Microscopy (Oxford, England)最新文献

This paper provides an overview of phonon measurement using electron energy loss spectroscopy (EELS) in the electron microscope, with polar cubic boron nitride (c-BN) and nonpolar diamond crystals as representative examples. Differential scattering cross-sections for phonon creation and annihilation are reviewed, highlighting the influence of crystal polarity under kinematical and dynamical scattering conditions. The temperature dependence of EELS intensity is examined, with local absolute temperature evaluated by analysing the ratio of phonon annihilation to creation intensities. Practical aspects and challenges associated with phonon measurement in EELS are also discussed, together with future perspectives in this evolving field.

Aberration correctors are essential for achieving high-resolution imaging in advanced electron microscopy. However, their complexity and cost have limited their integration into conventional scanning electron microscopes (SEMs), particularly in low-voltage applications. In this study, we present a wire aberration corrector that utilizes symmetrically arranged current lines to generate multipole fields. The corrector was implemented in a cold field emission SEM equipped with a bright-field STEM detector and operated at 30 kV. Experimental results demonstrate successful generation of quadrupole to dodecapole fields, effective correction of spherical aberration, and improved imaging of carbon multilayers. These findings demonstrate that wire correctors offer a compact and cost-effective means to enhance imaging performance in standard SEM systems, and the underlying principle could be adapted for other electron microscopy platforms such as TEM or STEM.

The development of radiation tolerant materials is of technological importance for establishing safe operating systems in the nuclear industry, from power generation to the immobilization of high-level radioactive waste. Harsh radiation environments generate interstitials and vacancies in materials, and their accumulation leads to structural changes, including order-to-disorder phase transformations and amorphization. These structural changes are induced locally on an atomic scale; therefore, transmission electron microscopy is a useful technique for analyzing radiation effects in materials. In addition, the strong interaction between matter and electrons enables the detection of weak signals associated with phase transformations, such as diffuse scattering and halo rings. This article provides an overview of radiation-induced amorphous structures in materials consisting of light elements, such as boron carbide and silicon oxycarbide, as well as the short-range ordered structure that appears during an order-to-disorder phase transformation in fluorite structural derivatives.

As interest in fast real-space frame-rate scanning transmission electron microscopy for both structural and functional characterization of materials increases, so does the need for precise and fast electron detection techniques. Electron counting, with monolithic, segmented, or 4D detectors, has been explored for many years. Recent studies have shown that a retrofittable signal digitizer for a monolithic or segmented detector can be a sustainable and accessible way to enhance the performance of existing detectors, especially for imaging at fast scan speeds. Since such signal digitization uses a threshold on the gradient of the detector signal to identify electron events, appropriate threshold choice is key. Previously, this threshold has been set manually by the operator and is therefore inherently susceptible to human bias. In this work, we introduce an auto-thresholding approach for electron counting to determine the optimal threshold by maximizing the difference in identified counts from a stream with real electron events and a stream with only noise. This leads to easier operation, increased throughput and eliminates human bias in signal digitization. When pixel dwell time becomes shorter than scintillator response time, digitization of the detector signal is needed to avoid artefacts in STEM images. Optimizing the threshold for this digitization process automatically is crucial to achieve high-quality quantitative digitized images, free of human bias for what threshold yields the best digitization.

Histological examination using optical microscopy is essential in life sciences and diagnostic medicine, particularly for formalin-fixed paraffin-embedded (FFPE) tissue sections stained with hematoxylin and eosin or 3,3'-diaminobenzidine. However, conventional electron microscopy faces challenges, such as sample destruction, complex processing and difficulty in correlating light and electron microscopy images. The NanoSuit method overcomes these limitations by forming an ultrathin protective membrane that enhances conductivity and preserves hydrated tissue architecture, enabling high-resolution scanning electron microscopy imaging. In this study, we applied NanoSuit-correlative light and electron microscopy (CLEM) to FFPE sections to assess its potential for non-destructive and reversible electron microscopy characterization. Using NanoSuit-CLEM, we successfully visualized endothelial structures, amyloid deposits, sarcomeres, mitochondria, bacteria, viruses and foreign body deposits in FFPE sections. Energy-dispersive X-ray spectrometry further facilitated elemental analysis of foreign materials. These findings demonstrate that NanoSuit-CLEM allows for the precise visualization of ultrastructural details in FFPE sections without requiring new equipment. This method holds promise for advancing pathology by improving diagnostic accuracy and enabling multimodal tissue analysis.

Traditional three-dimensional (3D) reconstruction is labor-intensive owing to manual segmentation; this can be addressed by developing artificial intelligence (AI)-driven automated segmentation. However, it is limited by a lack of user-friendly tools for morphologists. We present a workflow for 3D reconstruction using our AI-powered segmentation tool. Specifically, we developed an interactive toolset, 'Seg & Ref', to overcome the abovementioned challenges by enabling AI-powered segmentation and easy mask editing without requiring a command-line setup. We demonstrated a 3D reconstruction workflow using serial sections of a Carnegie Stage 15 human embryo. Automated segmentation (Step 1) was performed using the graphical user interface, 'SAM2 GUI for Img Seq', which utilizes the Segment Anything Model 2 and supports interactive segmentation through a web-based interface. Users specify target structures via box prompts, and the results are propagated across all images for batch segmentation. The segmentation masks were reviewed and corrected (Step 2) using 'Segment Editor PP', a PowerPoint-based tool enabling interactive mask refinement. Finally, the corrected masks were imported into the 3D Slicer application for reconstruction (Step 3). Our 3D reconstruction visualized key structures, including the spinal cord, veins, aorta, mesonephros, gut, heart, trachea, liver and peritoneal cavity. The reconstructed models accurately represented their spatial relationships and morphologies. This provides a labor-saving approach for 3D reconstruction workflows owing to their optimization for serial sections, versatility and accessibility without programming expertise. Therefore, morphological research can be enhanced by precise segmentation using intuitive and user-friendly interfaces of 'Seg & Ref'.

The mechanism of voltage contrast formation under ultra-low landing energy condition is discussed, by which a binder contained in lithium-ion battery anode material has been visualized with high contrast. Since the anode material is a complex experimental system with multiple contrast formation factors, a standard sample simulating it was fabricated for simplification. The binder was observed to be darker than the substrate at landing energies of 30-50 eV. The binder exhibited a distinct appearance reflecting its shape (in the 3D-particle mode) at 20 eV. The mirroring phenomenon occurred at 10 eV, in which the primary electrons bounced off the sample before irradiating the surface. The surface potential at the electron beam irradiation moment was presumed to affect the contrast formation, but direct measurement of it was difficult. Thus, the sample was transferred to an Atomic Force Microscope without exposure to the atmosphere to measure the 'residual' potential of the binder in KPFM mode after the SEM observations. Under darker binder observed conditions of 30-50 eV, KPFM measured residual potential was positive relative to the substrate. Under conditions of the 3D-particle mode at 20  eV and the mirroring phenomenon at 10 eV, the residual potentials were negative. Therefore, a correlation between the behavior of the voltage contrast and the residual potential was obtained. Finer landing-energy step measurement revealed hysteresis responses of voltage contrast and the residual potential to the landing energy. The Cause of the hysteresis was discussed.

Scientific research relies on microscopy. However, manual image acquisition and analysis are inefficient and susceptible to errors. Fully automated workflows are often task-specific, and current AI-based systems are costly and may face difficulties in new scenarios. Here, we introduce a semi-automated system utilizing macro keyboards to streamline workflows. Programming multi-action keys for tasks such as focusing, image capture and data analysis reduces the manual input, boosting efficiency and accuracy. This intuitive system saves time for both experienced users and trainees. This cost-effective solution improves accessibility, flexibility and usability, supporting not only diverse imaging applications but also broader scientific instrumentation processes.

Imaging performance with 120 and 200 keV electrons was evaluated with an integration-type silicon-on-insulator pixel detector called INTPIX4 installed in a conventional transmission electron microscope. We demonstrated that single-electron events can be detected with INTPIX4 quantitatively. The gain and signals of single-electron events were measured. On the basis of the results, the yields of the collected charge for 120 and 200 keV electrons were estimated to be 96±5% and 97±5%, respectively. The modulation transfer function and detective quantum efficiency were also measured. INTPIX4 was clarified to have high detection efficiency and high sensitivity. We also found that it is necessary to use electron beams with energies less than 120 keV for INTPIX4 because multiple scattering of primary electrons at the silicon sensor degrades image resolution. This detector is expected to be applicable to low-dose observations in transmission electron microscopy.

Improvement of a commercially available soft X-ray emission spectrometer was tested by introducing a fine-pixel-sized CMOS detector. The peak width of Mg Kα-emission was reduced to one-fourth of that obtained by the CCD detector presently used. Furthermore, the differences in the energy positions of satellite lines of Mg Kα- and also Kβ-emission profiles of Mg and MgO were observed. O K-emission profile of MgO exhibited a few structures reflecting the chemical bonding state. This spectrometer easily discriminated the intensity profiles of Fe Lα,β-emission reflecting the chemical bonding states of Fe atoms in Fe, FeO, Fe3O4 and Fe2O3.