Electret or permanent electrical charge is used as a part of mechano-electric energy conversion system for vibrational energy harvesting device. Microscopic capacitors are produced by silicon micromachining or MEMS (microelectromechanical systems) fabrication process, and the surfaces are turned into impurity-rich silicon oxide, which is later processed to make an electret by displacing the impurity ions by the same mechanism as the anodic bonding. The built-in potential of the electret is used to produce electrical current through the electrostatic induction when the movable electrode is periodically shaken by the external vibrations. In this article, the fabrication processes for the electret as well as the MEMS vibrational energy harvester are discussed. The fundamental characteristics of the energy harvesters are reported, along with a demonstration result as an autonomous powerpack for an IoT (internet-of-things) type wireless sensor node.

Soil is defined as a mixture of weathering products of rocks (sand, silt, and clay) and humus (or soil organic matter) derived from plant or animal. World soils are divided into 12 groups and their distribution is not uniform. Soil degradation includes soil acidification in humid region, salinization in arid regions, and loss of soil organic matter in both regions. Minimum tillage or optimized fallow systems can minimize loss of soil organic matter and improve soil fertility. Understanding of complex soil system is required for food supply and human survival.

Digital Annealer developed by Fujitsu is a new architecture to solve “combinatorial optimization problems” at high speed with digital circuit inspired by quantum phenomena. The features are stable operation with digital circuit at room temperature, easy miniaturization, and easy mapping more complex problems with a fully-connected architecture. The Digital Annealer is easy to apply actual problems and contributes to customers in a wide range of businesses, including drug discovery, chemistry, manufacturing, transportation, finance, and logistics. In this article, we explain the fundamental of the Digital Annealer including the speedup technique. We also introduce an application to the material development using the Digital Annealer. The Digital Annealer is used to evaluate the structural similarity of the flavor molecules. We found that the molecules with high structural similarity show a similar flavor. We also extracted the common substructure of molecules having the similar flavor, which is considered to be the key structure of the flavor.

The fundamentals for understanding metal corrosion in aqueous solutions are first explained in terms of thermodynamics and kinetics of electrochemical corrosion reactions, illustrating the validity of a local cell model for the uniform corrosion behavior of iron and stainless steels. Then, the passivation process of stainless steels and the important properties of their passive films are described. Finally, recent studies on the pit initiation mechanism at sulfide inclusions of stainless steels are introduced, which provides a valuable information to develop a next-generation green stainless steel.

Recent progress of the microfabricated field emitter array (FEA) and the planar type electron source is overviewed. The volcano-structured double-gate FEA is promising for obtaining matrix driven and focused electron beams. The beam half angle less than one degree was achieved by using this structure. High current density of more than 25 A/cm² is also achieved by using nickel-based alloy as an emitter material. A major breakthrough in the field of planar type electron sources is a using graphene as a top electrode in Metal/Oxide/Semiconductor type emitter, which is owing to the development of the direct deposition technique of graphene on insulating material. The emission efficiency of more than 30% is achieved. The graphene/oxide/semiconductor type electron source can emit electrons not only in poor vacuum but also in liquid. This unique feature enables new application, such as hydrogen production using non-electrolyte aqueous solution by injecting low energy electrons.

Based on the “Sustainable Zoom-Zoom” plan, Mazda's long-term vision for technology development, we have been advancing what is called a “Building Block Strategy”.

With use of a new-generation technology called “SKYACTIV TECHNOLOGY”, we intend to thoroughly improve Mazda's base technologies with an eye to improving the powertrain efficiency, reducing the vehicle weight, and eventually combining them with electric device technologies in a phased manner so as to reduce total CO₂ emissions.

As the second step of this approach, Mazda has developed a new regenerative braking system called “i-ELOOP”, where the energy generated during deceleration is recovered and reused as electric energy necessary for a vehicle to move.

This paper introduces the Electric Double Layer Capacitor (hereinafter referred to as EDLC) and as device technologies of the “i-ELOOP”, a regenerative braking technology developed as the second step of the Building Block Strategy.

In recent years, imaging quality of a CMOS image sensor (CIS) is remarkably improving. This paper reviews the technology development of CIS for mobile devices.

Conventional semiconductor heterojunctions with two-dimensional (2D) interfaces have been an important topic, both in solid state physics and in electronics and optoelectronics applications. Recently, the in-plane heterostructures based on 2D materials are expected to provide a novel one-dimensional (1D) interface with unique physical properties and applications. Even though there have been many reports on the growth studies of such heterostructures, it is still an important challenge to develop a sophisticated growth process of novel heterostructures/superlattices and high-quality samples without interface degradation, contamination and/or alloying. In this article, the author introduces our recent progresses of thermal chemical vapor deposition (CVD) growth of 2D materials including graphene, hexagonal boron nitride, and transition metal dichalcogenide (TMDC), and their heterostructures.

X-ray photoelectron spectroscopy (XPS), which is capable of analyzing the elemental composition and the oxidation states of surfaces and interfaces placed in a vacuum, was applied to observe ionic species dissolved in aqueous solutions. An environmental cell using a 5-nm thick silicon nitride membrane as a quasi-transparent window for incident x-rays and emitted photoelectrons was developed, and cesium chloride aqueous solutions with a variety of concentrations enclosed in the cells were measured using a laboratory-based XPS apparatus equipped with an Al-Kα source. Cs 4d photoelectrons emitted from cesium ions in the solutions were detected passing through the membrane. Moreover, the peak intensity increased proportionally with the concentration of cesium chloride, proving that this technique allows us to conduct quantitative analysis of solution species.

We fabricated metastable palladium hydride by hydrogen ion implantation to a 10 nm-thick Pd film at 7 K, and monitored the hydride formation and relaxation to a stable state by resistivity measurements. By heating the sample, we observed a substantial change in resistivity below 100 K without accompanying hydrogen desorption. While the resistivity change was observed at 80 K for both H and D, it was observed only for H at 6 K. This irreversible resistivity change is attributed to transition from the metastable state to its stable state by hydrogen diffusion. It is considered that hydrogen atoms undergo diffusion thermally at 80 K and by quantum tunneling at 6 K.

We have established the original methodology that enable to observe atomic orderings and arrangements of “surfaces with arbitrary directions” on 3D figured structures, by developing diffraction and microscopy techniques. An original technique, namely, the directly and quantitatively viewing of the side- and facet-surfaces in atomic scale using reflection high-energy electron diffraction (RHEED) and scanning tunneling microscope (STM), can feedback to the determination of process parameters in the etching procedure. The scientifically optimized etching recipe enabled the creation of atomically-ordered side-surfaces, which are perpendicular to planar substrate surfaces on 3D patterned Si substrates. RHEED and STM prove atomically-reconstructed Si{100}2×1, {110}16×2, and {111}7×7 side-surfaces that were realized for the first time. We have also developed the atomically-ordered 3D nanofabrication technique, where the material stacking direction is switched from the general out-of-plane to in-plane direction, and realized the formation ultra-thin epitaxial films in 3D space.

SuperKEKB is an electron–positron collider with asymmetric energies at KEK aiming at a high luminosity of 8.0×10³⁵ cm^－2 s^－1. During the Phase-1 commissioning from February to June 2016 and the Phase-2 commissioning from March to July 2018, the vacuum system worked well as a whole, and the increase in pressure per unit beam current decreased steadily. The photodesorption coefficients at arc sections reached approximately 1×10^－6 molecules photon^－1 and 7×10^－8 molecules photon^－1 finally for the positron and electron rings, respectively. The beam lifetime was mainly limited by the Touschek effect in both rings, rather than the beam-gas scattering. The electron cloud effect was observed in the positron ring during Phase-1, but it was suppressed by additional countermeasures applied before Phase-2.

Two ISO standards related to quadrupole mass spectrometer (QMS) are introduced ; one is ISO 14291:2012 Definitions and specifications for quadrupole mass spectrometer and the other is ISO/TS 20175:2018 Characterization of quadrupole mass spectrometers for partial pressure measurement. This paper consits of two parts. This first part includes the background that these ISO standards were developed and the definition of sensitivity and relative sensitivity factor of QMS.

Cryo-TEM and atmospheric SEM (ASEM) have enabled direct observation of protein molecules, cells, and tissues in hydrophilic environments. By using cryo-TEM, we have determined the conformation of receptors and ion channels in thin ice layer under vacuum. For the observation in water, we have developed the ASEM. The resolution near the SiN film is 8 nm. The detachable specimen dish can hold a few ml liquid, and allows various types of cells to be cultured in a stable environment, e.g., in a CO₂ incubator. The film surface has glass-like nature, and can be coated variously, which allows different types of cells to be cultured, including primary neurons. The system is an efficient immuno-electron microscope, because antigenicity is protected in hydrophilic environments. Using this system, the distributions of proteins in cells are determined at high resolution, and the time and effort required for these experiments are comparable with those for immuno-fluorescence optical microscopy. This system was applied to microbes, bacterial biofilm, host-microbe interactions and neurons, as well as various tissues including glands e.g. the islet of Langerhans in pancreas and blood cells in the capillaries, and further to cancer metastases.

Interface plays crucial roles for mechanical and functional properties. Despite its importance, the structure-property relationships of the interface have not been fully understood because a determination of the interface structure accompanies huge computations which is caused by the degrees of geometrical freedom of the interface. The acceleration of the interface structure searching is important for the comprehensive understanding of the structure-property relationships of the interface. Here, we applied machine learning techniques for the interface structure searching. Two methods, virtual screening and kriging, are mainly introduced. Our methods achieved considerably high efficiency and can be applied to any materials.

Kyoto Collection of Human Embryo and Fetus is a valuable collection for human developmental research during pregnancy. Although serial sections contain huge morphological information, specimens are sliced and destroyed. Three-dimensional imaging in non-destructive way are developed and now applied to the human specimens. Now, morphological changes of embryo and fetus are analyzed by geometric morphometrics as well as conservative morphometric technique using obtained images.

Development of efficient fuel cell and electrochemical cell devices to retrieve energy in a renewable manner lies in the molecular level understanding of the catalytic chemical transformation processes at surfaces and interfaces. This article demonstrates the use of operando soft x-ray photoelectron spectroscopy to correlate the chemical state of electrode and the electrochemical performance of electrochemical devices. Examples are shown for oxygen reduction reaction on the Pt cathode catalyst in proton exchange membrane fuel cells, and oxygen evolution on the IrO₂ anode in water electrolyzer.

Semiconductor devices with complicated structures have been developed, and it is becoming increasingly important to understand three-dimensional (3D) structures of devices with nanometer resolution. The key to successful nanometer-scale 3D analysis is sample preparation technology and it has been highly developed. By combining or correlating multiple physical analyses, limitations of single analysis method are well covered and new information of 3D devices is obtained. Simultaneously acquired multi-signal STEM images are effective for internal structure analysis of 3D devices.

We present an overview of recent studies on the moiré superlattices in Van der Waals atomic layer materials. We first introduce typical moiré superlattices such as twisted bilayer graphene and graphene h-BN superlattice. We also argue about the Hofstadter fractal energy spectrum in magnetic fields, the strain effect and domain formation, and the graphene quasicrystals.

Frequency modulation atomic force microscopy (FM-AFM) can simultaneously detect the conservative and non-conservative force interactions between a tip and a sample, based on the resonance frequency shift (Δf) and the mechanical energy dissipation of an oscillating cantilever, respectively. Here, we outline the energy dissipation measured by FM-AFM and introduce our recent results obtained through measurement of the energy dissipation. First, surface resistances can be evaluated in non-contact using the proportional relationship between the energy dissipation due to Joule heat and Δf due to the electrostatic attractive force. Second, Si adatoms on a Si(111)-(7×7) surface, which are observed to be static by FM-AFM, can move back and force between their stable sites and their neighboring quasi-stable sites, detected by measuring of the energy dissipation.