Japanese Journal of Applied Physics

Metal oxide semiconductor (MOX) chemiresistive gas sensors used in gas alarms have contributed to the safe use of city gas and liquid petroleum gas. In this study, we successfully fabricated hot-wire-type MOX sensors using micro-electro-mechanical systems (MEMS) technology. The hot-wire type structure, in which an electrode plays dual roles in detecting and heating, was adopted for efficient production. Owing to the miniaturization together with the thermal insulation, the sensors exhibited a fast thermal response. The average power consumption of the sensor in the pulsed operation was less than 100 μW. The sensor exhibited high sensitivity of more than 100 mV to 3000 ppm methane and showed low cross-sensitivity to interference gases such as ethanol and hydrogen. These sensing properties were retained for more than five years, demonstrating excellent long-term stability of the sensors.

The present study aims to detect helium-3 in nickel-based metal nano-composites doped with zirconia, which exhibited anomalous heat generation when exposed to hydrogen gas at approximately 450 °C. Two complementary analytical techniques were employed: nuclear reaction analysis utilizing 1.4 MeV deuteron beams from a tandem accelerator, and thermal desorption spectrometry using a quadrupole mass spectrometer. Both methods successfully detected helium-3 in the samples. Given the extreme rarity of this isotope, its presence strongly suggests the occurrence of nuclear reactions within the nickel-containing materials. These findings lend support to the 4 hydrogen/tetrahedral symmetric condensate (4H/TSC) model, which uniquely predicts helium-3 as one of the primary reaction products.

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.

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.

Benefitted from progress on the large-diameter Ga₂O₃ wafers and Ga₂O₃ processing techniques, the Ga₂O₃ power device technology has witnessed fast advances toward power electronics applications. Recently, reports on large-area (ampere-class) Ga₂O₃ power devices have emerged globally, and the scope of these works have gone well beyond the bare-die device demonstration into the device packaging, circuit testing, and ruggedness evaluation. These results have placed Ga₂O₃ in a unique position as the only ultra-wide bandgap semiconductor reaching these indispensable milestones for power device development. This paper presents a timely review on the state-of-the-art of the ampere-class Ga₂O₃ power devices (current up to >100 A and voltage up to >2000 V), including their static electrical performance, switching characteristics, packaging and thermal management, and the overcurrent/overvoltage ruggedness and reliability. Exciting research opportunities and critical technological gaps are also discussed.

Breakdown voltage (BV) is arguably one of the most critical parameters for power devices. While avalanche breakdown is prevailing in silicon and silicon carbide devices, it is lacking in many wide bandgap (WBG) and ultra-wide bandgap (UWBG) devices, such as the gallium nitride high electron mobility transistor and existing UWBG devices, due to the deployment of junction-less device structures or the inherent material challenges of forming p-n junctions. This paper starts with a survey of avalanche and non-avalanche breakdown mechanisms in WBG and UWBG devices, followed by the distinction between the static and dynamic BV. Various BV characterization methods, including the static and pulse I–V sweep, unclamped and clamped inductive switching, as well as continuous overvoltage switching, are comparatively introduced. The device physics behind the time- and frequency-dependent BV as well as the enabling device structures for avalanche breakdown are also discussed. The paper concludes by identifying research gaps for understanding the breakdown of WBG and UWBG power devices.

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.

We have reported that hydrogen or helium ion implantation can suppress the expansion of stacking faults in SiC devices. These results suggest that point defects caused by ion implantation are an important factor in suppressing the expansion. On the other hand, the depth distribution of point defects introduced by implantation of these ions has not been fully elucidated. In this study, we evaluated the point defect and carrier lifetime distributions inside SiC diodes implanted with hydrogen or helium ions by cathodoluminescence and microscopic free carrier absorption methods.

The structural stability and miscibility of ScAlN are theoretically investigated on the basis of density functional calculations. The calculations demonstrate that the relative stability between wurtzite and rocksalt structures depends on Sc composition. The lattice constraint of AlN and GaN substrates enhances the stability of the wurtzite structure as well as the miscibility of ScAlN alloys. Furthermore, the calculated energy barrier for polarization switching is also influenced by the lattice constraint. The results give insights into understanding the effect of substrate on structural stability and miscibility of ScAlN alloys.

Modern dynamic random-access memories (DRAMs) have ultra-high densities due to the high integration of cell arrays, and the length of word-line (WL) has become considerably longer. In particular, maintaining the uniform line profile in the WL of modern 10 nm-class DRAMs is extremely challenging. In this paper, our goal is to investigate the causes of the WL break and propose a new method to solve it. We discuss a novel gate oxide (Gox) formation technology that is able to relieve the WL wiggling and disconnection. 10 nm-class DRAMs are fabricated with the novel Gox technology, and their structure and characteristics are studied.

A uniform vibration distribution over the working surface of ultrasonic bonding tools is important for industrial applications, but its design requires much expertise owing to wave effects. Topology optimization using level-set functions progresses with a clear interface rather than grayscale density. Therefore, when the tools designed on the basis of optimization results are reflected in the actual fabrication, there is little error in the resonance frequency and flatness of vibration. In this study, we perform optimization to obtain a uniform vibration distribution by using commercial finite element software to create a three-dimensional model by extruding a shape obtained from a level-set function in a two-dimensional space. The tool obtained from the optimization is fabricated and the transducer performance, the vibration distribution, and the flatness of the vibration are measured.

This study proposes a nonlinear thermo-acoustic phase modulator for application in physical reservoir computing. We designed and fabricated the modulator, and then investigated the properties such as insertion loss and modulation effects. Finally, we constructed a physical reservoir system with the proposed modulator and demonstrated benchmark tasks. The modulator makes use of surface acoustic waves, which contributes to fast processing and low power consumption. The modulator has a waveguide which also acts as a microheater. The modulation principle is a wave-velocity reduction caused by heating the surface of the substrate with the microheater, which provides nonlinearity and short-term memory required for the reservoir system. We confirmed these characteristics in the measurements of the modulator, and we verified the effectiveness of the modulator in the reservoir system with 2.3 of memory capacity in short-term memory task and 0.066 of normalized mean square error in NARMA2 task.

We present a method for the on-line estimation of the depth of single shallow nitrogen-vacancy (NV) centers in diamond. This method combines photon detection simulation with maximum likelihood estimation (MLE) to produce faster results and can be performed at the same time as data arrives. The results show that MLE produces a depth estimate close to the true NV center depth in a shorter measurement duration, as compared to the conventional data fitting of the power spectral density. Also, real-time estimation with this technique is feasible using a computer equipped with hardware accelerators, such as high-performance graphical processing units.

Core⎯shell nanoparticles (NPs) composed of an Au core and a Pt shell (Au@Pt NPs) were synthesized. We started with the synthesis of the Au core by sonochemical reduction, followed by the Pt shell deposition by chemical reduction in the presence of a non-ionic surfactant and ultrafine bubbles (UFBs). The Pt shell thickness increased with the UFB concentration. During the shell formation, Pt NPs were thought to adsorb on the surface of UFBs by electrostatic and hydrophobic interactions, which was subsequently followed by UFBs approaching the Au NP surface and providing additional Pt NPs onto the surface. The catalytic activity of Au@Pt NPs for the reduction of 4-nitrophenol was evaluated. At Pt/Au molar ratios of 0.10, 0.20, and 0.33, the catalytic activity was enhanced as the Pt shell thickness decreased. For Pt/Au molar ratios of 0.02 and 0.05, Au@Pt NPs synthesized with UFBs exhibited better catalytic performance than those without UFBs.

We established an atomic layer deposition (ALD) process of InZnO_x (IZO) and fabricated ALD IZO FETs for comprehensive characterization, aimed at advancing nanosheet structure and monolithic 3D (M3D) integration technologies. Thermal stability and composition/thickness dependence on device characteristics are systematically explored. Our findings reveal that ALD IZO FETs maintain high thermal stability at temperatures up to 400 °C, and we identify critical trade-offs among key parameters such as mobility, threshold voltage (V_th), and initial V_th shift (ΔV_th) under positive bias stress conditions. ALD IZO FETs show higher mobility, lower V_th, and especially smaller initial ΔV_th than previously reported in ALD InGaO_x (IGO) FETs. These improvements are linked to the intrinsic differences in oxygen dissociation energy between Zn and Ga in the compound of InO_x. The material properties and device behavior of IZO FETs obtained in this work will provide insights into their application in M3D integration.

The bottom-up fabrication technique is one of the key technologies taking place in conventional top-down approaches to create nanoporous (NP) thin film materials with tailorable nanostructures such as film thickness, film density, pore form, and pore size with nanometer (or sub-nanometer)-scale accuracy. This progress review specifically highlights bottom-up fabrication techniques using two-phase interfaces including solid–gas interfaces, solid–liquid interfaces, liquid–liquid interfaces, and gas–liquid interfaces by referring to recent publications. Moreover, experimental techniques to analyze nanostructures of NP thin film materials from well-ordered regular structures to non-periodic structures are introduced. Finally, some emerging potential applications and future perspectives of NP thin film materials are mentioned by using the latest literature.

Thin films of ferroelectric materials have been investigated for various applications because of their high dielectric constants, as well as piezoelectric and ferroelectric properties. Ferroelectricity has been explored for memory applications because of its two stable states after releasing an electric field, depending on the direction. Perovskite-based ferroelectrics have been studied for the last 30 years for these applications and have already been commercialized. However, the degradation of their ferroelectricity with decreasing film thickness (below about 30 nm) makes high-density memory applications difficult. A recent "discovery" of novel ferroelectrics, e.g., fluorite-type structure HfO₂-based films and wurtzite structure AlN-, GaN-, and ZnO-based films, have enabled significant reductions in film thickness without noticeable degradation. In this article, we discuss the status and challenges of these novel non-perovskite-based ferroelectric films mainly for memory device applications.

This paper describes the concepts for achieving n-type and p-type WSe₂ field-effect transistors (FETs) and their complementary metal-oxide-semiconductor (CMOS) inverter operation. First, n-type and p-type WSe₂ FETs were demonstrated using molecular chemistry approaches that offer the manipulation of WSe₂ properties through low-temperature, low-energy processes. Next, the advancement in device technology was explained to achieve symmetric characteristics in n-type and p-type WSe₂ FETs. WSe₂ single-channel CMOS offers a promising pathway for simplifying device integration to suppress variability and fluctuations in FET characteristics, although many challenges remain to be addressed. Further fundamental research holds the potential to advance the development of WSe₂ single-channel CMOS devices.

Ion channels regulate membrane potential by mediating the permeation of specific ion species via their transmembrane pore with gating. Understanding the structural dynamics of ion channels is important for elucidating their functional mechanisms. This review highlights the application of high-speed atomic force microscopy (HS-AFM) in investigating structural dynamics of ion channels and ligands. The use of oriented reconstitution techniques allowed for high-resolution, real-time visualization of ion channel dynamics such as pH-dependent clustering in KcsA potassium channels, induced-fit binding of agitoxin-2 (AgTx2), ligand-induced fluctuations in transient receptor potential vanilloid 1 (TRPV1), and voltage sensor dissociation in voltage-gated sodium channels (Na_v). These studies provide valuable insights into the molecular mechanisms that govern ion channel function and contribute to a deeper understanding of their physiological roles. Additionally, the findings underscore the potential of HS-AFM in exploring ion channel behavior under various conditions.

Macroscopic responses of magnets are often governed by magnetization and thus have been restricted to ferromagnets. However, such responses are found strikingly large in the newly developed topological magnets, breaking the conventional scaling with magnetization. Taking the antiferromagnetic Weyl semimetals as a prime example, we highlight the two central ingredients driving the significant macroscopic responses: the Berry curvature enhanced due to nontrivial band topology in momentum space, and the cluster magnetic multipoles in real space and we show our recent results on the electrical switching of the chiral antiferromagnetic state in its heterostructure using heavy metals and the tunneling magnetoresistance effect using all antiferromagnetic tunnel junctions. Besides, recent studies have indicated that topological magnets exhibit a gigantic anomalous Nernst effect that is a few orders of magnitude larger than previously thought according to its linear relationship to magnetization. Topological electronic structures such as nodal points, lines, and planes are found to generate large Berry curvature and enhance the transverse responses in magnetic states. The discoveries of the novel thermoelectric properties of thin films of recently developed topological magnets pave the path for their application of these effects for the fabrication of heat current sensors.

Reservoir computing (RC) is one of the hottest research topic as an application of many physical devices because the device characteristics can be used directly in computing sequences. Quantum RC is also a promising candidate for application in small-number qubit systems. Here, we propose a quantum RC based on the spin qubit system that reflects the status of the spin qubits in experiments comprising a one-dimensional qubit array. Spin qubits are coupled via the Heisenberg interaction, and data sequences are inputted to one of the spin qubits via pulsed rotations. By introducing dissipation, we obtained a relatively good performance in the quantum RC.

Physical reservoir computing (PRC) harnesses the intrinsic nonlinear dynamics of physical systems for efficient temporal data processing, offering significant advantages in energy-efficient hardware implementation. This study explores the potential of oriented semiconducting polymer (SCP) thin films as reservoirs for PRC, focusing on two types of SCP benzo[c]cinnoline-based conjugated polymer diketopyrrolopyrrole benzo[c]cinnoline p(DPP-BZC) and regioregular poly(3-hexyl thiophene) (RR-P3HT). To enable anisotropic charge transport, uniaxially oriented thin films with edge-on molecular orientation were fabricated using the floating film transfer method. The films were electrically evaluated for anisotropic nonlinear responses, phase-shifting capabilities, and high-dimensional mapping in PRC tasks. Performance metrics, including waveform generation accuracy, were systematically investigated under varying device configurations and molecular structures. The study underscores the critical role of different conjugated polymers and their orientations in PRC performance, paving the way for developing next-generation materials for temporal signal processing and low-power intelligent hardware.

A method to measure the electrical resistivity of materials using magnetic- force microscopy (MFM) is discussed, where MFM detects the magnetic field caused by the tip-oscillation-induced eddy current. To achieve high sensitivity, a high cantilever oscillation frequency is preferable, because it induces large eddy currents in the material. Higher-order resonance modes of the cantilever oscillation lead to higher frequency. To discuss such high-order-mode oscillation, a differential equation governing MFM cantilever oscillation in the high-order resonance mode is formulated, and an analytical solution of the phase difference is obtained. The result shows that the phase difference decreases at higher modes, because the effective spring constant increases faster than the force from the eddy current.

This paper discusses modelling of in-plane diffraction in SAW resonators. The theory is based on the simple conventional one-dimensional coupling-of-modes (COM) theory, and its result is used to estimate power leakage caused by the in-plane SAW diffraction. TC-SAW on SiO2/131-LN structure and I.H.P. SAW on 42-LT/SiO2/Si structure are used for discussions. First, parameters required for the analysis are determined by fitting with periodic 2D FEM results. Then, the impact of the in-plane diffraction is estimated by the proposed model. The numerical results can explain variation of the Bode Q with NI and W obtained by full 3D FEM well. It is also shown that the Bode Q of I.H.P. SAW decreases with the frequency much slower than that of TC SAW. This is due to the difference in the SAW slowness shape in these configurations, which explains the reason why I.H.P. SAW offer larger anti-resonance Q than TC SAW.

Ultraviolet-induced degradation (UV-ID) of various PV cell types was analyzed under optical UV filters with different cutoff wavelengths. Cell types studied included interdigitated back contact (IBC), passivated emitter and rear totally diffused (PERT), and heterojunction technology (HJT) based on crystalline Si (c-Si), and metal halide perovskite (MHP) cells. Analyzing degradation rates in two distinct regimes proved beneficial for all cell types. We used empirical linearizing functions ln(t) for c-Si technologies and ²√t for MHP samples where t is time. These were applied to extrapolate UV-induced degradation over the lifetime of PV modules under various levels of optical UV filtering and used to predict the relative economic benefits for PV power plants. Degradation rates for all technologies were generally faster under the long pass optical filters having shorter cutoff wavelengths transmitting more UV irradiation and at elevated temperatures when testing MHP samples in the range between 60 °C and 90 °C.

Reservoir computing (RC) is one of the hottest research topic as an application of many physical devices because the device characteristics can be used directly in computing sequences. Quantum RC is also a promising candidate for application in small-number qubit systems. Here, we propose a quantum RC based on the spin qubit system that reflects the status of the spin qubits in experiments comprising a one-dimensional qubit array. Spin qubits are coupled via the Heisenberg interaction, and data sequences are inputted to one of the spin qubits via pulsed rotations. By introducing dissipation, we obtained a relatively good performance in the quantum RC.

Physical reservoir computing (PRC) harnesses the intrinsic nonlinear dynamics of physical systems for efficient temporal data processing, offering significant advantages in energy-efficient hardware implementation. This study explores the potential of oriented semiconducting polymer (SCP) thin films as reservoirs for PRC, focusing on two types of SCP benzo[c]cinnoline-based conjugated polymer diketopyrrolopyrrole benzo[c]cinnoline p(DPP-BZC) and regioregular poly(3-hexyl thiophene) (RR-P3HT). To enable anisotropic charge transport, uniaxially oriented thin films with edge-on molecular orientation were fabricated using the floating film transfer method. The films were electrically evaluated for anisotropic nonlinear responses, phase-shifting capabilities, and high-dimensional mapping in PRC tasks. Performance metrics, including waveform generation accuracy, were systematically investigated under varying device configurations and molecular structures. The study underscores the critical role of different conjugated polymers and their orientations in PRC performance, paving the way for developing next-generation materials for temporal signal processing and low-power intelligent hardware.

Methods for visualizing charged particles in water have been extensively studied, whether for observing subatomic particles originating from space or monitoring charged particle beams used in radiation therapy. At the Heavy Ion Medical Accelerator in Chiba (HIMAC) facility of the National Institute of Radiological Sciences, we conducted ultrasound echo imaging of a water volume irradiated with 500 MeV n⁻¹ Fe ions using an ultrasound imaging device. The resulting ultrasound echo images revealed microbubble-like signals near the Fe ion Bragg peak. Although the intensity of the Fe ion beam pulses was insufficient to boil the water, and the ultrasound device did not generate sound pressure levels high enough to induce cavitation, microbubbles were nonetheless observed in the ultrasound echo images. These microbubbles likely formed through a mechanism in which microscopic cavities (bubble nuclei) created by individual Fe ions aggregated to form larger cavities, leading to the appearance of microbubbles.

Ultraviolet-induced degradation (UV-ID) of various PV cell types was analyzed under optical UV filters with different cutoff wavelengths. Cell types studied included interdigitated back contact (IBC), passivated emitter and rear totally diffused (PERT), and heterojunction technology (HJT) based on crystalline Si (c-Si), and metal halide perovskite (MHP) cells. Analyzing degradation rates in two distinct regimes proved beneficial for all cell types. We used empirical linearizing functions ln(t) for c-Si technologies and ²√t for MHP samples where t is time. These were applied to extrapolate UV-induced degradation over the lifetime of PV modules under various levels of optical UV filtering and used to predict the relative economic benefits for PV power plants. Degradation rates for all technologies were generally faster under the long pass optical filters having shorter cutoff wavelengths transmitting more UV irradiation and at elevated temperatures when testing MHP samples in the range between 60 °C and 90 °C.

Optical coating to maintain clear views in harsh environments is a vital technology to meet the increasing demand for vision assistance cameras or fully automated vehicles. In this study, the hierarchical nanostructured super-hydrophobic coating was fabricated without an expensive lithography process. First, the self-assembled Ag nano-mask was deposited on top of the SiO₂ layer instead of a lithography-patterned nano-mask. Next, isotropic etching to carve the SiO₂ layer and anisotropic etching to reshape the Ag nano-mask were alternatively applied to create a well-controlled hierarchical nanostructure of SiO₂ in one process. The size and pitch of the nanostructure were optimized by the deposition condition of Ag and the etching condition of Ag to gradually re-shape the Ag mask during the etching process. These techniques have achieved a productive etching process to form a rigid hierarchical nanostructure on a lens surface without a lithography technique.

We synthesized ionic liquids (ILs) containing Cu cations in which the stable valence state of the Cu cations was systematically controlled by introducing a cyano group (CN) into a cationic side chain. We also explored the current waveform and underlying electrochemical reaction appropriate for physical reservoir computing. An IL-based physical reservoir device (IL-PRD) using ILs with CN showed higher short-term memory capability, nonlinearity, and effective data dimensionality than an IL-PRD using an IL without CN. We found that the ratio of the oxidation current to the reduction current was an influencing factor for the computing capability of IL-PRDs.

In EUV lithography, residual hydrocarbon gas in a vacuum chamber causes the carbon contamination of the mask and optics, resulting in a reflectance drop. To mitigate this issue, several pascals of hydrogen gas are introduced into the EUV scanner. In a hydrogen atmosphere, high-power EUV irradiation generates EUV-induced hydrogen plasma, which might destroy the absorber layer or Mo/Si multilayer of the EUV mask. This damage is called a "blister." To evaluate the damage, a high-power EUV irradiation tool with hydrogen gas was installed at the BL09 beamline of the NewSUBARU synchrotron light facility. The durability of a normal TaBO/TaBN absorber on an EUV mask was evaluated. No blister occurred on this absorber at a high EUV dose of 2600 kJ/cm2. The hydrogen ion dose was estimated as 1.3×1014 ions/s by current and voltage measurements with an EUV intensity of 43 W/cm2 (89 mW) and hydrogen pressure of 70 Pa.

This review focuses on research and development aimed at integrating biology and devices, with a particular emphasis on approaches utilizing biomolecules in device fabrication. Specifically, it highlights the four key elemental technologies of the Bio-nano-process proposed by Yamashita et al. around 2000: (1) design and synthesis of protein supramolecules, (2) synthesis of inorganic nanomaterials using bio-templates and biomineralization, (3) the arrangement of bio-nanomaterial composites on substrates or their integration into functional materials, and (4) the selective elimination of proteins from bio-nanomaterial composites when necessary. The review discusses various examples of applications of these technologies. As devices shrink to biomolecular sizes, nanoscale interfaces enabling seamless signal transmission and physically connecting biomolecules and devices become crucial. The integration through this interface is expected to evolve into devices becoming part of biological systems, achieving a symbiosis between biomolecules and nanodevices. This fusion of fluctuating living systems and deterministic devices marks a new chapter in nanotechnology, paving the way for hybrid bio-device systems and innovative applications.

We studied the classification of threading dislocations in an ammonothermal GaN substrate by analyzing the spot size in dislocation images obtained via synchrotron back-reflection X-ray topography. The spot size reflects the lattice distortion or strain surrounding the dislocations, enabling us to categorize the dislocation types based on their respective spot sizes. To achieve this, we employed both a high-quality X-ray camera and a high monochromatic X-ray. Consequently, we classified the dislocations based on spot size in X-ray topography images using the 0008-reflection plane and experimentally determined that the small, middle, and large spots correspond to edge dislocations, mixed dislocations with b = na + 1c (n = 1, 2), and mixed dislocations with Burgers vectors with b = na + 2c(n = 1, 2), respectively. This method is promising for the non-destructive classification of dislocations across an entire surface in a short time.

Using focused helium-ion irradiation by helium-ion microscopy (HIM), we demonstrated the formation of nanosized hole arrays (nanopore arrays) on ultrathin (< 3.6 nm) silicon nanosheets. Nanoscale patterning was conducted by setting the helium ion (He⁺) acceleration energy to 30 keV and modulating the ion dose to the irradiated area from 1×10¹⁷ to 10¹⁹ cm^-1. The He⁺ irradiated area was observed as a bright spot on the HIM image at a low dose, which changed to an etch pit-like shape as the dose increased. Cross-sectional transmission electron microscopy (XTEM) observations indicated that the nanosheet where the He⁺ was irradiated vanished under the increased dose condition, and the area without irradiation was preserved. Simultaneously, blistering was observed over the entire area where the nanopore array was formed. In the XTEM image, a space was formed between the buried oxide film and the Si layer owing to ion implantation.

We evaluated surface activated bonding (SAB), a room temperature bonding, for hybrid surfaces bonding. At first, SAB process was evaluated on copper and silicon oxide full sheet surfaces, in order to separately study the impact of the SAB activation on both types of materials embedded in a hybrid surface layer. Then, 200 mm wafers with 2.5 μm copper pads 2.5 μm apart in a silicon oxide matrix were used to probe the impact of activation with atomic force microscopy. Two test vehicles were then manufactured in order to morphologically and electrically study the bonding interface. Thus, hybrid wafers were aligned and bonded in an EVG^®COMBOND^® equipment. Cross-sectional scanning and transmission electron microscopy characterizations were performed on both test vehicles in order to observe the bonding interface. Electrical tests were also performed at the end of full 3D integration on daisy chain structures to demonstrate a high connectivity through the bonding interface.

We experimentally demonstrate the anti-ferroelectric (AFE) behavior of a Hf_1−xZr_xO₂ (HZO)/Si FET and its potential for high-endurance nonvolatile memory operation. The AFE-HZO FET with Zr content of 75% exhibits a double polarization switching and half-loop switching of its double hysteresis under bipolar and unipolar bias conditions, respectively. The counterclockwise hysteresis in the transfer I_d–V_g characteristics is demonstrated under unipolar V_g sweep through half-loop polarization in AFeFET. The steep subthreshold swing values were observed for both forward and backward V_g sweeps of I_d–V_g curves for AFeFET under unipolar bias condition. The nonvolatile feature of AFeFET is achieved by introducing the optimized hold voltage of 1.3 V during the retention period. The threshold voltage shift can be realized by utilizing the unipolar program/erase V_g pulses. Also, the high-endurance properties of HZO/Si AFeFET are demonstrated under unipolar V_g stress with observable memory window up to 10⁹ cycles without gate insulator breakdown.

We elucidate the role of gallium (Ga) in the structural and electronic properties of amorphous indium gallium oxide (a-IGO) for different Ga concentrations with oxygen interstitial defects using hybrid density functional methods. Ab initio molecular dynamic simulations reveal that Ga substitution significantly affects the structural characteristics, and that Ga–O coordination is particularly sensitive to changes in oxygen stoichiometry. The electronic structure indicates the formation of an O–O dimer in the neutral state. The stability of this dimer upon capturing electrons is influenced by the local atomic structure around the dimer. When the bond breaks, the dimer's antibonding defect level is significantly lowered from the conduction band, approaching the valence band. This makes it more energetically advantageous for the dimer to capture two electrons. We statistically studied the Ga concentration dependence on the impact of O₂ dimer generation in a-IGO. Formation transition energy indicates that O–O bond is broken easily with more Ga, which acts as an electron trap identifying the origin of positive bias stress observed in the transistor behavior.

Dynamic ultrasound scattering methods are becoming established to allow measurements of the dynamics of microparticles in Brownian motion. Using a focused transducer, nanoparticles can be analyzed, but applying strong ultrasound to large submicron particles causes problems with excessive acoustic energy that interferes with the dynamics of the particles. Backscattering is an attractive setup that maximizes spatial resolution, but when the sample thickness is reduced to eliminate the acoustic flow effects, the reflected waves of two cell windows that sandwich the suspension and the weak particle scattering signal interfere with each other. Therefore, a new technique was attempted to remove the reflected waves and extract only the scattered waves. After showing that the acoustic energy does not interfere with the analysis of nanoparticles even in the presence of large particles, we showed that these sizes can be extracted simultaneously, using a mixture of particles with diameters of 50 and 500 nm.

This work presents a comprehensive study on the sensitivity optimization of electrical impedance flow cytometry devices for identifying analytes suspended in a flowing liquid. The optimization is achieved by investigating the influence of various parameters, including applied frequency, electrode geometry dimensions, bacterial properties, and buffer characteristics. The study utilizes COMSOL Multiphysics simulation to analyze the impedance variation based on differential Maxwell's equations solved using finite element methods. The frequency optimization reveals that the sensitivity peak is around 12.6 kHz when considering imaginary impedance due to medium conductivity. Geometry optimization involves electrode dimensions with a length of 30 µm and a gap of 15 μm, as well as a channel width and height of 20 μm. Furthermore, the paper explores the effect of buffer conductivity, showing that it plays a significant role in defining total impedance with or without cells/particles. Higher buffer conductivity leads to dominant changes in real impedance, while lower conductivity affects imaginary impedance more prominently. The study also investigates the impact of variations in bacterial parameters, such as cell membrane permittivity and cytoplasm conductivity. These parameters influence total impedance, with cell radius showing a notable effect on sensitivity. By optimizing these parameters, the sensitivity and performance of impedance-based flow cytometry devices can be enhanced, making them more effective for bacterial analysis and characterization in various applications.

We examined the stability of writing in a magnetic domain wall device from the Oersted field induced by electrical current flowing in an embedded metal line. We found that the Joule heating from the writing current raises the device temperature, leading to destabilization of its magnetization after the pulse ends abruptly. To address this issue, we suggested adding a falling trailing edge to the main writing pulse, providing a stabilizing Oersted magnetic field while the device temperature reduces. We found the adequate trailing edge length fits to the thermal transient obtained from the 3D thermal simulations. This approach improved the writing stability of the device and highlights the importance of writing pulse shape and thermal management for stable writing of domain wall devices.

The current directed self-assembly (DSA) process utilizes a diblock copolymer composed of polystyrene (PS) and polymethylmethacrylate (PMMA) as standard materials. However, domain spacing of the self-assembled PS-b-PMMA is limited to ∼20–30 nm due to weak segregation strength. In this study, we explore a potential to overcome this size limitation through a multiblock approach that has previously been demonstrated with (PS-b-PI)_n. Specifically, we simulate the self-assembled morphology of the linear multiblock copolymer, (PS-b-PMMA)_n, using the so-called theoretically informed coarse-grained model developed for symmetric PS-b-PMMA. The simulation results demonstrate that the lamella pitch of (PS-b-PMMA)_n can be reduced by ∼20%–25% compared to that of diblock copolymer. This reduction is attributed to loop and bridge conformations of the multiblock copolymer chains. These findings indicate that (PS-b-PMMA)_n could be advantageous for DSA, not only by enabling the size reduction, but also by potentially enhancing the guiding effects through physically cross-linked, self-assembled domains via bridged chains.

We developed a systematic measurement method that simultaneously captures pump detuning, the optical spectrum, RF beat noise, and the linewidth of a microresonator frequency comb. This comprehensive measurement approach enables us to investigate and visualize the phase transition between two distinct states within the modulation instability (MI) comb: a low-noise state (MI comb phase 1) and a high-noise state (MI comb phase 2). While phase 2 is typically recognized as the MI comb, our findings suggest that phase 1 represents a transition from the Turing pattern to the MI comb, maintaining a low-noise profile despite exhibiting the spectral characteristics of an MI comb.

Photodynamic therapy (PDT) is one of the treatment methods used for brain tumors. In PDT, red laser light is irradiated onto photosensitizers accumulated in tumor tissues. However, the red light used in PDT has low tissue penetration, requiring the opening of the head for surgery, which imposes a significant burden on the patient. Therefore, in this study, we proposed wireless optically stimulable implant devices using upconversion nanoparticles (UCNPs), including the UCNP fiber and the waveguiding (WG)-UCNP mesh sheet. The proposed devices enable wireless red light emission by external NIR irradiation, resulting in non-invasive PDT. Furthermore, the UCNP fiber and WG-UCNP mesh sheet have separate NIR light receiving and red light emitting areas, which reduces the attenuation of the entering NIR light in bone, tissue, and so on. In this study, the UCNP fiber and WG-UCNP mesh sheet were successfully fabricated, and the light strength characteristics were evaluated using emission tests.

The Ge_0.75Sn_0.25 alloy, which is lattice matched to the InP, has the potential to create a high-quality GeSn-on-insulator (GeSnOI) structure for group IV optoelectronic devices. A Ge_0.75Sn_0.25OI metal-semiconductor-metal (MSM) photodetector was fabricated through the layer transfer technique using DiVinyl Siloxane bis-Benzocyclobuten (DVS-BCB) polymer as an adhesive and highly selective wet etching of InP substrate over GeSn, Si, SiO₂ and DVS-BCB. The photoresponse of the Ge_0.75Sn_0.25OI MSM photodetector at a wavelength of 1550 nm was evaluated using a modulated laser and lock-in method, achieving a responsivity and a noise equivalent power (NEP) of ∼3 × 10⁻⁶ A W⁻¹ and ∼1 × 10⁻⁶ W/Hz^0.5, respectively. The thermal budget for fabricating Ge_0.75Sn_0.25OI MSM photodetector is below 220 °C, which is compatible with conventional Si back-end-of-the-line (BEOL) processing toward three-dimensional (3D) heterogeneous-integrated devices.