Plasma processing plays an important role in manufacturing leading-edge electronic devices. Fine patterns with anisotropic features can be achieved in metal–oxide–semiconductor field-effect transistors (MOSFETs) using reactive ion etching (RIE). However, RIE degrades the performance and reliability of MOSFETs, generating defects in materials such as crystalline Si substrates and dielectric films. This negative aspect is defined as plasma process-induced damage (PID), which is primarily categorized into three mechanisms—physical, electrical, and photon-irradiation interactions. This article provides a brief overview of PID modeling and characterization techniques, focusing on the physical interactions and offering future perspectives. As pointed out, electrical characterizations employing specifically designed devices can help obtain an understanding of PID mechanisms and design future electronic devices.

In the Japanese Island, typhoons, heavy rains, earthquakes, volcanic eruptions, and other natural phenomena occur frequently. Thus, protection from natural phenomena requires an understanding of past disaster situations, to assess potential disaster risks and raise disaster prevention awareness. Knowing the characteristics of natural phenomena that cause disasters is useful, necessitating analytical techniques for a scientific understanding. To characterize the extent of active faults that cause inland earthquakes, this paper introduces technologies that clarify when, where, and how far they occurred. Specifically, these technologies include radiocarbon dating, tephra analysis, luminescence dating, unmanned aerial vehicle (UAV) laser survey, methane gas measurement, ground-penetrating radar exploration, and magnetic susceptibility measurement.

Bioiontronics is an emerging interdisciplinary field that integrates the principles of bioelectronics and ionics to develop responsive and biocompatible interfaces for information processing and therapeutic applications. Unlike conventional electronics relying on electrons, bioiontronics employs ions—the natural information carriers in biological systems—to achieve seamless communication with living tissues. This article presents a comprehensive overview of the fundamental theories of ion transport, including diffusion, migration, and nanochannel phenomena, as well as interfacial mechanisms, such as electric double layers and pseudocapacitance. Furthermore, it highlights recent advances in neuromorphic devices, flexible iontronic memory, and ion-driven therapeutic systems. These developments demonstrate the potential of bioiontronics to pioneer next-generation computing and intelligent medical technologies.

Atmospheric-pressure low-temperature plasma jets are widely used in diverse applications and appear jet-like due to the repeated high-speed propagation of localized discharges, known as plasma bullets, rather than simple downstream gas flow. These plasma bullets give rise to phenomena distinct from those of conventional jets. This study outlines the fundamental properties of plasma bullets and describes phenomena in which a plasma jet appears to tunnel through a dielectric wall, as well as the generation of surface-launched plasma bullets that are launched like rockets from a planar dielectric surface. The applications of these phenomena to the hydrophilic modification of continuous porous dielectrics are discussed, and ongoing efforts to realize large-volume atmospheric-pressure low-temperature plasmas, which have not yet been achieved, are also addressed.

Ultrafast lasers enable high-quality processing that is not achievable using conventional lasers because of their ultrashort pulse widths. The extremely high peak intensity allows nonlinear absorption in transparent materials, making it possible to construct complex three-dimensional micro- and nanostructures. Laser beam shaping can further improve processing performance. This review describes three-dimensional processing inside transparent materials, hybrid laser processing, and beam shaping technologies developed by the author using ultrafast lasers. This technology allows transparent material to be directly modified and processed three-dimensionally. Applications of the developed techniques in the fabrication of 3D microfluidic devices, high-sensitivity analysis chips, and through-glass holes are introduced.

Superconducting Josephson junctions are nonlinear inductors arising from macroscopic quantum states, making them one of the core elements of quantum technology. For example, numerous Josephson junctions are used in superconducting quantum computers. Recently, frequency-modulated terahertz wave emission has been demonstrated using stacked intrinsic Josephson junctions in high-temperature superconductor single crystals. In semiconductor-based terahertz sources, frequency modulation is inherently challenging, highlighting the unique advantages of superconducting devices. With further research, superconducting technology is poised to become a promising option for terahertz high-speed communication.

Wireless power transfer (WPT) is a technology that has been increasingly applied in recent years parallel with progress in research. It can be broadly categorized into “coupled” WPT, which uses magnetic or electric fields, and “radiative” or “uncoupled” WPT via radio waves. The basic theory for both in based on Maxwell’s equations, and they can be considered the same technology in general. Furthermore, since broadcasting/wireless communication technology and remote sensing use the same electromagnetic fields/radio waves, the basic theory is the same; however, the emphasis on “efficiency” in WPT differs slightly from that of other wireless technologies. The basic principles, current state of practical applications, and future perspective of radiative WPT are introduced in this article.

Improving the energy efficiency of electric motors has been widely recognized as a critical research direction as their power density continues to increase. At present, Nd-Fe-B magnets are the predominant choice for high-efficiency motor applications due to their superior magnetic properties. However, improving their thermal stability necessitates the use of heavy rare-earth elements such as dysprosium (Dy) and terbium (Tb), which are subject to significant supply constraints. These limitations have driven growing interest in samarium-based (Sm-based) magnetic materials. Among these, Sm-Co magnets exhibit exceptional thermal stability, which makes them especially suitable for high-temperature environments. In contrast, Sm-Fe magnets are expected to deliver superior magnetic performance in future applications. In this study, we present a comprehensive review of recent advancements in research on Sm-Co and Sm-Fe magnets.

The increasing volume of waste generated from used electronic devices (e-waste) has recently sparked global discussions on environmentally sound disposal methods for electronic components. As a fundamental solution to the e-waste problem, environmentally conscious electronics—where all components are designed for safe and low-environmental-impact disposal—are gaining considerable attention. This study demonstrates an all-carbon complementary integrated circuit (IC) composed of printed p-type and n-type organic semiconductor single-crystal thin films, graphite-based carbon electrodes/wiring, and polymer dielectrics and substrates, thereby eliminating the generation of metal waste. The all-carbon complementary IC can be disposed of as combustible waste, thereby minimizing the environmental impact of device disposal.

Magnetic recording systems for hard disk drives (HDDs) have evolved from longitudinal magnetic recording to perpendicular magnetic recording, and more recently to energy-assisted magnetic recording, to achieve greater capacities and higher areal densities. In this process, signal processing systems have also evolved from amplitude detection with peak detection, partial-response maximum-likelihood (PRML), and iterative decoding, which have contributed to higher densities without compromising the reliability of information while compensating for the characteristics of read/write systems. In this study, the PRML system is explained. In particular, PRML has become the basis for signal processing in magnetic recording and has supported a rapid improvement in the areal density of HDDs along with the adoption of magnetoresistive heads and the iterative decoding system used in current HDDs.

The rapid proliferation of generative AI has increased the demand for higher-speed optical communication networks. However, single-core optical fibers are approaching their capacity limits, and space-division multiplexing using multicore fibers is attracting significant attention. Employing 1.55 µm quantum-dot surface-emitting lasers as light sources for multicore fibers is expected to boost the transmission speed while reducing power consumption and cost. This paper presents a review of optical communication networks and long-wavelength surface-emitting lasers studied to date, and discusses our experimental results.

Implantable device technologies are being developed as next-generation medical technologies and are expected to enable next-generation diagnostics and therapeutics. Recent advances in materials technologies highlight the critical role of combining safety with functionality in implantable devices. In particular, the development of functional biomaterials is driving innovation in medical devices for minimally invasive and long-term use in the body. This paper discusses future directions of implantable medical device research from the perspective of recent advances in biomaterials research. Biomaterials with enhanced mechanical, optical, and electrochemical properties, beyond biocompatibility, are expected to open new possibilities for implantable medical devices that enable safe and effective medical applications.

Fluorescent nanodiamonds with nitrogen-vacancy (NV) centers are emerging as versatile quantum sensors at room temperature. They enable the assessment of temperature, magnetic fields, and biochemical environments inside living systems. This article reviews recent progress in biological applications, including intracellular thermometry in cells and organisms, and integration with on-chip devices. Challenges associated with the improvement of material quality, such as extending spin coherence, are discussed along with future perspectives for applying nanodiamond quantum sensors in the life sciences and medicine.

Laser Thomson scattering (LTS) has been applied to a wide variety of plasmas as a method of precisely measuring electron temperature (T_e) and electron density (n_e), which are the most fundamental physical quantities in plasmas. The author has performed LTS measurements over a wide range of T_e (0.1–100 eV) and n_e (10¹⁶–10²⁶ m⁻³). Generally, LTS is considered to be a difficult measurement owing to a small scattering signal. Examples of LTS measurements could be beneficial to researchers who require this technique. Based on some actual cases, this paper introduces methods of estimating Thomson scattering signals and designing adequate optical systems.

Solid-state quantum sensors have garnered attention as novel sensors capable of measuring magnetic fields, temperature, pressure, and other parameters with high sensitivity and high spatial resolutions. Studies on quantum sensors based on nitrogen-vacancy (NV) complexes (known as NV centers) in diamond are ongoing for a variety of applications. Silicon carbide, which is used as a substrate material for power semiconductors, also have defects that function as quantum sensors. This paper introduces the latest research trends on silicon-vacancy-based quantum sensors, which enable direct observation inside power semiconductors.

The development of a solution-based atmospheric pressure functional thin-film fabrication method has attracted attention from the viewpoint of energy conservation. In particular, mist chemical vapor deposition (CVD) can synthesize various thin films, including thin films that are difficult to synthesize using conventional methods. Researchers and research institutes using mist CVD are not limited to Japan but are deployed around the world. This research introduction describes mist CVD and discusses research on the state of mist droplets in a reactor. This report informs readers about one area where mist CVD can be used effectively, which can only be understood by understanding the principles of mist CVD and considering its characteristics.

Water ice has been regarded as a “p-type semiconductor,” with the excess protons in ice serving as the positive charge carrier. Although ice is considered to be an insulator at very low temperatures, we recently found that ice has electrical conductivity via negative charge delivery even at temperatures around 10 K when simultaneously irradiated with ultraviolet photons and electrons, indicating that ice serves as an “n-type semiconductor” as well. Based on experimental and theoretical investigations, we propose that the carrier of the negative charge conductivity is the OH⁻ ion, called the proton-hole, and OH⁻ moves toward the interior of ice by repeated proton abstractions from neighboring H₂O molecules, namely the proton-hole transfer mechanism.

The study of the electrochemical conversion of atmospheric CO₂ into value-added products has attracted attention as a topic of active research since the 1970s. Early investigations revealed a wide distribution of reduced carbonaceous species derived from copper (Cu) metal cathodes. Extensive research has been conducted on systems that combine Cu cathodes with zero-gap configurations because zero-gap reactors operate at relatively low full-cell voltages and high current densities. In this article, we provide a comprehensive overview of the historical development of electrochemical CO₂ reduction. Furthermore, we address key challenges in enhancing the long-term operational durability of zero-gap reactors and clarify the phenomena of flooding and salt precipitation at the cathode.

Photon detection devices based on superconducting nanostrips have been applied in a wide range of advanced applications in photonics owing to their excellent performance, including quantum techniques. However, the fabrication of such nanostrips with a width of ∼100 nm requires advanced nanofabrication technology, which impedes the mass production of high-performance detectors. In this study, we realized the high-performance operation of a superconducting photon detector based on a strip with a width more than 200 times greater than that of conventional nanostrips by introducing a novel superconducting-strip structure that focuses on the bias-current distribution within the strip. The proposed detector is expected to contribute to the development of various scientific and technological fields as a high-performance, mass-producible photon detector. Thus, our approach is also applicable to the process of scaling up quantum technologies.

Circularly polarized light (CPL) carries diverse pieces of information, such as birefringence and stress distribution in materials that cannot be generally distinguished by the human eye. In this study, we aim to achieve highly sensitive CPL detection by developing crystalline thin films with one-dimensional (1D) helical structures, created through hybridization of organic chiral molecules and inorganic semiconductors, as well as corresponding photodetectors. For example, lead halide perovskites, through interaction with organic chiral molecules, can acquire a 1D helical structure, exhibiting an exceptionally strong circular dichroism of up to 5000 mdeg. Furthermore, by employing these 1D helical crystalline thin films as a photoactive layer, we successfully fabricated photodetectors capable of selectively detecting the handedness of CPL. This represents the first demonstration of direct CPL detection utilizing a helical structure, achieving the highest sensitivity reported for CPL photodetectors.

The development of high-energy, high-repetition-rate lasers is essential for next-generation applications, such as inertial fusion energy and high-intensity laser science. However, efficiently managing the heat generated by the gain medium remains a major challenge. We have adopted the cryogenic, conduction-cooled active mirror architecture and developed unique core technologies to address this issue. Using a prototype system, we successfully produced 10 J pulses at 100 Hz, achieving a world-leading performance level. A larger-aperture laser system is currently under construction. This article presents the current status of this development project and discusses its future prospects.

Chirality refers to the structural characteristic of an object or phenomenon that is not superposable to its mirror image. Various properties emerge from the chirality of a material. Circularly polarized light consists of an electromagnetic wave with a chiral structure and exhibits characteristic behavior when it interacts with chiral materials. Herein, we introduce unique characteristics of the optical force that circularly polarized light exerts on chiral materials, as well as research into imaging that uses this force.

The application of magnetic fields to plasmas used for materials processing is expected to have novel functionality for plasma control. The motion of electrons that governs the response and structure of plasmas becomes quite complex owing to the interconnected effect of electric and magnetic fields. Therefore, understanding the fundamental effects of magnetic fields on electrons based on theoretical and numerical analyses is crucial in the advanced design and control of plasma equipment. This article presents an overview of elementary electron behaviors under electric and magnetic fields and introduces some particle simulation-based investigations on interesting functional effects of magnetic fields with specific arrangements on the electron motion.

Amid intensive research on two-dimensional (2D) materials as key candidates for next-generation electronics, the discovery of layered compounds that exhibit stable ferromagnetism at room temperature has enabled new developments in spintronic devices. In this study, we focus on the 2D layered ferromagnet Fe₃GaTe₂, which has strong perpendicular magnetic anisotropy at room temperature. We present an overview of its magnetic, electrical, and thermoelectric properties and demonstrate that the material exhibits a remarkably large anomalous Nernst angle. Furthermore, by focusing on the van der Waals gap characteristic of layered materials, we reveal that the modulation of the interlayer spacing through pressure or strain can actively control both magnetic anisotropy and transverse responses. These findings highlight the potential of room-temperature 2D ferromagnets as core components for low-power, non-volatile spintronic devices.

We developed a frequency up-conversion single-photon detector based on the quantum pulse-gate method and demonstrated femtosecond time-resolved time-of-flight (ToF) measurements with strong temporal-mode selectivity in the 1550 nm band. When applied to optical tomography of the mouse brain, this ToF technique produced clear cross-sectional images. Using an average probe-beam power of 1.5 mW, the system achieved a sensitivity exceeding 110 dB and an axial resolution of 57 µm (refractive index: 1.37). This approach offers a promising alternative for noncontact, noninvasive three-dimensional structural imaging, which is essential for biological, medical, and industrial applications.

Optically pumped magnetometers (OPMs) are ultrahigh-sensitivity sensors attracting attention as an alternative to superconducting quantum interference devices, as they do not require liquid helium cooling. This article first provides an overview of their development and then discusses the characteristics of the representative OPM types—spin-exchange relaxation-free (SERF) OPM and scalar-mode OPM—based on experimental results.