A5050053589- GaN-based semiconductor devices and materials
- Silicon and Solar Cell Technologies
- Metal and Thin Film Mechanics
- Semiconductor materials and interfaces
- ZnO doping and properties
- Semiconductor materials and devices
- Topological Materials and Phenomena
- Quasicrystal Structures and Properties
- Silicon Nanostructures and Photoluminescence
- Thin-Film Transistor Technologies
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Advanced Condensed Matter Physics
- Diamond and Carbon-based Materials Research
- Nanowire Synthesis and Applications
- Mineralogy and Gemology Studies
- Semiconductor Quantum Structures and Devices
- Ga2O3 and related materials
- Advanced Thermoelectric Materials and Devices
- Acoustic Wave Resonator Technologies
- X-ray Diffraction in Crystallography
- Iron-based superconductors research
- Advanced Materials Characterization Techniques
- Photonic and Optical Devices
- Ion-surface interactions and analysis
The University of Tokyo
2007-2024
Tohoku University
2009-2018
Institute for Materials Research, Tohoku University
2009-2015
Abstract Van der Waals layered transition-metal chalcogenides are drawing significant attention owing to their intriguing physical properties. This group of materials consists abundant members with various elements, having a variety different structures. However, they all crystalline materials, and the properties van quasicrystals have never been studied date. Here, we report on discovery superconductivity in quasicrystal Ta 1.6 Te. The electrical resistivity, magnetic susceptibility,...
Gold nanoparticles with an average diameter of ≈8 nm (Au ≈ 15 000) were irradiated a tightly focused pulse laser at 355 in aqueous solution sodium dodecyl sulfate (SDS). Transient absorption spectra the measured 25−100 ns after irradiation. The observed transient around 720 is assignable to 2p ← 1s transition solvated electrons produced via multiple ionization gold nanoparticles. nascent charge state was estimated from absorbance. dependence on SDS concentration shows gradual increase +60...
Abstract Superconductivity in quasicrystals poses a new challenge condensed matter physics. We measured the resistance and ac magnetic susceptibility of Ta 1.6 Te dodecagonal quasicrystal, which is superconducting below T c ~ 1 K. show that upper critical field increases linearly with large slope − 4.4 T/K decreasing temperature down to 0.04 K, no tendency level off. The extrapolated zero-temperature exceeds Pauli limit by factor 2.3. also observed flux-flow thermally activated behavior an...
We attempted to control grain boundary propagation in mono-like Si utilizing functional boundaries introduced by multi-seeds with specific configurations, and demonstrated that can suppress multi-crystallization during growth. The suppression mechanism was studied on the basis of character. nucleate at crucible surface, which generally leads multi-crystallization, interact boundaries, resulting a change their character configuration. This would increase yield wafers an ingot enable large...
We propose a new growth method for mono-like silicon (Si): the suppression of multicrystallization using functional grain boundaries artificially formed by multiseed crystals. In our previous study, we demonstrated such in an ingot 30 mm diameter. this paper, grew Si ingots 100 and 400 on side. Functional successfully suppressed increase area multicrystalline grains nucleated crucible side walls, which indicates large volume quasi-monocrystalline up to top ingots. This enables yield wafers...
Previous theoretical works have predicted that when a specific condition is satisfied, dislocations in three-dimensional topological insulators form one-dimensional gapless states, which are topologically protected against disorder scattering. Here, the dislocation conduction experimentally investigated Bi-Sb insulators. High-density with Burgers vector satisfying conductivity introduced into single crystals by plastic deformation. Conductivity measurements for deformed and undeformed...
Three-dimensional distribution of impurities (boron, phosphorus, oxygen, and copper) at Σ3{111} grain boundaries was determined in a Czochralski-grown silicon single crystal by laser-assisted atom probe tomography (APT) combined with transmission electron microscopy, detection limit as low the order 0.001 at. %. The location boundary APT even when not contaminated. Unlike multicrystalline grown casting method, did segregate impurity concentrations were high. gettering ability discussed.
GaN-based light-emitting diodes (LEDs) have been widely accepted as highly efficient solid-state light sources capable of replacing conventional incandescent and fluorescent lamps. However, their applications are limited to small devices because fabrication process is expensive it involves epitaxial growth GaN by metal-organic chemical vapor deposition (MOCVD) on single crystalline sapphire wafers. If a low-cost such sputtering metal foil can be used, will possible fabricate large-area...
Abstract We demonstrate a series of procedures to prepare clean surface micro-sized graphite, mined from bulk flake and securely affixed onto macroscopic Si plate by focused ion beam scanning electron microscope. Analyses structure electronic (chemical) states were made using micro-beam X-ray photoelectron spectroscopy angle-resolved photoemission spectroscopy. At the micro band dispersion single-domain was observed. The proposed methodology showcases its capability produce high-quality...
Variation in stacking fault energy with annealing at 1173 K were identified Czochralski-grown silicon crystals heavily doped n- or p-type dopant atoms. In n-type crystals, the decreased increasing time. The higher concentration of atoms, larger degree decrease. On other hand, was unchanged during and nondoped crystals. These results imply that atoms segregate nearby a fault, via their thermal migration, under an electronic interaction leading to reduction energy.
The dynamic behavior of dislocations in heavily impurity (Ga, As, O) -doped Ge crystals was investigated as a function stress and temperature by means the etch-pit technique. Ga O impurities effectively suppressed dislocation generation from surface scratch, while As did not strongly do so. Dislocations Ga- O-doped were supposed to be immobilized stable complexes formed through segregation reaction. Remarkably, impurity, even at low concentration 1016 cm−3, induced suppression generation....
We fabricated conductive nanowires in insulating AlN thin films by doping Mn along high-density unidirectional threading dislocations. Investigation of the dislocation microstructures transmission electron microscopy (TEM) and high-resolution scanning TEM revealed that segregates to cores. Strain analysis around dislocations suggests strong attractive interaction between ions strain field enhances confinement only vicinity Atomic force measurements under contact-current mode detected local...
The hardness of wurtzite indium nitride (α-InN) films 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation crystalline quality x-ray diffraction, and Young’s modulus were determined be 8.8 ± 0.4 184 5 GPa, respectively, for In (0001)- N (0001̄)-growth faces InN films. bulk shear moduli then derived 99 3 77 2 respectively. Poisson’s ratio evaluated 0.17 0.03. results examined comprehensively comparison with previously reported data as...
To elucidate dislocation generation and propagation processes in AlN films containing a high density of grown-in threading dislocations (TDs), situ nanoindentation (NI) was performed transmission electron microscope at room temperature. Dislocations with the Burgers vector b = 1/3<12¯10> were introduced not only on primary slip plane, i.e., (0001) basal planes, but also {101¯1} {101¯2} pyramidal planes. The results are explained by considering distribution resolved shear...
A series of $\mathrm{Pb}{(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{b}}_{x})}_{2}\mathrm{T}{\mathrm{e}}_{4}$ topological-insulator crystals with various Sb molar ratios $x$ was fabricated, and a systematic study their transport properties performed, aiming at realizing enhanced bulk insulation in this system. Hall-effect measurements showed that $n$- to $p$-type transition conduction occurred $x\ensuremath{\approx}0.80$. Semiconducting behavior negative temperature...
Gate-voltage dependent quantum oscillations in topological insulator Sn0.02Bi1.08Sb0.9Te2S (Sn-BSTS) are analyzed on the basis of Lifshitz−Kosevich theory. The angular dependence and Landau-level fan diagram analysis show that originate from surface states with Berry phase π. control allows precise Fermi energy, a very weak energy relaxation time τ is revealed. By simple algebraic argument using linear response theory, it shown validates constant approximation [τE,T=τ0] calculation Seebeck...
We report the results of specific heat measurements for Al–Cu–Ru icosahedral quasicrystals (i-QCs) and 1/1 crystal approximants (1/1-CAs) in temperature range from 350 to 1250 K. The i-QCs 1/1-CAs showed a marked upward deviation value Dulong-Petit's law above 600 K, reaching approximately 1.5 times at 1100 In addition, some large broad peak 1200 origin these excessive values Dulong-Petit is discussed considering high-dimensional nature structural order QCs CAs.
Abstract Quasicrystals (QCs) have a peculiar structural order characterized by quasiperiodicity and non-crystallographical point group symmetry. To reveal their characteristic physical property reflecting the order, specific heat measurements were performed for Al–Pd–Mn icosahedral QCs (i-QCs) series of crystal approximants (CAs) 2/1- 1/1- 1/0-cubic types at 400–1200 K. The measured per atom constant pressure <?CDATA ${c}_{P}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...