JSAP Review
Online ISSN : 2437-0061
Volume 2024
Displaying 1-45 of 45 articles from this issue
Comprehensive Review
  • Tetsuo Kodera
    Article type: Comprehensive Review
    2024 Volume 2024 Article ID: 240101
    Published: 2024
    Released on J-STAGE: March 05, 2024
    JOURNAL OPEN ACCESS

    The development of fault-tolerant quantum computers that can solve diverse, complex, and large-scale problems is highly anticipated. Achieving this requires both high-fidelity and highly-integrated qubits. Research and development is progressing on various physical systems, and semiconductor qubits are one of the leading candidates. This report provides an overview of the fundamental knowledge of semiconductor qubits. Then, it introduces the global research and development trends related to high fidelity, various efforts toward integration, and research and development of peripheral technologies.

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  • Yutaka Yamada
    Article type: Comprehensive Review
    2024 Volume 2024 Article ID: 240102
    Published: 2024
    Released on J-STAGE: July 03, 2024
    JOURNAL OPEN ACCESS

    Nearly 40 years after the discovery of high-temperature superconductivity (HTS), a promising application has emerged: compact fusion comprising the use of REBa2Cu3Ox (REBCO, RE: rare-earth element) HTS wires. The key technology here is a large and high field HTS magnet, with a supply of REBCO wire extending over several hundred million kilometers. This report presents a review of the technical path toward the mass production of REBCO wires, primarily using the ion beam assisted deposition–pulsed laser deposition (IBAD–PLD) method. Furthermore, the challenges of the wire research and development (R&D) and compact-fusion application prospects are briefly outlined. The effort described in the R&D history should serve as a reference for young researchers, engineers, and entrepreneurs to lead the next generation of industries and economies.

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Tutorial Review
  • Haruyoshi Katayama
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240201
    Published: 2024
    Released on J-STAGE: February 07, 2024
    JOURNAL OPEN ACCESS

    Infrared detectors onboard earth observation satellites are required to have excellent performance. JAXA is studying the Type II superlattice infrared detector as a next-generation infrared detector to replace the HgCdTe detector widely used in conventional earth observation satellites. This paper describes the principle and current development status of the Type II superlattice infrared detector in JAXA.

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  • Masahiko Kanaoka
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240202
    Published: 2024
    Released on J-STAGE: February 28, 2024
    JOURNAL OPEN ACCESS

    Synchrotron radiation facilities, which are compared to giant microscopes, are used for cutting-edge research in various fields because the characteristics of the emitted X-rays enable observations with extremely-high resolution that cannot be achieved with laboratory-scale analytical equipment. High-precision optical elements are indispensable to obtain this high resolution, and the author’s company is the only one that provides a stable supply of X-ray total-reflection mirrors with surfaces smoothed to a remarkable accuracy of less than 2 nm. This paper describes the existence of a unique nanofabrication technology behind this global niche top business, its successful practical application and commercialization, and introduces an example of an application development of the new technology.

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  • Shun-ichiro Ohmi
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240203
    Published: 2024
    Released on J-STAGE: February 29, 2024
    JOURNAL OPEN ACCESS
    Supplementary material

    In this article, nonvolatile memory transistors using Hf-based ferroelectric thin films are described. Ferroelectric-gate transistors, metal–oxide–Si field-effect transistors, are explained using ferroelectric HfO2 and HfN thin films, which can be formed directly on the Si substrate as a gate insulator. Furthermore, FeNOS-type nonvolatile memory transistors that is the metal–oxide–nitride–oxide–Si-type flash memory with ferroelectric HfO2 thin films, which achieves precise threshold voltage control using polarization and charge trap characteristics, are explained.

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  • Masaki Uchida, Yusuke Nakazawa, Masashi Kawasaki
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240204
    Published: 2024
    Released on J-STAGE: March 06, 2024
    JOURNAL OPEN ACCESS

    Dirac semimetals have a so-called Dirac cone in their three-dimensional bulk electronic structures. They also have a unique bulk–surface coupled electronic state. Consequently, they have attracted growing attention as a material system for next-generation electronics. In this review, we will explain the fundamental features of Cd3As2, a typical Dirac semimetal, and introduce various results ranging from the fabrication of high-quality thin films to the determination of a unique quantum Hall state. We will also summarize future prospects for possible applications.

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  • Toshiro Kaneko
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240205
    Published: 2024
    Released on J-STAGE: March 26, 2024
    JOURNAL OPEN ACCESS

    Non-equilibrium plasmas are characterized by high electron temperatures (tens of thousands of degrees) and low gas temperatures (about room temperature), and thereby, are termed as low-temperature plasmas. High-energy electrons collide with gas atoms and molecules to produce ions, excited species, and reactive species to accelerate chemical reactions, which are used in a wide range of environmental, medical, and agricultural applications, such as sterilization, cancer treatment, and plant disease control. Furthermore, they are used in the applications for materials science involving thin film growth and nanomaterial synthesis. Additionally, high reactivity and controllability can be realized by physically controlling the behavior of electrons and ions by means of electric and magnetic fields. In this review, the methods for physically and chemically controlling plasmas are described, and applied research, utilizing controlled non-equilibrium plasmas, is introduced.

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  • Hideki Narita, Teruo Ono
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240206
    Published: 2024
    Released on J-STAGE: April 06, 2024
    JOURNAL OPEN ACCESS

    The superconducting diode effect (SDE) is a phenomenon that results in a superconducting state with zero electrical resistance in the forward direction, but a normal conducting state with finite resistance in the reverse direction. The similarity of this effect to the operation of a semiconductor diode, which is one of the building blocks of modern electronic devices. Exploiting the SDE is promising for the development of diodes and rectifiers with ultra-low power consumption. Recently, a method for controlling the zero-field SDE using magnetization has been demonstrated. This opens up new possibilities for using magnetization to control superconductivity. Here, we provide an overview of the SDE and discuss its future prospects.

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  • Yuji Okuyama
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240207
    Published: 2024
    Released on J-STAGE: May 02, 2024
    JOURNAL OPEN ACCESS

    Defect-structure-type proton conductors are ceramics in which hydrogen ions (protons) dissolve in oxides and diffuse in the crystal. The material has attracted considerable attention as an electrolyte for hydrogen sensors and fuel cells. In this review, the material properties and polarization characteristics of defect-structure-type proton conductors will be described, and the application to hydrogen sensors and fuel cells will be introduced.

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  • Masaki Takata
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240208
    Published: 2024
    Released on J-STAGE: June 01, 2024
    JOURNAL OPEN ACCESS

    NanoTerasu is expected to start operation in April 2024. It is a next-generation synchrotron radiation facility constructed at Tohoku University Aobayama New Campus (Sendai City). Regarding synchrotron radiation facilities, SPring-8 in Hyogo Prefecture, which began operation in 1997, is well known to the general public. After approximately a quarter of a century, the new facility of NanoTerasu was established and will be operated by the government. The accelerator technology that produces light is based on the unique technology of synchrotron radiation science in Japan, which has been refined at SPring-8. However, SPring-8 and NanoTerasu have different uses; SPring-8 has capability in using hard X-rays, whereas the strength of NanoTerasu lies in using soft X-rays. Leveraging this strength, we are aiming to contribute to solving social issues such as the creation of a carbon-neutral society. In this article, our challenges with NanoTerasu are described in detail.

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  • Shinpei Ogawa
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240209
    Published: 2024
    Released on J-STAGE: June 14, 2024
    JOURNAL OPEN ACCESS

    Graphene is a carbon-based, atomically thin, two-dimensional material that exhibits remarkable optical and electronic properties that have not been demonstrated by conventional bulk materials. In particular, its broadband photodetection capability, high carrier mobility, and low environmental impact are advantageous for infrared (IR) sensor applications. This paper discusses the prospects and challenges of graphene-based optical sensors. In addition, the photodetection mechanism of graphene-based optical sensors is explained. Subsequently, a promising optical-sensor performance-enhancing method of photogating is discussed. Finally, graphene-photogated diodes (GPDs), which exhibit high responsivity and low dark current, and graphene-based IR image sensors using an array format of such GPDs are reviewed.

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  • Thermal phonon transport at the nanoscale: challenges and opportunities
    Masahiro Nomura
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240210
    Published: 2024
    Released on J-STAGE: June 29, 2024
    JOURNAL OPEN ACCESS

    Thermal energy is generated by all activities that consume energy and dissipate into the environment. However, for the proper function and performance of logic semiconductors, power semiconductors, optical devices, and living organisms, it is important to manage heat appropriately. Accurate understanding of thermal transport requires a deep understanding of the behavior of phonons, which are heat carriers. Phonons are more difficult to track and control than photons or electrons, but the exploration of their unique physics and development of control technologies are progressing steadily. Various applications have been introduced, owing to the understanding and control of thermal phonons, based on the fundamentals of thermal phonon transport at the nanoscale.

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  • Daisuke Koyama
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240211
    Published: 2024
    Released on J-STAGE: August 08, 2024
    JOURNAL OPEN ACCESS

    Objects can be levitated, transported, and deformed by the radiation force of ultrasound. In this paper, we introduce non-contact transportation techniques and optical lenses using acoustic radiation force. Small objects and liquid droplets can be transported without contact by controlling acoustic fields, which is expected to be applied to cell manipulation techniques. Additionally, optical lenses with a focal length that can be controlled by changing their shape via acoustic radiation force can help downsize camera modules.

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  • Mizuki Tenjimbayashi
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240212
    Published: 2024
    Released on J-STAGE: October 17, 2024
    JOURNAL OPEN ACCESS

    Wetting is ubiquitous in nature and contributes significantly to industrial processes. This commentary focuses on solid/fluid interaction, which summarizes the fundamentals of wetting phenomena (surface tension, droplet shape, capillary force, and wetting models), the design strategy for liquid-repellent interfaces (superhydrophobic/superoleophobic surfaces and liquid marble), and the associated cutting-edge applications. The relevant equations utilize only thermodynamics concepts taught in high school and are explained concisely such that even beginners can understand them sensibly. Additionally, typical examples are provided.

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  • Takuma Morimoto
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240213
    Published: 2024
    Released on J-STAGE: November 06, 2024
    JOURNAL OPEN ACCESS

    When we refer to “a green car,” it might sound as if that the color is an inherent characteristic of the object. However, color is a sensation produced by our visual system based on the light reflected from an object. Changes in scene illuminant alter the reflected light, so the color of the object should change as well. Yet, why does a green car parked in the morning still appear green when we return to it at dusk? This is due to color constancy, a phenomenon that maintains stable color perception despite changes in surrounding lighting environments. How does our visual system create a robust visual world from highly variable sensory signals? This article explains the mechanisms supporting human color constancy.

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  • Masahiro Hiramoto
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240214
    Published: 2024
    Released on J-STAGE: November 06, 2024
    JOURNAL OPEN ACCESS

    The efficiency of organic solar cells has attained 20%. To achieve 25% efficiency (which is comparable to that of silicon), it is essential to suppress all recombinations, particularly geminate recombination, bimolecular recombination, and trap-assisted recombination. In the long term, exciton-free, highly-efficient photocurrent generation similar to that of inorganic semiconductors may be realized.

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  • Kyoko K. Tanaka
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240215
    Published: 2024
    Released on J-STAGE: December 05, 2024
    JOURNAL OPEN ACCESS

    The nucleation process during the initial stage of a phase change is a fundamental process related to various fields. However, the theoretically predicted nucleation rate is known to be highly indeterminate. This study performed direct, large-scale molecular dynamics (MD) simulations of homogeneous nucleation processes including vapor-to-liquid nucleation and liquid-to-vapor nucleation. MD simulations are used to investigate the details of the nucleation process at the molecular level, and provide the nucleation rate, critical nuclei, Gibbs free energy for nucleation, sticking probabilities, and other information for verifying the theory from various aspects. Using systems with a large number of particles, such as nucleation from the gas phase using 8 billion Lennard-Jones or 4 million water molecules and bubble nucleation from the liquid phase with 500 million Lennard-Jones molecules, low nucleation rates were produced under the same conditions as that of experimental data. Moreover, the nucleation models exhibited high accuracy.

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  • Kazuaki Sawada
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240216
    Published: 2024
    Released on J-STAGE: December 05, 2024
    JOURNAL OPEN ACCESS

    Many types of ions and neurotransmitters exist in our bodies and play important roles. We believe that if we can directly visualize them, we will be able to elucidate previously unknown phenomena. We have developed an ion image sensor that combines CMOS and biosensor technologies. This technology is being developed as an extracellular imaging technology to simultaneously visualize and analyze multiple types of chemical information that are intricately intertwined in the extracellular microenvironment with the aim of elucidating the neurotransmission mechanisms, thus clarifying the causes of diseases and supporting drug discovery.

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  • Atsushi Kamimura, Yuki Sughiyama, Tetsuya J. Kobayashi
    Article type: Tutorial Review
    2024 Volume 2024 Article ID: 240217
    Published: 2024
    Released on J-STAGE: December 25, 2024
    JOURNAL OPEN ACCESS

    Understanding the inherent properties and origins of biological systems based on the laws of physics is a fundamental challenge in biophysics. Among others, identifying the necessary and sufficient conditions of self-replication is essential. In this study, we derive the thermodynamic conditions necessary for self-replication based on our new theory, which geometrically characterizes the conjunction of autocatalytic reactions and volume growth. This theory can be applied to comprehend complex thermodynamic and stoichiometric constraints in growth states and the associated thermal dissipation. Grounded solely on the second law of thermodynamics, this framework is broadly applicable to systems with diverse chemical molecules and reaction kinetics and provides a fundamental thermodynamic basis not only for understanding living systems but also for realizing artificial self-replicating molecular systems.

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Perspective
  • Kosuke Mitarai
    Article type: Perspective
    2024 Volume 2024 Article ID: 240301
    Published: 2024
    Released on J-STAGE: February 07, 2024
    JOURNAL OPEN ACCESS

    In recent years, the rapid advancements in machine learning have significantly influenced its broader application within society. Concurrently, the prospects of utilizing the computational strengths of quantum computers for machine learning have been a focal point since the 2010s. As quantum hardware continues to evolve, a notable shift is occurring toward developing algorithms specifically for current and near-future quantum systems. This article presents a concise overview of machine learning assisted by quantum computing.

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  • Teruo Onishi
    Article type: Perspective
    2024 Volume 2024 Article ID: 240302
    Published: 2024
    Released on J-STAGE: April 26, 2024
    JOURNAL OPEN ACCESS

    The radio radiation protection guidelines and evaluation methods for the human safety assessment of wireless power transmission using microwaves are described. Microwave power transmission has been institutionalized among wireless power transmissions, and human safety evaluation is required for its operation. This paper introduces radio radiation protection guidelines, their evaluation procedures, and trends in their international standardization.

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  • Norio Kumada
    Article type: Perspective
    2024 Volume 2024 Article ID: 240303
    Published: 2024
    Released on J-STAGE: June 20, 2024
    JOURNAL OPEN ACCESS

    Owing to its high carrier mobility and weak interaction with phonons, graphene demonstrates remarkable carrier dynamics in the terahertz (THz) range. Our recent experimental results for the active spatial control of graphene plasmons and ultrafast optical-to-electrical conversion processes in graphene photodetectors are presented herein, in addition to an explanation of the on-chip THz spectroscopy method developed for the time-domain measurement of ultrafast electrical currents excited at the photodetector.

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  • Takayuki Hoshi
    Article type: Perspective
    2024 Volume 2024 Article ID: 240304
    Published: 2024
    Released on J-STAGE: August 31, 2024
    JOURNAL OPEN ACCESS

    The advent of airborne ultrasonic phased arrays marked a significant turning point in the fields of mid-air haptics and acoustic levitation. This breakthrough has not only revolutionized academic research but also paved the way for industrialization through the emergence of startups. The author has witnessed this evolution from its inception to the present day. This paper discusses the historical background and related aspects of this technology, while also addressing recent trends and future prospects.

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  • Wakana Kubo
    Article type: Perspective
    2024 Volume 2024 Article ID: 240305
    Published: 2024
    Released on J-STAGE: October 31, 2024
    JOURNAL OPEN ACCESS

    This study reports on the metamaterial thermoelectric conversion in an environment with uniform thermal radiation. Generally, thermoelectric conversion, driven by the Seebeck effect, cannot operate in an environment with uniform thermal radiation where temperature gradients across the thermoelectric elements disappear. To address this issue, we utilized a metamaterial absorber to drive the thermoelectric conversion in an environment with uniform thermal radiation. The metamaterial absorbs the thermal radiation emitted from the surrounding environment and converts it into local heat. This local heat leads to a thermal gradient across the thermoelectric element, which drives the thermoelectric power generation. The power generation characteristics of the metamaterial thermoelectric conversion were investigated. Furthermore, nonradiative cooling, a mechanism that cools the space surrounded by an opaque absorber, is introduced.

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  • Shuzi Hayase
    Article type: Perspective
    2024 Volume 2024 Article ID: 240306
    Published: 2024
    Released on J-STAGE: December 20, 2024
    JOURNAL OPEN ACCESS

    The efficiency of lead halide perovskite solar cells has been demonstrated to exceed 26%, and the research focus on solar cells is shifting toward practical application research, such as fabricating solar cells with a large area and stability. Tin halide perovskite solar cells have attracted attention as post-lead halide perovskite solar cells. Tin halide perovskite cells are expected to exhibit high efficiency since their theoretical electronic properties are similar to those of lead halide perovskite solar cells. Although the efficiency of the latter has been improved by 15–16%, issues such as lattice defects need to be explored further in future research. This study reviews the current state of the research on perovskite solar cells and proposes future considerations.

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  • Toshifumi Irisawa
    Article type: Perspective
    2024 Volume 2024 Article ID: 240307
    Published: 2024
    Released on J-STAGE: December 27, 2024
    JOURNAL OPEN ACCESS

    Two-dimentional (2D) semiconductor materials are now intensively examined with the aim of the application to advanced CMOS logic transistors for 1-nm node and beyond. The expectation for 2D materials toward ultimate scaling of CMOS can be observed in the IRDS road map. Here, the reasons for high expectations from 2D materials and the latest progress on the research of 2D material transistors with transition metal dichalcogenides, such as MoS2 and WSe2, are reviewed. Furthermore, challenges and prospects of 2D material transistor technologies for real CMOS application are discussed.

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Research Report
  • Miho Tagawa
    Article type: Research Report
    2024 Volume 2024 Article ID: 240401
    Published: 2024
    Released on J-STAGE: January 23, 2024
    JOURNAL OPEN ACCESS

    Inorganic nanoparticles made of inorganic materials are difficult to arrange in an ordered manner and form higher-order structures by themselves. However, surface modification with DNA, which has selective binding properties, as a guiding molecule can control the interaction and binding between nanoparticles to assemble them into desired crystal structures. In this report, the author presents recent work on determining the structural conditions for DNA-functionalized nanoparticle superlattices that can maintain crystalline symmetry not only in the hydrated state but also after drying by precisely characterizing crystallinity using small-angle X-ray scattering.

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  • Jun Tatebayashi, Yasufumi Fujiwara
    Article type: Research Report
    2024 Volume 2024 Article ID: 240402
    Published: 2024
    Released on J-STAGE: February 08, 2024
    JOURNAL OPEN ACCESS

    This paper reviews our recent research about the formation and optical characteristics of GaN:Eu/GaN nanowires (NWs) by organometallic vapor phase epitaxy for application in GaN-based red LEDs. Two types of GaN:Eu/GaN NWs with different configurations are introduced, core–shell and axial geometries. The configuration of GaN:Eu layers on GaN core NWs can be controlled by changing the growth conditions, and affects the properties of Eu luminescence in the GaN NWs. Next, the fabrication process of the NW LEDs towards future possible realization of flexible devices is established, including an etch-back process of the PDMS membranes to expose the top p-GaN contact layers. Finally, a prototype of p-GaN/GaN:Eu/n-GaN NW LEDs on sapphire substrates is fabricated to determine the device characteristics. Sharp red luminescence at room temperature from Eu3+ ions is observed under current injection.

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  • Fumitaro Ishikawa
    Article type: Research Report
    2024 Volume 2024 Article ID: 240403
    Published: 2024
    Released on J-STAGE: February 16, 2024
    JOURNAL OPEN ACCESS

    Using molecular beam epitaxial crystal growth, we synthesized large-capacity, high-quality compound semiconductor GaAs-based nanowires on a 2-inch silicon substrate. In addition, we explored novel nanowire materials through the growth of GaInNAsBi compounds, crystal polymorphism including stable zincblende and metastable hexagonal structures, and material conversion by oxidation. These materials show various potential applications as a light source in the near-infrared band or white light, and exhibit nonlinear optical effects.

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  • Tetsuya Yamamoto, Rajasekaran Palani, Hisashi Kitami, Hisao Makino
    Article type: Research Report
    2024 Volume 2024 Article ID: 240404
    Published: 2024
    Released on J-STAGE: March 23, 2024
    JOURNAL OPEN ACCESS

    We present the size effects on the electrical and optical properties of high Hall mobility transparent conductive oxide (TCO) films, where the size effects were characterized by the disorder parameter. First, we deposited amorphous W-doped In2O3 (IWO) films with thicknesses ranging from 5 to 10 nm on glass substrates using reactive plasma deposition with dc-arc discharge. Then, we obtained polycrystalline IWO films by solid-phase crystallization, and elucidated the dominant factors determining the states of the carrier electrons and their carrier transport of the films. Decreasing the thickness from 10 to 5 nm, while retaining the carrier concentration, leading to a 2D-like films with induced a lattice disorder, resulting in reduced Hall mobility. A theoretically obtained electron–phonon coupling factor, which is found to be governed by the Debye temperature, carrier concentration, and disorder parameter, provided the cause of the above carrier transport behavior. In addition, based on the above electron–phonon coupling factor, we propose theoretical predictions of materials design to achieve high carrier transport ultra-thin TCO films.

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  • Yuki Uematsu
    Article type: Research Report
    2024 Volume 2024 Article ID: 240405
    Published: 2024
    Released on J-STAGE: May 02, 2024
    JOURNAL OPEN ACCESS

    Most electrolytes increase the surface tension of water. According to thermodynamics, this leads to a repulsive force between the gas–liquid interface and the ions. The thermodynamic properties and the computational theory of surface tension are first introduced. Subsequently, a quantitative comparison of ion adsorption for individual ion species is presented based on a theoretical analysis of experimental data. The analysis of experimental data on surface tension and contact angle at the oil–water interface and hydrophobic solid–liquid interface also reveals the universal nature of the interaction between ions and hydrophobic interfaces.

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  • Yoshiaki Hattori
    Article type: Research Report
    2024 Volume 2024 Article ID: 240406
    Published: 2024
    Released on J-STAGE: May 29, 2024
    JOURNAL OPEN ACCESS

    Optical observation of ultrathin crystals on substrates is important in research on layered materials. Ultrathin crystals are conventionally visualized using the optical interference effect in thermally-grown silicon substrates. Herein, a visualization technique that focuses on the optical properties of the substrate was developed. This method allows recognition of a monolayer and reliable identification of the number of layers in hexagonal boron nitride crystals. Furthermore, the difference in the thickness of the monolayer in a thick crystal was visualized, enabling the selection of mechanically exfoliated crystals.

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  • Motoki Yako, Yoshikazu Yamaoka, Koji Shibuno, Atsushi Ishikawa
    Article type: Research Report
    2024 Volume 2024 Article ID: 240407
    Published: 2024
    Released on J-STAGE: July 30, 2024
    JOURNAL OPEN ACCESS
    Supplementary material

    With the advancement of machine vision, image analysis utilizing high-dimensional data has become feasible, and its application has been vigorously studied. Hyperspectral cameras, which can capture wavelength information and spatial information at the same time, have been developed for practical use in various fields such as food, agriculture, chemistry, and medicine. However, existing hyperspectral cameras are limited by significantly low sensitivity and shutter speed associated with the spectrometry process, as well as by the increased size of the systems, hindering their widespread adoption in industrial applications. In this paper, we show an overview of an ultra-sensitive hyperspectral camera we developed by employing compressive sensing technology, its implementation into a digital camera, and its performances.

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  • Masashi Miyata
    Article type: Research Report
    2024 Volume 2024 Article ID: 240408
    Published: 2024
    Released on J-STAGE: August 02, 2024
    JOURNAL OPEN ACCESS

    Image sensors are the eyes of machines and the primary components in cutting-edge technologies such as smartphones and self-driving cars. These technologies require high-sensitivity sensors capable of high-speed or dark-scene imaging. However, in conventional color-image sensors, the total amount of light received is inherently limited because the light-absorptive color filters are integrated on all pixels, which hinders improvement to sensitivity. Hence, we develop light-transmissive metalenses that can separate and focus primary colors on high-density pixels and propose a filter-free sensor architecture to utilize them. This paper introduces such full-color-sorting metalenses and discusses their effect on image-sensor sensitivity.

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  • Makusu Tsutsui
    Article type: Research Report
    2024 Volume 2024 Article ID: 240409
    Published: 2024
    Released on J-STAGE: August 08, 2024
    JOURNAL OPEN ACCESS
    Supplementary material

    Nanopores, the tiny apertures within a thin membrane, offer a remarkably efficient pathway for harnessing electricity from the salinity gradient between ubiquitous seawater and freshwater resources. Over the past decade, significant efforts have been devoted to leveraging the exceptional capabilities of single-nanopore osmotic power generators in the form of coupon-scale nanoporous membranes. This article provides a comprehensive review of the latest advancements in this field, elucidating future opportunities and obstacles toward the real-world deployment of nanopore-based power generation systems.

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  • Toshiaki Kato
    Article type: Research Report
    2024 Volume 2024 Article ID: 240410
    Published: 2024
    Released on J-STAGE: August 10, 2024
    JOURNAL OPEN ACCESS

    Transition metal dichalcogenides (TMDs) are atomically thin layered materials that have attracted intense attention because of their outstanding optical and electrical properties. Despite recent advances in production, the quality of TMD crystals still requires improvement. Elucidating details of the TMD crystal-growth mechanism is therefore critically important. To this end, we have developed a technique for in-situ monitoring of chemical vapor deposition, allowing direct and detailed observation of the crystal nucleation and growth dynamics of monolayer and single-crystal TMD. Here, we review our recent experimental and theoretical findings about the TMD growth mechanism, including the diffusion length of precursors, non-classical nucleation, and liquid–solid-transfer growth.

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  • Nobuyuki Yoshioka, Tsuyoshi Okubo, Yasunari Suzuki, Wataru Mizukami
    Article type: Research Report
    2024 Volume 2024 Article ID: 240411
    Published: 2024
    Released on J-STAGE: August 22, 2024
    JOURNAL OPEN ACCESS

    In the era of the rapid development of quantum devices, the next milestone to be achieved is to surpass the performance of classical computers with quantum computers in practical problems, that is, to achieve the quantum advantage. In this paper, we introduce recent studies that argue that the main field for this purpose is envisioned to be condensed matter physics. The main contributions of this paper are summarized in three points: (1) the proposal of a method for analyzing the execution time of classical computation algorithms based on the tensor network method, (2) the evaluation of the execution time of fault-tolerant quantum computation algorithms at the instruction level, and (3) the discovery of a quantum advantage region in two-dimensional strongly correlated quantum many-body systems. The lattice model discussed in this paper is expected to play a guiding role in the research and development of fault-tolerant quantum computers, as it requires fewer resources in terms of the number of qubits and execution time than other known platforms for the quantum advantage.

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  • Tomoya Asaba
    Article type: Research Report
    2024 Volume 2024 Article ID: 240412
    Published: 2024
    Released on J-STAGE: September 07, 2024
    JOURNAL OPEN ACCESS

    Recently, we developed a novel method to fabricate quantum wires for a Mott insulator on graphite substrates using pulsed-laser deposition, which afforded structures such as stripes, junctions, and nanorings. These single-crystalline wires are one-unit-cell in thickness and precisely two- to four-unit-cell in width, and can extend to several micrometers in length. Spectroscopy measurements and theoretical calculations reveal strong electron correlations. Moreover, our findings emphasize the importance of non-equilibrium reaction-diffusion processes in atomic-scale self-organization, which can realize exotic fractionalized states in purely one-dimensional quantum wires.

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  • Keisuke Kondo
    Article type: Research Report
    2024 Volume 2024 Article ID: 240413
    Published: 2024
    Released on J-STAGE: October 22, 2024
    JOURNAL OPEN ACCESS

    In this article, we describe the development of an unprecedented ultracompact optical pulse measurement device. The device was fabricated using silicon photonics technology, and integrated on a millimeter-scale chip. We fabricated an on-chip optical correlator consisting of a waveguide-type-photodetector array, and demonstrated the measurement of correlation waveforms of picosecond pulses. Furthermore, using the on-chip optical correlator and a tunable filter, we demonstrated the measurement of complex amplitude waveforms of optical pulses using a short-pulse measurement method called the sonogram method. We expect that our study will lead to the development of a user-friendly optical pulse measurement device that can be used outside of laboratories.

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  • Shinichiro Mouri, Tsutomu Araki
    Article type: Research Report
    2024 Volume 2024 Article ID: 240414
    Published: 2024
    Released on J-STAGE: October 24, 2024
    JOURNAL OPEN ACCESS

    Recently, moiré superlattice systems, which are formed when atomically thin layered materials are stacked with an arbitral angle, have attracted considerable attention because of their unique physical properties. On the other hand, there are still several unresolved issues concerning their phonon and thermophysical properties. In this paper, we introduce a thermal conductivity measurement method depending on the stacking angle of a suspended moiré superlattice system by using Raman spectroscopy.

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  • Takafumi Kojima, Sho Masui
    Article type: Research Report
    2024 Volume 2024 Article ID: 240415
    Published: 2024
    Released on J-STAGE: November 02, 2024
    JOURNAL OPEN ACCESS

    The ALMA telescope, operating in the Republic of Chile, has achieved various results since 2011. However, advanced enhancements are required for it to continue as the leading technology in the field of astronomy. This telescope is termed ALMA 2 in Japan, and one of the most important developments is the wide instantaneous bandwidth of the telescope system. This article introduces part of the research on wideband technologies for the superconducting receiver frontend.

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  • Tomohiro Nozaki, Dae-Yeong Kim, Xiaozhong Chen
    Article type: Research Report
    2024 Volume 2024 Article ID: 240416
    Published: 2024
    Released on J-STAGE: November 21, 2024
    JOURNAL OPEN ACCESS

    With the increasing demand for renewable energy, research on plasma catalysis has been gaining momentum as an emerging low-carbon technology. An advantage of nonthermal plasma is that it facilitates large-scale nonequilibrium catalytic reactions that are inaccessible through conventional thermal approaches. Electrical energy activates stable molecules, paving the way for low-temperature chemical reactions in energy-intensive, heat-dependent systems. This article introduces a new concept of plasma-driven nonequilibrium catalysis and describes our research efforts to elucidate the plasma-surface interaction mechanisms, aiming for effective CO2 recycling toward a low-carbon society.

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  • Masaya Shigeta
    Article type: Research Report
    2024 Volume 2024 Article ID: 240417
    Published: 2024
    Released on J-STAGE: December 04, 2024
    JOURNAL OPEN ACCESS

    This article presents the following under the concept of “to engineer plasma as fluid”: computational demonstrations based on novel mathematical modeling for various phenomena in plasma-fluid-utilized manufacturing processes, such as the mass production of nanoparticles and arc welding, and additionally the recent study on lava flow simulation. Although the figures in this article are still images, the corresponding movies are available online.

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  • Nobuyuki Zettsu
    Article type: Research Report
    2024 Volume 2024 Article ID: 240418
    Published: 2024
    Released on J-STAGE: December 05, 2024
    JOURNAL OPEN ACCESS

    Lithium-ion batteries have been installed in various mobility applications, such as automobiles, and the performance requirements for these batteries have become increasingly stringent. To control ion diffusion dynamics at the electrode/electrolyte interface, it is essential to develop advanced technologies for designing the active material surface and forming a reaction field at the electrode/electrolyte interface to transport ions and electrons more efficiently, in addition to current passivation film techniques. In this paper, we summarize our research results on the phase interface control of lithium-ion battery electrode material, which addresses the compatibility of high durability and high power.

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  • Hiroyuki Yoshida, Hiroyuki Ishii
    Article type: Research Report
    2024 Volume 2024 Article ID: 240419
    Published: 2024
    Released on J-STAGE: December 12, 2024
    JOURNAL OPEN ACCESS

    In organic semiconductors, electron mobilities are generally lower than hole mobilities. It has not been apparent whether this is due to extrinsic factors, such as the electron trap formed by the atmosphere, or whether the electron mobility is inherently low. We developed angle-resolved low-energy inverse photoelectron spectroscopy and succeeded in measuring the energy band structure (the energy–momentum relation) of the conduction band of organic semiconductor for the first time. Through a detailed analysis of the bandwidth, we clarified that the polaron is formed and proposed a new model called a partially dressed polaron model. We incorporate this model into the wave-packet diffusion method to calculate the electron/hole mobilities and proved that the electron mobility is inherently lower than the hole mobility owing to the electron–phonon interaction.

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