Japanese Journal of Applied Physics - IOPscience

Japanese Journal of Applied Physics - IOPscience
Japanese Journal of Applied Physics
The Japan Society of Applied Physics (JSAP)
serves as an academic interface between science and engineering and an interactive platform for academia and the industry. JSAP is a "conduit" for the transfer of fundamental concepts to the industry for development and technological applications.
JSAP was established as an official academic society in 1946, and since then, it has been one of the leading academic societies in Japan. The society's interests cover a broad variety of scientific and technological fields, and JSAP continues to explore state-of-the-art and interdisciplinary topics.
To this end, the JSAP holds annual conferences; publishes scientific journals; actively sponsors events, symposia, and festivals related to science education; and compiles information related to state-of-the-art technology for the public.
SUPPORTS OPEN ACCESS
The
Japanese Journal of Applied Physics
(JJAP) is an international journal for the advancement and dissemination of knowledge in all fields of applied physics.
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Median submission to first decision before peer review
5 days
Median submission to first decision after peer review
26 days
Impact factor
1.8
Citescore
2.9
The following article is
Open access
Factors determining bond wave speed in wafer bonding
Ryosuke Sato
et al
2025
Jpn. J. Appl. Phys.
64
03SP55
View article
, Factors determining bond wave speed in wafer bonding
PDF
, Factors determining bond wave speed in wafer bonding
Wafer-level direct bonding has become a critical process for advanced 3D architectures in logic, memory, and CMOS image sensors. The minimization of the wafer distortion caused by wafer bonding is essential for a precise overlay for the subsequent backside lithography. Although numerous studies have reported a strong connection between distortion and bond wave speed, discussion of the relationship between the pre-bonding surface and the bond wave speed has been inadequate. This study aimed to clarify the latter correlation using 300 mm wafers. Through the application of surface-sensitive techniques, we found that the plasma activation process enhances the amount of Si–OH groups on the surface, thereby enhancing the bond wave speed. Conversely, high-power plasma results in a slight decrease in bond wave speed because of the influence of excessive adsorbed water. In addition, the present study reveals no correlation between bond wave speed and adherence energy.
Material science and device physics in SiC technology for high-voltage power devices
Tsunenobu Kimoto 2015
Jpn. J. Appl. Phys.
54
040103
View article
, Material science and device physics in SiC technology for high-voltage power devices
PDF
, Material science and device physics in SiC technology for high-voltage power devices
Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600–1700 V) SiC Schottky barrier diodes (SBDs) and power metal–oxide–semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.
The following article is
Open access
Progress report on high aspect ratio patterning for memory devices
Meihua Shen
et al
2023
Jpn. J. Appl. Phys.
62
SI0801
View article
, Progress report on high aspect ratio patterning for memory devices
PDF
, Progress report on high aspect ratio patterning for memory devices
High aspect ratio (HAR) silicon nitride and silicon oxide (ONON) channel hole patterning in 3D NAND flash presents great challenges. This report summarizes some of the recent progress in patterning from the perspective of HAR etching and deposition-etch co-optimization (DECO). HAR etching mechanisms will be discussed, with a focus on how to reduce the aspect ratio-dependent etching (ARDE) effect. Highlights of the new low-temperature etch process will be presented, with significant improvement in the ARDE being observed. New simulation results from a Monte Carlo feature-scale model provide insights into ion scattering and mask interactions on the control of the channel hole profile. DECO is a new frontier to enable better control of the channel hole shape at HAR. Film tier optimization and carbon liner insertion results show improvement in channel hole profile control.
TiO
Photocatalysis: A Historical Overview and Future Prospects
Kazuhito Hashimoto
et al
2005
Jpn. J. Appl. Phys.
44
8269
View article
, TiO2 Photocatalysis: A Historical Overview and Future Prospects
PDF
, TiO2 Photocatalysis: A Historical Overview and Future Prospects
Photocatalysis has recently become a common word and various products using photocatalytic functions have been commercialized. Among many candidates for photocatalysts, TiO
is almost the only material suitable for industrial use at present and also probably in the future. This is because TiO
has the most efficient photoactivity, the highest stability and the lowest cost. More significantly, it has been used as a white pigment from ancient times, and thus, its safety to humans and the environment is guaranteed by history. There are two types of photochemical reaction proceeding on a TiO
surface when irradiated with ultraviolet light. One includes the photo-induced redox reactions of adsorbed substances, and the other is the photo-induced hydrophilic conversion of TiO
itself. The former type has been known since the early part of the 20th century, but the latter was found only at the end of the century. The combination of these two functions has opened up various novel applications of TiO
, particularly in the field of building materials. Here, we review the progress of the scientific research on TiO
photocatalysis as well as its industrial applications, and describe future prospects of this field mainly based on the present authors' work.
The following article is
Open access
Interface formation and optical design of EUV reflective multilayer mirrors
Takeo Ejima 2026
Jpn. J. Appl. Phys.
65
050802
View article
, Interface formation and optical design of EUV reflective multilayer mirrors
PDF
, Interface formation and optical design of EUV reflective multilayer mirrors
Reflective multilayer mirrors are indispensable optical components in the extreme ultraviolet (EUV) wavelength region, where conventional refractive and single-layer reflective optics are ineffective. This review summarizes the design, fabrication, and performance limitations of EUV reflective multilayer films, with emphasis on material selection, optical design, deposition processes, and interface formation. Established systems such as Mo/Si multilayers for 13.5 nm lithography demonstrate that EUV performance is approaching intrinsic limits imposed by absorption and unavoidable interfacial mixing. When extending these design concepts toward shorter wavelengths in the beyond-EUV (BEUV) region around 6.
nm, additional challenges emerge, including increased absorption, reduced optical contrast, and enhanced sensitivity to interfacial reactions and non-equilibrium growth processes. This review clarifies the fundamental differences between BEUV and EUV multilayers and emphasizes the importance of interface control for improving performance, providing general guidelines for next-generation EUV and BEUV reflective optics.
The following article is
Open access
Atomic layer deposition and its derivatives for extreme ultraviolet (EUV) photoresist applications
Dan N. Le
et al
2023
Jpn. J. Appl. Phys.
62
SG0812
View article
, Atomic layer deposition and its derivatives for extreme ultraviolet (EUV) photoresist applications
PDF
, Atomic layer deposition and its derivatives for extreme ultraviolet (EUV) photoresist applications
Solution-processed photoresists have been forerunners in semiconductor patterning for decades. Even with the drastic reduction in photolithography wavelength, traditional spin-on resists still support the fabrication of the most advanced, sub-5 nm node logic and memory devices using EUV lithography (EUVL) (
= 13.5 nm). However, trade-off between resolution, sensitivity, and roughness in the conventional resists pose a critical challenge in the race towards device downscaling to 1 nm node. While great efforts are being made to improve spin-on EUV photoresist performance, there has been emergence of new approaches focused on developing novel resists via vapor-phase processing routes, such as atomic layer deposition (ALD) and its analogs. This review summarizes recent advances in EUVL photoresist development based on ALD and its derivative techniques, which include ALD-based inorganic–organic dry resists and hybrid resists synthesized by infiltrating conventional spin-on resists. Despite being in the early stage, initial studies have shown the great potential of ALD applications in EUVL photoresist development.
Physical reservoir computing—an introductory perspective
Kohei Nakajima 2020
Jpn. J. Appl. Phys.
59
060501
View article
, Physical reservoir computing—an introductory perspective
PDF
, Physical reservoir computing—an introductory perspective
Understanding the fundamental relationships between physics and its information-processing capability has been an active research topic for many years. Physical reservoir computing is a recently introduced framework that allows one to exploit the complex dynamics of physical systems as information-processing devices. This framework is particularly suited for edge computing devices, in which information processing is incorporated at the edge (e.g. into sensors) in a decentralized manner to reduce the adaptation delay caused by data transmission overhead. This paper aims to illustrate the potentials of the framework using examples from soft robotics and to provide a concise overview focusing on the basic motivations for introducing it, which stem from a number of fields, including machine learning, nonlinear dynamical systems, biological science, materials science, and physics.
The following article is
Open access
A review of SRAM-based compute-in-memory circuits
Kentaro Yoshioka
et al
2024
Jpn. J. Appl. Phys.
63
120802
View article
, A review of SRAM-based compute-in-memory circuits
PDF
, A review of SRAM-based compute-in-memory circuits
This paper presents a tutorial and review of Static Random Access Memory-based compute-in-memory (CIM) circuits, with a focus on both digital CIM (DCIM) and analog CIM (ACIM) implementations. We explore the fundamental concepts, architectures, and operational principles of CIM technology. The review compares DCIM and ACIM approaches, examining their respective advantages and challenges. DCIM offers high computational precision and process scaling benefits, while ACIM provides superior power and area efficiency, particularly for medium-precision applications. We analyze various ACIM implementations, including current-based, time-based, and charge-based approaches, with a detailed look at charge-based ACIMs. The paper also discusses emerging hybrid CIM architectures that combine DCIM and ACIM to leverage the strengths of both approaches.
The following article is
Open access
Single-field-plate GaN HEMTs achieving >2200 V breakdown voltage and 106% dynamic on-resistance at 600 V stress
Zhichao Yang
et al
2026
Jpn. J. Appl. Phys.
65
066501
View article
, Single-field-plate GaN HEMTs achieving >2200 V breakdown voltage and 106% dynamic on-resistance at 600 V stress
PDF
, Single-field-plate GaN HEMTs achieving >2200 V breakdown voltage and 106% dynamic on-resistance at 600 V stress
This work reports GaN power high-electron-mobility transistors (HEMTs) that achieve a breakdown voltage (BV) exceeding 2400 V (defined at
DSS
<1 μA mm
−1
) through the implementation of a single gate field plate (FP). This design establishes a simplified yet optimized electric field profile, which is key to achieving a high BV while maintaining favorable dynamic performance. The dynamic ON-resistance (
on
) remains as low as 106% after OFF-state
DS
stress at 600 V. The combination of high BV and robust dynamic characteristics demonstrates that the single gate FP technique is a promising approach for the mass production of high-performance GaN power HEMTs, offering the potential for reduced process complexity and cost without compromising device performance.
The following article is
Open access
InGaN-based red light-emitting diodes: from traditional to micro-LEDs
Zhe Zhuang
et al
2022
Jpn. J. Appl. Phys.
61
SA0809
View article
, InGaN-based red light-emitting diodes: from traditional to micro-LEDs
PDF
, InGaN-based red light-emitting diodes: from traditional to micro-LEDs
InGaN-based LEDs are efficient light sources in the blue–green light range and have been successfully commercialized in the last decades. Extending their spectral range to the red region causes a significant reduction in LED efficiency. This challenge hinders the integration of red, green, and blue LEDs based on III-nitride materials, especially for full-color micro-LED displays. We review our recent progress on InGaN-based red LEDs with different chip sizes from hundreds to tens of micrometers, including the epitaxial structures, device fabrication, and optical performance (peak wavelength, full-width at half-maximum, light output power, efficiency, temperature stability, and color coordinates).
Selective wiring of receive electrodes for simplified ultrasound arrays with phase-coherence fusion of dense and sparse apertures
Wenlan Dong and Norio Tagawa 2026
Jpn. J. Appl. Phys.
65
08SP14
View article
, Selective wiring of receive electrodes for simplified ultrasound arrays with phase-coherence fusion of dense and sparse apertures
PDF
, Selective wiring of receive electrodes for simplified ultrasound arrays with phase-coherence fusion of dense and sparse apertures
We propose an ultrasonic imaging framework that simplifies the receive-side hardware configuration by selectively wiring multiple array elements to a limited number of receive electrodes, and compensates for the resulting image degradation by phase-based fusion of complex images obtained from dense and sparse receive apertures. In the considered design, a 64-element linear array is connected to 16 receive electrodes to form two wiring patterns: a dense grouping that improves stability and a sparse grouping that expands the effective aperture. For each pattern, complex images are reconstructed using coherence factor weighted delay-and-sum beamforming. We then investigate three fusion methods driven by the phase relationship between the dense and sparse complex images: (i) pixel-wise phase-difference weighting, (ii) phase-coherence weighting with a five-pixel cross-shaped neighborhood, and (iii) phase-coherence weighting with a 3 × 3 neighborhood. Simulations using carotid artery, wire target, and cyst phantoms show that the pixel-wise method best preserves fine spatial details, while the coherence-based methods more effectively suppress phase-inconsistent clutter and improve contrast, especially for low-contrast cyst targets. The five-pixel coherence-based fusion provides a favorable trade-off between boundary sharpness and clutter suppression under the selectively wired configuration studied in this work.
Non-invasive real-time sheath diagnostics using RF wall sensor: application to transformer coupled plasma-reactive ion etch system
Kanghyuk Seo
et al
2026
Jpn. J. Appl. Phys.
65
08SP01
View article
, Non-invasive real-time sheath diagnostics using RF wall sensor: application to transformer coupled plasma-reactive ion etch system
PDF
, Non-invasive real-time sheath diagnostics using RF wall sensor: application to transformer coupled plasma-reactive ion etch system
This study investigates plasma sheath dynamics in electronegative oxygen plasmas using a non-invasive plasma sheath monitoring sensor (PSMS). The PSMS detects radio-frequency (RF) magnetic field variations induced by sheath displacement currents, enabling real-time monitoring of sheath dynamics without perturbing the plasma. Variations in the PSMS signal are primarily attributed to changes in sheath capacitance caused by plasma density evolution and ion species transitions. Experiments on power and pressure-dependency in O
plasma reveal continuous E–H mode transitions and shifts in electron heating mechanisms from collisionless to ohmic heating. Experiment on Ar and O
gas mixing ratio demonstrates that the PSMS is sensitive to gas composition, and it successfully captured sheath stabilization and saturation behavior arising from increased electronegativity. These results indicate that the PSMS provides a potential of a non-invasive plasma process diagnostics for monitoring complex sheath dynamics, offering significant potential for optimizing high-aspect-ratio etching processes.
Acoustic impedance image of granite and soil aggregate by using high-frequency ultrasound
Rikuta Uehara
et al
2026
Jpn. J. Appl. Phys.
65
08SP12
View article
, Acoustic impedance image of granite and soil aggregate by using high-frequency ultrasound
PDF
, Acoustic impedance image of granite and soil aggregate by using high-frequency ultrasound
In soil health monitoring, understanding the spatial distribution of organic and inorganic soil components is crucial. However, these components are currently measured mainly by methods that involve destructive processing. Therefore, this study proposes a non-destructive method for visualizing their distribution in soil using high-frequency ultrasound. Specifically, we evaluated acoustic-impedance imaging with an 80 MHz ultrasonic transducer, which provides a spatial resolution of several tens of micrometers. First, to verify the effectiveness of the method, we investigated mineral identification in a granite specimen composed solely of inorganic material. The results confirmed that mineral species could be distinguished based on differences in acoustic-impedance distribution with a cross-correlation-based analysis. Furthermore, by applying the method to soil aggregates, we demonstrated non-destructive, simultaneous visualization of the spatial distributions of organic and inorganic matter. These findings indicate that high-frequency ultrasound is a promising tool for non-destructive soil characterization.
The following article is
Open access
Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Kislon Voïtchovsky 2026
Jpn. J. Appl. Phys.
65
080802
View article
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
PDF
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Solid-liquid interfaces (SLIs) are ubiquitous and play a central role in science and technology. Their properties control processes such as crystal growth, protein folding and function, heterogeneous catalysis, lubrication and wetting. All these processes occur at the molecular level where a continuum thermodynamics description often breaks down. The ability to get local and nanoscale experimental insights is therefore crucial. Atomic force microscopy (AFM) is a tool of choice to explore SLIs, especially for systems where the solid exhibits structural or chemical heterogeneity at the nanoscale and spatial averaging is not possible. This paper reviews some of the recent advances in the field relying on AFM, usually in conjunction with other techniques. The focus is placed on the emergence of order leading to novel phenomena across scales, rendered possible by the unique properties of SLIs and specific molecular effects. The review also proposes new research directions for the field.
Analysis of physical and virtual nodes of ion-gating reservoir for network size reduction
Hina Kitano
et al
2026
Jpn. J. Appl. Phys.
65
08SP11
View article
, Analysis of physical and virtual nodes of ion-gating reservoir for network size reduction
PDF
, Analysis of physical and virtual nodes of ion-gating reservoir for network size reduction
The rapid expansion of artificial intelligence (AI) applications has intensified concerns regarding excessive energy consumption and training speed. To address these issues, physical reservoir computing (PRC), an energy-efficient machine learning framework, is a suitable approach. However, the network remains highly redundant, and the training efficiency has not yet been fully optimized. To improve training efficiency, we optimized the network size of the electric double layer transistor ion-gating reservoir, a PRC device, using a backward method while evaluating performance on the NARMA2 task. This approach successfully reduced the number of nodes by nearly half without degrading accuracy. Analysis of the remaining nodes revealed that those retaining information from previous input steps contribute most strongly to computation. The ability to reduce node count without loss of performance suggests the potential for faster training and lower power consumption. These findings offer a practical strategy for developing compact and energy-efficient PRC systems suitable for edge-AI applications.
The following article is
Open access
Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Kislon Voïtchovsky 2026
Jpn. J. Appl. Phys.
65
080802
View article
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
PDF
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Solid-liquid interfaces (SLIs) are ubiquitous and play a central role in science and technology. Their properties control processes such as crystal growth, protein folding and function, heterogeneous catalysis, lubrication and wetting. All these processes occur at the molecular level where a continuum thermodynamics description often breaks down. The ability to get local and nanoscale experimental insights is therefore crucial. Atomic force microscopy (AFM) is a tool of choice to explore SLIs, especially for systems where the solid exhibits structural or chemical heterogeneity at the nanoscale and spatial averaging is not possible. This paper reviews some of the recent advances in the field relying on AFM, usually in conjunction with other techniques. The focus is placed on the emergence of order leading to novel phenomena across scales, rendered possible by the unique properties of SLIs and specific molecular effects. The review also proposes new research directions for the field.
The brush model for atomic force microscopy: progress in measuring absolute values of Young’s modulus and pericellular layer properties in biological cells and soft matter
Igor Sokolov 2026
Jpn. J. Appl. Phys.
65
080801
View article
, The brush model for atomic force microscopy: progress in measuring absolute values of Young’s modulus and pericellular layer properties in biological cells and soft matter
PDF
, The brush model for atomic force microscopy: progress in measuring absolute values of Young’s modulus and pericellular layer properties in biological cells and soft matter
Atomic force microscopy is a powerful tool to measure the mechanics of soft materials and cells. Standard methods, like the Hertz model, often yield confusing results because they ignores rough surfaces and the fuzzy pericellular layer surrounding cells. This progress report reviews a better approach, the brush model. This model accounts for the rough, brush-like outer layer of cells and solid surfaces. By separating this surface layer from the main cell body, the model reveals the absolute value of Young’s modulus of the cell body. It also measures the thickness and density of the brush layer itself. We review recent progress with this method, covering its basic theory, lab tests, and error analysis. We also highlight its growing success in detecting cancer and studying diseases. Overall, the brush model provides accurate absolute measurements that improve our understanding of cell mechanics as well as the mechanics of soft materials at the nanoscale.
Advances in picosecond ultrasonics for the characterization of mechanical properties of nanomaterials: a review
Akira Nagakubo 2026
Jpn. J. Appl. Phys.
65
070804
View article
, Advances in picosecond ultrasonics for the characterization of mechanical properties of nanomaterials: a review
PDF
, Advances in picosecond ultrasonics for the characterization of mechanical properties of nanomaterials: a review
The mechanical properties of nanomaterials frequently deviate from bulk values, necessitating precise characterization. While conventional methods are limited by substrate interference, picosecond ultrasonics offers a powerful non-contact, sub-THz probe for evaluating these properties. This review provides an overview of the fundamental theory and advanced instrumentation, such as asynchronous optical sampling. Key applications are discussed, including: (i) characterizing low-temperature structural phase transitions in SrTiO
; (ii) determining elastic constants and lattice anharmonicity in superhard diamond and nanocrystalline boron nitride, while addressing hardness overestimation from elastic recovery; and (iii) controlling the temperature coefficient of sound velocity in doped SiO
thin films. These results underscore the efficacy of picosecond ultrasonics in elucidating nanomechanics.
The following article is
Open access
On the influence of microstructure on fluorite ferroelectric embedded memories
Maximilian Lederer
et al
2026
Jpn. J. Appl. Phys.
65
070803
View article
, On the influence of microstructure on fluorite ferroelectric embedded memories
PDF
, On the influence of microstructure on fluorite ferroelectric embedded memories
The rise in artificial intelligence (AI) has led to a high demand for embedded non-volatile memories to reduce computation cost and power consumption. Fluorite-structure ferroelectrics have received growing attention with the discovery of ferroelectric hafnium oxide in 2008 and recent large-scale integration into industrial technology nodes, e.g. 1 Mbit ferroelectric RAM (FRAM) arrays by Sony. The ferroelectric layers are commonly of a polycrystalline nature, and due to the metastability of the ferroelectric orthorhombic phase, monoclinic phase fractions are often present. Since the crystallographic phase and its orientation will impact the observable polarization, the microstructure of the integrated film will be a major aspect for the device performance. Therefore, this work will explore the influence of the microstructure on different ferroelectric devices, i.e., ferroelectric field-effect transistors (FeFETs), ferroelectric metal field-effect transistors (FeMFETs), and FRAMs, and address its impact on vector-matrix multiplications used for hardware-accelerated AI.
Impact of excess oxygen on electrical characteristics and bias stability in plasma-enhanced atomic layer deposition ultrathin InOx FETs
Chia-Tsong Chen
et al
2026
Jpn. J. Appl. Phys.
65
070802
View article
, Impact of excess oxygen on electrical characteristics and bias stability in plasma-enhanced atomic layer deposition ultrathin InOx FETs
PDF
, Impact of excess oxygen on electrical characteristics and bias stability in plasma-enhanced atomic layer deposition ultrathin InOx FETs
Indium-based (In-based) oxide semiconductor channels fabricated by atomic layer deposition (ALD) has become a promising candidate for back-end of line (BEOL) transistors and memory devices integrated with advanced CMOS technology. Although high reactivity plasma-enhanced ALD (PEALD) effectively removed the impurity ligands, the incorporation of excess oxygen into oxide semiconductor channels introduces the acceptor-like traps, which degrade device performance and bias stability. In this work, we characterize PEALD AlO
-passivated InO
FETs with channel thickness ranging from 1.8 to 2.6 nm, under different annealing ambient and temperatures. The 1.8 nm InO
FET subjected to oxidizing annealing shows current degradation, voltage hysteresis, and bias instability due to subgap trap formation caused by excess oxygen incorporation. Increasing the channel thickness to 2.6 nm mitigates these issues by reducing the interfacial effect from accumulated oxygen. This study provides design guidelines for BEOL-compatible oxide semiconductor FET fabricated by PEALD, enabling monolithic 3-dimensional integration.
Spectral irradiance distribution at AM 1.5 in the Arabian desert and its influence on the current balance of multijunction PV technologies
Saw et al
View accepted manuscript
, Spectral irradiance distribution at AM 1.5 in the Arabian desert and its influence on the current balance of multijunction PV technologies
PDF
, Spectral irradiance distribution at AM 1.5 in the Arabian desert and its influence on the current balance of multijunction PV technologies
The performance of multijunction PV devices, such as two-terminal perovskite/silicon cells, is strongly influenced by spectral irradiance distributions, as current matching among sub-cells is highly sensitive to spectral variations. In desert regions, the increasing frequency of dust and sandstorms may significantly alter the spectral distribution of solar irradiance and thus can adversely affect PV module performance. In this work, we present an experimental investigation of the distribution of spectral irradiances measured in clear-sky conditions at AM1.5 in Abu Dhabi and assess its impact on the current balance of multijunction PV technologies. High-resolution spectral measurements were obtained using a dual-axis tracked spectroradiometer covering the wavelength range of 300nm–2500 nm. The results reveal substantial deviations of local spectra at AM1.5 from the standard reference AM1.5 spectrum, along with significant spectral shifts: these shifts were found to induce current imbalances of up to 10% in perovskite/silicon-based multijunction devices. The findings highlight the importance of realistic, location-specific spectral data in the design and optimisation of multijunction PV technologies.
DPD simulation and FMO interaction analysis for electropore generated by voltage application on POPC membrane
Okuwaki et al
View accepted manuscript
, DPD simulation and FMO interaction analysis for electropore generated by voltage application on POPC membrane
PDF
, DPD simulation and FMO interaction analysis for electropore generated by voltage application on POPC membrane
Electroporation occurs when voltage is applied to lipid membranes. It has various applications, including transfection of DNA into cells. However, the molecular mechanisms underlying pore formation are not well understood. Therefore, dissipative particle dynamics (DPD) simulations were performed on a POPC membrane model. A field-electrostatic method was used to apply voltage, and a set of effective interaction parameters among particles was obtained through fragment molecular orbital (FMO) calculations. Using a reverse-mapping technique, an FMO-based interaction analysis was performed near the generated pore, revealing that a balance between electrostatic and dispersion interactions plays a key role in electropore stabilization.
Realizing high performance flexible multilevel memory based on charge storage in Au nanoparticles and electrets
LI et al
View accepted manuscript
, Realizing high performance flexible multilevel memory based on charge storage in Au nanoparticles and electrets
PDF
, Realizing high performance flexible multilevel memory based on charge storage in Au nanoparticles and electrets
In this paper, we report on the pentacene based field-effect transistors (FETs) and flexible nano-floating gate-based transistor memory (NFGM) devices that fabricated on ultra-flexible 2 μm Parylene C, deposited on different substrates. All thin-film layers are organic materials, which can be deposited at low temperatures. The electrical characteristics of the various FETs were evaluated and compared. Additionally, the flexible NFGM, with the structure of Pentacene (30 nm)/HSQ (19 nm)/Au NPs (10 nm)/PC (100 nm)/PMMA (160 nm)/PC (2 μm)/Kapton showed stable performance and achieved a large window of 23 V under ±40 V pulses operation, the IDS current on/off ratio exceeded 105 and the retention time was determined to be more than 108 seconds under bending conditions. Moreover, the NFGM device exhibited high-performance multilevel charge storage with five distinct current levels, and the underlying mechanisms were discussed, these results signify the potential for organic memory devices in various applications.
Design of SiGe films with uniform compositions on Si substrates towards applications for MAPbI
/SiGe tandem solar cells
Yagi et al
View accepted manuscript
, Design of SiGe films with uniform compositions on Si substrates towards applications for MAPbI3/SiGe tandem solar cells
PDF
, Design of SiGe films with uniform compositions on Si substrates towards applications for MAPbI3/SiGe tandem solar cells
Perovskite/silicon tandem solar cells have attracted attention as a promising approach to overcome the efficiency limit of single-junction devices. Mixed-halide perovskites are generally used as top-cell absorbers; however, they suffer from stability issues due to the light-induced phase separation. In this study, we propose a potentially more stable configuration consisting of a single-halide perovskite, methylammonium lead iodide (MAPbI3), and silicon–germanium (SiGe). We establish design targets for SiGe composition and thickness and develop a fabrication process based on a liquid-phase epitaxy, in which Al–Ge alloy paste is screen-printed onto Si substrates and subsequently annealed. Simulations indicate an optimal Ge content of 39 mol% and a minimum SiGe thickness of 0.5 μm. Rapid cooling during liquid-phase epitaxy enabled the growth of compositionally-uniform, epitaxial SiGe layers on Si substrates with thicknesses exceeding the target. These results lay the groundwork for the device design and process development of MAPbI3/SiGe tandem solar cells.
The following article is
Open access
Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
Yashiro et al
View accepted manuscript
, Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
PDF
, Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
A simple optical system capable of acquiring large-area projections from five or more directions within the same plane is proposed. The proposed method employs Laue-case Bragg reflections from a single crystal to split a white synchrotron radiation beam into multiple beamlets, each over 5 mm wide. This offers the advantage of rapid adjustment using relatively inexpensive components. Simultaneous acquisition of projection images from five directions using this novel method was also successfully demonstrated.
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The following article is
Open access
Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Kislon Voïtchovsky 2026
Jpn. J. Appl. Phys.
65
080802
View article
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
PDF
, Exploring the quirks of solid–liquid interfaces with atomic force microscopy
Solid-liquid interfaces (SLIs) are ubiquitous and play a central role in science and technology. Their properties control processes such as crystal growth, protein folding and function, heterogeneous catalysis, lubrication and wetting. All these processes occur at the molecular level where a continuum thermodynamics description often breaks down. The ability to get local and nanoscale experimental insights is therefore crucial. Atomic force microscopy (AFM) is a tool of choice to explore SLIs, especially for systems where the solid exhibits structural or chemical heterogeneity at the nanoscale and spatial averaging is not possible. This paper reviews some of the recent advances in the field relying on AFM, usually in conjunction with other techniques. The focus is placed on the emergence of order leading to novel phenomena across scales, rendered possible by the unique properties of SLIs and specific molecular effects. The review also proposes new research directions for the field.
The following article is
Open access
Extremely stable virus sensing using graphene FET with suppressed drift characteristics due to reduction of gate leakage current by passivation layer
Kaori Yamamoto
et al
2026
Jpn. J. Appl. Phys.
65
08SP07
View article
, Extremely stable virus sensing using graphene FET with suppressed drift characteristics due to reduction of gate leakage current by passivation layer
PDF
, Extremely stable virus sensing using graphene FET with suppressed drift characteristics due to reduction of gate leakage current by passivation layer
We have improved the drift characteristics of the graphene FET biosensor that have been a great problem in the previous graphene FET biosensing, enabling stable virus detection. Among the various origins of the drift characteristics, we found out the gate leakage current through the ionic electrolyte solution between the reference gate electrode and the metal source/drain electrodes exposed to the solution attributes largely to the drift characteristics. Moreover, this gate leakage current decreases over time and shows the drift characteristics. The gate leakage current was dramatically suppressed by passivating the source/drain metal electrodes with the photoresist (SU-8) and/or SiO
. As a result, the drift slope of the substrate with the passivation layer is improved and becomes one-sixth of that without the passivation layer. Furthermore, the electrical charge of SARS-CoV-2 could be clearly detected by suppressing the drift characteristics using the antibody modified graphene field-effect transistor with the passivation layer.
The following article is
Open access
Etch profiles in silicon in SF
and O
plasma based on etch-depth-dependent O/F transport gradient model
Shuto Tsuchioka
et al
2026
Jpn. J. Appl. Phys.
65
08SP06
View article
, Etch profiles in silicon in SF6 and O2 plasma based on etch-depth-dependent O/F transport gradient model
PDF
, Etch profiles in silicon in SF6 and O2 plasma based on etch-depth-dependent O/F transport gradient model
This study quantitatively investigates the “bowing” mechanism in high-aspect-ratio (HAR) silicon etching using SF
/O
inductively coupled plasmas through a multi-scale simulation. By integrating reactor-scale and feature-scale modeling, we analyzed the dynamic radical balance at the etch front. Results provide numerical proof for the “transport gradient model,” demonstrating that the localized O/F flux ratio [%]—accounting for Knudsen transport and sticking probabilities—is the decisive factor for sidewall protection, advancing the qualitative O/F intensity ratio from our previous work. We identified a critical threshold for this flux ratio between 3.5% and 3.6%. Below this threshold, the surface coverage transitions from oxygen-dominant to fluorine-dominant, triggering a nonlinear surge in the chemical etching rate. This explains why the 30% O
condition maintains verticality at shallow depths, while the 20% O
condition causes immediate bowing. These findings provide a theoretical foundation for optimizing radical fluxes in high-fidelity HAR etching.
The following article is
Open access
Depth control of protective layer for HF gas etching via TMSDMA vapor exposure
Tsubasa Imamura
et al
2026
Jpn. J. Appl. Phys.
65
08SP04
View article
, Depth control of protective layer for HF gas etching via TMSDMA vapor exposure
PDF
, Depth control of protective layer for HF gas etching via TMSDMA vapor exposure
In this study, we demonstrate that diluted tri-methyl silyl dimethyl amine (TMSDMA) enables time-controlled formation of a protective layer for HF-based gas etching of SiO
film. A threshold TMSDMA dose of
required for effective passivation was identified through water contact angle measurements, ToF-SIMS analysis, and etching-resistance tests. Cavity-structure experiments showed that the protection depth increases systematically with exposure time of TMSDMA, confirming diffusion-limited penetration of TMSDMA molecules. The measured depth profiles were well explained by a Knudsen-diffusion-based model, enabling predictive estimation of protection depth for various cavity gap distances. These findings indicate that diluted TMSDMA exposure provides a controllable and predictable method to regulate protection depth, offering a promising approach for taper correction in high-aspect-ratio channel holes of advanced 3D NAND devices.
The following article is
Open access
Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
Wataru Yashiro
et al
2026
Jpn. J. Appl. Phys.
View article
, Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
PDF
, Large-area multi-beam imaging using Laue-case Bragg reflections from single crystal
A simple optical system capable of acquiring large-area projections from five or more directions within the same plane is proposed. The proposed method employs Laue-case Bragg reflections from a single crystal to split a white synchrotron radiation beam into multiple beamlets, each over 5 mm wide. This offers the advantage of rapid adjustment using relatively inexpensive components. Simultaneous acquisition of projection images from five directions using this novel method was also successfully demonstrated.
The following article is
Open access
Topological optimization of diffraction grating in slow-light grating nonmechanical beam scanner
Keisuke Hirotani
et al
2026
Jpn. J. Appl. Phys.
View article
, Topological optimization of diffraction grating in slow-light grating nonmechanical beam scanner
PDF
, Topological optimization of diffraction grating in slow-light grating nonmechanical beam scanner
To improve the performance of silicon-photonics-based light detection and ranging (LiDAR), we investigated the optimal design and experimental performance of slow-light grating (SLG), a nonmechanical beam scanner integrated into LiDAR system. The SLG structure was topologically optimized via covariance matrix adaptation evolution strategy to suppress beam divergence, sidelobes, and their wavelength dependence, while enhancing the field of view (FOV) and output efficiency. We identified SLG designs that improve specific performance while maintaining the others, which was also confirmed experimentally. A symmetric SLG, particularly suitable for small footprint and simple control, achieves the widest FOV of 56°, representing 1.4-fold increase over conventional SLGs, while suppressing beam divergence. An asymmetric SLG, suitable for high efficiency, enhances the radiation efficiency by 4.5 dB and LiDAR signal intensity by >10 dB, while maintaining a wide FOV of 50°. These improvements will relax the requirements for beam-collimating lens and enhance the LiDAR sensitivity.
The following article is
Open access
Direct thermal imaging of influence of transition metal dichalcogenide interlayer on spin-current injection in Pt/Y
Fe
12
heterostructure
Shun-ichi Takano
et al
2026
Jpn. J. Appl. Phys.
View article
, Direct thermal imaging of influence of transition metal dichalcogenide interlayer on spin-current injection in Pt/Y3Fe5O12 heterostructure
PDF
, Direct thermal imaging of influence of transition metal dichalcogenide interlayer on spin-current injection in Pt/Y3Fe5O12 heterostructure
The spin Peltier effect (SPE) in Pt/WSe
/Y
Fe
12
(YIG) and Pt/WS
/YIG heterostructures is investigated using lock-in thermography. Since inserting atomically thin transition metal dichalcogenides (TMDs), such as WSe
, between Pt and YIG is known to enhance the voltage induced by the spin Seebeck effect, similar enhancement is expected for SPE. Contrary to this expectation, the SPE-induced temperature modulation is strongly suppressed in the TMD-inserted regions compared with bare Pt/YIG regions. Raman spectroscopy reveals sputtering-induced structural degradation of WSe
, hindering spin-current injection into YIG. These results highlight the sensitivity of spin-current transport to interface quality in spin-caloritronic devices incorporating atomically thin TMDs.
The following article is
Open access
Effect of Ge doping on the elastic properties of Au: softening in shear modulus
Mikio William Yoshioka-Hunter and Kentaro Kyuno 2026
Jpn. J. Appl. Phys.
65
078004
View article
, Effect of Ge doping on the elastic properties of Au: softening in shear modulus
PDF
, Effect of Ge doping on the elastic properties of Au: softening in shear modulus
By evaluating the elastic constants of an AuGe alloy by first-principles calculation, it is found that the shear modulus of Au is significantly reduced by alloying with Ge. This finding could explain not only the low melting temperature of the eutectic system but also the fluidity of AuGe alloy, which seems to facilitate low-temperature growth of crystalline Ge nanowires and thin films induced by Au. The shear modulus could be considered as an additional factor in exploring a new system for metal-induced crystallization of semiconductors.
The following article is
Open access
Clarifying the physical origin of long-period charge fluctuations in Si fin-type quantum dots
Hiroshi Oka
et al
2026
Jpn. J. Appl. Phys.
View article
, Clarifying the physical origin of long-period charge fluctuations in Si fin-type quantum dots
PDF
, Clarifying the physical origin of long-period charge fluctuations in Si fin-type quantum dots
Si quantum bits (qubits) have attracted attention as the building block of highly integrated quantum computers due to their compatibility with the modern complementary metal-oxide-semiconductor (CMOS) technology. For the practical operation of quantum computers, it is important not only to pursue the highest performance of qubits, but also to minimize their long-period instability in performance as they necessitate the frequent monitoring and calibration of parameters. With the Si spin qubits, fluctuations of performance over a period of minutes or even hours have been reported, which originate from the charge fluctuations. However, the cause-and-effect of long-period charge fluctuations in Si spin qubits has not been thoroughly discussed. This paper provides a brief overview of the Si spin qubit technology, focusing on the issue of long-period charge fluctuations, and presents our experimental results to clarify the physical origin of long-period charge fluctuations in fin-type quantum dots through random telegraph noise (RTN) characterization.
The following article is
Open access
Achieving smooth and transferable AlN films on h-BN via in-situ dual-step preflow treatment
Kailai Yang
et al
2026
Jpn. J. Appl. Phys.
View article
, Achieving smooth and transferable AlN films on h-BN via in-situ dual-step preflow treatment
PDF
, Achieving smooth and transferable AlN films on h-BN via in-situ dual-step preflow treatment
AlN epitaxy was performed on multilayer h‑BN via MOCVD under varying in‑situ preflow conditions. A dual‑step preflow strategy—sequential NH₃ followed by TMAl—was developed to obtain mechanically transferable AlN films with smooth morphology and single-crystalline quality. Contrast experiments suggest that the NH₃ step enhances nucleation density, while the subsequent TMAl step suppresses mixed polarity in early growth. This fully in‑situ process replaces conventional ex‑situ surface modifications of h-BN, offering improved reproducibility and MOCVD compatibility, and benefiting the integration of transferable AlN‑based heterostructures into deep‑UV optoelectronic and high‑power electronic devices.
More Open Access articles
Multi-scale simulation of the full-scale demolding process for slanted gratings and optimization of demolding directions and mechanical properties of the working stamp
Takahide Nakamura
et al
2026
Jpn. J. Appl. Phys.
65
08SP09
View article
, Multi-scale simulation of the full-scale demolding process for slanted gratings and optimization of demolding directions and mechanical properties of the working stamp
PDF
, Multi-scale simulation of the full-scale demolding process for slanted gratings and optimization of demolding directions and mechanical properties of the working stamp
Understanding the demolding behavior in nanoimprint lithography is essential for improving pattern fidelity in slanted grating structures formed using high-refractive-index (HRI) resins. However, the macroscopic demolding behavior governing the actual peeling process has not been fully clarified. In this study, we developed a multi-scale finite element simulation consisting of macroscale and microscale models to analyze demolding under practical conditions. The macroscale model captures global peeling deformation, and the microscale model evaluates detailed strain in patterned structures during demolding. The simulation revealed that strain distribution strongly depends on the demolding direction and the modulus of the working stamp, showing good agreement with experimental observations. The proposed approach provides a basis for developing a full-scale simulation platform applicable to diverse molding geometries and demolding methods, supporting process and material design for direct nanoimprint technologies.
Development of two-terminal perovskite/Si tandem solar modules and their application to building-integrated and vehicle-integrated photovoltaics
Daisuke Adachi
et al
2026
Jpn. J. Appl. Phys.
65
07SP17
View article
, Development of two-terminal perovskite/Si tandem solar modules and their application to building-integrated and vehicle-integrated photovoltaics
PDF
, Development of two-terminal perovskite/Si tandem solar modules and their application to building-integrated and vehicle-integrated photovoltaics
We report our recent progress in the development of practical technologies for two-terminal perovskite/Si tandem solar modules, using fabrication methods developed for perovskite single-junction modules. These methods enabled us to confirm an independently measured efficiency of 19.4% for a 700 cm
perovskite single-junction module. We also present tandem solar cell technology represented by a typical baseline perovskite/Si tandem solar cell that achieved an independently measured efficiency of 32.6% (active area: 1.02 cm
). Using upsized perovskite/Si tandem solar cells, we obtained a module power output of 59.2 W (in-house measurement). We discuss color‑tone stability under process variation, evaluate the impact of color-tone variations on current matching between the top and bottom cells, and demonstrate prototypes of a building-integrated photovoltaic (BIPV) module and a three-dimensional curved vehicle-integrated photovoltaic (VIPV) module to gain insights into the optical design required to tune module appearance for BIPV/VIPV deployment. These results outline a development pathway coupling efficiency gains, long-term durability, and aesthetic control for perovskite/Si tandem solar modules.
Thickness-extensional second order mode bulk wave resonator using face-bonded X-cut quartz thin plates
Chihana Ukawa
et al
2026
Jpn. J. Appl. Phys.
65
06SP08
View article
, Thickness-extensional second order mode bulk wave resonator using face-bonded X-cut quartz thin plates
PDF
, Thickness-extensional second order mode bulk wave resonator using face-bonded X-cut quartz thin plates
The demand for high-frequency oscillators has been increasing due to high-speed, large-capacity communications at base stations and data centers. Therefore, a Quartz (Qtz) resonator with a high resonance frequency is also highly desired, so we investigated a Qtz bulk acoustic wave (BAW) resonator using the thickness-extension (TE) mode, which has a higher velocity than the thickness-shear (TS) mode. This study presents the simulation and fabrication results of a TE mode resonator using an X-Qtz plate bonded with geometrically similar polarity planes (face-bonded Qtz plate). In the simulation, we investigated the influences of the third Euler angle when bonding and the difference in Qtz thickness. As a result of the fabrication using 10 μm or 20 μm thickness Qtz, the face-bonded Qtz samples excited a TE second mode with less spurious and ripples. In a face-bonded sample where each Qtz layer is 20 μm thick, the resonance frequency is about 155 MHz, the impedance ratio was 42.5 dB,
mr
was 1,720, and
ma
was 3,870. Taking 25 °C as the reference, the temperature coefficient of frequency (TCF) between 25 °C and 85 °C is −7.3 ppm °C for
and −7.5 ppm °C for
100 Gbaud data transmission over 500 m multimode fibers using a 1060 nm single-mode coupled-cavity VCSEL with SMF center-launch scheme
Hameeda R Ibrahim
et al
2026
Jpn. J. Appl. Phys.
65
05SP32
View article
, 100 Gbaud data transmission over 500 m multimode fibers using a 1060 nm single-mode coupled-cavity VCSEL with SMF center-launch scheme
PDF
, 100 Gbaud data transmission over 500 m multimode fibers using a 1060 nm single-mode coupled-cavity VCSEL with SMF center-launch scheme
We demonstrate 100 Gbaud data transmission over 500 m of standard multimode fibers (MMFs) (OM2, OM3, and OM4) using a 1060 nm single-mode coupled-cavity vertical-cavity surface-emitting laser (VCSEL) combined with a simple single-mode-fiber (SMF) patch-cord center-launch scheme. The proposed launch configuration preferentially excites the fundamental fiber mode, thereby suppressing higher-order mode propagation and eliminating modal dispersion in legacy MMFs without the need for bulk optics or complex mode conditioning. The employed VCSEL exhibits a 45 GHz small-signal modulation bandwidth, enabling an end-to-end optical link bandwidth exceeding 50 GHz. Consequently, 100 Gbaud transmission over 500 m is successfully achieved for all tested MMF types. These results indicate that 1060 nm VCSEL-based MMF links can provide practical, scalable, and modal-dispersion-free operation, offering a promising solution for cost-effective, high-bandwidth short-reach optical interconnects and bridging the gap between multimode and SMF systems.
Thermally induced evolution of on-surface-synthesized crown ether polymers on Cu(111): transition from semiconductor chains to metallic nanoflakes
Toyo Kazu Yamada
et al
2026
Jpn. J. Appl. Phys.
65
05SP24
View article
, Thermally induced evolution of on-surface-synthesized crown ether polymers on Cu(111): transition from semiconductor chains to metallic nanoflakes
PDF
, Thermally induced evolution of on-surface-synthesized crown ether polymers on Cu(111): transition from semiconductor chains to metallic nanoflakes
We present a scanning tunneling microscopy study of on-surface synthesis using bromine-terminated crown ether (BrCR) molecules adsorbed on Cu(111) under ultra-high vacuum. Although theoretical models predict that high-temperature annealing yields energetically stable linear or trident-linked crown ether (CR) structures forming ordered two-dimensional (2D) networks, our experiments reveal alternative reaction pathways. A self-assembled BrCR monolayer prepared at 300 K with semiconducting characteristics transforms into one-dimensional polymer chains upon annealing at 450–500 K. In contrast, annealing at 600–700 K induces a drastic transition to 2D nanoflakes with metallic properties. This transformation is accompanied by a significant reduction in apparent molecular height and pronounced changes in the local density of states. These results demonstrate that annealing temperature enables controlled tuning of CR-derived nanocompounds and electronic properties from semiconducting to metallic.
Volume-shrinkage-driven curling behavior of dual-composition Al/Ni multilayer thin films for bonding applications
Sarankamol Athichaikhongphat
et al
2026
Jpn. J. Appl. Phys.
65
05SP01
View article
, Volume-shrinkage-driven curling behavior of dual-composition Al/Ni multilayer thin films for bonding applications
PDF
, Volume-shrinkage-driven curling behavior of dual-composition Al/Ni multilayer thin films for bonding applications
Dual-composition Al/Ni multilayer thin films with various architectural designs were fabricated to investigate curling motion driven by volume shrinkage and to assess their potential to enhance the direct bonding of Al busbars. The reacted films exhibited pronounced, composition-dependent curling deformation, with a higher Al fraction yielding a smaller radius. In contrast, total film thickness and bilayer period had only a minor influence. A theoretical curvature analysis was conducted to compare predicted deformation with experimental results, and to estimate the mismatch strain and the bending-generated energy. Bonding between two Al busbars was demonstrated. Larger curvature led to increased cracking in the reacted layer, which is expected to facilitate easier removal of the reacted interlayer after bonding. These results demonstrate that tailoring the Al/Ni film’s multilayer architecture provides effective control of curvature after reaction, offering a promising pathway for reactive bonding systems that require simple post-bonding removal of the reacted NiAl film or reduced mechanical damage.
High-conductivity carbon nanotube fibers via wet spinning of long carbon nanotubes
Satoshi Yamazaki
et al
2026
Jpn. J. Appl. Phys.
65
050901
View article
, High-conductivity carbon nanotube fibers via wet spinning of long carbon nanotubes
PDF
, High-conductivity carbon nanotube fibers via wet spinning of long carbon nanotubes
Carbon nanotube (CNT) fibers are promising lightweight conductors, yet their electrical conductivity remains limited compared with metallic benchmarks. Here, we demonstrate the fabrication of highly aligned and densely packed CNT fibers by wet spinning CNTs with long effective lengths. Wet-spun fibers prepared from chlorosulfonic acid dispersions exhibit an as-spun conductivity of 11.4 MS m
−1
. Subsequent doping with fuming nitric acid increases the conductivity to 15.9 MS m
−1
, representing one of the highest values reported for wet-spun CNT fibers. These results establish effective nanotube length and high packing density as key design parameters for high-performance lightweight conductors.
A mass-loaded topological switching mechanism for phononic biosensors
Hiroki Okita
et al
2026
Jpn. J. Appl. Phys.
65
03SP30
View article
, A mass-loaded topological switching mechanism for phononic biosensors
PDF
, A mass-loaded topological switching mechanism for phononic biosensors
We propose a switchable topological phononic biosensor that exploits interface modes protected by band topology. The device is based on a hexagonal unit cell consisting of six tungsten pillars embedded in an acrylic resin matrix, arranged with an equilateral-triangle-based motif that, when unrotated, enforces threefold symmetry. Two topologically distinct domains are formed by slightly rotating this internal triangular structure, creating robust zero-line modes localized at their interface. Finite-element simulations show that surface mass loading shifts the interface-mode dispersion and switches the propagation path at a fixed excitation frequency, providing a new biosensing mechanism based on topological mode switching.
Orientation-dependent electrochemical characteristics of the LiNi
1/3
Mn
1/3
Co
1/3
epitaxial thin films
Makoto Takayanagi
et al
2026
Jpn. J. Appl. Phys.
65
03SP28
View article
, Orientation-dependent electrochemical characteristics of the LiNi1/3Mn1/3Co1/3O2 epitaxial thin films
PDF
, Orientation-dependent electrochemical characteristics of the LiNi1/3Mn1/3Co1/3O2 epitaxial thin films
The effects of the crystal orientation of an electrode on the electrochemical characteristics in liquid electrolyte systems were investigated using thin-film batteries (TFBs) with LiNi
1/3
Mn
1/3
Co
1/3
(NMC) epitaxial (003) and (104) thin films. Clear orientation dependence was observed in the cycling performances. NMC(003)-based TFB exhibited an initial discharge capacity of 117 mAh g
−1
and retained 50% after 100 cycles, whereas NMC(104)-based TFB exhibited 146 mAh g
−1
and retained 57%. Density functional theory calculations revealed that hydrofluoric acid (HF) adsorption was more energetically favorable on the NMC(003) than on the NMC(104), suggesting a higher chemical stability of NMC(104) against the HF attack and, consequently, better cycling stability. Furthermore, the rate performance strongly depended on the crystal orientation, with NMC(104)-based TFB maintaining 59% of its 1 C-rate capacity under 10 C-rate condition compared with 30% for NMC(003)-based TFB. The results indicate that appropriate crystal orientation is key for achieving high operating speed and long-lifetime ionic devices.
Programmable anisotropic actuation of hydrogel-composite mechanical metamaterials
Yamato Kato
et al
2026
Jpn. J. Appl. Phys.
65
03SP17
View article
, Programmable anisotropic actuation of hydrogel-composite mechanical metamaterials
PDF
, Programmable anisotropic actuation of hydrogel-composite mechanical metamaterials
Hydrogel actuators hold great potential for soft robotics but suffer from isotropic swelling and low structural rigidity. We propose a composite actuator integrating hydrogels with 3D-printed mechanical metamaterial scaffolds to achieve programmable anisotropic actuation. We investigated two scaffold materials: UV-curable resin and Thermoplastic Polyurethane (TPU). While resin scaffolds provided high interfacial strength, TPU scaffolds demonstrated superior durability, accommodating large swelling deformations without failure. Leveraging the robust TPU composite, we developed cylindrical actuators designed for specific deformation modes. The radial-expansion model successfully achieved diameter increase while suppressing the axial shortening phenomenon typical of conventional stents. This work establishes a design strategy balancing material properties and geometric programming to realize robust, complexly deforming soft actuators.
More Spotlight Articles
High-quality β-Ga
single crystals grown by edge-defined film-fed growth
Akito Kuramata
et al
2016
Jpn. J. Appl. Phys.
55
1202A2
View article
, High-quality β-Ga2O3 single crystals grown by edge-defined film-fed growth
PDF
, High-quality β-Ga2O3 single crystals grown by edge-defined film-fed growth
β-Ga
bulk crystals were grown by the edge-defined film-fed growth (EFG) process and the floating zone process. Semiconductor substrates containing no twin boundaries with sizes up to 4 in. in diameter were fabricated. It was found that Si was the main residual impurity in the EFG-grown crystals and that the effective donor concentration (
) of unintentionally doped crystals was governed by the Si concentration. Intentional n-type doping was shown to be possible. An etch pit observation revealed that the dislocation density was on the order of 10
cm
−3
for the samples annealed in nitrogen ambient was almost the same as the Si concentration, while for the samples annealed in oxygen ambient, it was around 1 × 10
17
cm
−3
and independent of the Si concentration.
Material science and device physics in SiC technology for high-voltage power devices
Tsunenobu Kimoto 2015
Jpn. J. Appl. Phys.
54
040103
View article
, Material science and device physics in SiC technology for high-voltage power devices
PDF
, Material science and device physics in SiC technology for high-voltage power devices
Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600–1700 V) SiC Schottky barrier diodes (SBDs) and power metal–oxide–semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.
TiO
Photocatalysis: A Historical Overview and Future Prospects
Kazuhito Hashimoto
et al
2005
Jpn. J. Appl. Phys.
44
8269
View article
, TiO2 Photocatalysis: A Historical Overview and Future Prospects
PDF
, TiO2 Photocatalysis: A Historical Overview and Future Prospects
Photocatalysis has recently become a common word and various products using photocatalytic functions have been commercialized. Among many candidates for photocatalysts, TiO
is almost the only material suitable for industrial use at present and also probably in the future. This is because TiO
has the most efficient photoactivity, the highest stability and the lowest cost. More significantly, it has been used as a white pigment from ancient times, and thus, its safety to humans and the environment is guaranteed by history. There are two types of photochemical reaction proceeding on a TiO
surface when irradiated with ultraviolet light. One includes the photo-induced redox reactions of adsorbed substances, and the other is the photo-induced hydrophilic conversion of TiO
itself. The former type has been known since the early part of the 20th century, but the latter was found only at the end of the century. The combination of these two functions has opened up various novel applications of TiO
, particularly in the field of building materials. Here, we review the progress of the scientific research on TiO
photocatalysis as well as its industrial applications, and describe future prospects of this field mainly based on the present authors' work.
Physical reservoir computing—an introductory perspective
Kohei Nakajima 2020
Jpn. J. Appl. Phys.
59
060501
View article
, Physical reservoir computing—an introductory perspective
PDF
, Physical reservoir computing—an introductory perspective
Understanding the fundamental relationships between physics and its information-processing capability has been an active research topic for many years. Physical reservoir computing is a recently introduced framework that allows one to exploit the complex dynamics of physical systems as information-processing devices. This framework is particularly suited for edge computing devices, in which information processing is incorporated at the edge (e.g. into sensors) in a decentralized manner to reduce the adaptation delay caused by data transmission overhead. This paper aims to illustrate the potentials of the framework using examples from soft robotics and to provide a concise overview focusing on the basic motivations for introducing it, which stem from a number of fields, including machine learning, nonlinear dynamical systems, biological science, materials science, and physics.
Base-Metal Electrode-Multilayer Ceramic Capacitors: Past, Present and Future Perspectives
Hiroshi Kishi
et al
2003
Jpn. J. Appl. Phys.
42
View article
, Base-Metal Electrode-Multilayer Ceramic Capacitors: Past, Present and Future Perspectives
PDF
, Base-Metal Electrode-Multilayer Ceramic Capacitors: Past, Present and Future Perspectives
Multilayer ceramic capacitor (MLCC) production and sales figures are the highest among fine-ceramic products developed in the past 30 years. The total worldwide production and sales reached 550 billion pieces and 6 billion dollars, respectively in 2000. In the course of progress, the development of base-metal electrode (BME) technology played an important role in expanding the application area. In this review, the recent progress in MLCCs with BME nickel (Ni) electrodes is reviewed from the viewpoint of nonreducible dielectric materials. Using intermediate-ionic-size rare-earth ion (Dy
, Ho
, Er
, Y
) doped BaTiO
)-based dielectrics, highly reliable Ni-MLCCs with a very thin layer below 2 µm in thickness have been developed. The effect of site occupancy of rare-earth ions in BaTiO
on the electrical properties and microstructure of nonreducible dielectrics is studied systematically. It appears that intermediate-ionic-size rare-earth ions occupy both
- and
-sites in the BaTiO
lattice and effectively control the donor/acceptor dopant ratio and microstructural evolution. The relationship between the electrical properties and the microstructure of Ni-MLCCs is also presented.
Growth of β-Ga
Single Crystals by the Edge-Defined, Film Fed Growth Method
Hideo Aida
et al
2008
Jpn. J. Appl. Phys.
47
8506
View article
, Growth of β-Ga2O3 Single Crystals by the Edge-Defined, Film Fed Growth Method
PDF
, Growth of β-Ga2O3 Single Crystals by the Edge-Defined, Film Fed Growth Method
The successful growth of 2-in. β-Ga
crystals by the edge-defined, film fed growth (EFG) method was demonstrated. The optimization of growth conditions for larger single crystalline β-Ga
is discussed in detail. The seeding conditions of temperature and neck width were found to be the most important factors to grow single crystals. X-ray rocking curve measurements of β-Ga
crystals were conducted to estimate the dislocation densities of the grown crystals. Etch pit densities (EPDs) of the β-Ga
crystals were also measured using KOH solution to measure the dislocation densities. The results were discussed combining with crystal growth parameters such as neck width to clarify the mechanisms of propagation and the origin of dislocations in crystals from phenomenological and crystallographic points of view.
Fundamental aspects, recent progress and future prospects of inorganic scintillators
Takayuki Yanagida
et al
2023
Jpn. J. Appl. Phys.
62
010508
View article
, Fundamental aspects, recent progress and future prospects of inorganic scintillators
PDF
, Fundamental aspects, recent progress and future prospects of inorganic scintillators
The present work reviews some fundamental aspects of scintillators, including the light yield, decay time, emission wavelength, afterglow, timing resolution and energy resolution. Following fundamental aspects, recently developed inorganic ceramic, glass and single crystal scintillators are introduced with some future prospects.
High-NA EUV lithography: current status and outlook for the future
Harry J. Levinson 2022
Jpn. J. Appl. Phys.
61
SD0803
View article
, High-NA EUV lithography: current status and outlook for the future
PDF
, High-NA EUV lithography: current status and outlook for the future
High-NA extreme ultraviolet (EUV) lithography is currently in development. Fabrication of exposure tools and optics with a numerical aperture (NA) equal to 0.55 has started at ASML and Carl Zeiss. Lenses with such high NA will have very small depths-of-focus, which will require improved focus systems and significant improvements in wafer flatness during processing. Lenses are anamorphic to address mask 3D issues, which results in wafer field sizes of 26 mm × 16.5 mm, half that of lower NA EUV tools and optical scanners. Production of large die will require stitching. Computational infrastructure is being created to support high-NA lithography, including simulators that use Tatian polynomials to characterize the aberrations of lenses with central obscurations. High resolution resists that meet the line-edge roughness and defect requirements for high-volume manufacturing also need to be developed. High power light sources will also be needed to limit photon shot noise.
Valence band ordering in β-Ga
studied by polarized transmittance and reflectance spectroscopy
Takeyoshi Onuma
et al
2015
Jpn. J. Appl. Phys.
54
112601
View article
, Valence band ordering in β-Ga2O3 studied by polarized transmittance and reflectance spectroscopy
PDF
, Valence band ordering in β-Ga2O3 studied by polarized transmittance and reflectance spectroscopy
The polarized transmittance and reflectance spectra of β-Ga
crystals are investigated, and the data are interpreted in terms of the monoclinic crystal band structure. The energies of the absorption edge can be divided into six ranges, and these ranges can be assigned to the transitions from the valence bands to the conduction band minimum according to the selection rules. The indirect bandgap-energy of 4.43 eV is smaller than the direct bandgap-energy of 4.48 eV at RT; and the energy difference of 0.05 eV nearly matches the theoretically calculated values of 0.03–0.04 eV.
Heteroepitaxy of Corundum-Structured α-Ga
Thin Films on α-Al
Substrates by Ultrasonic Mist Chemical Vapor Deposition
Daisuke Shinohara and Shizuo Fujita 2008
Jpn. J. Appl. Phys.
47
7311
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, Heteroepitaxy of Corundum-Structured α-Ga2O3 Thin Films on α-Al2O3 Substrates by Ultrasonic Mist Chemical Vapor Deposition
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, Heteroepitaxy of Corundum-Structured α-Ga2O3 Thin Films on α-Al2O3 Substrates by Ultrasonic Mist Chemical Vapor Deposition
Ga
thin films of the α-phase, that is, the corundum structure (in the trigonal system), have been epitaxially obtained on sapphire (α-Al
) substrates, in contrast to the strong tendency of Ga
to assume a heterogeneous crystal structure, that is, the β-gallia structure (in the monoclinic system) on sapphire. This result is advantageous for high-quality films and is due to the growth by mist chemical vapor deposition (CVD) at low temperatures of 430–470 °C. The α-Ga
films have narrow full-widths at half maximum (FWHMs) in their X-ray diffraction rocking curves, for example, about 60 arcsec. The root mean square (RMS) roughness of the surface was as small as 1 nm. The optical band gap energy obtained was 5.3 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The epitaxial growth of α-Ga
films on sapphire is beneficial for the fabrication of oxide optical and electronic devices.
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1962-present
Japanese Journal of Applied Physics
Online ISSN: 1347-4065
Print ISSN: 0021-4922