Pub Date : 2025-12-26DOI: 10.1016/j.ultramic.2025.114305
Dana O. Byrne , Stephanie M. Ribet , Demie Kepaptsoglou , Quentin M. Ramasse , Colin Ophus , Frances I. Allen
Tetravacancies in monolayer hexagonal boron nitride (hBN) with consistent edge termination (boron or nitrogen) form triangular nanopores with electrostatic potentials that can be leveraged for applications such as selective ion transport and neuromorphic computing. In order to quantitatively predict the properties of these structures, an atomic-level understanding of their local electronic and chemical environments is required. Moreover, robust methods for their precision manufacture are needed. Here we use electron irradiation in a scanning transmission electron microscope (STEM) at a high dose rate to drive the formation of boron-terminated tetravacancies in monolayer hBN. Characterization of the defects is achieved using aberration-corrected STEM, monochromated electron energy-loss spectroscopy (EELS), and electron ptychography. Z-contrast in STEM and chemical fingerprinting by core-loss EELS enable identification of the edge terminations, while electron ptychography gives insight into structural relaxation of the tetravacancies and provides evidence of enhanced electron density around the defect perimeters indicative of bonding effects.
{"title":"Fabrication and characterization of boron-terminated tetravacancies in monolayer hBN using STEM, EELS and electron ptychography","authors":"Dana O. Byrne , Stephanie M. Ribet , Demie Kepaptsoglou , Quentin M. Ramasse , Colin Ophus , Frances I. Allen","doi":"10.1016/j.ultramic.2025.114305","DOIUrl":"10.1016/j.ultramic.2025.114305","url":null,"abstract":"<div><div>Tetravacancies in monolayer hexagonal boron nitride (hBN) with consistent edge termination (boron or nitrogen) form triangular nanopores with electrostatic potentials that can be leveraged for applications such as selective ion transport and neuromorphic computing. In order to quantitatively predict the properties of these structures, an atomic-level understanding of their local electronic and chemical environments is required. Moreover, robust methods for their precision manufacture are needed. Here we use electron irradiation in a scanning transmission electron microscope (STEM) at a high dose rate to drive the formation of boron-terminated tetravacancies in monolayer hBN. Characterization of the defects is achieved using aberration-corrected STEM, monochromated electron energy-loss spectroscopy (EELS), and electron ptychography. Z-contrast in STEM and chemical fingerprinting by core-loss EELS enable identification of the edge terminations, while electron ptychography gives insight into structural relaxation of the tetravacancies and provides evidence of enhanced electron density around the defect perimeters indicative of bonding effects.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"282 ","pages":"Article 114305"},"PeriodicalIF":2.0,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897877","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}
Scanning tunneling microscopy (STM) has significantly influenced the fields of nanoscience and nanotechnology. However, the tip effect and thermal drift cause loss and distortion of data in the STM images. Here, we propose a physics-guided optimization model for extracting STM imaging parameters, including tip shape, thermal drift, depth of field, current, and height. The model uses partial charge densities from density functional theory (DFT) simulation and works based on the mass comparison of experimental and simulated images using a two-dimensional Pearson correlation. Testing the model on Si(111)-7 × 7 reconstruction images provided higher than 96 % correlations for both biases. The fitting showed the highest correlation for only two bands in each image instead of the integration of all bands. Gaussian functions were used in the model to simulate the tip effect, which could recover 1.5-6 % of the lost data due to the blurring effect. Additionally, thermal drift was detected and corrected in the negative bias image, which could linearly distort the data by about 19 %. An important advantage of using this model is increasing the microscopy speed because there is no need to slow down the scanning process in microscopy experiments to evade thermal drift.
{"title":"A correlation-based optimization model to recover lost and distorted data from scanning tunneling microscopy images based on density functional theory","authors":"Ehsan Moradpur-Tari , Andreas Kyritsakis , Mohadeseh Karimkhah , Veronika Zadin","doi":"10.1016/j.ultramic.2025.114306","DOIUrl":"10.1016/j.ultramic.2025.114306","url":null,"abstract":"<div><div>Scanning tunneling microscopy (STM) has significantly influenced the fields of nanoscience and nanotechnology. However, the tip effect and thermal drift cause loss and distortion of data in the STM images. Here, we propose a physics-guided optimization model for extracting STM imaging parameters, including tip shape, thermal drift, depth of field, current, and height. The model uses partial charge densities from density functional theory (DFT) simulation and works based on the mass comparison of experimental and simulated images using a two-dimensional Pearson correlation. Testing the model on Si(111)-7 × 7 reconstruction images provided higher than 96 % correlations for both biases. The fitting showed the highest correlation for only two bands in each image instead of the integration of all bands. Gaussian functions were used in the model to simulate the tip effect, which could recover 1.5-6 % of the lost data due to the blurring effect. Additionally, thermal drift was detected and corrected in the negative bias image, which could linearly distort the data by about 19 %. An important advantage of using this model is increasing the microscopy speed because there is no need to slow down the scanning process in microscopy experiments to evade thermal drift.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"281 ","pages":"Article 114306"},"PeriodicalIF":2.0,"publicationDate":"2025-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884239","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}
Pixelated differential phase contrast (DPC) is a four-dimensional scanning transmission electron microscopy (4D-STEM) technique in which the position of the transmitted beam is tracked to reconstruct the electromagnetic fields of a sample. Although it can provide (semi-) quantitative information for a range of different applications, the measurements are greatly affected by the microscope’s optical and acquisition settings in terms of sensitivity, accuracy, and spatial resolution, particularly when measuring weak electric fields. Herein, we focus on the nano-beam 4D-STEM configuration and systematically study the way in which all the parameters typically selected by users for pixelated-DPC experiments influence the lowest achievable electric field sensitivity. First, we define the metric by which the sensitivity is assessed, discussing the optimal ranges for parameters including convergence semi-angle, electron dose, and camera length in absence of external field, while also evaluating the effect of the scanning system. Next, the sensitivity and its error are assessed under field-bound conditions, realized by a coplanar capacitor that allows the position of the transmitted beam to be shifted controllably using an external bias. Comparison of the experimental results with finite element method calculations yields quantitative information about the accuracy that can be attained for these measurements, while the effects of microscope drift and sample charging are also discussed. Our findings provide a platform for the quantitative assessment of weak electric fields as calculated by pixelated-DPC experiments, while highlighting the challenges associated with these measurements.
{"title":"Assessing the electric field sensitivity measured by pixelated differential phase contrast imaging in vacuum both in the absence of external fields and under field-bound conditions","authors":"Pierpaolo Ranieri , Reinis Ignatans , Victor Boureau , Vasiliki Tileli","doi":"10.1016/j.ultramic.2025.114307","DOIUrl":"10.1016/j.ultramic.2025.114307","url":null,"abstract":"<div><div>Pixelated differential phase contrast (DPC) is a four-dimensional scanning transmission electron microscopy (4D-STEM) technique in which the position of the transmitted beam is tracked to reconstruct the electromagnetic fields of a sample. Although it can provide (semi-) quantitative information for a range of different applications, the measurements are greatly affected by the microscope’s optical and acquisition settings in terms of sensitivity, accuracy, and spatial resolution, particularly when measuring weak electric fields. Herein, we focus on the nano-beam 4D-STEM configuration and systematically study the way in which all the parameters typically selected by users for pixelated-DPC experiments influence the lowest achievable electric field sensitivity. First, we define the metric by which the sensitivity is assessed, discussing the optimal ranges for parameters including convergence semi-angle, electron dose, and camera length in absence of external field, while also evaluating the effect of the scanning system. Next, the sensitivity and its error are assessed under field-bound conditions, realized by a coplanar capacitor that allows the position of the transmitted beam to be shifted controllably using an external bias. Comparison of the experimental results with finite element method calculations yields quantitative information about the accuracy that can be attained for these measurements, while the effects of microscope drift and sample charging are also discussed. Our findings provide a platform for the quantitative assessment of weak electric fields as calculated by pixelated-DPC experiments, while highlighting the challenges associated with these measurements.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"281 ","pages":"Article 114307"},"PeriodicalIF":2.0,"publicationDate":"2025-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884240","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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