A5028641699- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Ga2O3 and related materials
- Copper Interconnects and Reliability
- ZnO doping and properties
- Metal and Thin Film Mechanics
- Acoustic Wave Resonator Technologies
- Advanced X-ray Imaging Techniques
- Silicon Carbide Semiconductor Technologies
- Electronic Packaging and Soldering Technologies
- Advanced X-ray and CT Imaging
- Photocathodes and Microchannel Plates
- EEG and Brain-Computer Interfaces
- Advanced ceramic materials synthesis
- Semiconductor Quantum Structures and Devices
- Electrodeposition and Electroless Coatings
- Optical Coatings and Gratings
- Particle Detector Development and Performance
- Ion-surface interactions and analysis
- Plasma Diagnostics and Applications
- Motor Control and Adaptation
- Medical Imaging Techniques and Applications
- Strong Light-Matter Interactions
- Gas Sensing Nanomaterials and Sensors
- Anodic Oxide Films and Nanostructures
Tohoku University
1991-2025
Osaka University
2024-2025
Osaka Health Science University
2025
Saiseikai Nakatsu Hospital
2025
University of Miyazaki
2024
University of Maryland, Baltimore County
2024
Kyoto University
2024
The University of Tokyo
2013-2023
University of Tsukuba
2018-2022
National Institute of Advanced Industrial Science and Technology
2018-2022
1. Single-unit activity in the cingulate cortex of monkey was recorded during performance sensorially (visual, auditory, or tactile) triggered self-paced forelimb key press movements. 2. Microelectrodes were inserted into broad rostrocaudal expanse cortex, including upper and lower banks sulcus hemispheric medial wall gyrus. 3. A total 1,042 task-related neurons examined, majority which related to execution In greater than 60% them, movement-related preceded distal flexor muscles. 4. The...
Two motor areas are known to exist in the medial frontal lobe of cerebral cortex primates, supplementary area (SMA) and presupplementary (pre-SMA). We report here on an aspect cellular activity that characterizes pre-SMA. Monkeys were trained perform three different movements sequentially a temporal order. The correct order was planned basis visual information before its execution. A group pre-SMA cells (n = 64, 25%) active during process when monkeys required discard current plan develop...
Complementary time-resolved photoluminescence and positron annihilation measurements were carried out at room temperature on Mg-doped p-type GaN homoepitaxial films for identifying the origin estimating electron capture-cross-section (σn) of major nonradiative recombination centers (NRCs). To eliminate any influence by threading dislocations, free-standing substrates used. In GaN, defect complexes composed a Ga-vacancy (VGa) multiple N-vacancies (VNs), namely, VGa(VN)2 [or even VGa(VN)3],...
Cathodoluminescence (CL) spectroscopy is a powerful technique for studying emission properties of optoelectronic materials because CL free from excitable bandgap limits and ambiguous signals due to simple light scattering resonant Raman potentially involved in the photoluminescence (PL) spectra. However, direct measurements atomically thin two-dimensional materials, such as transition metal dichalcogenides hexagonal boron nitride (hBN), have been difficult small excitation volume that...
Uterine broad ligament hernia is a rare type of internal hernia, with symptoms similar to those adnexal torsion. Distinguishing these disorders crucial. We treated 49-year-old Japanese woman history gravida (n=5), parity (n=3), and cesarean sections (n=2). After visiting physician due abdominal pain vomiting, she was referred our hospital based on suspicion ovarian Emergency surgery at revealed that the patient's small intestine contained within defective hilar membrane, resulting in uterine...
The Soft X-ray Imager (SXI) is the charge-coupled device (CCD) camera for soft imaging telescope Xtend installed on Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission Hitomi satellite successfully launched 2023 September 7 (JST). In order to maximize science output of XRISM, we set requirements find that CCD employed in Hitomi/SXI or similar, i.e., $2 \times 2$ array back-illuminated CCDs with $200~\mu$m-thick depletion layer, would be practically best among...
Abstract The Soft X-ray Imager (SXI) is the charge-coupled device (CCD) camera for soft imaging telescope Xtend installed on Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission Hitomi satellite successfully launched 2023 September 7 (JST). In order to maximize science output of XRISM, we set requirements found that CCD employed in Hitomi/SXI or similar, i.e., $2 \times 2$ array back-illuminated CCDs with $200\, \mu$m-thick depletion layer, would be practically...
Roles of Al-vacancy (VAl) complexes on the cathodoluminescence (CL) spectra Si-doped AlN grown by halide vapor phase epitaxy (HVPE) a physical-vapor-transported (0001) substrate are described, making connection with results positron annihilation measurements. A combination HVPE and enabled decreasing deleterious carbon concentration dislocation density, respectively, thus accentuating influences VAl-complexes luminescence processes. low-temperature CL spectrum unintentionally doped exhibited...
Abstract We report measurements of the linear polarisation degree (PD) and angle (PA) for hard X-ray emission from Crab pulsar wind nebula. Measurements were made with XL-Calibur (∼15–80 keV) balloon-borne Compton-scattering polarimeter in July 2024. The parameters are determined using a Bayesian analysis Stokes obtained scattering angles. Well-constrained (∼8.5σ) results ∼19–64 keV signal integrated over all phases: PD=(25.1±2.9)% PA=(129.8±3.2)○. In off-pulse (nebula-dominated) phase...
Photoluminescence (PL) spectra of (0001¯) N-polar p-type GaN fabricated by using the sequential ion-implantation Mg and H with subsequent high temperature annealing exhibited near-band-edge (NBE) emission at 300 K. The longest PL lifetime (τPL) for NBE sample concentrations 1 × 1019 2 1020 cm−3, respectively, annealed 1230 °C was 18 ps This value is almost comparable to that (0001) Ga-polar Mg-doped (p-GaN:Mg) homoepitaxial film same concentration. By correlating τPL concentration major...
Abstract For accelerating the development of GaN power-switching devices, current knowledge on origins and dynamic properties major intrinsic nonradiative recombination centers (NRCs) in Mg-doped (GaN:Mg) are reviewed, as lightly to heavily doped p-type planar segments required but certain compensating defects including NRCs hinder their formation. The results complementary time-resolved photoluminescence positron annihilation spectroscopy measurements epitaxial ion-implanted GaN:Mg formed...
Vacancy‐type defects in Mg‐implanted GaN with and without hydrogen (H) implantation are probed by using monoenergetic positron beams. Mg + H ions implanted into GaN(000) to obtain 0.1 0.7‐µm‐deep box profiles concentrations of 1 × 10 19 2 20 cm −3 , respectively. For the as‐implanted samples, major defect species is determined be Ga‐vacancy ( V Ga ) related such as divacancy N ), their complexes impurities. an agglomeration vacancies starts at 800 °C annealing, leading formation vacancy...
Abstract Seeded growth of 2-inch-diameter GaN crystals via low-pressure (∼100 MPa) acidic ammonothermal method is demonstrated. Nearly bowing- and mosaic-free exhibiting full-width at half-maximum values for the 0002 X-ray rocking curves below 20 arcsec were achieved on high lattice coherency c -plane SCAAT TM seeds with gross dislocation densities in order 10 4 cm −2 . The photoluminescence spectra grown exhibited a predominant near-band-edge emission 295 K, which intensity was one...
XRISM (X-ray Imaging and Spectroscopy Mission) is an X-ray astronomy satellite developed in collaboration with JAXA, NASA ESA. It successfully launched on Sept. 7, 2023. Two complementary telescopes, Resolve Xtend are on-board XRISM. uses the pixelized micro calorimeter by NASA/GSFC has very high energy resolution of 5 eV. On other hand, CCD camera as its focal plane detector which spatial a wide field view. We evaluated performance Mirror Assembly (XMA) for using data observed during...
Seeded ammonothermal growths of a few-mm-thick GaN crystals on 2 inch diameter c-plane and 45 mm longm-plane wafers were carried out by using an NH4F mineralizer in 60 Ag-lined autoclave. As result dynamic control the temperature profile, low dislocation density nearly bowing-free m-plane was grown: i.e. full-width at half-maximum values for X-ray rocking curves 100 10 reflections smaller than 28 arcsec radius curvature estimated to be 1460 m. In addition, its photoluminescence spectrum...
To accelerate the development of GaN power devices, reproducible fabrication p-type (p-GaN) segments by ion-implantation (I/I) that enables selective-area doping is preferred. In this Letter, results time-resolved photoluminescence (PL) and spatially resolved cathodoluminescence (CL) measurements on p-GaN fabricated I/I are presented. The samples a 220-nm-deep box-shaped Mg concentration profile ([Mg] = 3×1018 cm−3) were sequential N followed atmospheric-pressure post-implantation annealing...
A process for activating Mg and its relationship with vacancy-type defects in Mg-implanted GaN were studied by positron annihilation spectroscopy. Mg+ ions implanted an energy of 10 keV, the concentration subsurface region (≤ 50 nm) was on order 1019 cm-3. After Mg-implantation, N+ to provide a 300-nm-deep box profile N 6 × 1018 From capacitance-voltage measurements, sequential implantation found enhance activation Mg. For N-implanted before annealing, major defect species determined...
Degradation mechanisms of 275-nm-band AlxGa1-xN multiple quantum well deep-ultraviolet light-emitting diodes fabricated on a (0001) sapphire substrate were investigated under hard operation conditions with the current 350 mA and junction temperature 105 °C. The optical output power (Po) initially decreased by about 20% within operating time less than 102 h then gradually to 60% 484 h. For elucidating causes for initial subsequent degradations, complementary electrical, time-resolved...
Annealing behaviors of vacancy‐type defects in ion‐implanted GaN are studied by positron annihilation. Mg + and N ions implanted to obtain 700 nm deep box profiles with concentrations 1 × 10 18 cm −3 , the samples annealed using an ultrahigh‐pressure annealing system. For as‐implanted samples, major defect species is identified as Ga‐vacancy ( V Ga )‐type defects. N‐implanted GaN, size vacancies increases temperature up 1100 °C then shrank above 1200 °C. This behavior attributed...
To investigate the carrier recombination processes in GaN crystals grown by low-pressure acidic ammonothermal (LPAAT) method, photoluminescence (PL) spectra and PL lifetimes of LPAAT on (AAT) seed were correlated with growth polarity species/concentration point defects. The toward (0001¯) direction (−c region), which provided highest rate, exhibited a predominant near-band edge (NBE) emission. Neither bandgap narrowing nor Burstein–Moss shifts due to high concentration residual impurities...