Advanced Structural and Chemical Imaging

Abstract Nanosized or nanoconfined hydrides are promising materials for solid-state hydrogen storage. Most of these hydrides, however, degrade fast during the structural characterization utilizing transmission electron microscopy (TEM) upon the irradiation with the imaging electron beam due to radiolysis. We use ball-milled MgH 2 as a reference material for in-situ TEM experiments under low-dose conditions to study and quantitatively understand the electron beam-induced dehydrogenation. For this, valence electron energy loss spectroscopy (VEELS) measurements are conducted in a monochromated FEI Titan 3 80–300 microscope. From observing the plasmonic absorptions it is found that MgH 2 successively converts into Mg upon electron irradiation. The temporal evolution of the spectra is analyzed quantitatively to determine the thickness-dependent, characteristic electron doses for electron energies of both 80 and 300 keV. The measured electron doses can be quantitatively explained by the inelastic scattering of the incident high-energy electrons by the MgH 2 plasmon. The obtained insights are also relevant for the TEM characterization of other hydrides.

Alexander Surrey

Ludwig Schultz

Bernd Rellinghaus

Electron beam induced dehydrogenation of MgH2 studied by VEELS

电子束诱导MgH2脱氢的VEELS研究

Abstract Transmission electron microscopy allows the collection of multiple views of specimens and their computerized three-dimensional reconstruction and analysis with electron tomography. Here we describe development of methods for automated multi-tilt data acquisition, tilt-series processing, and alignment which allow assembly of electron tomographic data from a greater number of tilt series, yielding enhanced data quality and increasing contrast associated with weakly stained structures. This scheme facilitates visualization of nanometer scale details of fine structure in volumes taken from plastic-embedded samples of biological specimens in all dimensions. As heavy metal-contrasted plastic-embedded samples are less sensitive to the overall dose rather than the electron dose rate, an optimal resampling of the reconstruction space can be achieved by accumulating lower dose electron micrographs of the same area over a wider range of specimen orientations. The computerized multiple tilt series collection scheme is implemented together with automated advanced procedures making collection, image alignment, and processing of multi-tilt tomography data a seamless process. We demonstrate high-quality reconstructions from samples of well-described biological structures. These include the giant Mimivirus and clathrin-coated vesicles, imaged in situ in their normal intracellular contexts. Examples are provided from samples of cultured cells prepared by high-pressure freezing and freeze-substitution as well as by chemical fixation before epoxy resin embedding.

Sébastien Phan

Daniela Boassa

Phuong Nguyen

Xiaohua Wan

Jason Lanman

Albert Lawrence

Mark H. Ellisman

3D reconstruction of biological structures: automated procedures for alignment and reconstruction of multiple tilt series in electron tomography

生物结构的三维重建：电子断层扫描中多倾斜系列对齐与重建的自动化程序

We present experimental evidence under low-dose conditions transmission electron microscopy for the unfolding of the evolving changes in carbon soot during mechanical milling. The milled soot shows evolving changes as a function of the milling severity or time. Those changes are responsible for the transformation from amorphous carbon to graphenes, graphitic carbon, and highly ordered structures such as morphed graphenes, namely Rh6 and Rh6-II. The morphed graphenes are corrugated layers of carbon with cross-linked covalently nature and sp2- or sp3-type allotropes. Electron microscopy and numerical simulations are excellent complementary tools to identify those phases. Furthermore, the TEAM 05 microscope is an outstanding tool to resolve the microstructure and prevent any damage to the sample. Other characterization techniques such as XRD, Raman, and XPS fade to convey a true identification of those phases because the samples are usually blends or mixes of the mentioned phases.

H. A. Calderon

A. Okonkwo

I. Estrada-Guel

V. G. Hadjiev

F. Alvarez-Ramírez

F. C. Robles Hernández

HRTEM low dose: the unfold of the morphed graphene, from amorphous carbon to morphed graphenes

HRTEM低剂量：从无定形碳到变形石墨烯的展开

Serial block-face scanning electron microscopy (SBEM) is quickly becoming an important imaging tool to explore three-dimensional biological structure across spatial scales. At probe-beam-electron energies of 2.0 keV or lower, the axial resolution should improve, because there is less primary electron penetration into the block face. More specifically, at these lower energies, the interaction volume is much smaller, and therefore, surface detail is more highly resolved. However, the backscattered electron yield for metal contrast agents and the backscattered electron detector sensitivity are both sub-optimal at these lower energies, thus negating the gain in axial resolution. We found that the application of a negative voltage (reversal potential) applied to a modified SBEM stage creates a tunable electric field at the sample. This field can be used to decrease the probe-beam-landing energy and, at the same time, alter the trajectory of the signal to increase the signal collected by the detector. With decelerated low landing-energy electrons, we observed that the probe-beam-electron-penetration depth was reduced to less than 30 nm in epoxy-embedded biological specimens. Concurrently, a large increase in recorded signal occurred due to the re-acceleration of BSEs in the bias field towards the objective pole piece where the detector is located. By tuning the bias field, we were able to manipulate the trajectories of the primary and secondary electrons, enabling the spatial discrimination of these signals using an advanced ring-type BSE detector configuration or a standard monolithic BSE detector coupled with a blocking aperture.

James C. Bouwer

Thomas J. Deerinck

Eric Bushong

Vadim Astakhov

Ranjan Ramachandra

Steven T. Peltier

Deceleration of probe beam by stage bias potential improves resolution of serial block-face scanning electron microscopic images

探针束减速通过阶段偏置电位提高连续面扫描电子显微镜图像分辨率

The present work explores electron diffraction methods for studying the structure of metallic clusters stabilized with thiol groups, which are susceptible to structural damage caused by electron beam irradiation. There is a compromise between the electron dose used and the size of the clusters since they have small interaction volume with electrons and as a consequence weak reflections in the diffraction patterns. The common approach of recording individual clusters using nanobeam diffraction has the problem of an increased current density. Dosage can be reduced with the use of a smaller condenser aperture and a higher condenser lens excitation, but even with those set ups collection times tend to be high. For that reason, the methods reported herein collects in a faster way diffraction patterns through the scanning across the clusters under nanobeam diffraction mode. In this way, we are able to collect a map of diffraction patterns, in areas with dispersed clusters, with short exposure times (milliseconds) using a high sensitive CMOS camera. When these maps are compared with their theoretical counterparts, oscillations of the clusters can be observed. The stability of the patterns acquired demonstrates that our methods provide a systematic and precise way to unveil the structure of atomic clusters without extensive detrimental damage of their crystallinity.

Eduardo Ortega

Arturo Ponce

Ulises Santiago

Diego Alducin

Alfredo Benitez-Lara

Germán Plascencia-Villa

Miguel José-Yacamán

Structural damage reduction in protected gold clusters by electron diffraction methods

电子衍射方法在保护金团簇中减少结构损伤

Oleg S. Ovchinnikov

Andrew O’Hara

Stephen Jesse

Bethany M. Hudak

Shi‐Ze Yang

Andrew R. Lupini

Matthew F. Chisholm

Wu Zhou

Sergei V. Kalinin

Albina Y. Borisevich

Sokrates T. Pantelides

Adv Struct Chem Imag

Detection of defects in atomic-resolution images of materials using cycle analysis

利用循环分析检测材料原子分辨图像中的缺陷

Abstract Scanning transmission electron microscopy (STEM) at low energies (≤ 30 keV) in a scanning electron microscope is well suited to distinguish weakly scattering materials with similar materials properties and analyze their microstructure. The capabilities of the technique are illustrated in this work to resolve material domains in PTB7:PC 71 BM bulk-heterojunctions, which are commonly implemented for light-harvesting in organic solar cells. Bright-field (BF-) and high-angle annular dark-field (HAADF-) STEM contrast of pure PTB7 and PC 71 BM was first systematically analyzed using a wedge-shaped sample with well-known thickness profile. Monte-Carlo simulations are essential for the assignment of material contrast for materials with only slightly different scattering properties. Different scattering cross-sections were tested in Monte-Carlo simulations with screened Rutherford scattering cross-sections yielding best agreement with the experimental data. The STEM intensity also depends on the local specimen thickness, which can be dealt with by correlative STEM and scanning electron microscopy (SEM) imaging of the same specimen region yielding additional topography information. Correlative STEM/SEM was applied to determine the size of donor (PTB7) and acceptor (PC 71 BM) domains in PTB7:PC 71 BM absorber layers that were deposited from solution with different contents of the processing additive 1,8-diiodooctane (DIO).

Yonghe Li

Erich Müller

Christian Sprau

Alexander Colsmann

Dagmar Gerthsen

Imaging of polymer:fullerene bulk-heterojunctions in a scanning electron microscope: methodology aspects and nanomorphology by correlative SEM and STEM

聚合物：富勒烯体异质结的扫描电子显微镜成像：方法学方面与关联扫描电镜和透射电镜的纳米形貌

Abstract The standard technique for sub-pixel estimation of atom positions from atomic resolution scanning transmission electron microscopy images relies on fitting intensity maxima or minima with a two-dimensional Gaussian function. While this is a widespread method of measurement, it can be error prone in images with non-zero aberrations, strong intensity differences between adjacent atoms or in situations where the neighboring atom positions approach the resolution limit of the microscope. Here we demonstrate mpfit , an atom finding algorithm that iteratively calculates a series of overlapping two-dimensional Gaussian functions to fit the experimental dataset and then subsequently uses a subset of the calculated Gaussian functions to perform sub-pixel refinement of atom positions. Based on both simulated and experimental datasets presented in this work, this approach gives lower errors when compared to the commonly used single Gaussian peak fitting approach and demonstrates increased robustness over a wider range of experimental conditions.

Debangshu Mukherjee

Leixin Miao

Greg Stone

Nasim Alem

mpfit: a robust method for fitting atomic resolution images with multiple Gaussian peaks

mpfit：一种用于拟合具有多个高斯峰的原子分辨率图像的鲁棒方法

Abstract Hole-free phase plates (HFPPs), also known as Volta phase plates, were already demonstrated to be well suited for in-focus transmission electron microscopy imaging of organic objects. However, the underlying physical processes have not been fully understood yet. To further elucidate the imaging properties of HFPPs, phase shift measurements were carried out under different experimental conditions. Both positive and negative phase shifts occur depending on the diameter of the zero-order electron beam and the HFPP film temperature. The analysis of Thon ring patterns of an amorphous carbon test sample reveals that the phase-shifting patch can be significantly larger than the size of the zero-order beam on the HFPP film. An HFPP was used for in-focus phase contrast imaging of carbon nanotube (CNT) bundles under positive and negative phase-shifting conditions. The comparison of experimental and simulated images of CNT bundles gives detailed information on the phase shift profile, which depends on the spatial frequency in the vicinity of the zero-order beam. The shape of the phase shift profile also explains halo-like image artifacts that surround the imaged objects.

Rebecca Pretzsch

Manuel Dries

Simon Hettler

Martin Spiecker

Martin Obermair

Investigation of hole-free phase plate performance in transmission electron microscopy under different operation conditions by experiments and simulations

无孔相位板在透射电子显微镜中不同操作条件下的性能实验与模拟研究

STEM XEDS spectrum images can be drastically denoised by application of the principal component analysis (PCA). This paper looks inside the PCA workflow step by step on an example of a complex semiconductor structure consisting of a number of different phases. Typical problems distorting the principal components decomposition are highlighted and solutions for the successful PCA are described. Particular attention is paid to the optimal truncation of principal components in the course of reconstructing denoised data. A novel accurate and robust method, which overperforms the existing truncation methods is suggested for the first time and described in details.

Pavel Potapov

Axel Lubk

Optimal principal component analysis of STEM XEDS spectrum images

STEM XEDS 谱图像的最优主成分分析

ISSN	2198-0926
h-index	23

涉及主题	物理计算机科学光学工程类材料科学量子力学人工智能纳米技术化学数学程序设计语言化学工程复合材料计算机视觉透射电子显微镜医学有机化学操作系统电子显微镜扫描电子显微镜生物算法扫描透射电子显微镜分辨率（逻辑）图像（数学）核物理学病理
出版信息	出版商: SpringerOpen，出版周期: ，期刊类型: journal，开源期刊: 否
基本数据	创刊年份: 2015，原创研究文献占比: 0.00%，自引率:N.A.， Gold OA占比: 0.00%

Advanced Structural and Chemical Imaging

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