化,实现了信息技术与实验教学的深度融合。     

一种卷积码的VITERBI译码的实现

本文采用ＱＵＡＬＣＯＭ公司的Ｑ１６５０多码率ＶＩＴＥＲＢＩ译码器,设计了前向纠错编／译码器,对提高误码的纠错能力有一定参考价值。     

Sn-Zn-Ag系无铅钎料焊接性能研究

讨论了电子软钎料的钎焊性能及其影响因素，并采用铺张面积法对Sn-Zn-Ag系钎料钎焊性能进行评估。钎料的钎焊性能很大程度上取决于钎料对基板的润湿性能，而润湿性能与液态钎料在基板上的液、固、气三相界面的界面张力有关。对润湿角(θ)与铺展面积(S)之间的关系进行了探讨。     

“计算机组成原理”设计性实践教学模式研究

本文阐述了"计算机组成原理"设计性实验教学的重要性,对设计性实验教学的目的和基本特征进行了归纳,对"计算机组成原理"设计性实验教学的现状进行了调查,对存在的问题进行了较深入的分析;在此基础上.对组成原理设计性实验的教学模式进行了研究,对设计性实验的体系进行了初步设计,并对"计算机组成原理"设计性实验的实施方法进行了探讨.     

杂质吸收对光子晶体滤波器设计的影响

为了研究杂质的吸收对光子晶体滤波器设计的影响,引入复折射率并利用特征矩阵法,计算了滤波透射峰的峰值和半峰全宽。滤波透射峰的峰值随杂质的消光系数增加而迅速减小,滤波通道透射峰的半峰全宽随消光系数增加而增大,滤波透射峰的峰值和半峰全宽都随吸收杂质的光学厚度的增加而减小。结果表明,设计光子晶体滤波器时,必须考虑杂质吸收这一重要因素,应选择消光系数小于0.002的掺杂材料,并且杂质的光学厚度应设计在2(λ0/4)左右。