Ultramicroscopy最新文献

{"title":"Towards atom counting from first moment STEM images: Methodology and possibilities","authors":"Yansong Hao ,&nbsp;Annick De Backer ,&nbsp;Scott David Findlay ,&nbsp;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}

{"title":"Corrigendum to “Structure-preserving Gaussian denoising of FIB-SEM volumes” [Ultramicroscopy Volume 246, 113674]","authors":"V. González-Ruiz ,&nbsp;M.R. Fernández-Fernández ,&nbsp;J.J. Fernández","doi":"10.1016/j.ultramic.2024.114065","DOIUrl":"10.1016/j.ultramic.2024.114065","url":null,"abstract":"","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114065"},"PeriodicalIF":2.1,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142569693","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}

{"title":"On the instrument-dependent appearance of ion dissociation events in atom probe tomography mass spectra","authors":"Benjamin W. Caplins ,&nbsp;Ann N. Chiaramonti ,&nbsp;Jacob M. Garcia ,&nbsp;Luis Miaja-Avila ,&nbsp;Kayla H. Yano ,&nbsp;Daniel K. Schreiber ,&nbsp;Joseph H. Bunton","doi":"10.1016/j.ultramic.2024.114061","DOIUrl":"10.1016/j.ultramic.2024.114061","url":null,"abstract":"<div><div>The successful application of atom probe tomography (APT) relies on the accurate interpretation of the mass spectrum (<em>i.e.</em> <span><math><mrow><mi>m</mi><mo>/</mo><mi>z</mi></mrow></math></span> histogram) from a sample. Some materials yield mass spectra that are amenable to a straightforward peak assignment/ranging, however, there are many materials that produce mass spectra with features that defy simple interpretation. One such example is Ga<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> which yields mass spectra containing several broad and difficult to interpret features. Herein, we study the GaO<span><math><msup><mrow></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></math></span> <span><math><mo>→</mo></math></span> O<span><math><mrow><msup><mrow></mrow><mrow><mn>1</mn><mo>+</mo></mrow></msup><mo>+</mo></mrow></math></span> Ga<span><math><msup><mrow></mrow><mrow><mn>1</mn><mo>+</mo></mrow></msup></math></span> dissociation and we explain how this dissociation process gives rise to broad and previously unassigned features in the mass spectrum. Trajectory simulations are performed for the dissociation reaction utilizing realistic electrostatic models and compared to experiments using commercially available straight flight and reflectron based local electrode (LE) APT instruments. It is shown that the appearance of these features is strongly dependent on the specific design of the time-of-flight (ToF) mass analyzer. We explore how various experimental parameters can affect the appearance of the dissociation process in the one-dimensional (1D) mass spectrum and in the two-dimensional (2D) correlation histogram. While the focus of this work is on a particular dissociation process related to Ga<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>, the understanding gained in the course of these simulations and experiments should be applicable to the interpretation of dissociation processes in other materials.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114061"},"PeriodicalIF":2.1,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578087","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}

{"title":"A refined plan-view specimen preparation technique for high-quality electron microscopy studies of epitaxially grown atomically thin 2D layers","authors":"A.S. Prikhodko ,&nbsp;E. Zallo ,&nbsp;R. Calarco ,&nbsp;N.I. Borgardt","doi":"10.1016/j.ultramic.2024.114063","DOIUrl":"10.1016/j.ultramic.2024.114063","url":null,"abstract":"<div><div>The structural studies of two-dimensional (2D) van der Waals heterostructures and understanding of their relationship with the orientation of crystalline substrates using transmission electron microscopy (TEM) presents a challenge in developing an easy-to-use plan-view specimen preparation technique. In this report, we introduce a simple approach for high-quality plan-view specimen preparation utilizing a dual beam system comprising focused ion beam and scanning electron microscopy.</div><div>To protect the atomically thin 2D heterostructure during the preparation process, we employ an epoxy layer. This layer serves as a protective barrier and enables the creation of a TEM specimen comprising a thin substrate fragment with an overgrown 2D structure covered by a thin, electron-transparent epoxy layer. The coexistence of both 2D layers and substrate is essential for investigating the relative crystallographic orientations between the grown 2D structures and the substrates. The thickness of the specimen is monitored using low-voltage scanning electron microscopy.</div><div>We apply this technique to prepare plan-view specimens of 2D germanium-antimony-telluride (GST) on Si and hexagonal boron nitride (h-BN)/epitaxial graphene (EG) heterostructures grown on 6H-SiC substrates. The grain-like atomic structure observed in the 2.2 nm thick GST layer on Si substrate provides evidence of the mosaicity of GST during the early stages of epitaxial growth. H-BN/EG on 6H-SiC structural studies indicate a rotation of h-BN/EG around the 6H-SiC[0001] axis by an angle of 30°. The observed BN particles with sizes in the nanometer range on top of the sample have the wurtzite lattice type and random orientation.</div><div>The developed specimen preparation technique offers a powerful tool for TEM studies of atomically thin layers on crystals. Its simplicity and ability to provide valuable insights into the in-plane relationships between 2D structures and crystalline substrates make it a promising complement to grazing incident X-ray diffraction.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114063"},"PeriodicalIF":2.1,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528062","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}

{"title":"Development of ultrafast four-dimensional precession electron diffraction","authors":"Toshiya Shiratori ,&nbsp;Jumpei Koga ,&nbsp;Takahiro Shimojima ,&nbsp;Kyoko Ishizaka ,&nbsp;Asuka Nakamura","doi":"10.1016/j.ultramic.2024.114064","DOIUrl":"10.1016/j.ultramic.2024.114064","url":null,"abstract":"<div><div>Ultrafast electron diffraction/microscopy technique enables us to investigate the nonequilibrium dynamics of crystal structures in the femtosecond-nanosecond time domain. However, the electron diffraction intensities are in general extremely sensitive to the excitation errors (i.e., deviation from the Bragg condition) and the dynamical effects, which had prevented us from quantitatively discussing the crystal structure dynamics particularly in thick samples. Here, we develop a four-dimensional precession electron diffraction (4D-PED) system by which time (<em>t</em>) and electron-incident-angle <span><math><mrow><mo>(</mo><mi>ϕ</mi><mo>)</mo></mrow></math></span> dependences of electron diffraction patterns <span><math><mrow><mo>(</mo><mrow><msub><mi>q</mi><mi>x</mi></msub><mo>,</mo><mspace></mspace><msub><mi>q</mi><mi>y</mi></msub></mrow><mo>)</mo></mrow></math></span> are recorded. Nonequilibrium crystal structure refinement on VTe₂ demonstrates that the ultrafast change in the crystal structure can be quantitatively determined from 4D-PED. We further perform the analysis of the <span><math><mi>ϕ</mi></math></span> dependence, from which we can qualitatively estimate the change in the reciprocal lattice vector parallel to the optical axis. These results show the capability of the 4D-PED method for the quantitative investigation of ultrafast crystal structural dynamics.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114064"},"PeriodicalIF":2.1,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142523240","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}

{"title":"Parameter dependence of depth and lateral resolution of transmission Kikuchi diffraction","authors":"Glenn C. Sneddon ,&nbsp;Patrick W. Trimby ,&nbsp;Levi Tegg ,&nbsp;Julie M. Cairney","doi":"10.1016/j.ultramic.2024.114062","DOIUrl":"10.1016/j.ultramic.2024.114062","url":null,"abstract":"<div><div>The spatial resolution of transmission Kikuchi diffraction (TKD) depends on experimental parameters such as atomic number, accelerating voltage, sample backtilt and thickness. In this work, the dependence of spatial resolution on these parameters is explored by using bilayered coarse-grained/nanocrystalline samples to determine the depth resolution. Digital image correlation of the Kikuchi patterns across grain boundaries is used to measure the lateral resolution. The depth resolutions of TKD in aluminium, copper and platinum at 30 kV for an untilted sample were 80, 32 and 14 nm respectively. These worsened with increasing sample backtilt and slightly improved with decreasing accelerating voltage. The best physical lateral resolution obtained was 6 nm, at 30 keV in a 41 nm thick aluminium sample with no backtilt. The lateral resolution worsened with increasing sample thickness and backtilt, contrasting with some previous reports. Accelerating voltage and atomic number did not have a significant impact on the measured lateral resolution within the scatter in the data.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114062"},"PeriodicalIF":2.1,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142508922","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}

{"title":"The reference window for reduced perturbation of the reference wave in electrical biasing off-axis electron holography","authors":"Tolga Wagner ,&nbsp;Robin Kraft ,&nbsp;Franz Nowak ,&nbsp;Dirk Berger ,&nbsp;Christian M. Günther ,&nbsp;Hüseyin Çelik ,&nbsp;Christoph T. Koch ,&nbsp;Michael Lehmann","doi":"10.1016/j.ultramic.2024.114060","DOIUrl":"10.1016/j.ultramic.2024.114060","url":null,"abstract":"<div><div>The perturbation of the reference wave due to electric stray fields represents a major challenge in quantitative electron holographic investigations. By introducing a focused-ion-beam-milled rectangular hole, the reference window, in an area of nearly constant electrostatic potential of the sample, this perturbation can be significantly reduced. The edge of the window forms a closed conducting loop, acting similarly to a Faraday cage, shielding the influence of the stray field on the reference wave to some extent. In this work, the shielding effect of the reference window is systematically investigated by comparing electron holograms of an electrically biased coplanar capacitor, as a well-known reference sample, with finite element simulations. It is shown that the introduction of the reference window into electrical biasing samples both suppresses unknown lateral phase distortions substantially and in addition improves the agreement of the experimentally observed phase slope with that expected by simulation significantly, particularly for small object-reference wave distances. Consequently, a slight adjustment of the sample geometry results in an improved reproducibility of electron holographic electrical biasing experiments, which is a significant step towards quantitative evaluation.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114060"},"PeriodicalIF":2.1,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446267","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}

{"title":"Principle of TEM alignment using convolutional neural networks: Case study on condenser aperture alignment","authors":"Loïc Grossetête ,&nbsp;Cécile Marcelot ,&nbsp;Christophe Gatel ,&nbsp;Sylvain Pauchet ,&nbsp;Martin Hytch","doi":"10.1016/j.ultramic.2024.114047","DOIUrl":"10.1016/j.ultramic.2024.114047","url":null,"abstract":"<div><div>The possibility of automatically aligning the transmission electron microscope (TEM) is explored using an approach based on artificial intelligence (AI). After presenting the general concept, we test the method on the first step of the alignment process which involves centering the condenser aperture. We propose using a convolutional neural network (CNN) that learns to predict the x and y-shifts needed to realign the aperture in one step. The learning data sets were acquired automatically on the microscope by using a simplified digital twin. Different models were tested and analysed to choose the optimal design. We have developed a human-level estimator and intend to use it safely on all apertures. A similar process could be used for most steps of the alignment process with minimal changes, allowing microscopists to reduce the time and training required to perform this task. The method is also compatible with continuous correction of alignment drift during lengthy experiments or to ensure uniformity of illumination conditions during data acquisition.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114047"},"PeriodicalIF":2.1,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142437665","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}

{"title":"Exploring deep learning models for 4D-STEM-DPC data processing","authors":"Gregory Nordahl,&nbsp;Sivert Dagenborg,&nbsp;Jørgen Sørhaug,&nbsp;Magnus Nord","doi":"10.1016/j.ultramic.2024.114058","DOIUrl":"10.1016/j.ultramic.2024.114058","url":null,"abstract":"<div><div>For the study of magnetic materials at the nanoscale, differential phase contrast (DPC) imaging is a potent tool. With the advancements in direct detector technology, and consequent popularity gain for four-dimensional scanning transmission electron microscopy (4D-STEM), there has been an ongoing development of new and enhanced ways for STEM-DPC big data processing. Conventional algorithms are experimentally tailored, and so in this article we explore how supervised learning with convolutional neural networks (CNN) can be utilized for automated and consistent processing of STEM-DPC data. Two different approaches are investigated, one with direct tracking of the beam with regression analysis, and one where a modified U-net is used for direct beam segmentation as a pre-processing step. The CNNs are trained on experimentally obtained 4D-STEM data, enabling them to effectively handle data collected under similar instrument acquisition parameters. The model outputs are compared to conventional algorithms, particularly in how they process data in the presence of strong diffraction contrast, and how they affect domain wall profiles and width measurement.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114058"},"PeriodicalIF":2.1,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142401456","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}

{"title":"Application of a novel local and automatic PCA algorithm for diffraction pattern denoising in TEM-ASTAR analysis in microelectronics","authors":"Tony Printemps,&nbsp;Karen Dabertrand,&nbsp;Jérémy Vives,&nbsp;Alexia Valery","doi":"10.1016/j.ultramic.2024.114059","DOIUrl":"10.1016/j.ultramic.2024.114059","url":null,"abstract":"<div><div>This paper introduces a novel denoising method for TEM-ASTAR™ Diffraction Pattern (DP) datasets, termed LAT–PCA (Local Automatic Thresholding – Principal Component Analysis). This approach enhances the established PCA algorithm by partitioning the 4D dataset (a 2D map of 2D DPs) into localized windows. Within these windows, PCA identifies a basis where the physical signal predominantly resides in the higher-order principal components. By thresholding lower-order components, the method effectively reduces noise while retaining the essential features of the DPs. The locality of the approach, focusing on small windows, enhances computational efficiency and aligns with the localized nature of the crystallographic grain signals in ASTAR. The automatic aspect of the method employs a theoretical pure noise distribution, i.e. a Marchenko-Pastur Distribution, to set a threshold, beyond which the components are mostly noise.</div><div>The LAT–PCA method offers significant reductions in acquisition and post-processing times. With denoised data, selecting the correct parameters for accurate phase maps and grain orientations becomes more straightforward, facilitating robust quantitative grain analysis. Experiments performed on a silicon-germanium-carbon sample validate the method's efficacy. The sample was analyzed with varying acquisition times to produce a high signal-to-noise ratio reference dataset and a lower ratio test dataset. The LAT–PCA algorithm's denoising results on the test dataset were benchmarked against the reference, demonstrating considerable improvements and reliability.</div><div>In summary, LAT–PCA is an effective, automatic solution for denoising TEM DP datasets. Its adaptability to different noise levels and local processing capability makes it a valuable tool for enhancing dataset quality and reducing the time required for data acquisition and analysis. This method can minimize acquisition time, conserve microscope usage, and reduce sample drift and deterioration, leading to more accurate characterizations with fewer deformation artifacts.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114059"},"PeriodicalIF":2.1,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142381747","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}