Pub Date : 2024-10-18DOI: 10.1016/j.ultramic.2024.114062
Glenn C. Sneddon , Patrick W. Trimby , Levi Tegg , Julie M. Cairney
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.
{"title":"Parameter dependence of depth and lateral resolution of transmission Kikuchi diffraction","authors":"Glenn C. Sneddon , Patrick W. Trimby , Levi Tegg , 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}
Pub Date : 2024-10-11DOI: 10.1016/j.ultramic.2024.114060
Tolga Wagner , Robin Kraft , Franz Nowak , Dirk Berger , Christian M. Günther , Hüseyin Çelik , Christoph T. Koch , Michael Lehmann
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.
{"title":"The reference window for reduced perturbation of the reference wave in electrical biasing off-axis electron holography","authors":"Tolga Wagner , Robin Kraft , Franz Nowak , Dirk Berger , Christian M. Günther , Hüseyin Çelik , Christoph T. Koch , 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}
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.
我们采用一种基于人工智能（AI）的方法，探讨了自动对准透射电子显微镜（TEM）的可能性。在介绍了总体概念之后，我们在对准过程的第一步对该方法进行了测试，这一步涉及将聚光器光圈对准中心。我们建议使用卷积神经网络 (CNN)，通过学习来预测在一个步骤中重新对准光圈所需的 x 和 y 移位。学习数据集是在显微镜上使用简化的数字孪生系统自动获取的。我们对不同的模型进行了测试和分析，以选择最佳设计。我们已经开发出一种人类水平的估算器，并打算将其安全地用于所有光圈。类似的过程可用于校准过程中的大多数步骤，只需做出最小的改动，从而使显微镜操作员能够减少执行这项任务所需的时间和培训。该方法还可用于在长时间实验过程中持续校正对准漂移，或在数据采集过程中确保照明条件的一致性。
{"title":"Principle of TEM alignment using convolutional neural networks: Case study on condenser aperture alignment","authors":"Loïc Grossetête , Cécile Marcelot , Christophe Gatel , Sylvain Pauchet , 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}
Pub Date : 2024-10-05DOI: 10.1016/j.ultramic.2024.114058
Gregory Nordahl, Sivert Dagenborg, Jørgen Sørhaug, Magnus Nord
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.
在纳米尺度的磁性材料研究中，差分相衬（DPC）成像是一种有效的工具。随着直接探测器技术的进步和四维扫描透射电子显微镜（4D-STEM）的普及，STEM-DPC 大数据处理的新方法和增强方法也在不断发展。传统算法都是根据实验量身定制的，因此在本文中，我们将探讨如何利用卷积神经网络（CNN）进行监督学习，以实现 STEM-DPC 数据的自动化和一致性处理。我们研究了两种不同的方法，一种是通过回归分析直接跟踪光束，另一种是在预处理步骤中使用改进的 U 网直接分割光束。CNN 在实验获得的 4D-STEM 数据上进行了训练，使其能够有效处理在类似仪器采集参数下收集的数据。模型输出结果与传统算法进行了比较，特别是在出现强烈衍射对比的情况下如何处理数据，以及如何影响畴壁轮廓和宽度测量。
{"title":"Exploring deep learning models for 4D-STEM-DPC data processing","authors":"Gregory Nordahl, Sivert Dagenborg, Jørgen Sørhaug, 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}
Pub Date : 2024-10-01DOI: 10.1016/j.ultramic.2024.114059
Tony Printemps, Karen Dabertrand, Jérémy Vives, Alexia Valery
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.
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.
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.
{"title":"Application of a novel local and automatic PCA algorithm for diffraction pattern denoising in TEM-ASTAR analysis in microelectronics","authors":"Tony Printemps, Karen Dabertrand, Jérémy Vives, 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}
Pub Date : 2024-09-28DOI: 10.1016/j.ultramic.2024.114057
Hüseyin Çelik , Robert Fuchs , Simon Gaebel , Christian M. Günther , Michael Lehmann , Tolga Wagner
Electron holography is a powerful tool to investigate the properties of micro- and nanostructured electronic devices. A meaningful interpretation of the holographic data, however, requires an understanding of the 3D potential distribution inside and outside the sample. Standard approaches to resolve these potential distributions involve projective tilt series and their tomographic reconstruction, in addition to extensive simulations. Here, a simple and intuitive model for the approximation of such long-range potential distributions surrounding a nanostructured coplanar capacitor is presented. The model uses only independent convolutions of an initial potential distribution with a Gaussian kernel, allowing the reconstruction of the entire potential distribution from only one measured projection. By this, a significant reduction of the required computational power as well as a drastically simplified measurement process is achieved, paving the way towards quantitative electron holographic investigation of electrically biased nanostructures.
{"title":"A simple and intuitive model for long-range 3D potential distributions of in-operando TEM-samples: Comparison with electron holographic tomography","authors":"Hüseyin Çelik , Robert Fuchs , Simon Gaebel , Christian M. Günther , Michael Lehmann , Tolga Wagner","doi":"10.1016/j.ultramic.2024.114057","DOIUrl":"10.1016/j.ultramic.2024.114057","url":null,"abstract":"<div><div>Electron holography is a powerful tool to investigate the properties of micro- and nanostructured electronic devices. A meaningful interpretation of the holographic data, however, requires an understanding of the 3D potential distribution inside and outside the sample. Standard approaches to resolve these potential distributions involve projective tilt series and their tomographic reconstruction, in addition to extensive simulations. Here, a simple and intuitive model for the approximation of such long-range potential distributions surrounding a nanostructured coplanar capacitor is presented. The model uses only independent convolutions of an initial potential distribution with a Gaussian kernel, allowing the reconstruction of the entire potential distribution from only one measured projection. By this, a significant reduction of the required computational power as well as a drastically simplified measurement process is achieved, paving the way towards quantitative electron holographic investigation of electrically biased nanostructures.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114057"},"PeriodicalIF":2.1,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142366704","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 : 2024-09-21DOI: 10.1016/j.ultramic.2024.114055
Grzegorz Cios , Aimo Winkelmann , Gert Nolze , Tomasz Tokarski , Benedykt R. Jany , Piotr Bała
Electron backscatter diffraction (EBSD) patterns can exhibit Kikuchi bands with inverted contrast due to anomalous absorption. This can be observed, for example, on samples with nanoscale topography, in case of a low tilt backscattering geometry, or for transmission Kikuchi diffraction (TKD) on thicker samples. Three examples are discussed where contrast-inverted physics-based simulated master patterns have been applied to find the correct crystal orientation. As first EBSD example, self-assembled gold nanostructures made of Au fcc and Au hcp phases on single-crystal germanium were investigated. Gold covered about 12% of the mapped area, with only two thirds being successfully interpreted using standard Hough-based indexing. The remaining third was solved by brute force indexing using a contrast-inverted master pattern. The second EBSD example deals with maps collected at a non-tilted surface instead of the commonly used 70° tilted one. As TKD example, a jet-polished foil made of duplex stainless steel 2205 was examined. The thin part close to the hole edge producing normal-contrast patterns were standard indexed. The areas of the foil that become thicker with increasing distance from the edge of the hole produce contrast-inverted patterns. They covered three times the evaluable area and were successfully processed using the contrast-inverted master pattern. In the last example, inverted patterns collected at a non-tiled sample were mathematically inverted to normal contrast, and Hough/Radon-based indexing was successfully applied.
{"title":"EBSD and TKD analyses using inverted contrast Kikuchi diffraction patterns and alternative measurement geometries","authors":"Grzegorz Cios , Aimo Winkelmann , Gert Nolze , Tomasz Tokarski , Benedykt R. Jany , Piotr Bała","doi":"10.1016/j.ultramic.2024.114055","DOIUrl":"10.1016/j.ultramic.2024.114055","url":null,"abstract":"<div><div>Electron backscatter diffraction (EBSD) patterns can exhibit Kikuchi bands with inverted contrast due to anomalous absorption. This can be observed, for example, on samples with nanoscale topography, in case of a low tilt backscattering geometry, or for transmission Kikuchi diffraction (TKD) on thicker samples. Three examples are discussed where contrast-inverted physics-based simulated master patterns have been applied to find the correct crystal orientation. As first EBSD example, self-assembled gold nanostructures made of Au fcc and Au hcp phases on single-crystal germanium were investigated. Gold covered about 12% of the mapped area, with only two thirds being successfully interpreted using standard Hough-based indexing. The remaining third was solved by brute force indexing using a contrast-inverted master pattern. The second EBSD example deals with maps collected at a non-tilted surface instead of the commonly used 70° tilted one. As TKD example, a jet-polished foil made of duplex stainless steel 2205 was examined. The thin part close to the hole edge producing normal-contrast patterns were standard indexed. The areas of the foil that become thicker with increasing distance from the edge of the hole produce contrast-inverted patterns. They covered three times the evaluable area and were successfully processed using the contrast-inverted master pattern. In the last example, inverted patterns collected at a non-tiled sample were mathematically inverted to normal contrast, and Hough/Radon-based indexing was successfully applied.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114055"},"PeriodicalIF":2.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0304399124001347/pdfft?md5=805f0bcd2116a88f646294acc77c2b2c&pid=1-s2.0-S0304399124001347-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314617","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 : 2024-09-19DOI: 10.1016/j.ultramic.2024.114051
Ying-Xin Liang
In this work, a design of transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. TIA with the tip-sample component in CryoSTM is called as CryoSTM-TIA. With transimpedance gain of 1 G, the bandwidth of the CryoSTM-TIA is larger than 200 kHz. The distinctive feature of the proposed CryoSTM-TIA is that its pre-amplifier is made of a single cryogenic high electron mobility transistor (HEMT), so the apparatus equivalent input noise current power spectral density at 100 kHz is lower than 6 (fA)/Hz. In addition, “bias-cooling method” can be used to in-situ control the density of the frozen DX centers in the HEMT doping area, changing its structure to reduce the device noises. With this apparatus, fast scanning tunneling spectra measurements with high-energy-resolution are capable to be performed. And, it is capable to measure scanning tunneling shot noise spectra (STSNS) at the atomic scale for various quantum systems, even if the shot noise is very low. It provides a powerful tool to investigate novel quantum states by measuring STSNS, such as detecting the existence of Majorana bound states in the topological quantum systems.
{"title":"Ultra-low-noise transimpedance amplifier with a single HEMT in pre-amplifier for measuring shot noise in cryogenic STM","authors":"Ying-Xin Liang","doi":"10.1016/j.ultramic.2024.114051","DOIUrl":"10.1016/j.ultramic.2024.114051","url":null,"abstract":"<div><div>In this work, a design of transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. TIA with the tip-sample component in CryoSTM is called as CryoSTM-TIA. With transimpedance gain of 1 G<span><math><mi>Ω</mi></math></span>, the bandwidth of the CryoSTM-TIA is larger than 200 kHz. The distinctive feature of the proposed CryoSTM-TIA is that its pre-amplifier is made of a single cryogenic high electron mobility transistor (HEMT), so the apparatus equivalent input noise current power spectral density at 100 kHz is lower than 6 (fA)<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>/Hz. In addition, “bias-cooling method” can be used to in-situ control the density of the frozen DX<span><math><msup><mrow></mrow><mrow><mo>−</mo></mrow></msup></math></span> centers in the HEMT doping area, changing its structure to reduce the device noises. With this apparatus, fast scanning tunneling spectra measurements with high-energy-resolution are capable to be performed. And, it is capable to measure scanning tunneling shot noise spectra (STSNS) at the atomic scale for various quantum systems, even if the shot noise is very low. It provides a powerful tool to investigate novel quantum states by measuring STSNS, such as detecting the existence of Majorana bound states in the topological quantum systems.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114051"},"PeriodicalIF":2.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328350","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 : 2024-09-19DOI: 10.1016/j.ultramic.2024.114056
Jonathan J.P. Peters , Tiarnan Mullarkey , Julie Marie Bekkevold , Matthew Geever , Ryo Ishikawa , Naoya Shibata , Lewys Jones
Faster scanning in scanning transmission electron microscopy has long been desired for the ability to better control dose, minimise effects of environmental distortions, and to capture the dynamics of in-situ experiments. Advances in scan controllers and scan deflection systems have enabled scanning with pixel dwell times on the order of tens of nanoseconds. At these speeds, the finite response time of the electron detector must be considered as the signal from one electron detection event can contribute to multiple pixels, blurring the features within the image. Here we introduce a temporal transfer function (TTF) to describe and model the effects of detector response time on imaging, as well as a framework for incorporating these effects into simulation.
{"title":"On the temporal transfer function in STEM imaging from finite detector response time","authors":"Jonathan J.P. Peters , Tiarnan Mullarkey , Julie Marie Bekkevold , Matthew Geever , Ryo Ishikawa , Naoya Shibata , Lewys Jones","doi":"10.1016/j.ultramic.2024.114056","DOIUrl":"10.1016/j.ultramic.2024.114056","url":null,"abstract":"<div><div>Faster scanning in scanning transmission electron microscopy has long been desired for the ability to better control dose, minimise effects of environmental distortions, and to capture the dynamics of in-situ experiments. Advances in scan controllers and scan deflection systems have enabled scanning with pixel dwell times on the order of tens of nanoseconds. At these speeds, the finite response time of the electron detector must be considered as the signal from one electron detection event can contribute to multiple pixels, blurring the features within the image. Here we introduce a temporal transfer function (TTF) to describe and model the effects of detector response time on imaging, as well as a framework for incorporating these effects into simulation.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114056"},"PeriodicalIF":2.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328158","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 : 2024-09-18DOI: 10.1016/j.ultramic.2024.114052
Cedric Shaskey , Amun Jarzembski , Andrew Jue , Keunhan Park
Miniaturized quartz tuning forks (QTFs) have been adopted as force sensors for non-contact atomic force microscopy (AFM). However, the coupled oscillation behaviors of the QTF prongs are not well understood, preventing quantitative measurement of the nanoscale tip-sample interaction forces. This article presents a lumped model that accurately delineates the coupled mechanical oscillations of QTF prongs, establishing rigorous relationships between experimental observables and tip-sample interaction forces. The first-order resonance spectra of a commercial QTF were fully characterized by correlating its piezoelectric response with the actual mechanical oscillation measured with a Fabry-Pérot interferometer. In order to uniquely determine the modeling parameters (i.e., the effective masses, spring constants, and damping constants), the experimental results were compared with the lumped model predictions while masses were added to one prong. The results reveal that the QTF’s center of mass is highly damped, preventing the observation of a symmetric resonance mode. In addition, the mass loading experiment demonstrates that the mechanical oscillations of the QTF prongs are strongly coupled, accounting for 59% (84%) of the effective stiffness at the in-plane (out-of-plane), antisymmetric resonance mode. We believe that the obtained QTF characterization results will pave the way for quantitative measurements of non-contact interaction forces in QTF-based AFM platforms, significantly improving the precision and reliability of nanoscale force measurements.
{"title":"Characterization of strongly coupled quartz tuning fork sensors for precision force measurement in atomic force microscopy","authors":"Cedric Shaskey , Amun Jarzembski , Andrew Jue , Keunhan Park","doi":"10.1016/j.ultramic.2024.114052","DOIUrl":"10.1016/j.ultramic.2024.114052","url":null,"abstract":"<div><p>Miniaturized quartz tuning forks (QTFs) have been adopted as force sensors for non-contact atomic force microscopy (AFM). However, the coupled oscillation behaviors of the QTF prongs are not well understood, preventing quantitative measurement of the nanoscale tip-sample interaction forces. This article presents a lumped model that accurately delineates the coupled mechanical oscillations of QTF prongs, establishing rigorous relationships between experimental observables and tip-sample interaction forces. The first-order resonance spectra of a commercial QTF were fully characterized by correlating its piezoelectric response with the actual mechanical oscillation measured with a Fabry-Pérot interferometer. In order to uniquely determine the modeling parameters (i.e., the effective masses, spring constants, and damping constants), the experimental results were compared with the lumped model predictions while masses were added to one prong. The results reveal that the QTF’s center of mass is highly damped, preventing the observation of a symmetric resonance mode. In addition, the mass loading experiment demonstrates that the mechanical oscillations of the QTF prongs are strongly coupled, accounting for 59% (84%) of the effective stiffness at the in-plane (out-of-plane), antisymmetric resonance mode. We believe that the obtained QTF characterization results will pave the way for quantitative measurements of non-contact interaction forces in QTF-based AFM platforms, significantly improving the precision and reliability of nanoscale force measurements.</p></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"267 ","pages":"Article 114052"},"PeriodicalIF":2.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142271112","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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