The electromagnetic local density of states (EMLDOS) enhanced by surface plasmon modes of metal nanoparticles improves the light absorption and emission efficiency of nearby materials. Electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL) spectroscopy are powerful techniques for visualizing the distribution of EMLDOS at the nanoscale. CL has the advantage of being able to analyze not only the distribution of EMLDOS but also the polarization and emission angle characteristics of each mode. In particular, angle-resolved CL spectroscopy has been applied to periodic structures (plasmonic crystals), revealing the structure dependence of band dispersion and band-edge standing waves. However, plasmonic crystals have non-radiative modes, such as ones in the first band, that cannot be directly measured by CL, making EELS analysis important as well. This paper introduces mode analysis of plasmonic crystals with a triangular lattice (Tri-PlC) using EELS. Furthermore, as an advanced topic, this paper also introduces mode analysis of Tri-PlC with a polarity and a polarity inversion boundary introduced into that structure.

Isotopes are widely used as atomic-scale labels because they alter mass without significantly changing chemical properties, enabling the tracking of chemical reactions and mass transport. However, conventional isotope analysis techniques are limited in spatial resolution, making direct observation at the nanoscale challenging. Recent advances in electron energy-loss spectroscopy (EELS), driven by the development of monochromated electron sources, have enabled vibrational spectroscopy with unprecedented energy resolution. Combined with dark-field detection that selectively collects high-angle scattered electrons, vibrational EELS now achieves sub-nanometer spatial resolution for isotope identification. In this article, we review the recent progress of vibrational EELS as an emerging nanoscale spectroscopic technique. We highlight two representative examples: isotope discrimination of carbon in graphene with direct visualization of atomic diffusion processes, and nanoscale mapping of hydrogen and deuterium distributions in polymer systems. These studies demonstrate that vibrational EELS not only enables isotope identification at the nanoscale, but also provides insights into dynamic processes and molecular-level structures that were previously inaccessible. Vibrational EELS bridges the gap between high spatial resolution and vibrational spectroscopy, establishing a new platform for probing local chemical and physical phenomena. Continued developments in instrumentation and analysis are expected to further expand its applicability across materials science, chemistry, and related fields.

This article presents an overview of the characterization of optically functional materials using momentum transfer resolved electron energy-loss spectroscopy (q-EELS). By resolving the momentum transfer q in the inelastic scattering of electrons, q-EELS enables the evaluation of electronic excitations and dielectric responses at finite wave vectors, which are difficult to access by conventional optical techniques. In this study, the plasmon dispersion in a LaB₆ single crystal, a near-infrared scattering material, was measured, allowing for a quantitative evaluation of exchange–correlation effects among electrons and revealing their anisotropy. Furthermore, q-dependent EELS analysis was applied to anatase TiO₂, and the average distance between excited electron and hole was evaluated from the q-dependence of the excitonic absorption intensity. The evaluation results were consistent with theoretical studies, suggesting a correlation with the crystallographic orientation of the photocatalytically active surface. These findings demonstrate that q-EELS is a powerful technique that bridges momentum-space and real-space information, providing valuable insights into the origin of optical functionalities.

In recent years, advances in monochromator and spectrometer performance have enabled vibrational spectroscopy using electron energy loss spectroscopy (EELS) in transmission electron microscopes. This technique allows the measurement of lattice vibrations (phonons) and molecular vibrations within materials at the nanometer scale, and is expected to become a promising new method for thermal analysis. However, the principles and characteristics of vibrational spectroscopy using EELS in transmission electron microscopes have not been fully shared. In this paper, I explain the fundamentals of phonon measurement using EELS, and discuss selection rules and temperature dependence, incorporating experimental results. I also demonstrate that local temperature can be determined solely from EELS spectra.

Three-dimensional (3D) imaging of biological samples is an essential methodology for understanding biological phenomena in life sciences, including cell biology, developmental biology, and neuroscience. Traditional volumetric imaging techniques, such as confocal, light-sheet, and two-photon microscopy, require point, line, or plane scanning to acquire 3D information over time, which limits temporal resolution. Light-field microscopy (LFM), first reported in 2006, employs a microlens array to capture both spatial and angular information, referred to as the light field, thereby enabling single-shot volumetric imaging with high temporal resolution, albeit at the cost of spatial resolution. Recent advances in LFM have improved spatial resolution and overcome some optical limitations through computational approaches, particularly deep learning–based image reconstruction. In this article, we describe the principles of LFM, its major challenges and corresponding solutions, and recent developments that position LFM as a powerful computational imaging technique. In addition, we present our application of LFM to biological samples, including system characterization using fluorescent beads and whole-brain imaging of neuronal nuclei in the nematode Caenorhabditis elegans.

Semiconductor device performance is strongly influenced by carrier density and interfacial charge states. However, conventional electrical measurements have mainly treated these quantities as spatial averages. Spatial inhomogeneity and fluctuations have therefore been difficult to evaluate in real space. Scanning nonlinear dielectric microscopy (SNDM) is a microscopy technique that detects changes in tip-sample capacitance with high sensitivity. This technique enables nondestructive real-space observation of carrier density distributions in semiconductors and charge states at buried interfaces beneath insulating layers. More recently, the development of time-resolved SNDM has enabled broadband and highly accurate demodulation. This has provided a practical basis for local capacitance-voltage (CV) profiling and local deep-level transient spectroscopy (DLTS). As a result, interfacial charge density and interface defect density, which had previously been treated mainly as spatially averaged quantities, can now be evaluated in terms of their spatial distributions and fluctuations. This article describes the principles of SNDM and time-resolved SNDM. It also reviews their applications to wide-bandgap semiconductors and atomically thin semiconductors.

In this article, we introduce biological cross-sectional polishing scanning electron microscopy (bioCP-SEM) as an approach for wide-area, high-resolution visualization of plant–microbe–soil interfaces. Conventional techniques often face challenges in preserving spatial context in complex, mineral-rich samples such as non-sterilized rhizosphere soils. BioCP-SEM combines resin embedding, mechanical polishing, and scanning electron microscopy to enable ultrastructural observation while maintaining spatial relationships among biological and mineral components. This article outlines the principles of the method and highlights representative observations from recent studies, illustrating its ability to visualize microbial aggregates, biofilm-like structures, and host-associated features within intact environmental matrices. We also discuss the methodological advantages, current limitations, and potential future applications of bioCP-SEM in environmental and biological imaging.

The charge–discharge and degradation reactions in batteries involve competing process across a wide range of reaction steps, make it difficult to obtain a comprehensive understanding. In this study, multimodal analysis combining operando scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS)/Raman spectroscopy, and ex situ time-of-flight secondary ion mass spectrometry was applied to all-solid-state batteries. Furthermore, multimodal analysis using SEM-EDS and Raman spectroscopy was also extended to investigate degradation phenomena in all-solid-state batteries.