Pub Date : 2025-01-01Epub Date: 2024-11-26DOI: 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.
{"title":"State-of-the-art electron beams for compact tools of ultrafast science.","authors":"Peter Salén, Anatoliy Opanasenko, Giovanni Perosa, Vitaliy Goryashko","doi":"10.1016/j.ultramic.2024.114080","DOIUrl":"10.1016/j.ultramic.2024.114080","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"114080"},"PeriodicalIF":2.1,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142772741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Effect of the surrounding environment on electron beam irradiation damage of enhanced green fluorescent protein","authors":"Haruyoshi Osakabe , Mihiro Suzuki , Toshiki Shimizu , Hiroki Minoda","doi":"10.1016/j.ultramic.2024.114082","DOIUrl":"10.1016/j.ultramic.2024.114082","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114082"},"PeriodicalIF":2.1,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 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.
{"title":"Direct electron detection for EBSD of low symmetry & beam sensitive ceramics","authors":"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","doi":"10.1016/j.ultramic.2024.114079","DOIUrl":"10.1016/j.ultramic.2024.114079","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114079"},"PeriodicalIF":2.1,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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。
{"title":"Chinese knot inspired isotropic linear scanning method for improved imaging performance in AFM","authors":"Xiaolong Jia , Haitao Wu , Qubo Jiang , Qilin Zeng , Wentao Zhang , Yanding Qin","doi":"10.1016/j.ultramic.2024.114081","DOIUrl":"10.1016/j.ultramic.2024.114081","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114081"},"PeriodicalIF":2.1,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142699969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.ultramic.2024.114071
Simon Hettler , Mohammad Furqan , Andrés Sotelo , Raul Arenal
We explore the possibility to perform an in-situ transmission electron microscopy (TEM) thermoelectric characterization of materials. A differential heating element on a custom in-situ TEM microchip allows to generate a temperature gradient across the studied materials, which are simultaneously measured electrically. A thermovoltage was induced in all studied devices, whose sign corresponds to the sign of the Seebeck coefficient of the tested materials. The results indicate that in-situ thermoelectric TEM studies can help to profoundly understand fundamental aspects of thermoelectricity, which is exemplary demonstrated by tracking the thermovoltage during in-situ crystallization of an amorphous Ge thin film. We propose an improved in-situ TEM microchip design, which should facilitate a full quantitative measurement of the induced temperature gradient, the electrical and thermal conductivities, as well as the Seebeck coefficient. The benefit of the in-situ approach is the possibility to directly correlate the thermoelectric properties with the structure and chemical composition of the entire studied device down to the atomic level, including grain boundaries, dopants or crystal defects, and to trace its dynamic evolution upon heating or during the application of electrical currents.
我们探索了对材料进行原位透射电子显微镜（TEM）热电特性分析的可能性。在定制的原位 TEM 微芯片上安装一个差分加热元件，可以在所研究的材料上产生温度梯度，并同时进行电学测量。在所有研究装置中都会产生热电压，其符号与被测材料塞贝克系数的符号相对应。结果表明，原位热电 TEM 研究有助于深刻理解热电的基本方面，非晶态 Ge 薄膜原位结晶过程中的热电压跟踪就是一个很好的例子。我们提出了一种改进的原位 TEM 微芯片设计，它有助于对诱导温度梯度、电导率和热导率以及塞贝克系数进行全面的定量测量。原位方法的优势在于可以直接将热电性能与整个被研究器件的结构和化学成分（包括晶界、掺杂物或晶体缺陷）关联到原子水平，并跟踪其在加热或施加电流时的动态演变。
{"title":"Toward quantitative thermoelectric characterization of (nano)materials by in-situ transmission electron microscopy","authors":"Simon Hettler , Mohammad Furqan , Andrés Sotelo , Raul Arenal","doi":"10.1016/j.ultramic.2024.114071","DOIUrl":"10.1016/j.ultramic.2024.114071","url":null,"abstract":"<div><div>We explore the possibility to perform an <em>in-situ</em> transmission electron microscopy (TEM) thermoelectric characterization of materials. A differential heating element on a custom <em>in-situ</em> TEM microchip allows to generate a temperature gradient across the studied materials, which are simultaneously measured electrically. A thermovoltage was induced in all studied devices, whose sign corresponds to the sign of the Seebeck coefficient of the tested materials. The results indicate that <em>in-situ</em> thermoelectric TEM studies can help to profoundly understand fundamental aspects of thermoelectricity, which is exemplary demonstrated by tracking the thermovoltage during <em>in-situ</em> crystallization of an amorphous Ge thin film. We propose an improved <em>in-situ</em> TEM microchip design, which should facilitate a full quantitative measurement of the induced temperature gradient, the electrical and thermal conductivities, as well as the Seebeck coefficient. The benefit of the <em>in-situ</em> approach is the possibility to directly correlate the thermoelectric properties with the structure and chemical composition of the entire studied device down to the atomic level, including grain boundaries, dopants or crystal defects, and to trace its dynamic evolution upon heating or during the application of electrical currents.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114071"},"PeriodicalIF":2.1,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142629442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.ultramic.2024.114069
H. Hammami, S. Fakhfakh
A new experimental methodology is proposed which uses the electrostatic influence method (EIM) in scanning electron microscope (SEM) in order to estimate the second crossover energy EC2 for uncharged insulators. This experimental methodology based on simultaneous time measurement of the displacement and leakage currents, is approached to the short pulse irradiation technique but under stationary e-irradiation and allows determining the intrinsic secondary electron emission yield, σ0 (σ0 is the value of the total secondary electron yield just at the beginning of the irradiation before significant charge accumulation or before the formation of a surface potential). The obtained value of EC2 for soda-lime glass is confirmed by two additional experiments based on secondary electron imaging. This value is in good agreement with those previously obtained by other studies based on the surface potential measurement or the pulsed irradiation technique.
{"title":"New experimental methodology for determining the second crossover energy in insulators under stationary e-irradiation in a SEM","authors":"H. Hammami, S. Fakhfakh","doi":"10.1016/j.ultramic.2024.114069","DOIUrl":"10.1016/j.ultramic.2024.114069","url":null,"abstract":"<div><div>A new experimental methodology is proposed which uses the electrostatic influence method (EIM) in scanning electron microscope (SEM) in order to estimate the second crossover energy E<sub>C2</sub> for uncharged insulators. This experimental methodology based on simultaneous time measurement of the displacement and leakage currents, is approached to the short pulse irradiation technique but under stationary e-irradiation and allows determining the intrinsic secondary electron emission yield, σ<sub>0</sub> (σ<sub>0</sub> is the value of the total secondary electron yield just at the beginning of the irradiation before significant charge accumulation or before the formation of a surface potential). The obtained value of E<sub>C2</sub> for soda-lime glass is confirmed by two additional experiments based on secondary electron imaging. This value is in good agreement with those previously obtained by other studies based on the surface potential measurement or the pulsed irradiation technique.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114069"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142629440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-30DOI: 10.1016/j.ultramic.2024.114070
V.J. Keast
The low energy region (< 50 eV) of the electron energy loss spectrum (EELS) can contain a great deal of spectral detail associated with excitations of the valence electrons. Calculation of the spectra from first principles can assist with interpretation and the most widely used method is the random phase approximation (RPA), usually neglecting local field effects (LFE). For KBr this approach is insufficient due to the importance of quasiparticle and excitonic effects. Calculations including these multi-electron effects are shown to give much improved agreement with the experimental spectra, and the inclusion of spin-orbit coupling (SOC) reproduces the excitonic doublet just above band-edge onset. A review of the complex theory behind these methods is given along with practical guidance on performing these calculations.
{"title":"Beyond the random phase approximation (RPA): First principles calculation of the valence EELS spectrum for KBr including local field, quasiparticle, excitonic and spin orbit coupling effects","authors":"V.J. Keast","doi":"10.1016/j.ultramic.2024.114070","DOIUrl":"10.1016/j.ultramic.2024.114070","url":null,"abstract":"<div><div>The low energy region (< 50 eV) of the electron energy loss spectrum (EELS) can contain a great deal of spectral detail associated with excitations of the valence electrons. Calculation of the spectra from first principles can assist with interpretation and the most widely used method is the random phase approximation (RPA), usually neglecting local field effects (LFE). For KBr this approach is insufficient due to the importance of quasiparticle and excitonic effects. Calculations including these multi-electron effects are shown to give much improved agreement with the experimental spectra, and the inclusion of spin-orbit coupling (SOC) reproduces the excitonic doublet just above band-edge onset. A review of the complex theory behind these methods is given along with practical guidance on performing these calculations.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114070"},"PeriodicalIF":2.1,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142606608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.ultramic.2024.114068
Wenhui Xu , Shoucong Ning , Pengju Sheng , Huixiang Lin , Angus I Kirkland , Yong Peng , Fucai Zhang
Ptychography is now integrated as a tool in mainstream microscopy allowing quantitative and high-resolution imaging capabilities over a wide field of view. However, its ultimate performance is inevitably limited by the available coherent flux when implemented using electrons or laboratory X-ray sources. We present a universal reconstruction algorithm with high tolerance to low coherence for both far-field and near-field ptychography. The approach is practical for partial temporal and spatial coherence and requires no prior knowledge of the source properties. Our initial visible-light and electron data show that the method can dramatically improve the reconstruction quality and accelerate the convergence rate of the reconstruction. The approach also integrates well into existing ptychographic engines. It can also improve mixed-state and numerical monochromatisation methods, requiring a smaller number of coherent modes or lower dimensionality of Krylov subspace while providing more stable and faster convergence. We propose that this approach could have significant impact on ptychography of weakly scattering samples.
目前，层析成像技术已成为主流显微镜技术的一种工具，可在宽视场范围内进行定量和高分辨率成像。然而，在使用电子或实验室 X 射线源时，其最终性能不可避免地受到可用相干通量的限制。我们提出了一种通用的重建算法，对远场和近场层析成像的低相干性具有很高的容忍度。这种方法适用于部分时间和空间相干性，而且不需要事先了解光源特性。我们最初的可见光和电子数据表明，该方法能显著提高重建质量，并加快重建的收敛速度。这种方法还能很好地集成到现有的分色引擎中。它还能改进混合状态和数值单色化方法，需要更少的相干模式或更低维度的克雷洛夫子空间，同时提供更稳定和更快的收敛速度。我们认为，这种方法可以对弱散射样本的层析成像产生重大影响。
{"title":"A high-performance reconstruction method for partially coherent ptychography","authors":"Wenhui Xu , Shoucong Ning , Pengju Sheng , Huixiang Lin , Angus I Kirkland , Yong Peng , Fucai Zhang","doi":"10.1016/j.ultramic.2024.114068","DOIUrl":"10.1016/j.ultramic.2024.114068","url":null,"abstract":"<div><div>Ptychography is now integrated as a tool in mainstream microscopy allowing quantitative and high-resolution imaging capabilities over a wide field of view. However, its ultimate performance is inevitably limited by the available coherent flux when implemented using electrons or laboratory X-ray sources. We present a universal reconstruction algorithm with high tolerance to low coherence for both far-field and near-field ptychography. The approach is practical for partial temporal and spatial coherence and requires no <em>prior</em> knowledge of the source properties. Our initial visible-light and electron data show that the method can dramatically improve the reconstruction quality and accelerate the convergence rate of the reconstruction. The approach also integrates well into existing ptychographic engines. It can also improve mixed-state and numerical monochromatisation methods, requiring a smaller number of coherent modes or lower dimensionality of Krylov subspace while providing more stable and faster convergence. We propose that this approach could have significant impact on ptychography of weakly scattering samples.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114068"},"PeriodicalIF":2.1,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.ultramic.2024.114067
Florent Tournus
Conventional Transmission Electron Microscopy (TEM) is widely used for routine characterization of the size and shape of an assembly of (nano)particles. While the most basic approach only uses the projected area of each particle to infer its size (the “circular equivalent diameter” corresponding to the so-called “spherical approximation”), other shape descriptors can be determined and used for more elaborate analyses. In this article we present a generic model of particles, considered to be made of a few individual grains, and show how the equivalent size (i.e. a particle volume information) can be reliably deduced using only two basic parameters: the projected area and the perimeter of a particle. We compare this simple model to the spherical and ellipsoidal approximations and discuss its benefits. Then, partial coalescence of grains in a particle is also considered and we show how a simple analytical approximation, based on the circularity parameter of each particle, can improve the experimental determination of a particle size histogram. The analysis of experimental observations on nanoparticles assemblies obtained by mass-selected cluster deposition is presented, to illustrate the efficiency of the proposed approach for the determination of particle size just from conventional TEM images. We show how the presence of multimers offers an excellent opportunity to validate our improved and simple procedure. In addition, since the circularity plays a central role in this approach, attention is attracted on the perimeter determination in a pixelated image.
传统的透射电子显微镜（TEM）被广泛用于对（纳米）颗粒组件的尺寸和形状进行常规表征。虽然最基本的方法只是利用每个颗粒的投影面积来推断其大小（即所谓 "球面近似 "的 "圆形等效直径"），但也可以确定其他形状描述符，并用于更精细的分析。在这篇文章中，我们提出了一个通用的颗粒模型，认为它是由一些单独的颗粒组成的，并展示了如何仅使用两个基本参数就能可靠地推导出等效尺寸（即颗粒体积信息）：颗粒的投影面积和周长。我们将这一简单模型与球形和椭圆形近似模型进行了比较，并讨论了其优点。然后，我们还考虑了颗粒中颗粒的部分凝聚，并展示了基于每个颗粒的圆度参数的简单分析近似值如何改进粒度直方图的实验测定。我们介绍了对通过质量选择簇沉积获得的纳米粒子集合体的实验观察分析，以说明所提出的方法在仅从传统 TEM 图像确定粒度方面的效率。我们展示了多聚物的存在如何为验证我们改进的简单程序提供了绝佳的机会。此外，由于圆形在这种方法中起着核心作用，因此像素化图像中的周长测定也备受关注。
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Pub Date : 2024-10-26DOI: 10.1016/j.ultramic.2024.114066
Yansong Hao , Annick De Backer , Scott David Findlay , Sandra Van Aert
Through a simulation-based study we develop a statistical model-based quantification method for atomic resolution first moment scanning transmission electron microscopy (STEM) images. This method uses the uniformly weighted least squares estimator to determine the unknown structure parameters of the images and to isolate contributions from individual atomic columns. In this way, a quantification of the projected potential per atomic column is achieved. Since the integrated projected potential of an atomic column scales linearly with the number of atoms it contains, it can serve as a basis for atom counting. The performance of atom counting from first moment STEM imaging is compared to that from traditional HAADF STEM in the presence of noise. Through this comparison, we demonstrate the advantage of first moment STEM images to attain more precise atom counts. Finally, we compare the integrated potential extracted from first-moment images of a wedge-shaped sample to those values from the bulk crystal. The excellent agreement found between these values proves the robustness of using bulk crystal simulations as a reference library. This enables atom counting for samples with different shapes by comparison with these library values.
{"title":"Towards atom counting from first moment STEM images: Methodology and possibilities","authors":"Yansong Hao , Annick De Backer , Scott David Findlay , Sandra Van Aert","doi":"10.1016/j.ultramic.2024.114066","DOIUrl":"10.1016/j.ultramic.2024.114066","url":null,"abstract":"<div><div>Through a simulation-based study we develop a statistical model-based quantification method for atomic resolution first moment scanning transmission electron microscopy (STEM) images. This method uses the uniformly weighted least squares estimator to determine the unknown structure parameters of the images and to isolate contributions from individual atomic columns. In this way, a quantification of the projected potential per atomic column is achieved. Since the integrated projected potential of an atomic column scales linearly with the number of atoms it contains, it can serve as a basis for atom counting. The performance of atom counting from first moment STEM imaging is compared to that from traditional HAADF STEM in the presence of noise. Through this comparison, we demonstrate the advantage of first moment STEM images to attain more precise atom counts. Finally, we compare the integrated potential extracted from first-moment images of a wedge-shaped sample to those values from the bulk crystal. The excellent agreement found between these values proves the robustness of using bulk crystal simulations as a reference library. This enables atom counting for samples with different shapes by comparison with these library values.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"268 ","pages":"Article 114066"},"PeriodicalIF":2.1,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142629443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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