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Journal Articles

Difference between local and average structures of La$$_3$$Ga$$_5$$SiO$$_{14}$$ crystal

Yoneda, Yasuhiro; Takeda, Hiroaki*; Shiosaki, Tadashi*; Mizuki, Junichiro

Japanese Journal of Applied Physics, Part 1, 46(10B), p.7163 - 7166, 2007/10

 Times Cited Count:1 Percentile:5.72(Physics, Applied)

The langasite (La$$_3$$Ga$$_5$$SiO$$_{14}$$, LGS) crystal grown by the Czochralski technique was investigated by X-ray diffraction measurements. The X-ray diffraction profiles of the LGS were consisted with sharp Bragg peaks and large amount of diffuse scatterings. The diffuse scattering inducated the existence of the local structure which is different from the average structure. The local structure was analyzed by the pair-distrivution function method. The local structure fluctuated by the chemical ordering of Ga and Si, and the local disordering feature of La.

Journal Articles

Magnetic and dielectric properties of Tb$$_{0.5}$$Ca$$_{0.5}$$MnO$$_{3}$$

Hiramitsu, Yusuke*; Yoshii, Kenji; Yoneda, Yasuhiro; Mizuki, Junichiro; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu*; Morii, Yukio; Ikeda, Naoshi*

Japanese Journal of Applied Physics, Part 1, 46(10B), p.7171 - 7174, 2007/10

 Times Cited Count:15 Percentile:53.31(Physics, Applied)

Magnetic and dielectric properties of a perivskite manganite Tb$$_{0.5}$$Ca$$_{0.5}$$MnO$$_{3}$$ were investigated. Magnetic measurements showed three characteristic temperatures, originating from charge ordering (300 K), antiferromagnetic ordering (120 K) and a transition to a glassy state (50 K). The coexistence of the charge and antiferromagnetic ordering was consistent with the result of powder neutron diffraction. AC dielectric measurements showed large dielectric constants of about 5000 at around room temperature. A temperature dependence of the dielectric constant changed just below the charge-ordering temperature. From the analysis of tan$$delta$$;, the activation energy for a domain-boundary motion was calculated to be about 0.09 eV. These results strongly suggest that the dielectric properties of this material are governed by the ordering and transfer of the Mn-3d charges.

Journal Articles

Gasochromic properties of nanostructured tungsten oxide films prepared by sputtering deposition

Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Sugimoto, Masaki; Yoshikawa, Masahito; Nagata, Shinji*

Japanese Journal of Applied Physics, Part 1, 46(9B), p.6315 - 6318, 2007/09

 Times Cited Count:7 Percentile:31.64(Physics, Applied)

The amorphous, polycrystalline, and oriented films of the tungsten oxide were fabricated by sputtering deposition. It is found that each film has different roughness in the surface. The films with rough surface show fast coloration in 1% hydrogen. There is possibility that the gasochromic properties are improved effectively by the control of the surface morphology, and the films with large grains on the surface have better gasochromic coloration.

Journal Articles

Simultaneous proton and X-ray imaging with femtosecond intense laser driven plasma source

Orimo, Satoshi; Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Ogura, Koichi; Sagisaka, Akito; Li, Z.*; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.

Japanese Journal of Applied Physics, Part 1, 46(9A), p.5853 - 5858, 2007/09

 Times Cited Count:16 Percentile:55.33(Physics, Applied)

A laser-driven proton beam with a maximum energy of a few MeV is stably obtained using an ultra-short and high-intensity Titanium Sapphire laser. At the same time, keV X-ray is also generated at almost the same place where protons are emitted. Here, we show the successful demonstration of simultaneous proton and X-ray projection images of a test sample placed close to the source with a resolution of $$sim$$10$$mu$$m, which is determined from the source sizes. Although the experimental configuration is very simple, the simultaneity is better than a few hundreds of ps. A CR-39 track detector and imaging plate, which are placed as close as possible to the CR-39, are used as detectors of protons and X-ray. The technique is applicable to the precise observation of microstructures.

Journal Articles

Si(001) surface layer-by-layer oxidation studied by real-time photoelectron spectroscopy using synchrotron radiation

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

Japanese Journal of Applied Physics, Part 1, 46(5B), p.3244 - 3254, 2007/05

 Times Cited Count:25 Percentile:68.99(Physics, Applied)

In this study, layer-by-layer oxidation at Si(001) surface was studied experimentally by real-time photoelectron spectroscopy. Changes of band bending due to oxidation-induced midgap states in connection with the oxygen uptake and changes in oxidation states were observed. Oxidation experiments were performed using the surface reaction analysis apparatus (SUREAC2000) installed at the BL23SU in the SPring-8. O 1s and Si 2p core level photoelectron spectra were measured alternately at acquisition times of 24 and 65 s, respectively. Curve-fitting analyses for them were carried out and two and seven components were found, respectively. On the basis of the observed changes of each oxidation state, the Si emission kinetics during layer-by-layer oxidation is discussed.

Journal Articles

Observation of initial oxidation on Si(110)-16$$times$$2 surface by scanning tunneling microscopy

Togashi, Hideaki*; Takahashi, Yuya*; Kato, Atsushi*; Konno, Atsushi*; Asaoka, Hidehito; Suemitsu, Maki*

Japanese Journal of Applied Physics, Part 1, 46(5B), p.3239 - 3243, 2007/05

 Times Cited Count:13 Percentile:48.98(Physics, Applied)

On Si(110) surface, the hole mobility is enhanced as compared with that on Si(001) surface. This surface is also to be used in the next-generation three-dimensional devices. We conducted scanning-tunneling-microscopy (STM) observation on the initial oxidation of Si(110)-16$$times$$2 surface. The present result suggests less occurrence of etching under the oxidation condition. There is a possibility to form an abrupt oxide/Si interface on the Si(110) surface.

Journal Articles

Real-time observation of initial thermal oxidation on Si(110)-16$$times$$2 surfaces by O 1s photoemission spectroscopy using synchrotron radiation

Suemitsu, Maki*; Kato, Atsushi*; Togashi, Hideaki*; Konno, Atsushi*; Yamamoto, Yoshihisa*; Teraoka, Yuden; Yoshigoe, Akitaka; Narita, Yuzuru*; Enta, Yoshiharu*

Japanese Journal of Applied Physics, Part 1, 46(4B), p.1888 - 1890, 2007/04

 Times Cited Count:12 Percentile:46.58(Physics, Applied)

Initial oxidation of Si(110) surface has been investigated by using real-time X-ray photoemission spectroscopy. The time evolution of the O 1s spectrum shows occurrence of rapid oxidation just after the introduction of the oxygen molecules, which is evidenced by the considerable peak intensity corresponding to oxygen exposure of as low as 1.5L (1L=1.33$$times$$10$$^{-4}$$ Pa s). This initial oxide is dominated by a state with a relatively low binding energy, which is gradually replaced by a state with a relatively high binding energy with the increase of the oxygen exposure, resulting in the low-KE shift of the O 1s peak. Comparison with previously reported O 1s spectra from dry-oxidized Si(111) surface suggests oxidation at or around the adatoms of Si(110)-16$$times$$2 clean surface as a likely oxidation state for this low-binding-energy peak.

Journal Articles

Structure of beam tracks induced by swift heavy ions in Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8}$$ superconductors

Sasase, Masato*; Okayasu, Satoru; Yamamoto, Hiroyuki; Kurata, Hiroki*; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 46(2), p.783 - 786, 2007/02

Columnar defects are produced in semiconducting and insulating materials by swift heavy ion irradiation. In the present study, we investigate the columnar defects produced in the Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8}$$ superconductor by the heavy ion irradiation (Au$$^{+}$$, I$$^{+}$$, Br$$^{+}$$, Ni$$^{+}$$) in the energy range of 60-600 MeV. On the basis of the transmission electron microscopy, it is shown that the diameters of columnar defects become smaller and their distributions become narrower with the ion velocity. These facts are explained as the effect of nuclear collision by calculating the mean free path for the irradiated ions. Present results imply the nuclear collisions strongly affect the columnar defect formations even for the swift heavy ion irradiation.

Journal Articles

Orientation of thin films synthesized from silicon phthalocyanine dichloride on a highly oriented pyrolytic graphite investigated using near edge X-ray absorption fine structure

Deng, J.; Sekiguchi, Tetsuhiro; Baba, Yuji; Hirao, Norie*; Honda, Mitsunori

Japanese Journal of Applied Physics, Part 1, 46(2), p.770 - 773, 2007/02

 Times Cited Count:1 Percentile:5.72(Physics, Applied)

Molecular orientation of thin films of silicon phthalocyanine (SiPc) compounds on highly oriented pyrolytic graphite (HOPG) was investigated by near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). The films were prepared by a casting method using solution of SiPc dichloride. XPS results showed that the chlorine atoms in SiPc dichloride were substituted by oxygen atoms when the film was heated in the air. The orientation of the molecules with respect to the substrate plane was investigated by the polarization dependences of the Si $$K$$ edge NEXAFS spectra. For the sample heated in the air, two clear peaks appeared in the NEXAFS spectra at around 1847.2 and 1852.4 eV, which were assigned to the resonant excitation form Si 1s to $$sigma$$* orbitals around the Si-N bonds and those around the Si-O bonds, respectively. The intensities of the resonance peaks showed strong polarization dependence. A quantitative analysis of the polarization dependences revealed that the Si-N bond was lying down while the Si-O bond was out of the plane.

Journal Articles

Generation and application of ultrahigh monochromatic X-ray using high-quality $$^{57}$$FeBO$$_{3}$$ single crystal

Mitsui, Takaya; Seto, Makoto; Kikuta, Seishi*; Hirao, Naohisa*; Oishi, Yasuo*; Takei, Fumihiko*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Higashitaniguchi, Satoshi*; Masuda, Ryo*

Japanese Journal of Applied Physics, Part 1, 46(2), p.821 - 825, 2007/02

 Times Cited Count:27 Percentile:71.15(Physics, Applied)

Ultrahigh monochromatic 14.4 keV X-rays with a narrow bandwidth of 15.4 neV were generated successfully with a high counting rate of 12,000 counts/s at the undulator beamline (BL11XU) of SPring-8. It was achieved by combining an intense X-ray from the third generation synchrotron radiation facility SPring-8 and pure nuclear Bragg scattering of a very highquality $$^{57}$$FeBO$$_{3}$$ perfect single crystal at the N$'e$el temperature. We describe the detailed study of the beam characteristics and some performance test experiments of energy-domain synchrotron radiation M$"o$ssbauer spectroscopy, including a highpressure experiment using a diamond anvil cel.

Journal Articles

Structure of beam tracks induced by swift heavy ions in Bi$$_2$$Sr$$_2$$CaCu$$_2$$O$$_8$$ superconductors

Sasase, Masato*; Okayasu, Satoru; Yamamoto, Hiroyuki; Kurata, Hiroki*; Hojo, Kiichi

Japanese Journal of Applied Physics, Part 1, 46(2), p.783 - 786, 2007/02

 Times Cited Count:1 Percentile:5.72(Physics, Applied)

Columnar defects are produced in semiconductor and insulator materials by swift heavy ion irradiation. It has been considered that the electronic stopping power of irradiating ions is the dominant factor in the formation of defects. However, our recent results suggest that ion-velocity is also an important parameter for use in describing this phenomenon. We investigate the columnar defects produced in Bi$$_2$$Sr$$_2$$CaCu$$_2$$O$$_8$$ (Bi-2212) superconductor by heavy ion irradiation (Au$$^{8+,12+}$$, I$$^{8+,29+}$$, Br$$^{12+}$$, and Ni$$^{11+}$$) in the energy range of 60-600MeV. From tansmission electron microscopy, it is shown that the diameters of columnar defects become smaller and their distribution become narrower with an increase in ion velocity. This is explained as an effect of nuclear collision by calculation of the mean free path for the irradiated ions. The present results imply that nuclear collisions strongly affect the formation of columnar defects, even for swift heavy ion irradiation.

Journal Articles

Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing

Sugita, Akihiro; Yokoyama, Keiichi; Yamada, Hidetaka; Inoue, Norihiro*; Aoyama, Makoto; Yamakawa, Koichi

Japanese Journal of Applied Physics, Part 1, 46(1), p.226 - 228, 2007/01

 Times Cited Count:5 Percentile:23.89(Physics, Applied)

Generation of broadband mid-infrared (MIR) laser pulses by difference frequency mixing (DFM) is reported. Two-color femtosecond pulses from a Ti: Sapphire laser system is mixed in an AgGaS$$_{2}$$ crystal utilizing a noncollinear phase matching scheme. The relative bandwidth of the generated MIR pulse has been measured to be 23 % to the central frequency, the broadest in DFM-based MIR sources reported so far. It is found that the type-I crystal can give broader phase matching range of spectrum than the type-II crystal within this scheme.

Journal Articles

Surface treatment of poly(tetrafluoroethylene) and perfluoroethylene-propylene by radiation grafting

Ito, Naoki*; Mase, Atsushi*; Seko, Noriaki; Tamada, Masao; Sakata, Eiji*; Kogi, Yuichiro*

Japanese Journal of Applied Physics, Part 1, 45(12), p.9244 - 9246, 2006/12

 Times Cited Count:4 Percentile:17.99(Physics, Applied)

Polytetrafluoroethylene (PTFE) and perfluoro ethylene-propylene (PFEP) have many desirable properties for application to electronic devices, such as low dielectric constant and loss tangent. However, the weak adhesion of the polymer to various metals, associated with the chemical inertness of the fluorine resin surface, fails to satisfy many of the industry requirements. Surface treatment of PTFE and PFEP by radiation-induced graft polymerization was carried out to improve the adhesion. Peel adhesion strengths of 10.3 N/cm and 14.5 N/cm were attained for PTFE/Cu and PFEP/Cu, respectively by the treatment. In addition, the dielectric function of grafted PTFE and grafted PFEP remained almost unchanged after the graft polymerization.

Journal Articles

Local crystal structures of Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ revealed by the atomic pair distribution function analysis

Shamoto, Shinichi; Kodama, Katsuaki; Iikubo, Satoshi; Taguchi, Tomitsugu; Yamada, Noboru*; Proffen, T.*

Japanese Journal of Applied Physics, Part 1, 45(11), p.8789 - 8794, 2006/11

 Times Cited Count:14 Percentile:49.12(Physics, Applied)

Two types of optical recording crystalline material Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ have been studied by neutron and X-ray powder diffraction measurements. One is the crystalline cubic-phase Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$. The other is nanocrystalline-phase Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$. For the nanocrystalline phase, the local crystal structure and the particle size distribution were obtained simultaneously by PDF analysis using a spherical-particle form factor. The lattice parameter is longer than that of the crystalline phase, suggesting an antimony-richer composition than the matrix. This compositional deviation would form the nanoparticle, resulting in nucleation-dominated crystal growth.

Journal Articles

Particle modeling of transport of $$alpha$$-ray generated ion clusters in air

Tong, L.*; Nambu, Kenichi*; Hirata, Yosuke*; Izumi, Mikio*; Miyamoto, Yasuaki; Yamaguchi, Hiromi

Japanese Journal of Applied Physics, Part 1, 45(10B), p.8217 - 8220, 2006/10

 Times Cited Count:0 Percentile:0(Physics, Applied)

A particle model is developed using the test-particle Monte Carlo method to study the transport properties of alpha-ray generated ion clusters in a flow of air. The simulated transport properties provide a theoretical basis for designing the alpha radioactivity measurement system. An accurate ion-molecule collision model is proposed to simulate the collisions between ion and air molecule. The recombination between positive and negative ions is simulated using Nanu and Denpoh method [J. Phys. Soc. Jpn. 67(1998) 1288]. The calculations are performed from low gas pressures of 0.001 and 0.01 atm to high gas pressures of 0.1 and 1 atm in a circular pipe. The simulation presents such a steady state ion transport that the generation of ions reaches a quasi-equilibrium with the loss of ions, absorbed by a measuring sensor and lost on the pipe wall.

Journal Articles

Ratio of transverse diffusion coefficient to mobility of electrons in high-pressure xenon and xenon doped with hydrogen

Kobayashi, Shingo*; Hasebe, Nobuyuki*; Hosojima, Takehiro*; Ishizaki, Takeshi*; Iwamatsu, Kazuhiro*; Mimura, Mitsuteru*; Miyachi, Takashi*; Miyajima, Mitsuhiro*; Pushkin, K.*; Tezuka, Chikara*; et al.

Japanese Journal of Applied Physics, Part 1, 45(10A), p.7894 - 7900, 2006/10

 Times Cited Count:11 Percentile:41.69(Physics, Applied)

We have obtained the ratio of transverse diffusion coeffcient to mobility of electrons multiplied by the elementary charge, in Xe and Xe+H$$_{2}$$ under electric fields at a higher pressure of 1 MPa in comparison with preceding experiments. The result shows that the density effect (non-linear effect) of the ratio in both of pure Xe and Xe+H$$_{2}$$ is $$<$$15% below 1 MPa over the reduced electric field range from 0.08 to 0.6$$times$$10$$^{-17}$$V$$cdot$$cm$$^{2}$$. We also found that the diffusion of an electron swarm is suppressed by adding trace of hydrogen to high-pressure xenon gas. Discussion is made of Xe+H$$_{2}$$ gas to a new $$gamma$$-ray camera. Trace of hydrogen to high-pressure xenon gas. Discussion is made of Xe+H$$_{2}$$ gas to a new $$gamma$$-ray camera.

Journal Articles

Pair-distribution function analysis of bismuth titanate

Yoneda, Yasuhiro; Kohara, Shinji*; Mizuki, Junichiro

Japanese Journal of Applied Physics, Part 1, 45(9B), p.7556 - 7559, 2006/09

 Times Cited Count:11 Percentile:41.69(Physics, Applied)

no abstracts in English

Journal Articles

Anomalous increase in effective channel mobility on $$gamma$$-irradiated p-channel SiC metal-oxide-semiconductor field-effect transistors containing step bunching

Lee, K. K.*; Oshima, Takeshi; Oi, Akihiko*; Ito, Hisayoshi; Pensl, G.*

Japanese Journal of Applied Physics, Part 1, 45(9A), p.6830 - 6836, 2006/09

 Times Cited Count:15 Percentile:51.29(Physics, Applied)

no abstracts in English

Journal Articles

Channel-dependent fission barriers of n+$$^{235}$$U analyzed using selective channel scission model

Ota, Masayuki; Nakamura, Shoji

Japanese Journal of Applied Physics, Part 1, 45(8A), p.6431 - 6435, 2006/08

 Times Cited Count:2 Percentile:9.26(Physics, Applied)

Channel-dependent fission barriers of n+$$^{235}$$U were obtained from the analysis on the data of fission product yields by the selective channel scission model. This analysis showed good agreement with the change of the fission product yields by the incident neutron energies. Also, the degrees of the deformation of the nuclei obtained from the SCS model analysis were compared with those at scission configurations associated with the mass-symmetric and mass-asymmetric fission modes.

Journal Articles

Two-dimensional sodium fluctuation at high temperatures in high-temperature thermoelectric material $$gamma$$-Na$$_{0.7}$$CoO$$_{2}$$

Shamoto, Shinichi; Hasegawa, Yuki*; Kajitani, Tsuyoshi*

Japanese Journal of Applied Physics, Part 1, 45(8A), p.6395 - 6397, 2006/08

 Times Cited Count:4 Percentile:17.99(Physics, Applied)

A thermoelectric material, $$gamma$$-Na$$_{0.7}$$CoO$$_{2}$$, with a high figure of merit, ZT$$>$$1, at high temperatures has been studied using the atomic pair distribution function (PDF) analysis of pulsed neutron powder diffraction data. We have found significant PDF peak broadening in the correlation between sodium and oxygen atoms at high temperatures. The broad peak indicates that a sodium atom frequently leaves a NaO$$_{6}$$ prism. In other words, sodium atoms hop in a two-dimensional layer at high temperatures. The PDF intensity of the Na-O correlation below a critical length, where a sodium atom is leaving a prism, is inversely proportional to thermal conductivity. This suggests that the short phonon lifetime originates from the frequent sodium hopping in the two-dimensional layer, leading to high-performance thermoelectric generation.

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