Lattice Distortion Analysis Directly from High Resolution Transmission Electron Microscopy Images —the LADIA Program Package

Direct strain mapping from high resolution transmission electron microscopy images is possible for coherent structures. At proper imaging conditions the intensity peaks in the image have a constant spatial relationship with the projected atom columns. This allows the determination of the geometry of the projected unit cell without comparison with image simulations. The fast procedure is particularly suited for the analysis of large areas. The software package LADIA is written in the PV-WAVE code and provides all necessary tools for image processing and analysis. Image intensity peaks are determined by a cross-correlation technique, which avoids problems from noise in the low spatial frequency range. The lower limit of strain that can be detected at a sampling rate of 44 pixels/nm is≈2%.

High-resolution Transmission Electron Microscopy Characterization of the Structure of Cu Precipitate in a Thermal-aged Multicomponent Steel

High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.

Imaging Ultrafast Plasmon Dynamics within a Complex Dolmen Nanostructure Using Photoemission Electron Microscopy

We report direct nanoscale imaging of ultrafast plasmon in a gold dolmen nanostructure excited with the 7is laser pulses by combining the interferometric time-resolved technology with the three-photon photoemission electron microscopy （PEEM）. The interferometric time-resolved traces show that the plasmon mode beating pattern appears at the ends of the dimer slabs in the dolmen nanostructure as a result of coherent superposition of multiple localized surface plasmon modes induced by broad bandwidth of the ultrafast laser pulses. The PEEM measurement further discloses that in-phase of the oscillation field of two neighbor defects are surprisingly observed, which is attributed to the plasmon coupling between them. Furthermore, the control of the temporal delay between the pump and probe laser pluses could be utilized for manipulation of the near-field distribution. These findings deepen our understanding of ultrafast plasmon dynamics in a complex nanosystem.

Improvement of femtosecond SPPs imaging by two-color laser photoemission electron microscopy

Clear imaging of surface plasmon polaritons(SPPs)is a prerequisite for SPPs-based applications.In this work,we demonstrate an improvement of near-field imaging of SPPs via directly comparing the visibility of the photoemission electron microscopy(PEEM)image of SPPs under one-and two-color laser excitation(also known as one-or two-color laser PEEM).By measuring the photoelectron yield and the contrast of the interference fringes of SPPs,we demonstrate that in addition to enhancing the photoemission yield,two-color laser PEEM can significantly improve the contrast between bright and dark fringes(nearly 4 times higher than that of one-color laser case).By recording the nonlinear order of the photoelectrons ejected from the bright and dark fringes,respectively,the underlying mechanism for the improved visibility is revealed.In addition,the influences of the polarization direction of 400-nm laser on the PEEM images of the SPPs with different wave vector directions are shown.These results can provide technical support for the development of SPPs-based communication devices and catalysis.

基于电子扫描的Image J图像处理系统在多孔材料中的应用

扫描电镜由于其高分辨率而被广泛应用在材料微观结构的观察,为了能定性地分析出不同材料表面拓扑结构的差异,一种基于电子扫描的Image J图像处理算法系统被开发,结果表明:这种算法系统能够定性分析出材料表面微观拓扑结构的差异,具有较高精确性和广泛适用性。

Applications of Secondary Electron Composition Contrast Imaging Method in Microstructure Studies on Heterojunction Semiconductor Devices and Multilayer Materials

The principle, imaging condition and experimental method for obtaining high resolution composition contrast in secondary electron image were described. A new technique of specimen preparation for secondary electron composition contrast observation was introduced and discussed. By using multilayer P+Si1-xGex/pSi heterojunction internal photoemission infrared detector as an example, the applications of secondary electron composition contrast imaging in microstructure studies on heterojunction semiconducting materials and devices were stated. The characteristics of the image were compared with the ordinary transmission electron diffraction contrast image. The prospects of applications of the imaging method in heterojunction semiconductor devices and multilayer materials are also discussed.

Scanning Electron Acoustic Microscopy of GaInAsSb by Metalorganic Chemical Vapor Deposition

Scanning electron acoustic microscopy (SEAM) is a new technique for imasing and characterization ofthermal, elastic and pyroelectric property variations on a microscale resolution. The signal generation mechanisms and the application of scanning electron acoustic microscopy in GalnAsSb alloy grown by MOCVD wereinvestigated. Defects below the surface of GalnAsSb alloy were found by SEAM images and cathodelumi-nescence. The results show that electronacoustic imaging has its own features over secondary electron imag-ing.

SEM image analysis of endothelium of distended autogenous vein grafts

Femoral veins of 17 mongrel dogs were distended with 40 kpa, 80 kpa and 120 kpa respectively prior to grafting to colateral femoral arteries. The sections were harvested at intervals of immediatness, 1 week, 4 week and 16 week followed with scanning electron microscopy (SEM) examination. The endothelial cells of grafted veins were investigated by computerized imaging analysis system. The results showed that desquamation extent of intimal layer correlated positively with the pressure. 80 kpa and 120 kpa caused relatively severe damage to the endothelium, which was significantly different from that of control group (P<0. 05). We conclude that preimplantation distention shooed be employed with less than 80 kpa, and 120 kPa shoud be avoided due to its damage to the development of reendothelialization. Nevertheless, the distension makes little notable impact to graft Patency rate as demonstrated in this experiment.

Revisiting Sphere Unfolding Relationships for the Stereological Analysis of Segmented Digital Microstructure Images

Sphere unfolding relationships are revisited with a specific focus on the analysis of segmented digital images of microstructures. Since the features of such images are most easily quantified by counting pixels, the required equations are re-derived in terms of the histogram of areas (instead of diameters or radii) as inputs and it is shown that a substitution can be made that simplifies the calculation. A practical method is presented for utilizing negative number fraction bins (which sometimes arise from erroneous assumptions and/or insufficient numbers of observations) for the creation of error bars. The complete algorithm can be implemented in a spreadsheet. The derived unfolding equations are explored using both linear and logarithmic binning schemes, and the pros and cons of both binning schemes are illustrated using simulated data. The effects of the binning schemes on the stereological results are demonstrated and discussed with reference to their consequences for practical materials characterization situations, allowing for the suggestion of guidelines for proper application of this, and other, distribution-free stereological methods.

岩土材料中冰分布状态的冷冻电镜表征方法

为从微观角度定量描述冰在岩土材料中的分布特征,基于冷冻电镜技术提出了一种微观尺度的实验表征方法。针对不同冰饱和度人造岩芯样品的二次电子图像和能谱分析图,通过元素含量分布、升华前后图像对比确认了冰在岩土材料中的分布状态。随着冰饱和度的增加,骨架孔隙被冰填充、骨架颗粒表面被冰包裹区域增大,样品断面更密实平整,岩土骨架的堆积结构特征变弱。在背散射电子图像中,冰的图像比岩土骨架亮度低、灰度高,基于此构建了冰饱和度的数字图像计算方法。该方法计算的升华前冰饱和度与样品预制冰饱和度偏差小于5%,验证了其可靠性。

体电子显微学前沿

电子显微成像技术的快速发展使得对完整细胞、组织乃至整个机体进行高分辨三维结构解析研究成为可能,这些可进行大尺度生物样品三维结构研究的电子显微成像技术统称为体电子显微学技术(volume electron microscopy,vEM)。近年来,v EM在研究尺度、分辨率、吞吐量和易用性等方面发展迅速,在整个生命科学领域的应用呈爆炸式增长,该技术因此被《自然》(Nature)评为2023年最值得关注的七项前沿技术之一。然而,vEM相关技术的发展和应用在国内起步较晚,亟待进一步推广。本综述涵盖了vEM的发展历程、技术分类、样品制备、数据收集、图像处理等全方位的内容,便于生命科学、医学等领域研究人员去了解、学习、应用和进一步发展该技术。

基于自然图像模型微调的小鼠脑部电镜图像实例分割

分割模型的准确性和鲁棒性是小鼠脑电镜图像处理中的主要考虑因素。针对电镜图像的技术特点,提出了高度稳健的二维分割算法,准确识别每张切片中各物体的形态结构。本文提出了基于大型自然图像模型的主干网络微调的大尺度二维电镜图像分割模型EM-SAM,用于脑部电镜图像中的实例分割。模型主干网络采用大型自然图像模型SAM中的已训练完成的图像编码器,在电镜图像处理任务中最大化模型提取图像特征的能力。此外,模型采用了U型的解码器设计,并通过小鼠脑电镜图像分割任务进行微调。实验结果表明:在公开数据集SNEMI3D中A-Rand可达到0.054;在公开数据集MitoEM中AP-50和AP-75分别可达到0.883,0.604。EM-SAM在电镜图像神经分割任务中准确性高、鲁棒性强,并且可针对不同任务进行微调。

扫描电镜中透射-反射式STEM明场成像装置的研制及应用

本文研制了一套透射-反射式扫描透射(STEM)明场成像装置,该装置使用背散射电子探头接收经过铂片反射的透射电子信号,可安装在FEI Quanta FEG系列扫描电镜中实现STEM明场成像。分别以埃洛石、Au@ZIF-8纳米颗粒和喷金乳胶标样验证自制STEM明场成像装置的实用性。结果表明:埃洛石STEM明场像的衬度与透射电镜中STEM明场像一致,管腔和管壁具有明显的衬度差异,可以清晰辨识管腔结构;在Au@ZIF-8纳米颗粒的STEM明场像中,Au颗粒衬度较暗,ZIF-8衬度较亮,通过两者之间的衬度差异可以观察到核壳结构;喷金乳胶标样上纳米金颗粒之间可识别的最小距离为2.03 nm,进一步验证了自制STEM明场成像装置具有较高的分辨率。

卤化物钙钛矿半导体透射电镜表征的挑战与机遇

卤化物钙钛矿价格低廉,易于合成,具有优异的光电性能,广泛应用于太阳能电池、光电探测器和发光二极管等光电子器件,是当前国际上研究的热点领域,同时入选工信部和国资委评出的首批前沿材料之一。透射电子显微镜表征是揭示卤化物钙钛矿形貌、结构、成分等物理和化学信息的关键。然而,卤化物钙钛矿在电子束辐照下易分解,这种极端敏感性通常会阻碍我们获取钙钛矿本征信息,甚至引起假象。基于此,本文综述了近年来有关卤化物钙钛矿的透射电子显微学研究,重点讨论了卤化物钙钛矿电子束损伤机理、影响钙钛矿电子束敏感性因素、如何降低电子束损伤并获得钙钛矿原子尺度信息。本文旨在引起人们对卤化物钙钛矿电子束敏感性的关注,指导卤化物钙钛矿电子显微学表征,揭示卤化物钙钛矿分解机理,为构建高效稳定的钙钛矿光电器件提供实验指导。

改进分水岭算法的扫描电镜图像标定

针对不同探测器模式下扫描电镜图像特征复杂且易受阴影干扰的问题,提出了基于改进分水岭算法的扫描电镜图像标定方法。首先,通过自适应滤波、梯度变换等预处理流程减少噪声影响,同时保留真实信息;然后,针对分水岭标记存在的阴影干扰问题,采用自适应改进方法,使得标记的获取更具普适性,可适用于不同的探测器模式。棋盘格样品测试结果表明,该方法在InLens和SE2探测器模式下表现良好,并在综合评价指标上明显优于其他标定方法。将标定结果按照参考标尺与人工测量数据进行对比,两者相对误差在7%以内。

Electron-microscopical visualization on the interfacial and crystallographic structures of lithium metal anode

Lithium(Li)metal anodes(LMAs)have garnered significant attention as a potential solution for developing high-energy density batteries,given their theoretical specific capacity and redox potential.However,safety concerns and internal cycling stability issues originated from uncontrollable Li dendrite growth have impeded the practical application of LMAs.Probing the interface between Li metal and electrolyte is a crucial process that offers valuable insights into the characteristics and regularity of primary circular reactions.To illustrate the intrinsic characteristic of Li metal batteries(LMBs)in spatial and temporal,it is imperative to employ electron microscopes to characterize the structural components distribution of Li with atomic resolution.This paper summarizes the progress in the characterization and analysis of the interfaces in LMBs with electron microscopes based on the principles of electron-matter interactions.Finally,future trends and the potential of electron microscopes are also discussed to advance our understanding of LMBs.

Effects of cement content, polypropylene fiber length and dosage on fluidity and mechanical properties of fiber-toughened cemented aeolian sand backfill

Using aeolian sand(AS)for goaf backfilling allows coordination of green mining and AS control.Cemented AS backfill(CASB)exhibits brittle fracture.Polypropylene(PP)fibers are good toughening materials.When the toughening effect of fibers is analyzed,their influence on the slurry conveying performance should also be considered.Additionally,cement affects the interactions among the hydration products,fibers,and aggregates.In this study,the effects of cement content(8wt%,9wt%,and 10wt%)and PP fiber length(6,9,and 12 mm)and dosage(0.05wt%,0.1wt%,0.15wt%,0.2wt%,and 0.25wt%)on fluidity and mechanical properties of the fibertoughened CASB(FCASB)were analyzed.The results indicated that with increases in the three aforementioned factors,the slump flow decreased,while the rheological parameters increased.Uniaxial compressive strength(UCS)increased with the increase of cement content and fiber length,and with an increase in fiber dosage,it first increased and then decreased.The strain increased with the increase of fiber dosage and length.The effect of PP fibers became more pronounced with the increase of cement content.Digital image correlation(DIC)test results showed that the addition of fibers can restrain the peeling of blocks and the expansion of fissure,and reduce the stress concentration of the FCASB.Scanning electron microscopy(SEM)test indicated that the functional mechanisms of fibers mainly involved the interactions of fibers with the hydration products and matrix and the spatial distribution of fibers.On the basis of single-factor analysis,the response surface method(RSM)was used to analyze the effects of the three aforementioned factors and their interaction terms on the UCS.The influence surface of the two-factor interaction terms and the three-dimensional scatter plot of the three-factor coupling were established.In conclusion,the response law of the FCASB properties under the effects of cement and PP fibers were obtained,which provides theoretical and engineering guidance for FCASB filling.

Single Molecule Imaging with Liquid Phase Electron Microscopy

Few single-molecule experiments have enabled the direct imaging of functional biomacromolecules in real-time in their native liquid environments,resolving their conformational adaptations,transient interactions,and intermediate states.Liquid phase electron microscopy(LP-EM),due to its unique combination of spatial and temporal resolution,has shown to be a promising tool.Recent experiments have enabled successful imaging of intact structures of organic molecules and biological systems with an ordinary electron microscope.Adapting image processing methods and quantitative data analysis from single particle experiments based on the optical microscope,quantifying motion and relaxation of these interacting molecules allows the experimental observations of pathways,to test theoretical predictions,and discovery of new mechanisms.Combining LP-EM with tomography,fluorescence,and mass spectroscopy allows for probing multi-dimensional structural and dynamic information.Challenges remain in obtaining high-quality data in large quantities,which can be improved by developing new liquid cell platforms and machine learning-based data analysis.

基于自监督学习实现电子显微图像降噪

在电子显微镜的表征工作中,噪声可以掩盖或者干扰有用的信号并对后续研究造成不可忽视的影响。本文提出了一种使用自监督深度学习技术对电子显微图像进行降噪的新方法,该方法搭建了基于U⁃Net的新型降噪神经网络模型,利用最大模糊池化以及注意力机制提高降噪能力。最后,本研究通过多种电子显微实验数据验证了所提出方法的有效性。相比有监督学习,本方法更适合难以获得干净数据的电子显微图像场景,此外,本方法比传统机器学习拥有更好的降噪效果和效率。

一种强化汽车铝合金析出相的原子分辨电子显微学和谱学研究

原子分辨率的电子显微学和谱学技术是研究析出强化铝合金微结构的最有力的手段和方法,特别是原子分辨率的EDS能谱成像技术为更深入地研究和认识铝合金中的析出强化相颗粒结构及其与铝基体的界面匹配关系至关重要。然而,迄今为止,对于汽车轻量化用Al⁃Mg⁃Si合金中Mg、Si合金元素的亚稳析出聚集颗粒,原子分辨率的EDS能谱成像很难实现。本工作为国内首次报道对汽车用Al⁃Mg⁃Si合金中轻质Mg、Si元素的析出颗粒成功实现原子分辨率的EDS能谱成像的案例。作者利用最先进的透射电子显微镜技术研究了一种典型汽车用Al⁃Mg⁃Si合金在250℃时效强化过程中工艺-微结构-性能的演变关系。研究结果表明,富Mg合金在高温峰值时效阶段析出相的主要类型为β′相(Mg_(9)Si_(5))。通过先进原子分辨率的能谱成像揭示了β′相与Al基体界面层的精细原子结构和元素分布。β′相颗粒最外层总是以Mg原子层对接Al基体,这有助于帮助理解析出相界面能问题。本文的研究结果清楚解答了该合金硬度和屈服强度均得到显著提升的微结构原因。