硅纳米线的电学特性

总结了硅纳米线在电学特性方面的研究进展,重点分析了本征及掺杂硅纳米线的载流子浓度与迁移率、场发射及电子输运特性。研究表明通过对硅纳米线进行掺杂可提高载流子浓度及迁移率、场发射和电子输运性能,随硅纳米线直径的减小其电学性能增强。因此,硅纳米线在场效应晶体管及存储元件等纳米器件方面具有极大的应用前景。     

用高分辨电子能量损失谱和紫外光电子谱研究多孔硅的电子结构

本文首次使用分辨电子能量损失谱（ＨＲＥＥＬＳ）和紫外光电子能谱（ＵＰＳ）研究新腐蚀的多孔硅样品（ＰＳ）的电子结构．实验结果发现，从ＨＲＥＥＬＳ谱中能量损失阈值测得的多孔硅的能隙最可几值移到２．９ｅＶ左右，与文献报道的光激发谱（ＰＬＥ）的结果相近．ＵＰＳ结果发现多孔硅费米能级到价带顶的距离不同于单晶硅，结合ＨＲＥＥＬＳ和ＵＰＳ结果可以初步得出多孔硅与硅界面的能带排列．     

钴硅化合物的理论电子能量损失谱

本文采用扩展平面波加局域轨道方法和广义梯度近似对钴硅系中Co2Si，CoSi和CoSi：三种不同硅化物的电子结构以及电子能量损失近边结构（ELNEs）进行了理论计算。结果表明计算得到的硅化物中Co的ELNES很好反映了Co在费米能级以上d的未占据态密度分布，其中Co2Si和CoSi2具有金属性质；而CoSi呈现出半金属性质。计算还表明电子能量损失谱仪应具有足够高的能量分辨率（0．2ev），电子能量损失近边结构才能正确反映出钴硅化合物的电子结构特征。     

利用硅纳米线测量悬臂梁结构应力方法的研究

A silicon（SiNW） nanowire device,made by the bottom-up method,has been assembled in a MEMS device for measuring stress in cantilevers.The process for assembling a SiNW on a cantilever has been introduced.The current as a function of the voltage applied to a SiNW have been measured,and the different resistances before and after cantilever releasing have been observed.A parameter,η,has been derived based on the resistances.For a fixed sample,a linear relationship between η and the stress in the cantilever has been observed;and,so,it has been demonstrated that the resistance of SiNW can reflect the variation of the cantilever stress.     

多孔硅反射谱的测量与分析

测量了多孔硅的光反射谱，并进行了分析和讨论，得出了其能带展宽等特性。利用K－K关系，计算得出了多孔娃的折射率n等光学常数，并结合单晶硅的相应光学常数进行了比较和分析．     

表面钝化硅纳米线的能带结构

采用第一性原理的方法计算了不同尺寸的(100)硅纳米线在H饱和及F饱和下的电子结构.计算结果表明,F饱和与H饱和的(100)硅纳米线均为直接禁带半导体,但F饱和硅纳米线的禁带宽度和价带有效质量都远小于H饱和硅纳米线,这一现象可用价带顶的σ-n杂化效应来解释.计算结果还表明,H或F饱和的(100)硅纳米线的极限--硅单原子链则表现为间接带隙半导体,文中对这一现象进行了分析和讨论.     

各向异性材料的电子能量损失谱‘幻角’分析

电子能量损失谱(Electron Energy Loss Spectroscopy)在测量材料的电子结构及其电子空间分布方面有很广泛的应用.由于原子的各向异性排列,或是内(外)部电、磁场的作用,许多重要材料的电子结构及其能级之间的电子跃迁会显示出明显的方向性,如石墨、纳米碳管和磁化的铁磁材料等.近来,纳米材料和纳米器件的发展,使得检测纳米尺度的各向异性材料的电子结构成为当务之急.由于电子束斑尺寸可达纳米量级,EELS在这个方面体现了其独特优势,但是在一般情况下,各向异性材料的EELS谱会随样品取向而变化,这给定量分析带来了困难.     

基于表面等离激元的谐振腔侧面耦合MDM结构波导滤波器色散关系及透射谱

研究了一类L形和矩形谐振腔侧面耦合MDM结构亚波长表面等离激元滤波器的色散关系和透射谱。研究结果表明等效折射率的实部和虚部在短波部分变化较大,在长波部分（800 nm-2000 nm）趋于稳定值,传播距离随着波长的增加和介质层厚度的增加均增加,当波导宽度在50 nm以上时,SPPs的传播距离在所研究的波长范围为4-9 um,可以满足纳米光子器件的尺寸要求;通过对侧面 型谐振腔和矩形谐振腔耦合的透射谱研究表明在保持腔体总长度不变的情况下,两种耦合方式所产生的光谱曲线完全相似,说明禁带的出现只与谐振腔的长度有关系,对集成光子器件的研发具有一定的参考意义。     

氮离子注入形成的SOI结构的研究

用透射电子显微镜(TEM)、扫描透射电子显微镜(STEM)和电子能量损失谱(EELS)对高剂量氮离子注入再经热退火所形成的硅-绝缘层(SOI)结构的纵断面进行了微区分析并测定了氮-硅元素浓度比沿深度的分布. EELS的分析证明了在绝缘层的多孔区中可能有一些以气体形式出现的氮分子. 利用EELS的低能等离子峰形成的能量选择像能够对硅和氮化硅进行相分离,并有助于估计可能引起短路的因素.     

Si纳米线阵列波导光栅制备

采用绝缘层上Si(SOI)材料设计制备了3×5纳米线阵列波导光栅(AWG),器件大小为110μm×100μm。利用简单传输法模拟了器件的传输谱,并采用二维时域有限差分(FDTD)模拟中心通道输出光场的稳态分布,模拟结果表明,器件的通道间隔为11 nm,通道间的串扰为18 dB。通过电子束曝光(EBL)和感应耦合等离子(ICP)刻蚀制备了所设计的器件,光输出谱测试分析表明,器件中心通道的片上损耗为9 dB,通道间隔为8.36～10.40 nm,中心输出通道的串扰为6 dB。在误差允许范围内,设计和测试的结果一致。     

Electrical transport properties in electroless-etched Si nanowire field-effect transistors

We report the electrical transport of the Si nanowires in a field-effect transistor (FET) configuration, which were synthesized from B-doped p-type Si(1 1 1) wafer by an aqueous electroless etching method based on the galvanic displacement of Si by the reduction of Ag⁺ ions on the wafer surface. The FET performance of the as-synthesized Si nanowires was investigated and compared with Ag-nanoparticles-removed Si nanowires. In addition, high-k HfO₂ gate dielectric was applied to the Si nanowires FETs, leading to the enhanced performance such as higher drain current and lower subthreshold swing.     

Polarization mode dispersion in a single mode fiber

The Jones matrix method is used to measure the polarization mode dispersion (PMD) of a large variety of single mode fibers in the 1500 nm range. The dependence of PMD on wavelength, time, and temperature are studied in two different regimes: adiabatic and isothermal. In the adiabatic regime, time dependent stresses are introduced in the fiber by subjecting it to large and rapid changes in temperature. In this regime it is shown that the probability density function of PMD, obtained as a function of temperature and wavelength, fits very closely the theoretically predicted Maxwellian function. In the isothermal regime, the temperature of the fiber is held constant and the stresses are allowed to relax to their long term steady state conditions. In this regime the PMD exhibits a strong dependence on wavelength but otherwise is a bounded function which is nearly stationary with time. Test and analysis of the deterministic PMD in a specially constructed polarization maintaining fiber are used to study the dependence of PMD on temperature and wavelength. Finally, the system implications of this PMD study are described briefly     

Phonon–plasmon coupling in Si doped GaN nanowires

The vibrational properties of silicon doped GaN nanowires with diameters comprised between 40 and 100 nm are studied by Raman spectroscopy through excitation with two different wavelengths: 532 and 405 nm. Excitation at 532 nm does not allow the observation of the coupled phonon–plasmon upper mode for the intentionally doped samples. Yet, excitation at 405 nm results in the appearance of a narrow peak at frequencies close to that of the uncoupled A₁(LO) mode for all samples. This behavior points to phonon–plasmon scattering mediated by large phonon wave-vector in these thin and highly doped nanowires.     

基于Si纳米线AWG的超紧凑单纤三向滤波器设计

采用绝缘层上Si(SOI)纳米线阵列波导光栅(AWG)结构设计了超紧凑光纤到户(FTTH)单纤三向滤波器。二维时域有限差分(2D-FDTD)模拟输出光场表明,3个波长光信号输出光场清晰,实现了1490 nm和1550nm下行波长的解复用和1310 nm波长的上传复用功能;进一步的输出功率模拟表明,当各波长信号输入功率为1 mW时,1490 nm端口输出功率为0.49 mW,1550 nm端口输出功率为0.49 mW,1310 nm上传信号功率为0.55 mW,相应的插入损耗分别约为-3.1、-3.1和-2.6 dB。各端口的串扰光功率可被抑制到-25.2 dBm以下,相应的串扰小于-22.6 dB。采用电子束(EB)光刻结合诱导耦合等离子干法(ICP-RIE)刻蚀,制备出了Si纳米线单纤三向滤波器,经红外CCD成像观察到器件具有3个波长的分波功能。     

Measurement of human red blood cell deformability using a single micropore on a thin Si3N4 film

The filtration method for the evaluation of the RBC deformability has been further refined to simulate the deformations encountered in the recticuloendothelial system (in particular the spleen), a recognized site of aged and sickled cells removal. The core of the developed measuring system is a very thin (0.4 micron thick) filter that consists of single micropore (diameters down to 1 micron) on a Si3N4 film which has been constructed using silicon microfabrication techniques. Individual RBC's deformability is quantified measuring the cell pore passage time. From one blood sample 200 passage times are analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. In this paper the effectiveness of the developed system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability, such as temperature, addition of diamide and glutaraldehyde, and blood storage conditions. In addition, it is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 micron when the pore length is very short, thus broadening the experimental conditions under which the RBC deformability (fluidity) can be studied.     

Room temperature single electron effects in a Si nano-crystalmemory

An MOS memory based on Si nano-crystals has been fabricated. We have developed a repeatable process of forming uniform, small-size and high-density Si nano-crystals and spherical nano-crystals of about 4.5 nm in diameter with density of 5×10¹¹/cm² were obtained. Threshold voltage shift of 0.48 V corresponding to single electron storage in individual nano-crystals is obtained. For the first time, room temperature single electron effects are observed. These prove the feasibility of practical Si nano-crystal memory     

On the dispersion relation of ADI-FDTD

In this letter, we analyze the alternating direction implicit finite-difference time-domain (ADI-FDTD) dispersion relation and find the numerical plane-wave relationship between the magnetic and electric fields, showing that the scheme is not divergence-free. We also show that negative-group-velocity modes with positive phase velocities may appear for high Courant numbers. A parallel comparison is made with the behavior of the classical Yee FDTD and the Crank-Nicolson schemes.     

超导纳米线单光子探测现状与展望

超导纳米线单光子探测器（SNSPD）是一种量子极限灵敏度的光探测器。它的基本原理是利用光子能量实现超导纳米线库珀对的拆对,从而在超导纳米线局域发生超导-非超导相变。和传统半导体单光子探测器相比,具有探测效率高、暗计数低、时间抖动小、死时间短、宽谱响应以及自由运行等优势。高性能SNSPD已经在量子信息、激光通信、激光雷达等领域得到了广泛应用。文中概述了过去几年间国内外在SNSPD研发、应用成果及产业化等方面的进展,并对SNSPD未来的技术发展和应用进行了展望。     

银纳米线与二氧化硅衬底表面摩擦力的测量

银纳米线是制作纳米光电子器件的理想材料,了解银纳米线与特定衬底间的摩擦特性对于器件的设计和制备工艺具有重要参考价值.本文利用原子力显微镜(AFM)研究银纳米线与二氧化硅衬底表面的摩擦特性,为提高摩擦力测量准确性,依次借助斜面法和横向力曲线分别标定了AFM探针的扭转弹性常数和光杠杆横向灵敏度,同时对扫描器引入的横向误差进行了补偿.利用AFM纳米操纵技术记录了单根银纳米线由静止到整体滑动的全过程,实验测得直径50 nm银纳米线与二氧化硅衬底表面的最大静摩擦线密度和滑动摩擦线密度分别为1.07 nN/nm和0.56 nN/nm.