著者

Khan M. Ajmal Hara K. O. Du W. Baba M. Nakamura K. Suzuno M. Toko K. Usami N. Suemasu T.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.11, pp.112107, 2013-03

被引用文献数

72 15

---

B-doped p-BaSi2 layer growth by molecular beam epitaxy and the influence of rapid thermal annealing (RTA) on hole concentrations were presented. The hole concentration was controlled in the range between 1017 and 1020 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1 × 1020 cm−3 were achieved via dopant activation using RTA at 800 °C in Ar. The activation efficiency was increased up to 10%.

著者

Sun Jianhui Zhao Jialong Masumoto Yasuaki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.5, pp.053119, 2013-02

被引用文献数

49

---

We demonstrate the electron transfer (ET) processes from CuInS2/ZnS core/shell quantum dots (QDs) into porous anatase TiO2 films by time-resolved photoluminescence spectroscopy. The rate and efficiency of ET can be controlled by changing the core diameter and the shell thickness. It is found that the ET rates decrease exponentially at the decay constants of 1.1 and 1.4 nm–1 with increasing ZnS shell thickness for core diameters of 2.5 and 4.0 nm, respectively, in agreement with the electron tunneling model. This shows that optimized ET efficiency and QD stability can be realized by controlling the shell thickness.

著者

Hurley D. H. Wright O. B. Matsuda O. Shinde S. L.

出版者

American Institute of Physics

雑誌

Journal of Applied Physics (ISSN:00218979)

巻号頁・発行日

vol.107, no.2, pp.023521, 2010-01-15

被引用文献数

23

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We use ultrashort optical pulses to microscopically image carrier and thermal diffusion in two spatial dimensions in pristine and mechanically polished surfaces of crystalline silicon. By decomposing changes in reflectivity in the latter sample into a transient component that varies with delay time and a steady-state component that varies with pump chopping frequency, the influence of thermal diffusion is isolated from that of carrier diffusion and recombination. Additionally, studies using carrier injection density as a parameter are used to clearly identify the carrier recombination pathway.

著者

Casey T. A. Sakakibara J. Thoroddsen S. T.

出版者

American Institute of Physics

雑誌

Physics of fluids (ISSN:10706631)

巻号頁・発行日

vol.25, no.2, pp.025102, 2013-02

被引用文献数

30 1

---

We introduce a modified tomographic PIV technique using four high-speed videocameras and a scanning pulsed laser-volume. By rapidly illuminating adjacent subvolumesonto separate video frames, we can resolve a larger total volume of velocityvectors, while retaining good spatial resolution. We demonstrate this technique byperforming time-resolved measurements of the turbulent structure of a round jet,using up to 9 adjacent volume slices. In essence this technique resolves more velocityplanes in the depth direction by maintaining optimal particle image density andlimiting the number of ghost particles. The total measurement volumes contain between1 ×106 and 3 ×106 velocity vectors calculated from up to 1500 reconstructeddepthwise image planes, showing time-resolved evolution of the large-scale vorticalstructures for a turbulent jet of Re up to 10 000.

著者

Tsankov Tsanko V. Toko Kaoru Czarnetzki Uwe

出版者

American Institute of Physics

雑誌

Physics of plasmas (ISSN:1070664X)

巻号頁・発行日

vol.19, no.12, pp.123503, 2012-12

被引用文献数

13

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A novel plasma source with a magnetic X-point has been developed to probe an alternative for cesium-free negative hydrogen ion production. This study presents first results for the gas and vibrational temperatures in the source at 1 Pa and various RF powers. The temperatures are obtained from analysis of the intensity distribution of the molecular Fulcher-α bands. The gas temperature increases with the RF power, while the vibrational temperature remains constant in the studied range of RF powers. Both quantities show no appreciable spatial dependence. The obtained high values of the vibrational temperatures indicate a high population of the vibrational levels, favourable for the volume negative ion production. A theoretical concept indicates the presence of an optimum value for the vibrational temperature at which the negative hydrogen ion yield by volume processes has a maximum. Coincidently, the measured value is close to this optimum. This indicates that the novel concept can provide certain advantages compared to other sources based on volume production.

著者

Cuong Nguyen Thanh Otani Minoru Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.23, pp.233106, 2012-12

被引用文献数

10 1

---

Based on the first-principles total-energy calculations, we demonstrate the possibility of controlling the band-gap and carrier type of bilayer graphene using ionic molecules. Our calculations suggest that bilayer graphene sandwiched by a pair of cation-anion molecules is a semiconductor with a moderate energy gap of 0.26 eV that is attributable to the strong local dipole field induced by the cation-anion pair. Furthermore, we can control the semiconducting carrier type—intrinsic, p-type, or n-type—of bilayer graphene sandwiched by ionic molecules by changing the cation-anion pair.

著者

Sakakibara Jun Machida Nobuteru

出版者

American Institute of Physics

雑誌

Physics of fluids (ISSN:10706631)

巻号頁・発行日

vol.24, no.4, pp.041702, 2012-04

被引用文献数

32 9

---

We measured velocity distribution in cross sections of a fully developed turbulentpipe flow upstream and downstream of a 90◦ bend by synchronizing two sets ofa particle image velocimetry (PIV) system. Unsteady undulation of Dean vorticesformed downstream from the bend was characterized by the azimuthal position ofthe stagnation point found on the inner and outer sides of the bend. Linear stochasticestimationwas applied to capture the upstream flowfield conditioned by the azimuthallocation of the stagnation point downstream from the bend. When the inner-sidestagnation point stayed below(above) the symmetry plane, the conditional streamwisevelocity upstream from the bend exhibited high-speed streaks extended in a quasistreamwisedirection on the outer side of the curvature above (below) the symmetryplane.

著者

Ito T. Katanuma I.

出版者

American Institute of Physics

雑誌

Physics of Plasmas (ISSN:1070664X)

巻号頁・発行日

vol.12, no.8, pp.082512, 2005-08-16

被引用文献数

5 4

---

The neoclassical resonant plateau transport in a mirror cell is studied theoretically. The analytical expression for a non-square-well magnetic field is obtained. The analytical result is applied to the GAMMA10 tandem mirror [T. Cho, M. Yoshida, J. Kohagura et al., Phys. Rev. Lett. 94, 085002-1 (2005)], which consists of several mirror cells in it, and the confinement time due to the neoclassical resonant plateau transport is determined in each mirror cell. It is found that the neoclassical resonant transport of ions trapped in the nonaxisymmetric anchor mirror cell and transition mirror cells is significantly smaller than those trapped in the central cell.

著者

Sasagawa Y. Katanuma I. Mizoguchi Y. Cho T. Pastukhov V. P.

出版者

American Institute of Physics

雑誌

Physics of Plasmas (ISSN:1070664X)

巻号頁・発行日

vol.13, no.12, pp.122506, 2006-12-18

被引用文献数

9 9

---

Magnetohydrodynamic stabilization of an axisymmetric mirror plasma with a magnetic divertor is studied. An equation is found for the flute modes, which includes the stabilizing influence of ion temperature anisotropy and nonparaxial magnetic fields, as well as a finite ion Larmor radius. It is shown that if the density profile is sufficiently gentle, then the nonparaxial configuration can stabilize all modes as long as ion temperature is radially uniform. This can be demonstrated even when the density vanishes on the separatrix and even for small ion Larmor radii. It is found, however, that the ion temperature gradient makes the unstable region wider; high ion temperature is required to stabilize the flute mode.

著者

Katanuma I. Yagi K. Nakashima Y. Ichimura M. Imai T.

出版者

American Institute of Physics

雑誌

Physics of Plasmas (ISSN:1070664X)

巻号頁・発行日

vol.17, no.3, pp.032303, 2010-03

被引用文献数

8 7

---

The computer code by reduced magnetohydrodynamic equations were made which can simulate the flute interchange modes (similar to the Rayleigh–Taylor instability) and the instability associated with the presence of nonuniform plasma flows (similar to the Kelvin–Helmholtz instability). This code is applied to a model divertor and the GAMMA10 [ M. Inutake et al., Phys. Rev. Lett. 55, 939 (1985) ] with divertor in order to investigate the flute modes in these divertor cells. The linear growth rate of the flute instability determined by the nonlocal linear analysis agrees with that in the linear phase of the simulations. There is a stable nonlinear steady state in both divertor cells, but the nonlinear steady state is different between the model divertor and the GAMMA10 with divertor.

著者

Katanuma I. Yagi K. Haraguchi Y. Ichioka N. Masaki S. Ichimura M. Imai T.

出版者

American Institute of Physics

雑誌

Physics of plasmas (ISSN:1070664X)

巻号頁・発行日

vol.17, no.11, pp.112506, 2010-11

被引用文献数

8 7

---

The flute instability and the associated radial transport are investigated in the tandem mirror with a divertor mirror cell (the GAMMA10 A-divertor) with help of computer simulation, where GAMMA10 is introduced [ Inutake et al., Phys. Rev. Lett. 55, 939 (1985) ]. The basic equations used in the simulation were derived on the assumption of an axisymmetric magnetic field. So the high plasma pressure in a nonaxisymmetric minimum-B anchor mirror cell, which is important for the flute mode stability, is taken into account by redefining the specific volume of a magnetic field line. It is found that the flute modes are stabilized by the minimum-B magnetic field even with a divertor mirror although its stabilizing effects are weaker than that without the divertor mirror. The flute instability enhances the radial transport by intermittently repeating the growing up and down of the Fourier amplitude of the flute instability in time.

著者

Ikeda Atsushi Miyazaki Kunimasa

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.135, no.2, pp.024901, 2011

被引用文献数

15

---

We numerically study thermodynamic and structural properties of the one-component Gaussian core model at very high densities. The solid-fluid phase boundary is carefully determined. We find that the density dependence of both the freezing and melting temperatures obey the asymptotic relation, log Tf, log Tm∝ − ρ2/3, where ρ is the number density, which is consistent with Stillinger's conjecture. Thermodynamic quantities such as the energy and pressure and the structural functions such as the static structure factor are also investigated in the fluid phase for a wide range of temperature above the phase boundary. We compare the numerical results with the prediction of the liquid theory with the random phase approximation (RPA). At high temperatures, the results are in almost perfect agreement with RPA for a wide range of density, as it has already been shown in the previous studies. In the low temperature regime close to the phase boundary line, although RPA fails to describe the structure factors and the radial distribution functions at the length scales of the interparticle distance, it successfully predicts their behaviors at longer length scales. RPA also predicts thermodynamic quantities such as the energy, pressure, and the temperature at which the thermal expansion coefficient becomes negative, almost perfectly. Striking ability of RPA to predict thermodynamic quantities even at high densities and low temperatures is understood in terms of the decoupling of the length scales which dictate thermodynamic quantities from the interparticle distance which dominates the peak structures of the static structure factor due to the softness of the Gaussian core potential.

著者

Markland Thomas E. Morrone Joseph A. Miyazaki Kunimasa Berne B. J. Reichman David R. Rabani Eran

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.136, no.7, pp.074511, 2012

被引用文献数

34 7

---

A comprehensive microscopic dynamical theory is presented for the description of quantum fluids as they transform into glasses. The theory is based on a quantum extension of mode-coupling theory. Novel effects are predicted, such as reentrant behavior of dynamical relaxation times. These predictions are supported by path integral ring polymer molecular dynamics simulations. The simulations provide detailed insight into the factors that govern slow dynamics in glassy quantum fluids. Connection to other recent work on both quantum glasses as well as quantum optimization problems is presented.

著者

Konno Hidetoshi Watanabe Fumitoshi

出版者

American Institute of Physics

雑誌

Journal of Mathematical Physics (ISSN:00222488)

巻号頁・発行日

vol.48, no.10, pp.103303, 2007-10

被引用文献数

14 6

---

Maximum likelihood estimator (MLE) for a generalized Cauchy process (GCP) is studied with the aid of the method of information geometry in statistics. Our GCP is described by the Langevin equation with multiplicative and additive noises. The exact expressions of MLEs are given for the two cases that the two types of noises are uncorrelated and mutually correlated. It is shown that the MLEs for these two GCPs are free from divergence even in the parameter region wherein the ordinary moments diverge. The MLE relations can be regarded as a generalized fluctuation-dissipation theorem for the present Langevin equation. Availability of them and of some other higher order statistics is demonstrated theoretically and numerically.

著者

Galstian Anahit Kinoshita Tamotu Yagdjian Karen

出版者

American Institute of Physics

雑誌

Journal of mathematical physics (ISSN:00222488)

巻号頁・発行日

vol.51, no.5, pp.052501, 2010-05

被引用文献数

20 5

---

We consider the wave propagating in the Einstein and de Sitter space-time. The covariant d’Alembert’s operator in the Einstein and de Sitter space-time belongs to the family of the non-Fuchsian partial differential operators. We introduce the initial value problem for this equation and give the explicit representation formulas for the solutions. We also show the Lp−Lq estimates for solutions.

著者

Maczka M. Hanuza J. Baran J. Hushur A. Kojima S.

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.125, no.24, pp.244503, 2006-12

被引用文献数

8

---

The authors report the results of temperature-dependent Brillouin scattering from both transverse and longitudinal acoustic waves, heat capacity studies as well as room temperature Raman scattering studies on M2O–MgO–WO3–P2O5 glasses (M=K,Rb). These results were used to obtain information about structure and various properties of the studied glasses such as fragility, elastic moduli, ratio of photoelastic constants, and elastic anharmonicity. They have found that both glasses have similar properties but replacement of K+ ions by Rb+ ions in the glass network leads to decrease of elastic parameters and P44 photoelastic constant due to increase of fragility. Based on Brillouin spectroscopy they show that a linear correlation between longitudinal and shear elastic moduli holds over a large temperature range. This result supports the literature data that the Cauchy-type relation represents a general rule for amorphous solids. An analysis of the Boson peak revealed that the form of the frequency distribution of the excess density of states is in agreement with the Euclidean random matrix theory. The reason of the observed shift of the maximum frequency of the Boson peak when K+ ions are substituted for Rb+ ions is also briefly discussed.

著者

Kondo Takahiro Kato Hiroyuki S. Bonn Mischa Kawai Maki

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.126, no.18, pp.181103, 2007-05

被引用文献数

29 17

---

The isothermal crystallization process of thin amorphous solid water (ASW) films on Ru(0001) has been investigated in real time by simultaneously employing helium atom scattering, infrared reflection absorption spectroscopy, and isothermal temperature-programmed desorption. The measurements reveal that the crystallization mechanism consists of random nucleation events in the bulk of the ASW films, followed by homogeneous growth. Morphological changes of the solid water film during crystallization expose the water monolayer just above the substrate to the vacuum during the crystallization process.

著者

Shigeta Yasuteru

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.128, no.16, pp.161103, 2008-04

被引用文献数

14 11

---

We have derived a quantum distribution function in terms of cumulants that are expectation values of a (anti)symmetric-ordered product of position and momentum fluctuation operators. A second-order approximation leads a Gaussian distribution function, which is positive definite and has proper marginals so that the Shannon entropy can be evaluated.

著者

Ikeda Atsushi Miyazaki Kunimasa

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.135, no.5, pp.054901, 2011

被引用文献数

27 8

---

We numerically study crystal nucleation and glassy slow dynamics of the one-component Gaussian core model (GCM) at high densities. The nucleation rate at a fixed supercooling is found to decrease as the density increases. At very high densities, the nucleation is not observed at all in the time window accessed by long molecular dynamics (MD) simulation. Concomitantly, the system exhibits typical slow dynamics of the supercooled fluids near the glass transition point. We compare the simulation results of the supercooled GCM with the predictions of mode-coupling theory (MCT) and find that the agreement between them is better than any other model glassformers studied numerically in the past. Furthermore, we find that a violation of the Stokes-Einstein relation is weaker and the non-Gaussian parameter is smaller than canonical glassformers. Analysis of the probability distribution of the particle displacement clearly reveals that the hopping effect is strongly suppressed in the high density GCM. We conclude from these observations that the GCM is more amenable to the mean-field picture of the glass transition than other models. This is attributed to the long-ranged nature of the interaction potential of the GCM in the high density regime. Finally, the intermediate scattering function at small wavevectors is found to decay much faster than its self part, indicating that dynamics of the large-scale density fluctuations decouples with the shorter-ranged caging motion.

著者

Ikeda Atsushi Miyazaki Kunimasa

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.135, no.2, pp.024901, 2011-07

被引用文献数

15 16

---

We numerically study thermodynamic and structural properties of the one-component Gaussian core model at very high densities. The solid-fluid phase boundary is carefully determined. We find that the density dependence of both the freezing and melting temperatures obey the asymptotic relation, log Tf, log Tm∝ − ρ2/3, where ρ is the number density, which is consistent with Stillinger's conjecture. Thermodynamic quantities such as the energy and pressure and the structural functions such as the static structure factor are also investigated in the fluid phase for a wide range of temperature above the phase boundary. We compare the numerical results with the prediction of the liquid theory with the random phase approximation (RPA). At high temperatures, the results are in almost perfect agreement with RPA for a wide range of density, as it has already been shown in the previous studies. In the low temperature regime close to the phase boundary line, although RPA fails to describe the structure factors and the radial distribution functions at the length scales of the interparticle distance, it successfully predicts their behaviors at longer length scales. RPA also predicts thermodynamic quantities such as the energy, pressure, and the temperature at which the thermal expansion coefficient becomes negative, almost perfectly. Striking ability of RPA to predict thermodynamic quantities even at high densities and low temperatures is understood in terms of the decoupling of the length scales which dictate thermodynamic quantities from the interparticle distance which dominates the peak structures of the static structure factor due to the softness of the Gaussian core potential.