Microscopy (Oxford, England)最新文献

Detecting spin states of electrons at the atomic scale has been at the heart of progress in condensed matter physics. Spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM/STS) has provided important insights into understanding the nature of various spin-dependent phenomena, owing to its capability to visualize energy- and spin-resolved local density-of-states with atomic resolution. This review provides an overview of recent progress in SP-STS using functionalized superconducting tips, focusing on two approaches: conventional superconducting tips and Yu-Shiba-Rusinov (YSR) tips, which are formed by placing a single magnetic atom at the apex of a superconducting tip. Due to their nearly full spin polarization, both types allow for precise detection of the sample's spin polarization. These advanced techniques will be powerful probes for pursuing emergent quantum phenomena that demand ultra-high spin sensitivity, such as the spin polarization of Majorana zero modes around vortex cores in topological superconductors.

Controlling electromagnetic modes in nanostructures is vital for developing advanced optical devices. Metal surfaces with periodic structures, so-called plasmonic crystals (PlCs) form band structures of surface plasmon polaritons (SPPs), providing highly controllable confinement of SPPs and conversion to far-field light. Angle-resolved cathodoluminescence (CL) spectroscopy, where emitted light upon electron beam irradiation is analyzed with angle selection, can be combined with electron microscopy to visualize eigenmodes at specific wavenumbers. This method allows not only identifying the optical properties of Bloch modes appearing in PlCs, but also accessing functions emerging by local defects introduced into the lattice. This paper reviews applications of angle-resolved CL spectroscopy to mode analysis in one-dimensional and two-dimensional PlCs, and modified structures such as cavities and waveguides. Furthermore, this paper introduces an application of this method to the analysis of enhanced light emission from a phosphor film integrated in a PlC, where emitter-resonator coupling is visualized at the nanoscale.

Electron-beam irradiation often induces unintended structural and chemical changes in materials. Here, we show that damage and reduction in tungsten trioxide (WO3) nanowires are primarily driven by a carrier-mediated ionization process. In situ electron microscopy and electron energy-loss spectroscopy reveal structural degradation accompanied by the reduction of W6+ to W5+, while carrier dynamics simulations identify persistent, high-density electron-hole populations. Quantitative analyses and control experiments indicate that knock-on displacement and heating contribute minimally. This study establishes a microscopy-based quantitative framework for understanding electron-beam-induced damage and redox processes, highlighting the potential of electron microscopy for mechanistic insights and nanoscale chemical patterning in oxides.

Compact soft-X-ray emission spectroscopy (SXES) instrument, which was first applied to transmission electron microscope, was recently applied to scanning electron microscope and electron-probe microanalyzer, which improved the practical applicability of SXES as a tool investigating chemical bonding state of elements in bulk materials. Intensity profiles of Al-L, B-K and Si-L emission spectra which directly reflect the partial density of state of valence band (VB) were explained. Those energy positions are affected by core-level shift (chemical shift; CS) and a change of density of state (DOS) of VB, for example a bandgap formation. Those VB DOS measurements combined with electron-beam scanning technique can conduct a chemical bond mapping of a bulk material. It was presented that L-emission spectra of 3d transition-metal elements gives DOS+CS information in Lα,β emission, dielectric information in Lℓ,η, and the number of 3d electrons in the integrated intensity ratio of Lα,β/(Lα,β+ Lℓ,η). Since the electron-beam excited SXES experiment for bulk specimens can control the self-absorption effect, L-absorption profile of 3d-TM elements is obtainable from L-emission measurements by changing the accelerating voltage. Furthermore, CB information can be obtained from SXES spectra of semiconductor materials, Si and diamond cases were presented, by using the self-absorption effect on the background intensity of bremsstrahlung (BS) caused by electron-beam irradiation of the specimen.

In the fabrication of semiconductor devices, increased yield is achieved using Scanning Electron Microscopes (SEM) to measure and inspect circuit patterns. With recent decreasing scale and increasing complexity of semiconductor circuit patterns, it has become increasingly difficult to recognize patterns accurately using rule-based image processing methods. As such, we propose a method that uses semi-supervised learning for segmentation processing, to recognize which pattern level each pixel represents. With existing methods, the pseudo-labels used for training were not accurate enough, and there were issues such as inconsistent recognition of repeated-pattern layouts and mixed-up results in large unmarked areas distant from the pattern contour. Accordingly, the proposed method is able to perform highly accurate segmentation with the design of new types of loss for evaluating consistency in pattern structure at various scales. When compared with Unimatch and CAC, which are well-known high-performance segmentation methods, the accuracy relative to visual identification increased dramatically, from 10-12% to 100%. In quantitative evaluation using mean Intersection-over-Union (mIoU) at the pixel level, mean values also increased from a range between 0.45 and 0.65 to over 0.94, confirming that the proposed method is effective.

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.