A5101941637- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- ZnO doping and properties
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Semiconductor materials and devices
- Superconducting Materials and Applications
- Advanced X-ray Imaging Techniques
- Semiconductor Quantum Structures and Devices
- Gas Sensing Nanomaterials and Sensors
- Advanced Photocatalysis Techniques
- Photocathodes and Microchannel Plates
- Metal and Thin Film Mechanics
- Advancements in Photolithography Techniques
- Gyrotron and Vacuum Electronics Research
- Thin-Film Transistor Technologies
- Electronic and Structural Properties of Oxides
- Advanced Optical Sensing Technologies
- Acoustic Wave Resonator Technologies
- Transition Metal Oxide Nanomaterials
- Semiconductor Lasers and Optical Devices
- Magnesium Oxide Properties and Applications
- Copper-based nanomaterials and applications
- Photonic and Optical Devices
- Luminescence Properties of Advanced Materials
High Energy Accelerator Research Organization
2010-2024
National Astronomical Observatory of Japan
2024
Kogakuin University
2013-2023
Tokyo University of Science
1985-2023
The Graduate University for Advanced Studies, SOKENDAI
2017-2022
Kyoto University
2021
Tokyo Metropolitan Industrial Technology Research Institute
2021
Kyoto Katsura Hospital
2021
Kokugakuin University
2017-2020
National Institute for Materials Science
2017-2018
The polarized transmittance and reflectance spectra of β-Ga2O3 crystals are investigated, the data interpreted in terms monoclinic crystal band structure. energies absorption edge can be divided into six ranges, these ranges assigned to transitions from valence bands conduction minimum according selection rules. indirect bandgap-energy 4.43 eV is smaller than direct 4.48 at RT; energy difference 0.05 nearly matches theoretically calculated values 0.03–0.04 eV.
Anisotropic optical properties are investigated on β-Ga2O3 films and a single crystal by spectroscopic ellipsometry measurements. The grown (0001) α-Al2O3 contain threefold in-plane rotational domains, the refractive index absorption coefficient α obtained assuming an isotropic material found to be smaller than those in crystal. By measuring off-normal transmission spectra of (010) substrate, anisotropy biaxial as well gradual increase recognized origins scattering optically determined...
We have developed a new beam injection system with single pulsed sextupole magnet (PSM) at the photon factory storage ring (PF ring) in High Energy Accelerator Research Organization. demonstrated this and succeeded storing current of 450 mA, which is normal operating PF ring. Top-up was also achieved. Coherent dipole oscillation stored fluctuation intensity observed synchrotron radiation lines during PSM became very small compared bump that normally used This experiment first demonstration...
Abstract Single-phase rocksalt-structured Mg x Zn 1− O ( > 0.5) alloy films were grown on MgO substrates using the mist chemical vapor deposition method. A specular surface with a step and terrace structure was obtained. The bandgap tuned from 5.9 to 7.8 eV as varied 0.5 1. Deep ultraviolet cathodoluminescence, stemming near band edge transitions, observed for 0.57 0.43 in 4.8–5.5 range, peaking at ∼5.1 (∼240 nm) 12–100 K range.
Rocksalt-structured MgZnO thin films of optical band gaps as large about 5.8–6.6 eV were grown on MgO substrates by a mist chemical vapor deposition method using carbon-free precursors. with the dislocation density less than 107 cm−2 obtained. Pure deep-ultraviolet cathodoluminescence was observed without noticeable emission at longer wavelengths, being attributed to improved crystallinity well reduced carbon impurity. The highest energy (the shortest wavelength) luminescence peak 6.24 (199 nm) 6 K.
The GaN-based vertical cavity surface emitting laser operating in the ultraviolet spectral region is proposed and its threshold current density estimated. calculated result indicates that low-threshold lasers using a GaN layer as an active can be realized by employing reasonably highly reflective mirrors such AlN/AlGaN multilayer mirrors.
Electrochromism synchronous to the charge/discharge of a novel Li ion battery having 3 Fe 2 (PO 4 ) and Ti 5 O 12 thin-film electrodes fabricated by chemical process, molecular precursor method, was discovered. A cathode transparent thin film with thickness 80 nm heat treating ethanol solution including Li(I) complex nitrilotriacetic acid, an Fe(III) ethylenediaminetetraacetic (dibutylammonium) H P 7 ⋅ 0.5H at 550°C for 10 min in air. An anode 90 Ti(IV) identical organic ligand, hydrogen...
The KEKB injector linac has been continuously improved to enhance the stability of many devices and efficiency beam operation. These improvements include development new C-band accelerating structure, pulse compressor, klystron, rf window, compact modulator, positron production target using crystalline tungsten. We have also achieved two-bunch acceleration, an energy spread monitor, a safety system upgrade, event-based timing control system. developments practical applications for advanced...
Tail states near the valence band maximum (VBM) and in-gap of GaN bulk InxGa1−xN films are observed by hard X-ray photoemission spectroscopy, fine structures these defect characterized photothermal deflection spectroscopy. The defects enhanced with increasing InN mole fraction, indicating that they originate in cation-related their complexes. structural disorder, defined as inverse slope VBM, becomes larger. Taking semiconductor properties into account, we consider tail state strongly...
Temperature dependencies of optical reflectance and cathodoluminescence (CL) spectra were measured for the MgO single crystal using a custom-built vacuum ultraviolet (VUV) spectroscopic system. Simultaneous observation enabled us to identify free exciton (FE) bound (BE) emissions by comparing CL emission with resonance structures. The results indicated that BE dominates near-band edge emission, FE was observed as shoulder at 300 K. ensure strong excitonic nature potential rock...
Temperature-dependent cathodoluminescence spectra were measured for rock salt-structured MgxZn1−xO films with x = 0.95–0.61. The Mg0.95Zn0.05O film exhibited the shortest deep UV peak wavelength of 199 nm (6.24 eV) at 6 K. Relatively high equivalent internal quantum efficiencies 0.9%–11% obtained. Tauc plots, which obtained from temperature-dependent optical transmittance measurements, large Stokes-like shifts 0.7–0.9 eV 6–300 Time-resolved photoluminescence (PL) signals 7 K fast and slow...
The band-gap energies and effective masses of boron gallium nitride (BGaN) ternaries were estimated. B x Ga 1- N increase proportionally with the composition . However, electrons holes in BGaN are almost equal to those GaN. We have fabricated layers on 6H–SiC substrates using metal-organic vapor phase epitaxy (MOVPE). examined photoluminescence spectra these layers. estimated results consistent theoretically.
Relation between the electrical and optical properties of p‐type NiO films prepared either by RF sputtering or molecular precursor method is studied in terms changes crystallinity, resistivity ρ absorption coefficients α . Values are correlated with electronic structures near valence band maximum, which obtained from X‐ray photoelectron spectroscopy measurements density functional theory calculations. The values found to be strongly influenced crystallinity as well Ni vacancies acceptor‐type...
We characterize the behavior caused by thermal annealing for C, O, Si and Mg ions implanted in GaN films photothermal deflection spectroscopy (PDS) with respect to structural disorder defect levels related yellow luminescence. Although region damaged ion bombardment is recovered annealing, FWHM values of ω(0002) evaluated x-ray diffraction are almost independent temperature. However, Urbach energy, as an index disorder, PDS improved. Recovery likely depend on dose quantity rather than...
Strain-controlled AlN layers were grown on (0001) 6H–SiC with a (GaN/AlN) buffer layer by metalorganic vapor phase epitaxy using an alternating-source-feeding technique (ASF). The successful strain and quality control of the thin experimentally demonstrated down to 0.05 µm changing growth conditions layer. was evaluated not only X-ray diffraction (θ-2θ) but rocking curve (ω-scan) from viewpoint c -axis tilting. crystal dependent residual in (GaN/AlN)-buffer is effective improving
We have fabricated a SiO 2 /TiO dielectric multilayer mirror applicable for ZnSe-based surface emitting lasers operating at green to blue spectral regions. The mirrors exhibited reasonably high reflectivity, greater than 96% 493 nm. A photo-pumped ZnCdSe/ZnSe/ZnSSe single quantum well (SQW) with has shown the cavity mode emission in normal direction 10 K.
We propose a 3-D video display technique that allows multiple viewers to observe images from 360-degree horizontal arc without wearing glasses. This uses cylindrical parallax barrier and one-dimensional light source array. have developed an experimental using this demonstrated observation of the use Since is based on panoramagram, number resolution are limited by diffraction at barrier. To overcome these limits, we improved revolving incorporated new in our display. The capable displaying...
We studied the emissive pits in InGaN films grown on compressive and strain-free GaN underlying layers. Pit density decreased with full width at half maximum of ω(0002) InGaN. The grew layers spiral step-flow modes, respectively. Carbon impurities accumulated inside pits. Comparison cathodoluminescence steady-state photocapacitance spectra showed that energy level carbon appeared ∼2.8 eV below conduction band (Ec) for both types Deep-level defects Ec −2.4 resulting green fluorescence...