Pub Date : 2025-09-01DOI: 10.1016/j.ultramic.2025.114229
Ka Yin Lee , Elliot K. Beutler , Tifany Q. Crisolo , David J. Masiello , Maureen J. Lagos
Using vibrational electron energy loss spectroscopy (vib-EELS) combined with numerical modeling, we investigate the physical mechanisms governing the phonon coupling between a spherical particle sustaining multipolar surface phonon modes and an underlying thin film. Depending upon their dielectric composition, a variety of hybrid phonon modes arise in the EEL spectrum due to the interaction between polarization charges in the particle and film. Mirror charge effects and phonon mode hybridization are the active mechanisms acting on dielectric and metallic-type films, respectively. Processes beyond dipole-dipole interactions are required to describe the sphere-film coupling.
{"title":"Substrate matters: Coupled phonon modes of a spherical particle on a substrate probed with EELS","authors":"Ka Yin Lee , Elliot K. Beutler , Tifany Q. Crisolo , David J. Masiello , Maureen J. Lagos","doi":"10.1016/j.ultramic.2025.114229","DOIUrl":"10.1016/j.ultramic.2025.114229","url":null,"abstract":"<div><div>Using vibrational electron energy loss spectroscopy (vib-EELS) combined with numerical modeling, we investigate the physical mechanisms governing the phonon coupling between a spherical particle sustaining multipolar surface phonon modes and an underlying thin film. Depending upon their dielectric composition, a variety of hybrid phonon modes arise in the EEL spectrum due to the interaction between polarization charges in the particle and film. Mirror charge effects and phonon mode hybridization are the active mechanisms acting on dielectric and metallic-type films, respectively. Processes beyond dipole-dipole interactions are required to describe the sphere-film coupling.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"278 ","pages":"Article 114229"},"PeriodicalIF":2.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145060889","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 : 2025-08-26DOI: 10.1016/j.ultramic.2025.114227
Fan Peng , Xuemei Song , Yiling Huang , Xingyu Jin , Yuqing Jiang , Yue Sun , Yi Zeng
Electron backscatter diffraction (EBSD) is an important technique based on the scanning electron microscope (SEM) that provides a wide range of crystallographic information. There are limited available pattern indexing methods and most of them are mastered by commercial instrument manufacturers, which may probably restrict the sharing and development of indexing techniques. In this study, we present a new EBSD pattern indexing method based on a three-dimensional parameter space. This method extends the characterization of characteristic triangles into a three-dimensional parameter space. This work details the procedure of the new indexing algorithm. The utility of this new method is demonstrated using experimental patterns captured from a cubic yttria-stabilized zirconia (YSZ) bulk sample. Compared with commercial indexing results, the new method shows excellent consistency and achieves better indexing performance at grain boundaries.
{"title":"A new EBSD indexing method with enhanced grain boundary indexing performance using a three-dimensional parameter space","authors":"Fan Peng , Xuemei Song , Yiling Huang , Xingyu Jin , Yuqing Jiang , Yue Sun , Yi Zeng","doi":"10.1016/j.ultramic.2025.114227","DOIUrl":"10.1016/j.ultramic.2025.114227","url":null,"abstract":"<div><div>Electron backscatter diffraction (EBSD) is an important technique based on the scanning electron microscope (SEM) that provides a wide range of crystallographic information. There are limited available pattern indexing methods and most of them are mastered by commercial instrument manufacturers, which may probably restrict the sharing and development of indexing techniques. In this study, we present a new EBSD pattern indexing method based on a three-dimensional parameter space. This method extends the characterization of characteristic triangles into a three-dimensional parameter space. This work details the procedure of the new indexing algorithm. The utility of this new method is demonstrated using experimental patterns captured from a cubic yttria-stabilized zirconia (YSZ) bulk sample. Compared with commercial indexing results, the new method shows excellent consistency and achieves better indexing performance at grain boundaries.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114227"},"PeriodicalIF":2.0,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144907275","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 : 2025-08-25DOI: 10.1016/j.ultramic.2025.114228
Po-Cheng Kung , Rui Feng , Peter Liaw , Jian-Min Zuo , Jessica Krogstad
Complex face-centered-cubic (FCC) alloys frequently display chemical short-range ordering (CSRO), which can be detected through the analysis of diffuse scattering. However, the interpretation of diffuse scattering is complicated by the presence of defects and thermal diffuse scattering, making it extremely challenging to distinguish CSRO using conventional scattering techniques. This complexity has sparked intense debates regarding the origin of specific diffuse-scattering signals, such as those observed at 1/3{422} and 1/2{311} positions. To address this challenge, we introduce the method of spatial fluctuation and correlation (FluCor) analysis of local diffuse scattering captured using Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM). We demonstrate our methodology using a solution-treated (CrCoNi)93Al4Ti2Nb medium-entropy alloy (MEA) and show that the FluCor analysis can differentiate diffuse scattering of different origins. The results reveal two sets of overlapping diffuse-scattering signals at the 1/3{422} and 1/2{311} positions in the studied MEA and link both to non-CSRO origins. Specifically, the heterogeneous-domain diffuse-scattering signals are attributed to nanoscale planar defects, while the homogeneous diffuse-scattering of the matrix is best explained by thermal-diffuse scattering. The principles underlying our fluctuation and correlation analysis of diffuse scattering are general and broadly applicable to order-disordered crystals, including various complex alloy systems. This versatility promises to yield valuable insights into the interplay between microstructural characteristics and CSRO behavior in a wide range of materials, potentially resolving long-standing debates in the field.
{"title":"Differentiating electron diffuse scattering via 4D-STEM spatial fluctuation and correlation analysis in complex FCC alloys","authors":"Po-Cheng Kung , Rui Feng , Peter Liaw , Jian-Min Zuo , Jessica Krogstad","doi":"10.1016/j.ultramic.2025.114228","DOIUrl":"10.1016/j.ultramic.2025.114228","url":null,"abstract":"<div><div>Complex face-centered-cubic (FCC) alloys frequently display chemical short-range ordering (CSRO), which can be detected through the analysis of diffuse scattering. However, the interpretation of diffuse scattering is complicated by the presence of defects and thermal diffuse scattering, making it extremely challenging to distinguish CSRO using conventional scattering techniques. This complexity has sparked intense debates regarding the origin of specific diffuse-scattering signals, such as those observed at 1/3{422} and 1/2{311} positions. To address this challenge, we introduce the method of spatial fluctuation and correlation (FluCor) analysis of local diffuse scattering captured using Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM). We demonstrate our methodology using a solution-treated (CrCoNi)<sub>93</sub>Al<sub>4</sub>Ti<sub>2</sub>Nb medium-entropy alloy (MEA) and show that the FluCor analysis can differentiate diffuse scattering of different origins. The results reveal two sets of overlapping diffuse-scattering signals at the 1/3{422} and 1/2{311} positions in the studied MEA and link both to non-CSRO origins. Specifically, the heterogeneous-domain diffuse-scattering signals are attributed to nanoscale planar defects, while the homogeneous diffuse-scattering of the matrix is best explained by thermal-diffuse scattering. The principles underlying our fluctuation and correlation analysis of diffuse scattering are general and broadly applicable to order-disordered crystals, including various complex alloy systems. This versatility promises to yield valuable insights into the interplay between microstructural characteristics and CSRO behavior in a wide range of materials, potentially resolving long-standing debates in the field.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"278 ","pages":"Article 114228"},"PeriodicalIF":2.0,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144996997","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 : 2025-08-23DOI: 10.1016/j.ultramic.2025.114225
Songge Li , Nicolas Gauquelin , Hoelen L. Lalandec Robert , Arno Annys , Chuang Gao , Christoph Hofer , Timothy J. Pennycook , Jo Verbeeck
The single sideband (SSB) framework of analytical electron ptychography can account for the presence of residual geometrical aberrations induced by the probe-forming lens. However, the accuracy of this aberration correction method is highly sensitive to the invested electron dose, in part due to the necessity of phase unwrapping. In this work, we thus propose two strategies to improve the performance in low-dose conditions: confining phase unwrapping within the sidebands and selecting only well-unwrapped sidebands for calculating aberration coefficients. These strategies are validated through SSB reconstructions of both simulated and experimental 4D-STEM datasets of monolayer tungsten diselenide (WSe2). A comparison of results demonstrates significant improvements in Poisson noise tolerance, making aberration correction more robust and reliable for low-dose imaging.
{"title":"Improving the low-dose performance of aberration correction in single sideband ptychography","authors":"Songge Li , Nicolas Gauquelin , Hoelen L. Lalandec Robert , Arno Annys , Chuang Gao , Christoph Hofer , Timothy J. Pennycook , Jo Verbeeck","doi":"10.1016/j.ultramic.2025.114225","DOIUrl":"10.1016/j.ultramic.2025.114225","url":null,"abstract":"<div><div>The single sideband (SSB) framework of analytical electron ptychography can account for the presence of residual geometrical aberrations induced by the probe-forming lens. However, the accuracy of this aberration correction method is highly sensitive to the invested electron dose, in part due to the necessity of phase unwrapping. In this work, we thus propose two strategies to improve the performance in low-dose conditions: confining phase unwrapping within the sidebands and selecting only well-unwrapped sidebands for calculating aberration coefficients. These strategies are validated through SSB reconstructions of both simulated and experimental 4D-STEM datasets of monolayer tungsten diselenide (WSe<sub>2</sub>). A comparison of results demonstrates significant improvements in Poisson noise tolerance, making aberration correction more robust and reliable for low-dose imaging.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114225"},"PeriodicalIF":2.0,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144896513","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 : 2025-08-19DOI: 10.1016/j.ultramic.2025.114222
Florian Castioni , Patrick Quéméré , Sergi Cuesta , Vincent Delaye , Pascale Bayle-Guillemaud , Eva Monroy , Eric Robin , Nicolas Bernier
Recent advancements in high-resolution spectroscopy analyses within the scanning transmission electron microscope (STEM) have paved the way for measuring the concentration of chemical species in crystalline materials at the atomic scale. However, several artifacts complicate the direct interpretation of experimental data. For instance, in the case of energy-dispersive X-ray (EDX) spectroscopy, the linear dependency of local X-ray emission on composition is disrupted by channeling effects and cross-talk during electron beam propagation. To address these challenges, it becomes necessary to adopt an approach that combines experimental data with inelastic scattering simulations. This method aims to account for the effects of electron beam propagation on X-ray emission, essentially determining the quantity and the spatial origin of the collected signal. In this publication, we propose to assess the precision and sensitivity limits of this approach in a practical case study involving a focused ion beam (FIB)-prepared III-N multilayers device. The device features nominally pure ∼1.5-nm-wide GaN quantum wells surrounded by AlGaN barriers containing a low concentration of aluminum (∼5 at%). By employing atomic-scale EDX acquisitions based on the averaging of more than several thousand frames, calibrated factors combined with a multilayer X-ray absorption correction model for quantification, and by comparing the X-ray radiation obtained from the quantum well with a reference 10-nm-wide structure, we demonstrate that the quantitative impact of beam propagation on chemical composition can be precisely accounted for, resulting in a composition sensitivity at the atomic scale as low as 0.25 at%. Finally, practical aspects to achieve this high precision level are discussed, particularly in terms of inelastic multislice simulation, uncertainty determination, and sample quality.
{"title":"Impact of electron beam propagation on high-resolution quantitative chemical analysis of 1-nm-wide GaN/AlGaN quantum wells","authors":"Florian Castioni , Patrick Quéméré , Sergi Cuesta , Vincent Delaye , Pascale Bayle-Guillemaud , Eva Monroy , Eric Robin , Nicolas Bernier","doi":"10.1016/j.ultramic.2025.114222","DOIUrl":"10.1016/j.ultramic.2025.114222","url":null,"abstract":"<div><div>Recent advancements in high-resolution spectroscopy analyses within the scanning transmission electron microscope (STEM) have paved the way for measuring the concentration of chemical species in crystalline materials at the atomic scale. However, several artifacts complicate the direct interpretation of experimental data. For instance, in the case of energy-dispersive X-ray (EDX) spectroscopy, the linear dependency of local X-ray emission on composition is disrupted by channeling effects and cross-talk during electron beam propagation. To address these challenges, it becomes necessary to adopt an approach that combines experimental data with inelastic scattering simulations. This method aims to account for the effects of electron beam propagation on X-ray emission, essentially determining the quantity and the spatial origin of the collected signal. In this publication, we propose to assess the precision and sensitivity limits of this approach in a practical case study involving a focused ion beam (FIB)-prepared III-N multilayers device. The device features nominally pure ∼1.5-nm-wide GaN quantum wells surrounded by AlGaN barriers containing a low concentration of aluminum (∼5 at%). By employing atomic-scale EDX acquisitions based on the averaging of more than several thousand frames, calibrated <span><math><mrow><mi>ζ</mi></mrow></math></span> factors combined with a multilayer X-ray absorption correction model for quantification, and by comparing the X-ray radiation obtained from the quantum well with a reference 10-nm-wide structure, we demonstrate that the quantitative impact of beam propagation on chemical composition can be precisely accounted for, resulting in a composition sensitivity at the atomic scale as low as <span><math><mo>±</mo></math></span>0.25 at%. Finally, practical aspects to achieve this high precision level are discussed, particularly in terms of inelastic multislice simulation, uncertainty determination, and sample quality.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114222"},"PeriodicalIF":2.0,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144907274","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}
We have developed an operando laser-based photoemission electron microscope (laser-PEEM) with a ferroelectric characterization system. A Sawyer-Tower circuit was implemented to measure the polarization–voltage (P–V) characteristics of ferroelectric devices. Using this system, we successfully obtained the well-defined P–V hysteresis loops for a ferroelectric capacitor incorporating Hf0.5Zr0.5O2 (HZO), reproducing the typical field-cycling characteristics of HZO capacitors. After dielectric breakdown caused by field-cycling stress, we visualized a conduction filament through the top electrode without any destructive processing. Additionally, we successfully observed polarization contrast through the top electrode of an oxide semiconductor (InZnOx). These results indicate that our operando laser-PEEM system is a powerful tool for visualizing conduction filaments after dielectric breakdown, the ferroelectric polarization contrasts, and electronic state distribution of materials implemented in ferroelectric devices, including ferroelectric field-effect transistors and ferroelectric tunnel junctions.
{"title":"Breakdown and polarization contrasts in ferroelectric devices observed by operando laser-based photoemission electron microscopy with the AC/DC electrical characterization system","authors":"Hirokazu Fujiwara , Yuki Itoya , Masaharu Kobayashi , Cédric Bareille , Toshiyuki Taniuchi","doi":"10.1016/j.ultramic.2025.114221","DOIUrl":"10.1016/j.ultramic.2025.114221","url":null,"abstract":"<div><div>We have developed an <em>operando</em> laser-based photoemission electron microscope (laser-PEEM) with a ferroelectric characterization system. A Sawyer-Tower circuit was implemented to measure the polarization–voltage (<em>P</em>–<em>V</em>) characteristics of ferroelectric devices. Using this system, we successfully obtained the well-defined <em>P</em>–<em>V</em> hysteresis loops for a ferroelectric capacitor incorporating Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> (HZO), reproducing the typical field-cycling characteristics of HZO capacitors. After dielectric breakdown caused by field-cycling stress, we visualized a conduction filament through the top electrode without any destructive processing. Additionally, we successfully observed polarization contrast through the top electrode of an oxide semiconductor (InZnO<em><sub>x</sub></em>). These results indicate that our <em>operando</em> laser-PEEM system is a powerful tool for visualizing conduction filaments after dielectric breakdown, the ferroelectric polarization contrasts, and electronic state distribution of materials implemented in ferroelectric devices, including ferroelectric field-effect transistors and ferroelectric tunnel junctions.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114221"},"PeriodicalIF":2.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144840734","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 : 2025-08-10DOI: 10.1016/j.ultramic.2025.114223
Ranhao Zhang , Yuan Shen , Xueming Li
A tomogram is reconstructed from the micrographs of the tilt series using cryo-electron tomography (cryoET). Reconstruction frequently integrates image processing steps, such as filtering and contrast transfer function (CTF) correction, to support the downstream analysis of cellular and viral structures. Most image processing steps are based on Fourier space analysis, which is theoretically more efficient to be implemented in Fourier space than in real space. However, the substantial dimensions of tomograms present significant challenges for reconstruction and processing in Fourier space. Consequently, real-space reconstruction is prevalent in current practice. In this study, we proposed a Fourier-space algorithm for tomogram reconstruction, named MUltiple Slice Technique (MUST). MUST considers a tomogram composed of multiple parallel slices, with each slice independently reconstructed in Fourier space. A weighting strategy was used to enable MUST to achieve reconstruction compatible with real-space methods, including weighted back-projection (WBP) and the simultaneous iterative reconstruction technique (SIRT). A three-dimensional CTF model was formulated as pairs of conjugate central paraboloids in Fourier space and subsequently implemented for CTF correction in MUST. Alias-free reconstruction and pixel-level parallel computation are key features of MUST, demonstrated through tomogram-based subtomogram averaging at near-atomic resolutions.
{"title":"Fourier-based multiple-slice reconstruction in cryo-electron tomography","authors":"Ranhao Zhang , Yuan Shen , Xueming Li","doi":"10.1016/j.ultramic.2025.114223","DOIUrl":"10.1016/j.ultramic.2025.114223","url":null,"abstract":"<div><div>A tomogram is reconstructed from the micrographs of the tilt series using cryo-electron tomography (cryoET). Reconstruction frequently integrates image processing steps, such as filtering and contrast transfer function (CTF) correction, to support the downstream analysis of cellular and viral structures. Most image processing steps are based on Fourier space analysis, which is theoretically more efficient to be implemented in Fourier space than in real space. However, the substantial dimensions of tomograms present significant challenges for reconstruction and processing in Fourier space. Consequently, real-space reconstruction is prevalent in current practice. In this study, we proposed a Fourier-space algorithm for tomogram reconstruction, named MUltiple Slice Technique (MUST). MUST considers a tomogram composed of multiple parallel slices, with each slice independently reconstructed in Fourier space. A weighting strategy was used to enable MUST to achieve reconstruction compatible with real-space methods, including weighted back-projection (WBP) and the simultaneous iterative reconstruction technique (SIRT). A three-dimensional CTF model was formulated as pairs of conjugate central paraboloids in Fourier space and subsequently implemented for CTF correction in MUST. Alias-free reconstruction and pixel-level parallel computation are key features of MUST, demonstrated through tomogram-based subtomogram averaging at near-atomic resolutions.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114223"},"PeriodicalIF":2.0,"publicationDate":"2025-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144863736","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 : 2025-07-28DOI: 10.1016/j.ultramic.2025.114220
Bene Poelsema, Martina Tsvetanova, Harold J.W. Zandvliet, Arie van Houselt
We report Low Energy Electron Diffraction (LEED) diffraction patterns measured at energies up to 50 eV for a monolayer thick Bi film on Ni(111). Surprisingly, the intensity versus energy profiles of several from the ten unique (i.e., symmetry-independent) sets of spots show finite but pertinent intensity, each only at a well-defined energy. These are attributed to resonant scattering, involving transient capture in eigenstates of the image potential, followed by (multiple) scattering into the vacuum. By its nature, transient capture occurs closely before the energy crosses the Ewald sphere for each considered channel. These energies are one-to-one connected with the corresponding lattice parameters of the Bi-film with its centered rectangular structure, commensurate along Ni[11–2] and high order commensurate along Ni[-110].
In addition, a couple of more intense regular spots show anomalously high intensity at the low energy side upon crossing the Ewald sphere. This feature is attributed to resonant scattering as well. We claim that so far grossly disregarded resonant scattering is a general phenomenon and should be considered in very low energy LEED-IV structural analysis.
The intensity versus energy profile of the (0 2) peak does not show obvious evidence for resonant scattering but instead reveals that the Bi film is built up by long (> 20 nm) and narrow (<< 20 nm), translationally shifted domains, oriented along the [-110] azimuth.
{"title":"Resonant scattering in low energy electron diffraction: Bi/Ni(111)","authors":"Bene Poelsema, Martina Tsvetanova, Harold J.W. Zandvliet, Arie van Houselt","doi":"10.1016/j.ultramic.2025.114220","DOIUrl":"10.1016/j.ultramic.2025.114220","url":null,"abstract":"<div><div>We report Low Energy Electron Diffraction (LEED) diffraction patterns measured at energies up to 50 eV for a monolayer thick Bi film on Ni(111). Surprisingly, the intensity versus energy profiles of several from the ten unique (i.e., symmetry-independent) sets of spots show finite but pertinent intensity, each only at a well-defined energy. These are attributed to resonant scattering, involving transient capture in eigenstates of the image potential, followed by (multiple) scattering into the vacuum. By its nature, transient capture occurs closely before the energy crosses the Ewald sphere for each considered channel. These energies are one-to-one connected with the corresponding lattice parameters of the Bi-film with its centered rectangular structure, commensurate along Ni[11–2] and high order commensurate along Ni[-110].</div><div>In addition, a couple of more intense regular spots show anomalously high intensity at the low energy side upon crossing the Ewald sphere. This feature is attributed to resonant scattering as well. We claim that so far grossly disregarded resonant scattering is a general phenomenon and should be considered in very low energy LEED-IV structural analysis.</div><div>The intensity versus energy profile of the (0 2) peak does not show obvious evidence for resonant scattering but instead reveals that the Bi film is built up by long (> 20 nm) and narrow (<< 20 nm), translationally shifted domains, oriented along the [-110] azimuth.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114220"},"PeriodicalIF":2.0,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725135","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 : 2025-07-27DOI: 10.1016/j.ultramic.2025.114219
Mariusz Gołębiowski , Piotr Dróżdż , Ryszard Zdyb
Using low energy electron microscopy we investigate the origin of the contrast between domains in a heterostructure composed of twisted two-dimensional antimonene layers. The contrast is observed in the bright-field microscopy mode under normal incidence of the electron beam. The heterostructure consists of a single-domain β phase grown on a top of two-domain α phase antimonene on a W(110) surface. We show that the observed contrast is due to the formation of two different moiré superlattices and it directly reflects the two-domain structure of α antimonene. We also demonstrate that the contrast depends on the relative symmetry and crystallography of two moiré patterns.
{"title":"Observation of domain morphology in twisted antimonene layers via moiré superlattice contrast with low energy electron microscopy","authors":"Mariusz Gołębiowski , Piotr Dróżdż , Ryszard Zdyb","doi":"10.1016/j.ultramic.2025.114219","DOIUrl":"10.1016/j.ultramic.2025.114219","url":null,"abstract":"<div><div>Using low energy electron microscopy we investigate the origin of the contrast between domains in a heterostructure composed of twisted two-dimensional antimonene layers. The contrast is observed in the bright-field microscopy mode under normal incidence of the electron beam. The heterostructure consists of a single-domain β phase grown on a top of two-domain α phase antimonene on a W(110) surface. We show that the observed contrast is due to the formation of two different moiré superlattices and it directly reflects the two-domain structure of α antimonene. We also demonstrate that the contrast depends on the relative symmetry and crystallography of two moiré patterns.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114219"},"PeriodicalIF":2.0,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725136","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 : 2025-07-21DOI: 10.1016/j.ultramic.2025.114208
Simon Gaebel , Hüseyin Çelik , Dirk Berger , Christoph T. Koch , Michael Lehmann , Tolga Wagner
Interference gating (iGate) has emerged as a valuable and instrumentally easy-to-implement technique for time-resolved electron holography, allowing the study of dynamic processes on the nanosecond scale. Traditionally, iGate has relied on noise-based control signals, which, while effective, present challenges in achieving high repetition rates due to the complexity of signal generation and transmission. In this work, a square-wave-based control signal for iGate is introduced, offering a simpler and more robust alternative. Experimental validation indicates that this approach maintains comparable performance to the noise-based signal while enabling an order-of-magnitude improvement in temporal resolution, reaching with our current instrumentation. This advancement holds promise for improved time-resolved investigations of ultrafast nanoscale phenomena in TEM, providing a low barrier to entry.
{"title":"Approaching one nanosecond temporal resolution with square-wave-based control signals for interference gating","authors":"Simon Gaebel , Hüseyin Çelik , Dirk Berger , Christoph T. Koch , Michael Lehmann , Tolga Wagner","doi":"10.1016/j.ultramic.2025.114208","DOIUrl":"10.1016/j.ultramic.2025.114208","url":null,"abstract":"<div><div>Interference gating (iGate) has emerged as a valuable and instrumentally easy-to-implement technique for time-resolved electron holography, allowing the study of dynamic processes on the nanosecond scale. Traditionally, iGate has relied on noise-based control signals, which, while effective, present challenges in achieving high repetition rates due to the complexity of signal generation and transmission. In this work, a square-wave-based control signal for iGate is introduced, offering a simpler and more robust alternative. Experimental validation indicates that this approach maintains comparable performance to the noise-based signal while enabling an order-of-magnitude improvement in temporal resolution, reaching <span><math><mrow><mtext>1.9</mtext><mspace></mspace><mtext>ns</mtext></mrow></math></span> with our current instrumentation. This advancement holds promise for improved time-resolved investigations of ultrafast nanoscale phenomena in TEM, providing a low barrier to entry.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"277 ","pages":"Article 114208"},"PeriodicalIF":2.1,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144679807","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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