幻角和线性二向色性电子能量损失谱技术

很多重要的材料具有各向异性的电子结构。由于低对称性的空态电子结构的存在，它们的电子能量损失谱对样品的取向敏感，其敏感程度受到其他实验条件(如电子束的会聚角和散射电子的接收角)的调控。通过研究电子能量损失谱对方向的依赖性以及受实验条件影响的机制，可以通过合理的     

多元统计分析方法在各向异性材料电子能量损失谱中的应用

电子结构可以通过电子能量损失谱（EEIS）的近边精细结构（Near Edge Structure）来测量。在各向异性材料中，不同的选择则决定了具有不同对称性的电子跃迁过程在改变谱接收条件时可能处于不同程度的激发状态，从而造成精细结构上的差异。如何从这些差异分析中得到与其相关的电子结构的对称性？这个问题的解决对于各向异性材料的电子结构及其相关性能的研究是非常重要的。本文提出通过多元统计分析方法（Multivariate Statistical Analysis）处理系列实验谱线，从而确定电子结构的对称性信息。     

电子能量损失谱低能谱区的分析和应用

本文讨论电子能量损失谱低能谱区的分析及其在研究固体材料电子结构方面的应用。作为实例,给出了Bi_2Sr_2CaCu_2O_8高温超导体的体等离子色散试验结果和YBa_2Cu_3O_(7-x)高温超导体的电子能量损失谱低能谱区的计算机拟合分析试验结果。     

利用电子能量损失谱对二氧化铀电子结构的研究

锕系元素因具有复杂的5f电子结构,其显示出神秘而又独特的物理、化学特性.为了加深对锕系金属、合金和化合物的特异行为的理解,对其电子结构精确表征的重要性日益凸显.电子显微技术与电子能量损失谱技术的结合在锕系元素原子结构和电子结构研究中发挥了至关重要的作用.本文采用电子能量损失谱研究二氧化铀的5f电子结构,并讨论了铀5f电子的相互作用特性.     

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．     

电子能量损失谱微栅样品分析

对微栅样品上的碳元素及化合物进行了电子能量损失谱分析，得到了较为满意的结果。     

钢铁材料晶界结合和冲击断裂特征的电子能量损失谱研究

本文采用电子能量损失谱(EELS)研究了不同商用钢铁材料的晶界,计算了晶界处和晶粒内铁原子的3d电子占据态密度,并将其和晶界性质以及材料的宏观断裂性能相联系.结果表明,当样品晶界处铁的3d电子占据态密度高于晶粒内时,晶界结合强度低于晶内,晶界表现出脆性,材料的冲击断裂方式主要为脆性的沿晶断裂;反之,如果样品晶界处铁的3d电子占据态密度低于晶粒内时,晶界结合强度高于晶内,晶界表现出韧性,材料的冲击断裂方式主要为脆性的穿晶断裂.还发现元素在晶界的偏析对晶界结合强度影响很大.     

电子能量损失谱研究GaN的极性

ＧａＮ材料可以发蓝光 ,具有非常重要的实际应用价值。ＧａＮ的结构分析中 ,确定各种畴的极性是非常重要的。在过去的研究中 ,对于ＧａＮ这类非中心对称极性晶体 ,主要利用会聚束电子衍射的方法来测定极性[1] 。最近 ,Ｎ .Ｊｉａｎｇ等人利用通道效应对Ｘ 射线能量色散谱 (ＥＤＳ)强度的影响测定ＧａＮ的极性[2 ] 。但利用电子能量损失谱的方法研究晶体的极性目前尚不多见。入射电子在ＧａＮ晶体中传播时 ,由于布洛赫波的相干效应 ,使得Ｎ原子对入射电子的非弹性散射强度在ｇ =0 0 0 2双束条件和ｇ =0 0 0 2双束条件下并不相同。通过比较这…     

介电函数及其在电子能量损失谱低能区分析的应用

一、前言:电子能量损失谱学(EELS或ELS)是研究电子激发的一次过程。一幅电子能量损失谱大致可分为三个区域:零损失区、低能损失区(5～50eV)和高能损失区(>50eV)。对各谱区进行细致的分析研究、可获得与样品化学成分或电子结构有关的信息。利用电子能量损失谱低能区研究固体的电子结构、引起物理和电子显微学界的关注。因为它不仅能提供固体的电子结构信息、还能在同一台仪器上研究固体的微区晶体结构、成分和形貌。但在电子能量损失谱5～50eV的低能区很难直接确定有关电子结构方面的信息。这是由于在该区等离子激发占主导地位、而外     

由电子能量损失谱计算过渡金属d电子数的浮动窗口方法

材料宏观性能的差异归根到底来源于其电子结构的差异。在过去半个多世纪里，过渡金属的d电子一直是固体物理领域内研究的一个重要内容；同时，在过渡金属形成合金的过程中，究竟是发生了“电荷转移”，还是保持“局域电中性”，文献中一直存在着争议。所有这些都依赖于对过渡金属中d电子的精确测量。近年来，电子能量损失谱（EEKS）已发展成为一种具有高空间分辨率的原位测量物质电子结构的强有力工具。     

Light element analysis in oxycarbonate superconductors using EELS

Elemental analysis in an oxycarbonate superconductor ((Cu,N,C)Sr2CaCu2Oy) is conducted using transmission electron microscope-electron energy-loss spectroscopy with detector-gain correction. The gain correction enables highly sensitive elemental analysis and precise measurement of energy-loss near edge structures (ELNESs). It is found that carbon is included as a CO3 group, because the carbon K-edge in the oxycarbonate shows the same ELNES observed from CaCO3. Nitrogen ELNES is similar to that of Sr(NO3)2, so nitrogen is contained as a NO3 group. Although both CO3(2-) and NO3- have similar planar atomic arrangements, the nitrogen ELNES observed is different from that of carbon. EEL spectrum simulation based on DV-Xalpha method is used to interpret the difference.     

Spatially-resolved EELS analysis of multilayer using EFTEM and STEM

Spatially-resolved electron energy-loss spectroscopy (EELS) is applied to the multilayer (SiO2/Si3N4/SiOxNy/Si), a common semiconductor device structure. To observe depth profile at sub-nanometre spatial resolution, scanning transmission electron microscopy (STEM) and energy-filtering transmission electron microscopy (EFTEM)-based techniques are compared in practical application. STEM-based EELS is useful in simultaneously analysing plural elements. EFTEM-based EELS is suitable for analysing the chemical shift and core loss intensity of single element. The practical spatial resolution is of the same order for each technique, both involving beam damage, which can be reduced by decreasing current density in EFTEM and avoiding beam overlapping in STEM.     

Optical and electrical properties of two-dimensional anisotropic materials

Two-dimensional(2D) anisotropic materials, such as B-P, B-As, GeSe, GeAs, ReSe2, KP15 and their hybrid systems, exhibit unique crystal structures and extraordinary anisotropy. This review presents a comprehensive comparison of various 2D anisotropic crystals as well as relevant FETs and photodetectors, especially on their particular anisotropy in optical and electrical properties. First, the structure of typical 2D anisotropic crystal as well as the analysis of structural anisotropy is provided. Then, recent researches on anisotropic Raman spectra are reviewed. Particularly, a brief measurement principle of Raman spectra under three typical polarized measurement configurations is introduced. Finally, recent progress on the electrical and photoelectrical properties of FETs and polarization-sensitive photodetectors based on 2D anisotropic materials is summarized for the comparison between different 2D anisotropic materials. Beyond the high response speed, sensitivity and on/off ratio, these 2D anisotropic crystals exhibit highly conduction ratio and dichroic ratio which can be applied in terms of polarization sensors, polarization spectroscopy imaging, optical radar and remote sensing.     

Efficient finite element analysis of waveguides with lossyinhomogeneous anisotropic materials characterized by arbitrarypermittivity and permeability tensors

This paper presents a new finite element formulation for solving arbitrarily shaped waveguides including lossy inhomogeneous anisotropic media. The materials are characterized by simultaneous [ε] and [μ] full tensors. Complex-mode computation, spurious-mode suppression and the possibility of specifying the frequency as an input parameter are also achieved. The formulation leads to a quadratic eigenvalue problem of dimension N which is transformed into an efficient 2N-dimensional generalized eigensystem with sparse complex matrices. This eigensystem is solved by the subspace method, taking full advantage of the sparsity of the matrices. Permittivity and permeability tensors with some null terms allow an additional reduction from the N-dimensional quadratic eigenvalue problem to a N-dimensional sparse complex generalized eigensystem. The proposed method has been validated by analyzing different lossy, inhomogeneous and anisotropic waveguides. Results show good agreement with previously published data     

跃变比判别热解Si-C-N陶瓷EELS定量分析的有效性

电子能量损失谱（EELS）分析方法的运用为材料研究领域提供了有力的定性和定量手段。通过对内壳层电子激发谱跃变比的计算,能够获得样品相对厚度的参考信息。这一方法弥补了实验条件在同步采集等离子激发谱和内壳层电子激发谱方面的局限性,并为辨别EELS定量的可靠性提供依据。本文以Si3N4为例,对跃变比随样品相对厚度的变化规律进行了研究,并在低于最佳样品厚度的范围内得到了可靠的定量结果。类似的跃变比变化规律能够运用于成份均一的Si-C-N热解样品,然而对于非均一的Si-C-N退火样品则不适用。     

Full-wave analysis of circular microstrip resonators inmultilayered media containing uniaxial anisotropic dielectrics,magnetized ferrites, and chiral materials

In this paper, Galerkin's method in the Hankel transform domain is applied to the determination of the resonant frequencies, quality factors, and radiation patterns of circular microstrip patch resonators. The metallic patches are assumed to be embedded in a multilayered substrate, which may contain uniaxial anisotropic dielectrics, magnetized ferrites, and/or chiral materials. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies of the resonators when substrate dielectric anisotropy, substrate magnetic anisotropy and/or substrate chirality are ignored. Also, it is shown that the resonant frequencies of circular microstrip resonators on magnetized ferrites can be tuned over a wide frequency range by varying the applied bias magnetic field. Finally, the computed results show that the resonance and radiation properties of a circular microstrip patch on a chiral material is very similar to those of a circular patch of the same size printed on a nonchiral material of lower permittivity     

Variational analysis of anisotropic graded-index optical fibers

The variational principle for nonstandard eigenvalue problems recently introduced and used for step-index optical fiber analysis by the present authors is extended to anisotropic graded-index optical fibers. It is seen through an example of a round parabolic-index fiber that the choice of trial functions is more delicate than for the step-index fiber because of the more complicated field function. Certain two-parameter approximants, however, appear accurate enough and can be optimized with a simple calculator or desk computer analysis