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Improving the accuracy of temperature measurement on TEM samples using plasmon energy expansion thermometry (PEET): Addressing sample thickness effects 利用等离子体能量膨胀测温仪（PEET）提高TEM样品温度测量的准确性：解决样品厚度效应。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2025-01-04 DOI: 10.1016/j.ultramic.2025.114102

Yi-Chieh Yang , Luca Serafini , Nicolas Gauquelin , Johan Verbeeck , Joerg R. Jinschek

Advances in analytical scanning transmission electron microscopy (STEM) and in microelectronic mechanical systems (MEMS) based microheaters have enabled in-situ materials’ characterization at the nanometer scale at elevated temperature. In addition to resolving the structural information at elevated temperatures, detailed knowledge of the local temperature distribution inside the sample is essential to reveal thermally induced phenomena and processes. Here, we investigate the accuracy of plasmon energy expansion thermometry (PEET) as a method to map the local temperature in a tungsten (W) lamella in a range between room temperature and 700 °C. In particular, we address the influence of sample thickness in the range of a typical electron-transparent TEM sample (from 30 nm to 70 nm) on the temperature-dependent plasmon energy. The shift in plasmon energy, used to determine the local sample temperature, is not only temperature-dependent, but in case of W also seems thickness-dependent in sample thicknesses below approximately 60 nm. It is believed that the underlying reason is the high susceptibility of the regions with thinner sample thickness to strain from residual load induced during FIB deposition, together with increased thermal expansion in these areas due to their higher surface-to-volume ratio. The results highlight the importance of considering sample thickness (and especially thickness variations) when analyzing the local bulk plasmon energy for temperature measurement using PEET. However, in case of W, an increasing beam broadening (FWHM) of the bulk plasmon peak with decreasing sample thickness can be used to improve the accuracy of PEET in TEM lamellae with varying sample thickness.

分析扫描透射电子显微镜（STEM）和基于微电子机械系统（MEMS）的微加热器的进步使材料在高温下的纳米尺度上的原位表征成为可能。除了在高温下解析结构信息外，样品内部局部温度分布的详细知识对于揭示热诱导现象和过程至关重要。在这里，我们研究了等离子体能量膨胀测温（PEET）作为一种在室温到700°C范围内绘制钨(W)片层局部温度的方法的准确性。特别地，我们讨论了典型电子透明TEM样品（从30 nm到70 nm）范围内样品厚度对温度相关等离子体能量的影响。用于确定局部样品温度的等离子体能量的位移不仅与温度有关，而且在W的情况下，在样品厚度低于约60 nm时似乎也与厚度有关。据认为，其根本原因是样品厚度较薄的区域对FIB沉积过程中引起的残余载荷应变的敏感性较高，同时由于其较高的表面体积比，这些区域的热膨胀增加。结果强调了在使用PEET分析局部体等离子体能量用于温度测量时考虑样品厚度（特别是厚度变化）的重要性。然而，在W情况下，随着样品厚度的减小，体等离子体峰的波束展宽（FWHM）可以用来提高不同样品厚度的TEM片层中PEET的精度。

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引用次数: 0

State-of-the-art electron beams for compact tools of ultrafast science 最先进的电子束用于超快科学的紧凑工具。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2025-01-01 DOI: 10.1016/j.ultramic.2024.114080

Peter Salén , Anatoliy Opanasenko , Giovanni Perosa , Vitaliy Goryashko

We review state-of-the-art electron beams for single-shot megaelectronvolt ultrafast electron diffraction (MeV-UED) and compact light sources. Our primary focus is on sub-100 femtosecond electron bunches in the 2-30 MeV energy range. We demonstrate that our new and recent simulation results permit significantly improved bunch parameters for these applications.

我们回顾了最先进的电子束用于单次百万电子伏特超快电子衍射（MeV-UED）和紧凑光源。我们的主要重点是在2-30 MeV能量范围内的100飞秒以下的电子束。我们证明了我们新的和最近的模拟结果允许在这些应用中显著改善束参数。

引用次数: 0

Enhancing subsurface imaging in ultrasonic atomic force microscopy with optimized contact force 优化接触力增强超声原子力显微镜的亚表面成像。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-12-08 DOI: 10.1016/j.ultramic.2024.114094

Mingyu Duan , Chengjian Wu , Jinyan Tang , Yuyang Wang , Shiquan Liu , Bing-Feng Ju , Yuan-Liu Chen

Ultrasonic atomic force microscopy (UAFM) is a powerful nondestructive subsurface imaging tool that is widely used to inspect material defects and analyze biological cells. The contrast in UAFM images, which is crucial for subsurface imaging quality, is directly influenced by the contact force between the probe and material. This contact force affects the subsurface contrast by influencing the propagation of the stress field from the vibrating probe into the material. Therefore, optimizing the contact force is essential for achieving superior subsurface contrast with better resolution and greater detectable depth. This paper proposes a model for determining the optimal contact force for high-contrast, high-resolution subsurface imaging. The model was designed to improve UAFM imaging across samples with a wide range of Young's moduli, from tens to hundreds of GPa. The use of this model resulted in significant improvements to imaging quality, with a detectable depth exceeding 337.7 nm and lateral resolution below 56.9 nm. Hence, this model demonstrates better results than experiments conducted under arbitrary contact forces. This study provides a pathway for optimizing subsurface imaging and delivering enhanced contrast, higher resolution, and greater detectable depth. Consequently, the results of this study contribute to the advancement of the capabilities of subsurface imaging techniques.

超声原子力显微镜（UAFM）是一种功能强大的无损次表面成像工具，被广泛用于检测材料缺陷和分析生物细胞。超声原子力显微镜图像的对比度对次表层成像质量至关重要，它直接受到探头与材料之间接触力的影响。这种接触力通过影响应力场从振动探头向材料的传播来影响次表层对比度。因此，优化接触力对于获得更好的次表层对比度、更高的分辨率和更大的可探测深度至关重要。本文提出了一个模型，用于确定高对比度、高分辨率次表层成像的最佳接触力。该模型的设计目的是改善具有广泛杨氏模量（从几十到几百 GPa）的样品的 UAFM 成像。该模型的使用大大提高了成像质量，可探测深度超过 337.7 纳米，横向分辨率低于 56.9 纳米。因此，与在任意接触力条件下进行的实验相比，该模型显示了更好的结果。这项研究为优化地表下成像、增强对比度、提高分辨率和增加可探测深度提供了一条途径。因此，这项研究的结果有助于提高地表下成像技术的能力。

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引用次数: 0

Workflow automation of SEM acquisitions and feature tracking SEM获取和特征跟踪的工作流自动化。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-12-08 DOI: 10.1016/j.ultramic.2024.114093

Sabrina Clusiau , Nicolas Piché , Nicolas Brodusch , Mike Strauss , Raynald Gauvin

Acquiring multiple high magnification, high resolution images with scanning electron microscopes (SEMs) for quantitative analysis is a time consuming and repetitive task for microscopists. We propose a workflow to automate SEM image acquisition and demonstrate its use in the context of nanoparticle (NP) analysis. Acquiring multiple images of this type of specimen is necessary to obtain a complete and proper characterization of the NP population and obtain statistically representative results. Indeed, a single high magnification image only scans a small area of sample, containing only few NPs. The proposed workflow is successfully applied to obtain size distributions from image montages at three different magnifications (20,000x, 60,000x and 200,000x) on the same area of the sample using a Python based script. The automated workflow consists of sequential repositioning of the electron beam, stitching of adjacent images, feature segmentation, and NP size computation. Results show that NPs are best characterized at higher magnifications, since lower magnifications are limited by their pixel size. Increased accuracy of feature characterization at high magnification highlights the importance of automation: many high-magnification acquisitions are required to cover a similar area of the sample at low magnification. Therefore, we also present feature tracking with smart beam positioning as an alternative to blind acquisition of very large image arrays. Feature tracking is achieved by integrating microscope tasks with image processing tasks, and only areas of interest will be imaged at high resolution, reducing total acquisition duration.

使用扫描电子显微镜（sem）获取多个高倍率，高分辨率的图像进行定量分析是一项耗时且重复的任务。我们提出了一种自动化扫描电镜图像采集的工作流程，并演示了其在纳米颗粒（NP）分析中的应用。获取该类型标本的多个图像是必要的，以获得NP种群的完整和适当的特征，并获得具有统计学代表性的结果。事实上，一张高倍图像只扫描一小块样本区域，只包含少量np。所提出的工作流程成功地应用于使用基于Python的脚本在样本的同一区域上以三种不同的放大倍数（20,000倍，60,000倍和200,000倍）从图像蒙太奇中获得大小分布。自动化工作流程包括电子束的顺序重新定位、相邻图像的拼接、特征分割和NP大小计算。结果表明，NPs在较高的放大倍率下表现最好，因为较低的放大倍率受到其像素大小的限制。在高放大倍率下，特征表征的准确性提高，突出了自动化的重要性：在低放大倍率下，许多高放大倍率的采集需要覆盖样品的类似区域。因此，我们也提出了智能波束定位的特征跟踪，作为盲目获取超大图像阵列的替代方案。特征跟踪是通过集成显微镜任务和图像处理任务来实现的，只有感兴趣的区域才会以高分辨率成像，从而减少了总采集时间。

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引用次数: 0

Improved precision and accuracy of electron energy-loss spectroscopy quantification via fine structure fitting with constrained optimization 基于约束优化的精细结构拟合提高了电子能量损失谱定量的精密度和准确度。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-12-05 DOI: 10.1016/j.ultramic.2024.114084

Daen Jannis , Wouter Van den Broek , Zezhong Zhang , Sandra Van Aert , Jo Verbeeck

By working out the Bethe sum rule, a boundary condition that takes the form of a linear equality is derived for the fine structure observed in ionization edges present in electron energy-loss spectra. This condition is subsequently used as a constraint in the estimation process of the elemental abundances, demonstrating starkly improved precision and accuracy and reduced sensitivity to the number of model parameters. Furthermore, the fine structure is reliably extracted from the spectra in an automated way, thus providing critical information on the sample’s electronic properties that is hard or impossible to obtain otherwise. Since this approach allows dispensing with the need for user-provided input, a potential source of bias is prevented.

通过计算贝特求和规则，导出了电子能量损失谱中电离边缘精细结构的线性等式形式的边界条件。这一条件随后被用作元素丰度估算过程中的约束条件，显示出明显提高的精度和准确性，并降低了对模型参数数量的敏感性。此外，精细结构以自动化的方式可靠地从光谱中提取出来，从而提供了关于样品电子特性的关键信息，这些信息很难或不可能通过其他方式获得。由于这种方法可以不需要用户提供输入，因此可以防止潜在的偏见来源。

引用次数: 0

Relativistic EELS scattering cross-sections for microanalysis based on Dirac solutions 基于Dirac解的相对论EELS微分析散射截面。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-12-02 DOI: 10.1016/j.ultramic.2024.114083

Zezhong Zhang , Ivan Lobato , Hamish Brown , Dirk Lamoen , Daen Jannis , Johan Verbeeck , Sandra Van Aert , Peter D. Nellist

The rich information of electron energy-loss spectroscopy (EELS) comes from the complex inelastic scattering process whereby fast electrons transfer energy and momentum to atoms, exciting bound electrons from their ground states to higher unoccupied states. To quantify EELS, the common practice is to compare the cross-sections integrated within an energy window or fit the observed spectrum with theoretical differential cross-sections calculated from a generalized oscillator strength (GOS) database with experimental parameters. The previous Hartree–Fock-based and DFT-based GOS are calculated from Schrödinger’s solution of atomic orbitals, which does not include the full relativistic effects. Here, we attempt to go beyond the limitations of the Schrödinger solution in the GOS tabulation by including the full relativistic effects using the Dirac equation within the local density approximation, which is particularly important for core–shell electrons of heavy elements with strong spin–orbit coupling. This has been done for all elements in the periodic table (up to Z = 118) for all possible excitation edges using modern computing capabilities and parallelization algorithms. The relativistic effects of fast incoming electrons were included to calculate cross-sections that are specific to the acceleration voltage. We make these tabulated GOS available under an open-source license to the benefit of both academic users and to allow integration into commercial solutions.

电子能量损失谱（EELS）的丰富信息来自于复杂的非弹性散射过程，即快速电子将能量和动量传递给原子，将束缚电子从基态激发到更高的未占据态。为了量化EELS，通常的做法是比较能量窗口内集成的横截面，或者将观测到的光谱与从具有实验参数的广义振荡器强度（GOS）数据库计算的理论微分横截面拟合。以前基于hartree - fock和dft的GOS是根据Schrödinger的原子轨道解计算的，没有包括完整的相对论效应。在这里，我们试图超越GOS表中Schrödinger解的局限性，利用Dirac方程在局部密度近似中包含完整的相对论效应，这对于具有强自旋轨道耦合的重元素的核壳电子尤其重要。使用现代计算能力和并行化算法，对周期表中所有可能的激发边的所有元素（直到Z = 118）都进行了此操作。为了计算特定于加速电压的截面，考虑了快速进入电子的相对论效应。我们在开源许可下提供这些表格GOS，以使学术用户受益，并允许集成到商业解决方案中。

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引用次数: 0

Aberration calculation of microlens array using differential algebraic method 微透镜阵列像差的微分代数计算。

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-11-30 DOI: 10.1016/j.ultramic.2024.114085

Jintao Hu, Lei Yue, Yihao Ma, Fu Liu, Yongfeng Kang

Microlens array (MLA), through which all the sub-beams are focused, is widely used in multi-electron-beam systems. In this work, based on the differential algebraic (DA) method, we propose an approach in calculating the high-order aberrations for both axial and off-axial microlenses, considering the multipole fields that are introduced by the neighborhood structures in MLA, as well as the rotationally symmetric field. To perform the DA calculation, the electric fields of the microlenses are analyzed by using the azimuthal Fourier analysis and the Fourier-Bessel series Expansion. The resulting field components, including both rotationally symmetric field and the multipole fields, are transferred into DA arguments and operated as per DA methodology. Then, by developing and employing the DA theory and algorithm, the primary and high-order aberrations are calculated and obtained simultaneously for both the axial and off-axial microlenses by tracing only one reference ray. Finally, we calculate, analyze and discuss the primary and high-order aberrations of two example MLAs, for both axial and off-axial microlenses. The effects of the dodecapole fields on the aberrations are also analyzed.

微透镜阵列（Microlens array， MLA）是多电子束系统中广泛使用的一种集中所有子光束的阵列。在本文中，我们基于微分代数（DA）方法，提出了一种计算轴向和离轴微透镜高阶像差的方法，考虑了MLA中邻域结构引入的多极场以及旋转对称场。利用方位角傅里叶分析和傅里叶-贝塞尔级数展开对微透镜的电场进行了分析。得到的场分量，包括旋转对称场和多极场，被转换成数据分析参数，并按照数据分析方法进行操作。然后，通过发展和应用DA理论和算法，通过只跟踪一条参考射线，同时计算和获得轴向和离轴微透镜的初级和高阶像差。最后，我们计算、分析和讨论了两个例子MLAs的一次像差和高阶像差，包括轴向和离轴微透镜。分析了十二极子场对像差的影响。

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引用次数: 0

Effect of the surrounding environment on electron beam irradiation damage of enhanced green fluorescent protein 周围环境对电子束辐照增强绿色荧光蛋白损伤的影响

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-11-25 DOI: 10.1016/j.ultramic.2024.114082

Haruyoshi Osakabe , Mihiro Suzuki , Toshiki Shimizu , Hiroki Minoda

Fluorescent proteins exhibit fluorescence and photoconversion, which are used to study biological phenomena. Among these, enhanced green fluorescent protein (EGFP) emits cathodoluminescence when irradiated with electron beams; this phenomenon has numerous applications in new research tools for biological phenomena. However, bleaching during electron irradiation is a major problem. Generally, the presence of water is important for biological samples, and structural observations are often performed under cryogenic conditions. One of the advantages of cryogenic conditions is the stabilization of the sample due to cooling. However, it is unclear which factor is more effective: the presence of water molecules or cryogenic preservation. To explore the stabilizing factors of the sample structure, we prepared four environments around the sample–dry at room temperature, wet at room temperature, dry at low temperature, and under cryogenic conditions–and investigated the electron beam irradiation damage by measuring the fluorescence emission spectra. Emission intensity from EGFP was attenuated, and the peak was red-shifted by electron beam irradiation; however, the intensity attenuation was fast under dry conditions at low temperature and slow under wet conditions at room temperature. These results imply that sample cooling has no significant effect on the stability of the EGFP chromophore and that the presence of water molecules is extremely important.

荧光蛋白具有荧光和光转化特性，可用于研究生物现象。其中，增强型绿色荧光蛋白（EGFP）在电子束照射下发出阴极发光；这一现象在研究生物现象的新工具中有许多应用。然而，在电子辐照过程中，漂白是一个主要问题。一般来说，水的存在对生物样品很重要，结构观察通常在低温条件下进行。低温条件的优点之一是由于冷却而使样品稳定。然而，目前尚不清楚哪个因素更有效：水分子的存在还是低温保存。为了探讨样品结构的稳定因素，我们在样品周围制备了室温干燥、室温潮湿、低温干燥和低温四种环境，并通过测量荧光发射光谱来研究电子束辐照对样品结构的破坏。电子束辐照使EGFP的发射强度减弱，峰发生红移；低温干燥条件下强度衰减快，室温潮湿条件下强度衰减慢。这些结果表明，样品冷却对EGFP发色团的稳定性没有显著影响，水分子的存在是极其重要的。

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引用次数: 0

Direct electron detection for EBSD of low symmetry & beam sensitive ceramics 用于低对称性和光束敏感陶瓷 EBSD 的直接电子探测

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-11-23 DOI: 10.1016/j.ultramic.2024.114079

Nicolò M. Della Ventura , Andrew R. Ericks , McLean P. Echlin , Kalani Moore , Tresa M. Pollock , Matthew R. Begley , Frank W. Zok , Marc De Graef , Daniel S. Gianola

Electron backscatter diffraction (EBSD) is a powerful tool for determining the orientations of near-surface grains in engineering materials. However, many ceramics present challenges for routine EBSD data collection and indexing due to small grain sizes, high crack densities, beam and charge sensitivities, low crystal symmetries, and pseudo-symmetric pattern variants. Micro-cracked monoclinic hafnia, tetragonal hafnon, and hafnia/hafnon composites exhibit all such features, and are used in the present work to show the efficacy of a novel workflow based on a direct detecting EBSD sensor and a state-of-the-art pattern indexing approach. At 5 and 10 keV primary beam energies (where beam-induced damage and surface charge accumulation are minimal), the direct electron detector produces superior diffraction patterns with 10x lower doses compared to a phosphor-coupled indirect detector. Further, pseudo-symmetric variant-related indexing errors from a Hough-based approach (which account for at least 4%-14% of map areas) are easily resolved by dictionary indexing. In short, the workflow unlocks fundamentally new opportunities to characterize materials historically unsuited for EBSD.

电子反向散射衍射 (EBSD) 是确定工程材料近表面晶粒取向的有力工具。然而，由于晶粒尺寸小、裂纹密度高、光束和电荷敏感性高、晶体对称性低以及假对称图形变体等原因，许多陶瓷给常规 EBSD 数据采集和索引带来了挑战。微裂纹单斜铪、四方铪和铪/铪复合材料显示了所有这些特征，本研究利用这些特征展示了基于直接检测 EBSD 传感器和最先进图案索引方法的新型工作流程的功效。在 5 和 10 keV 主束流能量下（束流引起的损伤和表面电荷积累最小），与荧光粉耦合间接探测器相比，直接电子探测器能以低 10 倍的剂量产生卓越的衍射图样。此外，基于 Hough 方法的伪对称变体相关索引误差（至少占地图面积的 4%-14%）可通过字典索引轻松解决。总之，该工作流程从根本上开启了新的机遇，可以对历史上不适合 EBSD 的材料进行表征。

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引用次数: 0

Chinese knot inspired isotropic linear scanning method for improved imaging performance in AFM 受中国结启发的各向同性线性扫描方法可提高原子力显微镜的成像性能

IF 2.1 3区工程技术 Q2 MICROSCOPY

Ultramicroscopy

Pub Date : 2024-11-18 DOI: 10.1016/j.ultramic.2024.114081

Xiaolong Jia , Haitao Wu , Qubo Jiang , Qilin Zeng , Wentao Zhang , Yanding Qin

Atomic force microscope (AFM) is an important nano-scale surface characterization and measurement method. Raster scanning method (RSM), widely used in AFMs, faces limitations on scanning speed and imaging accuracy. In this paper, an isotropic linear scanning method (ILSM) is proposed to improve the AFM imaging performance. Inspired by Chinese knot, ILSM is constructed by integrating two iterative triangular scanning trajectories in X and Y axes, similar to triangular Lissajous. Compared with the other scanning methods, ILSM features isotropic scanning trajectory across the scanning region. It is also easy to increase either the scanning speed or scanning resolution using ILSM. Subsequently, to address the hysteresis associated with the piezoelectric actuator, a new tracking algorithm is proposed by combining adaptive Kalman filtering and direct inverse modeling approach. Finally, AFM imaging experiments are conducted to validate the effectiveness of the proposed method. It can be found that the artifacts in RSM can be efficiently eliminated using the proposed method, thus improving the imaging quality.

原子力显微镜（AFM）是一种重要的纳米级表面表征和测量方法。在原子力显微镜中广泛使用的光栅扫描法（RSM）在扫描速度和成像精度方面存在局限性。本文提出了一种各向同性线性扫描方法（ILSM），以提高原子力显微镜的成像性能。受中国结的启发，ILSM 是通过在 X 轴和 Y 轴上整合两个迭代三角形扫描轨迹来构建的，类似于三角形 Lissajous。与其他扫描方法相比，ILSM 扫描轨迹在扫描区域内各向同性。此外，使用 ILSM 还能轻松提高扫描速度或扫描分辨率。随后，为了解决与压电致动器相关的滞后问题，结合自适应卡尔曼滤波和直接逆建模方法，提出了一种新的跟踪算法。最后，进行了原子力显微镜成像实验，以验证所提方法的有效性。实验结果表明，使用所提出的方法可以有效消除 RSM 中的伪影，从而提高成像质量。

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引用次数: 0