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Search Results: 1 - 10 of 1313 matches for " Yasuhiro Shiraki "
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TEM Observation of Si0.99C0.01 Thin Films with Arsenic-Ion-, Boron-Ion-, and Silicon-Ion-Implantation Followed by Rapid Thermal Annealing  [PDF]
Junji Yamanaka, Shigenori Inoue, Keisuke Arimoto, Kiyokazu Nakagawa, Kentarou Sawano, Yasuhiro Shiraki, Atsushi Moriya, Yasuhiro Inokuchi, Yasuo Kunii
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51003
Strained Si and its related materials, such as strained SiGe and strained silicon-carbon alloy (Si-C), are receiving tremendous interest due to their high carrier mobility. In this study we carry out a basic investigation of the change in microstructure of ion-implanted Si-C solid solution caused by rapid thermal annealing, because it is very important to realize a field-effect transistor made of this new material. The microstructures of arsenic-ion-, boron-ion-, and silicon-ion-implanted Si0.99C0.01 specimens upon thermal annealing are observed using transmission electron microscopy, and it is revealed that the rate of solid-state crystallization of ion-implanted Si-C is slower than that of the ion-implanted Si.
The rate of symptomatic improvement of congenital nasolacrimal duct obstruction in Japanese infants treated with conservative management during the 1st year of age
Hirohiko Kakizaki,Yasuhiro Takahashi,Shinsuke Kinoshita,Kunihiko Shiraki
Clinical Ophthalmology , 2008,
Abstract: Hirohiko Kakizaki1, Yasuhiro Takahashi2, Shinsuke Kinoshita1, Kunihiko Shiraki2, Masayoshi Iwaki11Department of Ophthalmology, Aichi Medical University, Aichi, Japan; 2Department of Ophthalmology and Visual Sciences, Osaka City University Graduate School of Medicine, Osaka, JapanAbstract: This study aimed to examine the rate of symptomatic improvement of congenital nasolacrimal duct obstruction (CNLDO) in Japanese infants treated with conservative management within the 1st year of age. Thirty-five lacrimal ducts in 27 patients diagnosed with CNLDO were included in the study. During the observational period, lacrimal ducts were massaged. As well, antibiotic eye drops, to be administered 4 times a day, were sometimes prescribed for obvious conjunctivitis. Two lacrimal ducts in 2 patients were probed before the 1st year of age because of dacryocystitis or severe blepharitis; these patients were included in the unimproved group. Twenty-nine lacrimal ducts in 21 patients resolved during the period (82.9%); with 16 lacrimal ducts resolving before six months of age. Therefore, a comparatively high percentage of resolution for CNLDO (82.9%) following conservative management was shown before the 1st year of age in Japanese infants.Keywords: congenital nasolacrimal duct obstruction, symptomatic improvement, conservative management, massage, probing
Electronic Transport Properties of the Ising Quantum Hall Ferromagnet in a Si Quantum Well
Kiyohiko Toyama,Takahisa Nishioka,Kentarou Sawano,Yasuhiro Shiraki,Tohru Okamoto
Physics , 2008, DOI: 10.1103/PhysRevLett.101.016805
Abstract: Magnetotransport properties are investigated for a high mobility Si two dimensional electron systems in the vicinity of a Landau level crossing point. At low temperatures, the resistance peak having a strong anisotropy shows large hysteresis which is attributed to Ising quantum Hall ferromagnetism. The peak is split into two peaks in the paramagnetic regime. A mean field calculation for the peak positions indicates that electron scattering is strong when the pseudospin is partially polarized. We also study the current-voltage characteristics which exhibit a wide voltage plateau.
In-plane magnetic field dependence of cyclotron relaxation time in a Si two-dimensional electron system
Tasuku Chiba,Ryuichi Masutomi,Kentarou Sawano,Yasuhiro Shiraki,Tohru Okamoto
Physics , 2013, DOI: 10.1103/PhysRevB.86.045310
Abstract: Cyclotron resonance of two-dimensional electrons is studied for a high-mobility Si/SiGe quantum well in the presence of an in-plane magnetic field, which induces spin polarization. The relaxation time $\tau_{CR}$ shows a negative in-plane magnetic field dependence, which is similar to that of the transport scattering time $\tau_t$ obtained from dc resistivity. The resonance magnetic field shows an unexpected negative shift with increasing in-plane magnetic field.

Ji Zhen-guo,Norikata Usami,H Sunamura,Yasuhiro Shiraki,

中国物理 B , 1998,
Abstract: Pure Ge/Si short period superlattice (SPS) samples grown by gas source molecular beam epitaxy (GS-MBE) were studied by photoluminescence and Raman scattering. For SPS samples with Germanium layer thickness (LGe) of 1.5 monolayer (ML), a new band of photoluminescence is observed for silicon layer thickness (LSi) in an intermediate range of 1.9-2.9 nm. In contrast to pure Ge/Si quantum wells, the energy of the new band shows a red-shift with the increase of LSi. Raman scattering results show that when the intensity of the photoluminescence of the new band reaches a maximum, the Raman shift relating the vibration of Si-Si reaches a minimum. It is therefore considered that the new band of the pure Ge/Si SPS is related with some kind of strain relaxation process.
Well-width dependence of valley splitting in Si/SiGe quantum wells
Kohei Sasaki,Ryuichi Masutomi,Kiyohiko Toyama,Kentarou Sawano,Yasuhiro Shiraki,Tohru Okamoto
Physics , 2009, DOI: 10.1063/1.3270539
Abstract: The valley splitting in Si two-dimensional electron systems is studied using Si/SiGe single quantum wells (QWs) with different well widths. The energy gaps for 4 and 5.3 nm QWs, obtained from the temperature dependence of the longitudinal resistivity at the Landau level filling factor $\nu=1$, are much larger than those for 10 and 20 nm QWs. This is consistent with the well-width dependence of the bare valley splitting estimated from the comparison with the Zeeman splitting in the Shubnikov-de Haas oscillations.
Insulating Phases Induced by Crossing of Partially Filled Landau Levels in a Si Quantum Well
Tohru Okamoto,Kohei Sasaki,Kiyohiko Toyama,Ryuichi Masutomi,Kentarou Sawano,Yasuhiro Shiraki
Physics , 2009, DOI: 10.1103/PhysRevB.79.241302
Abstract: We study magnetotransport in a high mobility Si two-dimensional electron system by in situ tilting of the sample relative to the magnetic field. A pronounced dip in the longitudinal resistivity is observed during the Landau level crossing process for noninteger filling factors. Together with a Hall resistivity change which exhibits the particle-hole symmetry, this indicates that electrons or holes in the relevant Landau levels become localized at the coincidence where the pseudospin-unpolarized state is expected to be stable.
Metallic Behavior of Cyclotron Relaxation Time in Two-Dimensional Systems
Ryuichi Masutomi,Kohei Sasaki,Ippei Yasuda,Akihito Sekine,Kentarou Sawano,Yasuhiro Shiraki,Tohru Okamoto
Physics , 2011, DOI: 10.1103/PhysRevLett.106.196404
Abstract: Cyclotron resonance of two-dimensional electrons is studied at low temperatures down to 0.4 K for a high-mobility Si/SiGe quantum well which exhibits a metallic temperature dependence of dc resistivity $\rho$. The relaxation time $\tau_{\rm CR}$ shows a negative temperature dependence, which is similar to that of the transport scattering time $\tau_t$ obtained from $\rho$. The ratio $\tau_{\rm CR}/\tau_t$ at 0.4 K increases as the electron density $N_s$ decreases, and exceeds unity when $N_s$ approaches the critical density for the metal-insulator transition.
Effects of Land Surface Temperature on the Frequency of Convective Precipitation in the Tokyo Area  [PDF]
Yohei Shiraki, Yoshinori Shigeta
Journal of Geographic Information System (JGIS) , 2013, DOI: 10.4236/jgis.2013.53029

This study uses statistical evaluation by correlation analysis to examine the effects of thermal environment on the frequency of convective precipitation in the Greater Tokyo Area between 12:00 and 18:00 on summer days from 1997 to 2006. To extract the frequency of convective precipitation we used Automated Meteorological Data Acquisition System radar data to obtain detailed rainfall distribution maps, and to extract the urban thermal environment we used surface temperature data from a National Oceanic and Atmospheric Administration weather satellite. Results were a coefficient of determination of 0.01, indicating no clear relation between surface temperature and convective rain frequency in the study area. Examining the convective rain frequency distribution map in conjunction with an elevation map of the area indicates that higher elevation is a better predictor of increased frequency of convective rainfall than is surface temperature. Because this indicates that orographic precipitation has a large influence in the study area, we used an elevation map to exclude hilly and mountainous regions, regions bordering flat areas (under the assumption that wind could easily move orographic precipitation to such areas), and regions containing marine areas. Doing so resulted in a coefficient of determination of 0.38, a clear signal that differences in the thermal environment in the Greater Tokyo Area have an effect on the frequency of convective precipitation. We next focused on metropolitan Tokyo, the most developed part of the region and the part experiencing the most frequent occurrences of convective precipitation, and we performed correlation analysis considering parameters related to buildings. Results indicate that orographic precipitation has a strong influence in metropolitan Tokyo as well, so we excluded those areas that were excluded from the Greater Tokyo Area analysis and again performed correlation analysis. However, we found no clear relation of convective precipitation frequency with surface temperature or building parameters.

Excitonic Aharonov-Bohm Effect in Isotopically Pure 70Ge/Si Type-II Quantum Dots
Satoru Miyamoto,Oussama Moutanabbir,Toyofumi Ishikawa,Mikio Eto,Eugene E. Haller,Kentarou Sawano,Yasuhiro Shiraki,Kohei M. Itoh
Physics , 2010, DOI: 10.1103/PhysRevB.82.073306
Abstract: We report on a magneto-photoluminescence study of isotopically pure 70Ge/Si self-assembled type-II quantum dots. Oscillatory behaviors attributed to the Aharonov-Bohm effect are simultaneously observed for the emission energy and intensity of excitons subject to an increasing magnetic field. When the magnetic flux penetrates through the ring-like trajectory of an electron moving around each quantum dot, the ground state of an exciton experiences a change in its angular momentum. Our results provide the experimental evidence for the phase coherence of a localized electron wave function in group-IV Ge/Si self-assembled quantum structures.
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