bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Orientation of Rubbed and Unrubbed Polyimide Films Determined by Polarized Infrared Absorption
Authors: Sakamoto Kenji , Arafune Ryuichi , Ito Naoki , Ushioda Sukekastu , Suzuki Yasushi , Morokawa Shigeru
Published: October 2002

We have determined the orientations of poly[ 4,4′-oxydiphenylene-pyromellitimide] (PMDA-ODA) molecules in rubbed and unrubbed polyimide films ( ∼120 Å) on Si substrates by polarized IR absorption spectroscopy. We found that for rubbed films the polymer chains are oriented along the rubbing direction and are tilted up on average by 8.5° from the surface plane. We conclude that the polymer chain inclination induced by rubbing determines the tilt of the director of the bulk liquid crystal.
Modification of n-Si(100) Surface by Scanning Tunneling Microscope Tip-Induced Anodization under Nitrogen Atmosphere
Authors: Sugimura Hiroyuki , Kitamura Noboru , Hiroshi Masuhara Hiroshi Masuhara
Published: October 2002

A hydrogen-terminated silicon (Si) surface was modified under nitrogen atmosphere by the use of a scanning tunneling microscope (STM). Nanoscale silicon oxide ( SiO

x

) patterns were fabricated by STM tip-induced oxidation of Si with adsorbed water. Oxide formation was promoted in the sample bias range of +2.0∼+ 10.0 V (tip-induced anodization) 6–28 times as efficiently as that in the bias range of -3.0∼-5.0 V (field-enhanced oxidation). The spatial resolution of SiO

x

patterns was improved by increasing the tip scan rate, and line patterns of ∼20 nm in width were obtained under the optimized conditions.
Low-Temperature Si Epitaxy by Photochemical Vapor Deposition with SiH2Cl2
Authors: Oshima Takayuki , Alonso Juan Carlos , Yamada Akira , Konagai Makoto , Kiyoshi Takahashi Kiyoshi Takahashi
Published: October 2002

Epitaxial Si films were successfully grown by the mercury-sensitized photochemical vapor deposition (photo-CVD) method with SiH2Cl2 at a substrate temperature of as low as 200° C. The electrical and optical properties of the obtained films were characterized by Hall measurement, IR and Raman spectroscopy and transmission electron microscopy. Furthermore, the n-type doping was carried out by the addition of PH3 gas, and the electron concentration was varied from 1016 cm-3 to 1018 cm-3 by varying the PH3/SiH4 gas ratio. It was found from the experiments that there was a strong correlation between the SiH2Cl2 and H2 flow rates for obtaining the epitaxial Si films at a low temperature.
Crystal Growth of Hen Egg White Lysozyme under High Pressure
Authors: Suzuki Yoshihisa , Miyashita Satoru , Komatsu Hiroshi , Sato Kiyotaka , Yagi Takehiko
Published: October 2002

The effect of hydrostatic pressure on the crystallization of hen egg white (HEW) lysozyme was studied using a diamond anvil cell (DAC). The nucleation rate of crystals and the normal growth rates of {101} and {110} faces were measured in situ under hydrostatic pressure. Both rates were decreased when the pressure was increased. The observed pressure effects could be accounted for by Le Chateliers' law.
Fabrication of Silicon Quantum Wires Using Separation by Implanted Oxygen Wafer
Authors: Gen Hashiguchi Gen Hashiguchi , Hidenori Mimura Hidenori Mimura
Published: October 2002

A new fabrication method of silicon quantum wires using separation by implanted oxygen (SIMOX) wafer has been proposed, which combines Si KOH anisotropic etching and local oxidation of silicon (LOCOS) techniques. In the fabrication, the cross-sectional dimensions of Si wires are determined solely by the thickness of the SOI layer. Using this novel method, we have fabricated a Si quantum wire with dimensions less than 100 nm and confirmed its great potential for making ultrafine structures without the need for high-resolution lithography or etching.
Dominant Deep Level in Annealed Low-Temperature GaAs Layers Grown by Molecular Beam Epitaxy
Authors: Lin Tsai-Cheng , Hiromasa T. Kaibe Hiromasa T. Kaibe , Tsugunori Okumura Tsugunori Okumura
Published: October 2002

Deep levels in the annealed low temperature molecular beam epitaxial (LT-MBE) GaAs layer were characterized by using the capacitance-deep-level transient spectroscopy (DLTS) technique in combination with a unique sample structure. We have fabricated the samples by inserting the LT-GaAs layer between two n-type semiconductive layers grown at normal substrate temperatures, like a sandwich. DLTS measurements revealed that one electron trap dominates the annealed LT-MBE GaAs layer. This dominant electron trap was very similar to the so-called EL3 level. By changing growth parameters of LT-GaAs layers, we found that the trap concentration of this EL3-like level was strongly related to Si doping and excess arsenic.
High Quality Nb/Al–AlOx–Al/Nb Josephson Junctions by Electron Beam Evaporation
Authors: Janawadkar M. P. , Baskaran R. , Gireesan K. , Saha Rita , L. S. Vaidyanathan L. S. Vaidyanathan , T. S. Radhakrishnan T. S. Radhakrishnan
Published: October 2002

High quality Nb/Al–AlO
x
–Al/Nb Josephson tunnel junctions have been fabricated using electron beam evaporation
as the deposition technique. At 4.2 K, value of V
m, the quality factor, exceeding 60 mV has been achieved;
this value of V
m is the highest reported for electron beam evaporated Nb–AlO
x
–Nb junctions and compares well
with the best Nb–AlO
x
–Nb junctions fabricated by the sputtering technique. We discuss the fabrication process
used and present a detailed characterization of a typical Josephson junction.
Two Different Types of Antiferromagnetic Couplings and Magnetoresistances in Fe/Si Multilayers
Authors: Inomata Koichiro , Keiichiro Yusu Keiichiro Yusu , Yoshiaki Saito Yoshiaki Saito
Published: October 2002

Two different types of antiferromagnetic (AF) interlayer couplings as a function of Si layer thickness, t
Si, have been observed in a series of (2.6 nm Fe/ t

S
i
nm Si)22 multilayers. One of the AF-couplings was observed at around t
Si=1.2 nm at room temperature (RT) and changed to ferromagnetic (F) coupling at a low temperature. The other AF coupling was observed for t
Si thicker than 1.5 nm with a minimum around t
Si=2.5 nm, and was almost temperature independent. Negative magnetoresistance has been observed in the multilayers with the AF coupling, and has similar temperature dependence as that of the AF coupling.
Electron Beam Excitation of Zn2Excimer
Authors: Xing Da , Ken-ichi Ueda Ken-ichi Ueda , Hiroshi Takuma Hiroshi Takuma
Published: October 2002

Bound-free emission of the Zn2excimer, which was predicted as a possible long-lived excimer system, has been observed in dense Zn vapor with helium or argon buffer gas by means of electron beam excitation. A continuum emission band at 431–408 nm was assigned to Zn213Σ+u→11Σ+gexcimer transition. In addition, a strong diffuse emission at 427.6 nm was observed in He/Zn mixtures, which overlapped to the Zn2continuum. We suggest that this emission band is attributed to the ZnHe excimer.
Atomic Waveguide Using Evanescent Waves near Optical Fibers
Authors: Jhe W. , Ohtsu M. , Hori H. , Friberg S. R.
Published: October 2002

We discuss an atomic waveguide that guides atoms in a similar way a quadrupole mass spectrometer guides charged particles. A two dimensional guiding potential barrier is produced by repulsive optical dipole forces caused by evanescent waves from optical fibers. A realization of this new atom optical element is proposed.
Evidence of Homogeneously Broadened Spectra in the Visible Photoluminescence of Porous Silicon
Authors: Koyama Hideki , Shima Noriko , Tsuyoshi Ozaki Tsuyoshi Ozaki , Nobuyoshi Koshida Nobuyoshi Koshida
Published: October 2002

The visible photoluminescence (PL) of porous silicon (PS) has been investigated in terms of the behavior of PL excitation and emission spectra. It is shown that for appropriately prepared samples, the excitation and emission spectra become entirely independent of the emission and excitation wavelengths, respectively, while both their bandwidths and the large Stokes shift between them remain unchanged. The result indicates that the broad PL bands of PS are due to homogeneous broadening, and that carrier localization accompanied by a strong electron-phonon coupling plays an important role in the visible luminescence of PS.
Quantum Interference of Electron Wave in Metal (CoSi2)/Insulator (CaF2) Resonant Tunneling Hot Electron Transistor Structure
Authors: Suemasu Takashi , Kohno Yoshifumi , Saitoh Wataru , Suzuki Nobuhiro , Masahiro Watanabe Masahiro Watanabe , Masahiro Asada Masahiro Asada
Published: October 2002

We report the observation of multiple negative differential resistance (NDR) in nanometer-thick metal (CoSi2)/insulatro (CaF2)
resonant tunneling hot electron transistor (RHET) grown on a silicon substrate. In this transistor,
electrons from a resonant tunneling emitter with a 2.2-nm-thick CoSi2 quantum well are transferred to the
conduction band of a 4.0-nm-thick CaF2 collector barrier region. Multiple NDR observed here may be attributed
to the modulation of the transmission probability of electron waves due to quantum interference in the conduction
band of the insulator (CaF2) collector barrier layer between two metal (CoSi2) layers, which is a different
mechanism from the resonance in quantum wells previously reported.
Fundamental Studies on Quantum Interconnections between Ballistic Electrons and Cellular Architecture
Authors: Naruse Yujiro , Katoh Riichi , Tanamoto Tetsufumi , Minoru Saba Minoru Saba , Shigeki Takahashi Shigeki Takahashi
Published: October 2002

A novel scheme of quantum interconnections (QI) is proposed with a view to creating next-generation integrated circuits (IC's). The new mode of QI, that is, QI between ballistic electrons and cellular architecture (QIBBC), effectively combines the formerly proposed QI with ballistic and coherent electrons (QIB) and QI with cellular architecture (QIC). The core concept of QIBBC is “controlling electrons with electrons”, which will lead to the realization of the ultimate device function and density limit in future IC's. Through fundamental analyses, it was found that the velocity control of ballistic electrons is an essential factor for QIBBC.
In2O3/CdS/CuInS2 Thin-Film Solar Cell with 9.7% Efficiency
Authors: Ogawa Yoshitaka , Jäger-Waldau Arnulf , Yoshio Hashimoto Yoshio Hashimoto , Kentaro Ito Kentaro Ito
Published: October 2002

An efficient thin-film photovoltaic cell has been fabricated using the heterostructure consisting of a CuInS2 film obtained by sulfurization of a metallic precursor, a chemical-bath-deposited CdS layer, and an atom-beam-sputtered In2O3 film. A preceding KCN treatment of the Cu-rich CuInS2 film lowered the Cu/In ratio and raised the resistivity. A cell conversion efficiency of 9.7% (active area efficiency>10%) at air mass 1.5 has been achieved without antireflection coatings.
High-Resolution X-Ray Scattering Topography Using Synchrotron Radiation Microbeam
Authors: Chikaura Yoshinori , Yoshifumi Suzuki Yoshifumi Suzuki , Hideki Kii Hideki Kii
Published: October 2002

Although spatial resolution is the most essential factor determining the function of X-ray topography, it has not been improved in 30 years in spite of increasing requirements for highly-resolvable topography in materials science. X-ray scattering topography using a microbeam is a method capable of overcoming this resolution problem. Because the maximum resolution of an apparatus using a sealed-off tube is limited to 20 µ m, we designed and constructed scattering topography equipment using a synchrotron radiation microbeam. In the experiment, the slit system forms the microbeam 7 µ m in diameter. We observed a cellulose distribution in bamboo as a testing material. When the scanning step was 2 µ m, we attained spatial resolution less than 5 µ m.
Formation of Drawing- or Radiation-Induced Defects in Germanium-Doped Silica Core Optical Fiber
Authors: Hayashi Yoshinori , Okuda Yuki , Hisamitsu Mitera Hisamitsu Mitera , Keizo Kato Keizo Kato
Published: October 2002

The influence of the drawing process in optical fibers on the radiation resistance property was investigated. The ESR spectra for the optical fibers drawn under various conditions were measured at room temperature (R.T.) or 77 K. The fibers were drawn at three different temperatures (high, medium and low) and the drawing velocity was kept constant. The drawing defects were abundantly detected at R.T. in the sample drawn at high temperature. Many non-bridging oxygen hole centers (NBOHC) induced during the drawing process were observed at 77 K. The formation of NBOHC was also discussed.
Vapor-Phase Atomic Layer Epitaxy of CuGaS2 at Atmospheric Pressure Using Metal Chlorides and H2S
Authors: Tsuboi Nozomu , Isu Takehiro , Kakuda Noritoshi , Tomoaki Terasako Tomoaki Terasako , Seishi Iida Seishi Iida
Published: October 2002

In the alternate feeding of metal chlorides (CuCl, GaCl3) and H2S sources, the growth rate saturation of CuGaS2 on GaP was observed for substrate temperatures between 530° C and 570° C, and also for some range of H2S flow rate. Together with the growth rate saturation behavior for metal chlorides reported in our previous paper, these results can be considered to indicate achievement of atomic layer epitaxy (ALE) of CuGaS2. The growth orientation change leading to c-axis growth was observed for a large H2S flow rate. Some possibility of stoichiometry control by ALE was suggested from photoluminescence spectra.
Nanocrystalline Soft-Magnetic Cores Produced by Consolidation of Fe86Zr7B6Cu1 Amorphous Powder
Authors: Kawamura Yoshihito , Inoue Akihisa , Akinori Kojima Akinori Kojima , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

Soft magnetic cores with a nanoscale bcc structure were fabricated by consolidation of amorphous Fe86Zr7B6Cu1 (at%) powder using a hot-pressing machine. The compact obtained by pressing for 200 s at 850 K and 1.5 GPa has a high density of 99.9% of the theoretical density (TD) and exhibits good soft-magnetic properties. The saturation magnetization, coercive force, maximum permeability and effective permeability at a frequency of 1 kHz and a magnetic field of 0.8 A/m are 1.56 T, 33 A/m, 4300 and 1300, respectively. It is therefore established that the present compact possesses good soft-magnetic properties in combination with high magnetization.
Scanning Tunneling Microscopy of (NH4)2Sx-Treated GaAs Surfaces Annealed in Vacuum
Authors: Tanimoto Masafumi , Yokoyama Haruki , Masanori Shinohara Masanori Shinohara , Naohisa Inoue Naohisa Inoue
Published: October 2002

The atomic structure of (NH4)2S

x

-treated and annealed GaAs surface is revealed using scanning tunneling microscopy (STM). STM image observation reveals that the GaAs surface is terminated with Ga–S bonds and that the monolayer sulfur forms dimers. Surface structural parameters such as S–S dimer bond length and Ga–S distance in the [100] direction are determined. STM measurements reveal that the surface is covered not only with an S monolayer but also with an S multilayer even with high-temperature annealing at 510°C.
Low-Pressure Metalorganic Chemical Vapor Deposition of a CuGaSe2/CuAlSe2 Heterostructure
Authors: Chichibu Shigefusa , Sudo Ryo , Yoshida Nobuhide , Harada Yoshiyuki , Uchida Mei , Higuchi Satoru Matsumoto
Published: October 2002

A single-heterostructure of CuGaSe2/CuAlSe2 chalcopyrite semiconductors was successfully grown epitaxially on a GaAs(001) substrate using a low-pressure metal organic chemical vapor deposition technique. The valence-band discontinuity for the CuGaSe2/CuAlSe2 heterointerface was estimated to be 0.8±0.1 eV by means of X-ray photoelectron spectroscopy. The CuGaSe2/CuAlSe2 structure was found to have the straddling-type heterointerface, and the band discontinuity was found to be distributed mainly in the valence band.
New High-Tc Superconductor Ag1-xCuxBa2Can-1CunO2n+3-δ Family with Tc> 117 K
Authors: Ihara Hideo , Tokiwa Kazuyasu , Ozawa Hirotomo , Hirabayashi Masayuki , Matuhata Hirofumi , Song Akira Negishi
Published: October 2002

A new high-temperature and nontoxic superconductor Ag1-
x

Cu

x

Ba2Ca

n
-1Cu

n

O2
n
+3-δ family with T
c>117 K was discovered. These materials are prepared by the high-pressure technique. A superconductor sample with the highest T
c contains mainly a Ag1-
x

Cu

x

Ba2Ca3Cu4O11-δ (x=0.75) phase. The phase has a body-centered tetragonal structure with lattice constants of a=7.7270 Å and c=36.222 Å. The disordering of Ag sites leads to the space group of P4/mmm and the lattice constants of a=3.8635 Å and c=18.111 Å. The T
c value of the Ag1-
x

Cu

x

Ba2Ca3Cu4O11-δ phase is 117.1 K. The relationship between the lattice constant c and the number of CuO2 layers n is c/2=5.3+3.2n ( Å). The small CuO2-block spacing (8.5 Å) of this family suggests a lower anisotropy and higher J
c than Hg- and Tl-based superconductor families.
In/(Ba, Rb)BiO3/SrTiO3(Nb) Three-Terminal Device
Authors: Fumihiko Toda Fumihiko Toda , Hitoshi Abe Hitoshi Abe
Published: October 2002

A superconductor-based three-terminal device of In/(Ba, Rb)BiO3/SrTiO3(Nb) structure was produced. The (Ba, Rb)BiO3/SrTiO3(Nb) interface is a Schottky junction with a barrier height of 1.8 eV, while the (Ba, Rb)BiO3/In interface is a junction with rectifying characteristics. The static properties of the three-terminal device as a transistor were determined in common-base and common-emitter configurations. With a base thickness of up to 50 nm, α=0.94 and β=10 were obtained, confirming that this device operated as a transistor.
Comparison of Photoconductive Response Times of InGaAs/InAlAs and InGaAs/InGaAsP Multi-Quantum Well Waveguide Modulators
Authors: Moss David J. , Masahiro Aoki Masahiro Aoki , Hirohisa Sano Hirohisa Sano
Published: October 2002

We compare the pulsed photoconductive response of InGaAs/InAlAs and InGaAs/InGaAsP multiple quantum well waveguide modulators as a function of bias voltage. The InGaAsP device exhibits a substantially faster pulsed photoresponse for fields between 20 and 200 kV/cm and attains its optimum performance (minimum pulse width, maximum internal efficiency) for very low applied fields (30 kV/cm), while the InAlAs device does so only for very large fields of >200 kV/cm. While the electron and hole sweep-out times are within a factor of 3 of each other in both samples, we argue that the reduction in response time for the InGaAsP device arises mainly from a reduction in electron sweep-out times.
Cathodoluminescence and Electron Beam Irradiation Effect of Porous Silicon Studied by Transmission Electron Microscopy
Authors: Mitsui Tadashi , Yamamoto Naoki , Takemoto Kuniko , Nittono Osamu
Published: October 2002

Cathodoluminescence (CL) from n-type porous silicon was studied using the CL detection system combined with a transmission electron microscope. Two luminescence bands were observed with peaks at 420 nm and 660 nm. The 660 nm band peak decays more quickly with increasing accelerating voltage and decreasing temperature. The intensity profile along the cross-sectional trace shows that the 660 nm luminescence centers are mainly located near the top side of the porous layer. The 420 nm CL band was found at accelerating voltage higher than 160 kV at 20 K.
Preparation of Praseodymium-Doped Single Crystal Barium Fluoride Thin Film on CaF2 by Chemical Vapor Deposition
Authors: Hirotsugu Sato Hirotsugu Sato
Published: October 2002

Praseodymium(Pr)-doped BaF2(111) thin film was epitaxially grown on a CaF2(111) substrate by chemical vapor deposition. Fluorinated metal β-diketone chelates; Ba(dfhd)2 and Pr(ppm)3 were used as the source materials. The Pr doping could be controlled by changing the Pr source temperature and the pressure in the Pr source container. Pr was incorporated into BaF2 films at concentrations of up to 10 mol% without any marked deterioration in the crystal quality. The fluorescence spectra showed that a distinct Pr3+ emission ( 3P0→3H4) occurred at 481 nm which was strongly dependent on the Pr content without emission quenching.
Computational Studies on Lifetime of Primary Electrons in a Bucket-Type Ion Source with Grid Current
Authors: Shunji Ido Shunji Ido , Hiroki Hasebe Hiroki Hasebe
Published: October 2002

We developed a calculation code to trace electron orbits with collisions between electrons and argon gas atoms in a bucket-type ion source with grid current. By supplying grid current, the lifetime of a primary electron was extended and the number of electrons that escape from the plasma grid was reduced. This paper discusses the relationship between grid current and lifetime of primary electrons.
Gas-Evaporated Small InSb Particles with the Wurtzite Structure
Authors: Yoshiro Sasaki Yoshiro Sasaki , Masashi Kawashima Masashi Kawashima
Published: October 2002

We report the first observation of InSb with the wurtzite structure by X-ray diffraction for a small particle prepared by evaporation of InSb in Ar gas. The ratio ofc/a=1.642 is slightly larger than that of the ideal hcp lattice. The density of the crystal with the wurtzite structure is almost equal to that of the zincblende-type crystal. The value ofc/ais consistent with that for compounds which exhibit the wurtzite and zincblende structures.
Dominant Factors for Formation of Perovskite PbTiO3 Films Using Excimer Laser Ablation
Authors: Tanaka Hidekazu , Tabata Hitoshi , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

Ferroelectric PbTiO3 films have been formed on SrTiO3(100) substrates using ArF excimer laser ablation as a function of substrate temperature with oxygen ( O2+8%O3) pressure. Perovskite PbTiO3 is formed around the substrate temperature of 450° C and oxygen pressure of 10∼40 mTorr. Pyrochlore Pb2Ti2O7-
x

{111}, on the other hand, is formed at higher temperature and lower oxygen pressure than the perovskite phase. The {100}-oriented pyrochlore is formed at lower temperature (around 400° C) and higher oxygen pressure. In addition, PbO films are obtained under similar formation conditions as those of the perovskite phase. This result suggests that PbO formation plays an important role in the construction of the PbTiO3 structure.
Shape Transition of GaAs Islands Grown on InAs (001) Surfaces
Authors: Shunsuke Ohkouchi Shunsuke Ohkouchi , Nobuyuki Ikoma Nobuyuki Ikoma
Published: October 2002

We have observed the shape transition of three-dimensional (3D) GaAs islands grown on InAs (001) surfaces with increasing the GaAs deposition. A scanning tunneling microscopy image of a 1.0 monolayer (ML) GaAs-deposited on InAs surface showed 3D island formation with an island size of about 10 nm×20∼30 nm, extending in the [11̄0] direction. When 2.0 ML GaAs was deposited onto the InAs surface, this island shape changed to a compact, pyramid-like one. At this stage, smaller islands were formed on the InAs substrate surface, which was reconstructed to be an In-stabilized (4×2) structure. These islands coalesced and grew larger on the InAs substrate surface with increasing the amount of GaAs deposition.
Micro-Raman Study of the YBa2Cu3O7 with Y2BaCuO5 Dispersions
Authors: Ha Dong Han , Jeong In Kwon , Shin Eun Joo , Dongho Kim Dongho Kim , Yong Ki Park Yong Ki Park
Published: October 2002

We have prepared the YBa2Cu3O7 superconductor with fine Y2BaCuO5 dispersions without temperature gradient by the infiltration-reaction process and analyzed the microscopic characteristics of each part by means of micro-Raman measurements. The specimen consists of large YBa2Cu3O7 domains containing many parallel platelets. Polarization dependence of the Raman spectra from YBa2Cu3O7 matrix and embedded Y2BaCuO5 particles shows that all parts of a domain have the same crystal orientation although it also contains many randomly oriented Y2BaCuO5 particles. The c-axis of YBa2Cu3O7 matrix is perpendicular to the microcracks and the a- and b-axes of each domain are also assigned completely.
Epitaxial Growth of CaF2/Si/CaF2 on Si(111)
Authors: Cho Chih-Chen , Liu Hung-Yu , Park Joe A. Keenan
Published: October 2002

High quality CaF2/Si/CaF2/Si(111) structures have been grown epitaxially by molecular beam epitaxy and characterized by X-ray diffraction analysis, Rutherford backscattering spectroscopy and transmission electron microscopy. High crystalline quality CaF2 layers are achieved when the thickness of the middle Si layer is small. The films degrade if the thickness of the Si layer exceeds 10 nm. The epitaxial orientations of the two CaF2 layers can be identical or azimuthally rotated 180 degrees with respect to each other, depending on how the middle Si film is deposited.
Nondestructive Imaging of Internal Structures of Frog (Xenopus laevis) Embryos by Shadow-Projection X-Ray Microtomography
Authors: Aoki Sadao , Yoneda Ikuo , Nagai Takeharu , Ueno Naoto , Murakami Kazuo
Published: October 2002

Nondestructive high-resolution imaging of frog ( Xenopus laevis) embryos has been developed by X-ray microtomography. Shadow-projection X-ray microtomography with a brilliant fine focus laboratory X-ray source could image fine structures of Xenopus embryos which were embedded in paraffin wax. The imaging system enabled us to not only distinguish endoderm from ectoderm at the gastrula stage, but also to obtain a cross-section view of the tail bud embryo showing muscle, notochord and neural tube without staining. Furthermore, the distribution of myosin was also imaged in combination with whole-mount immunohistochemistry.
Evaluation of Double-Layered Magnetic Recording Medium Composed of Perpendicular and Longitudinal Anisotropy Layers
Authors: Osaka Tetsuya , Homma Takayuki , Toshihiko Watanabe Toshihiko Watanabe , Yoshiaki Kurokawa Yoshiaki Kurokawa
Published: October 2002

A double-layered (DL) medium composed of a CoNiReP perpendicular anisotropy top layer (0.20 µ m thick) and CoP longitudinal anisotropy underlayer (0.05 µ m thick) was fabricated and its recording characteristics were investigated with a combination of a ring-type head. The reproduced voltage of the DL medium was enhanced to be larger than that of the simple summation of the reproduced voltage of the CoNiReP single-layered medium and that of the CoP one. Moreover, the reproduced waveform of the DL medium showed a single peak pulse and it did not change even at higher recording magnetomotive force (MMF). These results suggest that the reproduced voltage enhancement comes from the phase synchronization effect even at higher recording MMF.
Optical Bistable Operation in Fabry-Perot Resonator Constructed with Thin-Film Faraday Medium
Authors: Masao Hirano Masao Hirano
Published: October 2002

This letter deals with observations and a study on optical bistability in a thin Fabry-Perot resonator made of a Faraday medium. Using a commercial TbBi-garnet film as the Fabry-Perot resonator, it was established experimentally that the resonator represents an optical bistability, by treating both the thermally induced nonlinear effect and the Faraday effect, and that its characteristics are controlled by an external magnetic field through the Faraday effect.
Cathodoluminescence of Wirelike GaAs/AlAs Quantum Well Structures Grown on Substrates Patterned with [001] Mesa Stripes
Authors: Matsuyama Isamu , López Máximo , Nobuyuki Tanaka Nobuyuki Tanaka , Tomonori Ishikawa Tomonori Ishikawa
Published: October 2002

We describe cathodoluminescence (CL) spectroscopy and imaging studies of GaAs/AlAs quantum well (QW) structures and AlGaAs alloys grown by molecular beam epitaxy on GaAs (100) substrates patterned with mesa stripes along the [001] direction. GaAs wirelike structures were formed on these mesas due to the large diffusibility of Ga atoms from the {110} sidewalls to the (100) mesa-top plane. The spatial variation of the QW thickness and that of an AlGaAs alloy composition were investigated by carrying out CL measurements at low temperature. On the mesa-top region we found considerably large variations in the QW thickness and Al content, i.e., a 110% increase in the QW thickness and a 60% decrease in Al content, compared to the (100) bottom region. This is very useful for the fabrication of quantum-wire/box structures; thus, the use of the [001] mesa geometry is advantageous over other geometries.
Transmission-Type X-Ray Phase Retarder Using Ge Crystal in Laue Diffraction Geometry
Authors: Hirano Keiichi , Ishikawa Tetsuya , Nakamura Ikuo , Makoto Mizutani Makoto Mizutani , Seishi Kikuta Seishi Kikuta
Published: October 2002

A transmission-type X-ray phase retarder (XPR) using an absorptive crystal in Laue diffraction geometry is discussed. Polarization conversion property of the XPR was tested using synchrotron radiation. Energy dependence of the phase shift reveals that this XPR becomes a quarter-wave plate at a certain energy value and a half-wave plate at another energy value. The achievement of easier helicity switching taking advantage of the crystal symmetry is demonstrated.
Effects of Annealing in Rb:KTiOPO4 Waveguides
Authors: Shi L. P. , Rasch W. Karthe
Published: October 2002

Experimental results about annealing effects in potassium titanyl phosphate ( KTiOPO4, KTP) waveguides fabricated by Rb–K ion exchange process are presented. The refractive index profiles on Rb:KTP waveguides and the field distributions in Rb:KTP channel waveguides were changed by an annealing process. The losses of Rb:KTP channel waveguides were decreased using the post annealing process. The annealing process is shown to be an effective method of improving and modifying the properties of KTP waveguides.
Configuration of Hydrogen in Sp3-Rich Amorphous Hydrogenated Carbon Films Prepared by RF Magnetron Sputtering of Graphite
Authors: Minoru Toguchi Minoru Toguchi , Akira Higa Akira Higa , Takaharu Shima Takaharu Shima , Masaki Miyazato Masaki Miyazato
Published: October 2002

Sp3-rich amorphous hydrogenated carbon (a-C:H) films were fabricated by reactive rf magnetron sputtering in argon and hydrogen gas mixture. To clarify the bonding configuration of hydrogen (i.e., CH, CH2 and CH3) in the film, the deconvolutions of the 2900 cm-1 IR absorption spectrum for the films were examined. As a result, the relationship between the bonding hydrogen and the physical properties of the film suggests that not only the bonding hydrogen concentration but also the relative ratio between the three configurations of hydrogen must be taken into account.
Synthesis of a Novel Organic-Solvent-Soluble Polyimide and Its Application to Alignment Film for Liquid Crystal Displays
Authors: Nishikawa Michinori , Yokoyama Yasuaki , Bessho Nobuo , Seo Dae-Shik , Iimura Yasufumi , Kobayashi Shunsuke
Published: October 2002

We have synthesized a novel organic-solvent-soluble polyimide to be used as alignment films for liquid crystal displays. The polyimide has an aliphatic structure and can be cured at temperatures below 200° C. The novel polyimide also shows better alignment properties judging from its birefringence and dichroic ratio than conventional polyimides derived from the precursor polyamic acids. The alignment of a nematic liquid crystal on the novel polyimide shows a good texture without irregular liquid crystal domains.
Novel Analysis System of Imaging-Plate Plane-Wave X-Ray Topography for Characterizing Lattice Distortion in Silicon
Authors: Kudo Yoshihiro , Kojima Shigeru , Liu Kuang Yu , Ishikawa Seiji Kawado
Published: October 2002

This letter reports that a novel analysis system has been developed to determine lattice distortion in silicon single crystals from plane-wave X-ray topographs taken using synchrotron radiation. The system analyzes the topographs recorded on the imaging plate and gives the distortion as local variations in spacing and orientation of the lattice plane. Line analysis and mapping of the distortion in any position on the topograph can be easily performed in the system due to the overall digitization by the imaging plate.
Effects of the Aspect Ratio on Stress-Induced Open Failure in an Aluminum Line of LSI Interconnects
Authors: Kazunori Hiraoka Kazunori Hiraoka
Published: October 2002

The changes in the stress and strain in a fine aluminum line with time are calculated as a function of an aspect ratio at a fixed cross sectional area of 0.35-µm2. In the high aspect region, the strain saturates with the increase in the aspect ratio. The lifetime due to the stress-induced open failure can be estimated using the assumption that when the creep strain exceeds the threshold value, failure occurs. The lifetime for a sample with the small threshold value decreases with the increase in the aspect ratio, whereas for a sample with the large threshold value, the lifetime slightly decreases.
The Growth of High Quality GaAs on GaAs (111)A
Authors: Sato Kenji , Michael R. Fahy Michael R. Fahy , Bruce A. Joyce Bruce A. Joyce
Published: October 2002

Whilst it is well known that the growth of GaAs on singular GaAs(111)A substrates frequently gives films with poor morphology, there is little understanding of the mechanisms involved. We have made a systematic study of the growth condition dependence of the surface morphology of such films and these results are discussed in terms of the sticking coefficient of As4 on the growing GaAs(111)A surface and the origin of the defects is attributed to excess Ga. We have determined the conditions necessary for high quality growth.
Reliability Improvement of Thin Oxide by Double Deposition Process of Silicon Using Chemical Vapor Deposition
Authors: Cheon Jin Seong Park
Published: October 2002

The degradation of thin oxide by polysilicon-diffused POCl3 and the reliability improvement of thin oxide by the silicon deposition method were studied. Phosphorus in polysilicon-doped POCl3 degraded the thin oxide qualities. Oxide degradation is increased with the decrement of sheet resistance and polysilicon thickness. I
n
s
i
t
u double deposition (IDD) of amorphous silicon and polysilicon at 540° C/30 nm and 625° C/220 nm, respectively, created a mismatched structure of the grain boundary at the interface. This structure suppresses the segregation of excess phosphorus on the oxide surface, thus maintaining the oxide property.
Resistance Oscillations Induced by Direct Current Electromigration
Authors: Shingubara Shoso , Fujiki Kazuyuki , Sano Atsushi , Inoue Kenji , Sakaue Hiroyuki , Saitoh Makoto , Horiike Yasuhiro
Published: October 2002

We observed two types of resistance oscillatory changes, downward spikes and upward spikes, which occurred abruptly during direct current electromigration in a polycrystal Al interconnection. These spikes are further classified into quasi-periodic and random ones. Investigation of the current density dependence revealed that the frequency of the downward spikes drastically increased with increasing current density, while the amplitude of upward spikes increased drastically. We also determined that downward spikes were local, while upward spikes were nonlocal. Modeling based on the annihilation and formation of a void and the current detour effect around the high-resistance region well explained the current density dependence of the frequency of the oscillations. It seems most likely that downward spikes correspond to the alternation of annihilation and formation of the single void, while dislocation dynamics such as generation and annihilation are candidates for the origins of the upward spikes.
Low-Temperature Growth of InGaAs on GaAs(100) by Chemical Beam Epitaxy Using Unprecracked Monoethylarsine, Triethylgallium and Trimethylindium
Authors: Ro Jeong-Rae , Park Seong-Ju , Kim Sung-Bock , El-Hang Lee El-Hang Lee
Published: October 2002

InGaAs layers were grown on GaAs(100) by chemical beam epitaxy (CBE) using triethylgallium (TEGa), trimethylindium (TMIn) and unprecracked monoethylarsine (MEAs). The temperature-dependent growth rates, carrier concentrations, and photoluminescence (PL) responses were measured at the growth temperature range from 410 to 590° C. The carrier concentrations and PL responses have shown little variation over the growth temperature range. This result indicates that the electrical property and photoluminescence response of InGaAs are not degraded even in the low-growth-temperature regions unlike those of molecular beam epitaxy (MBE)- and organometallic vapor-phase epitaxy (OMVPE)-grown InGaAs using arsine.
Electron Beam Patterning Mechanism of GaAs Oxide Mask Layers Used in In Situ Electron Beam Lithography
Authors: Tanaka Nobuyuki , López Máximo , Matsuyama Isamu , Tomonori Ishikawa Tomonori Ishikawa
Published: October 2002

In order to clarify the electron-beam (EB) patterning mechanism of GaAs photo-oxide mask layers used in “ in situ EB lithography”, the effects of surface stoichiometry and heat treatment of the photo-oxide mask layers on the patterning characteristics were studied. The threshold dose for EB patterning was shown to depend on the amounts of both oxygen and arsenic in the photo-oxide mask layers. For photo-oxide mask layers containing larger amounts of As and O, the threshold dose for EB patterning increased. Moreover, for photo-oxide mask layers heated at temperatures above 400° C, where arsenic was mostly desorbed and stable Ga oxides were thought to be dominant, the mask durability was enhanced and, as a result, EB/Cl2 patterning became impossible. These results strongly indicate that As oxides play an essential role in EB/Cl2 patterning of “ in situ EB lithography”.
Monostable-Bistable Transition Logic Elements (MOBILEs) Based on Monolithic Integration of Resonant Tunneling Diodes and FETs
Authors: Chen Kevin J. , Akeyoshi Tomoyuki , Koichi Maezawa Koichi Maezawa
Published: October 2002

A MOBILE (monostable-bistable transition logic element) is a functional logic gate employing two negative differential resistance devices connected in-series. This logic gate offers the advantages of multiple inputs and multiple functions. In this paper, a novel approach to achieving MOBILE operation is demonstrated based on monolithic integration of resonant tunneling diodes (RTDs) and field-effect transistors (FETs). In our new integrated structure, an RTD and FETs (one or more) are connected in-parallel. This structure offers several advantages including separate optimization of the RTDs and FETs, and flexible circuit design abilities. For a single-input MOBILE gate, inverter operation is demonstrated as an evidence of monostable-to-bistable transition. For a two-input gate, both NAND and NOR operation is achieved with different control voltages, which implies the possibility of a variable-function logic gate.
Interpretation of Perpendicular Magnetic Anisotropy in Transition Metal/Noble Metal Superlattice Films in Terms of Pair Model
Authors: Masuda Morio , Kobayashi Tadashi , Shigeru Shiomi Shigeru Shiomi
Published: October 2002

In the present work, we have attempted to interpret the perpendicular magnetic anisotropy in the transition metal/noble metal superlattice films, which has been calculated for different growth directions and crystal structures, in terms of the pair model. The surface anisotropy has been found to result from the pseudodipolar interaction energy at the interface or in a few layers near the interface, while it is cancelled out in the interior of the transition metal film. The volume magnetic anisotropy, another main origin in addition to the demagnetizing energy, has been interpreted in terms of the pseudodipolar interaction, taking into account strains which are due to misfit in lattice constants between the transition metal and noble metal films.
Simulation of Emitter Size Effects in the Coupled-Quantum-Well Base Resonant Tunneling Transistor
Authors: Taniyama Hideaki , Masaaki Tomizawa Masaaki Tomizawa , Akira Yoshii Akira Yoshii
Published: October 2002

A resonant tunneling transistor, which has a base in the well region of a coupled-quantum-well structure, was studied using a quantum distributed model. By investigating the relationship between the disappearance of the negative differential resistance and emitter size, a large potential drop near the base electrode was found to be crucial in the disappearance of the negative differential resistance, which causes localization in the collector current. It was shown that the negative characteristics disappear, when the potential drop in the well region parallel to the interface is as large as the difference of first and second resonant energy of electron.
Picosecond Optical Bistability of ZnS-ZnTe/GaAs Multiple Quantum Wells on Reflection at Room Temperature
Authors: Shen Dezhen , Fan Xiwu , Baojun Yang Baojun Yang
Published: October 2002

The optical bistability with picosecond switching time in ZnS-ZnTe/GaAs multiple quantum wells (MQWs) on reflection at room temperature has been studied for the first time. The research results indicate that the switching threshold from high to low state and contrast ratio for the optical bistability are about 1.2 MW/cm2 and 3:1, respectively. The major nonlinear mechanism for the optical bistability is due to the change of refractive index caused by the band filling effect.
Material Characterization and Optimization for Ultrahigh-Speed Metal-Semiconductor-Metal Photodetectors
Authors: Sickmöller Markus , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Metal-semiconductor-metal photodetectors fabricated on different epitaxial layers of GaAs are investigated and optimized for applications to high-speed optical transmission systems. The devices exhibit full width at half-maximum (FWHM) times from 1.5 ps to 7 ps corresponding to carrier velocities exceeding 5×107 cm/s. In contrast to previously reported results, our results indicate that the use of low doped materials is recommended due to much better linearity and dynamic responsivity.
Sub-Micron Vertical AlGaAs/GaAs Resonant Tunneling Single Electron Transistor
Authors: Austing David Guy , Honda Takashi , Tokura Yasuhiro , Seigo Tarucha Seigo Tarucha
Published: October 2002

We explore vertical transport phenomena in sub-micron asymmetric AlGaAs/GaAs double barrier structures (DBS's) by applying a bias to a special Schottky side gate which allows the effective area of the conducting channel to be adjusted or “tuned”. The AlGaAs barriers are selectively doped to generate excess electrons in the GaAs well, and thus single electron transistor (SET) operation is possible because the number of electrons in the quantum dot can be varied one-by-one with the side gate. Gate modulation of the drain current flowing through the conducting channel is found to be strong, and this allows us to study Coulomb blockade, electron-electron interactions and lateral confinement effects. Observation of a broad (≈18 mV) current plateau at low bias when the quantum dot is occupied by a single electron, suggests that this technology is very promising for the realization of SET operation at temperatures well above 4.2 K.
Correlation Field Analysis of the Influence of Device Geometry and Bulk Disorder on Electron Interference in Quantum Wires
Authors: Ochiai Yuichi , Yamamoto Kazunuki , Onishi Taizoh , Kawabe Mitsuo , Ishibashi Koji , Bird Jonathan P. , Aoyagi Yoshinobu , Sugano Takuo , Ferry David K.
Published: October 2002

We analyze the magnetic field dependence of the correlation fieldBcof universal conductance fluctuations (UCF), observed in GaAs/AlGaAs quantum wires. At sufficiently high magnetic fields, the Landau level quantization is resolved, andBcis found to increase as a power law of magnetic field with an exponent which depends sensitively upon temperature. We show that this behavior results from a change in the nature of the (zero field) phase-coherent region for electron interference in the quantum wire; at high temperatures the phase-breaking length is less than the width, and the region is determined by the bulk impurities, while at lower temperatures, it is strongly influenced by the boundaries of the wire. We compare our results with recent theoretical predictions for the UCF at high magnetic fields, and show that the correlation analysis field provides a valuable tool for analyzing electron interference in quantum wires.
AFM Observation of Self-Assembled Monolayer Films on GaAs (110)
Authors: Hirotaka Ohno Hirotaka Ohno , Makoto Motomatsu Makoto Motomatsu , Wataru Mizutani Wataru Mizutani , Hiroshi Tokumoto Hiroshi Tokumoto
Published: October 2002

We have confirmed that a self-assembled monolayer (SAM) film of octadecanethiol (ODT), CH3(CH2)17SH, can be formed on a cleaved GaAs (110) surface, by using an atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Circular depressions were observed on the surface after film formation. The area of the circular depressions increased with immersion time, indicating that the solution oxidized the interface between ODT molecules and the GaAs surface, resulting in removal of ODT molecules. The oxidation was considerably faster in pure ethanol solution than that in ODT solution, demonstrating that the SAM film protects the GaAs surface from oxidation. High-resolution lateral force microscope (LFM) images revealed a periodic structure that had two types of lines: periodic lines 0.57 nm apart and lines rotated 55° with respect to them. A structural model of the SAM successfully explained both the features in high-resolution LFM images and the depression depth observed in AFM images.
Broadening of Exciton Luminescence Line in Modified CdTe/ZnTe Multi-Quantum Wells
Authors: Yoshimura Satoshi , Nakata Hiroyasu , Ohyama Tyuji , Otsuka Eizo , Li Jie , Yuan Shixin
Published: October 2002

Photoluminescence in modified CdTe/ZnTe superlattice multi-quantum wells (MQW's) was investigated. In order to reduce the number of misfit dislocations, the well region is formed from a short-period strained-layer superlattice composed of CdTe and ZnTe. The observed peak energies of the free exciton line are higher than those calculated. The full width at half-maximum of the observed line has a minimum around 45 K in the temperature range between 1.8 and 210 K.
The broadening above 45 K is attributed to exciton scattering with phonons and ionized impurities, while the broadening below 45 K is due to localized states.
Calculation of Diffusion Component of Leakage Current in pn Junctions Formed in Various Types of Silicon Wafers (Intrinsic Gettering, Epitaxial, Silicon on Insulator)
Authors: Murakami Yoshio , Abe Hidenobu , Takayuki Shingyouji Takayuki Shingyouji
Published: October 2002

We derived a general analytical formula for the diffusion component of leakage current in pn junctions formed in various types of silicon wafers such as intrinsic gettering (IG), epitaxial (EPI), and silicon on insulator (SOI) wafers. From this analysis, it can be understood quantitatively that defect regions in IG wafers increase the diffusion current, although heavily doped regions in epitaxial wafers decrease the diffusion current, and in SOI wafers the diffusion current can be considerably reduced when there is a low recombination velocity at the Si/SiO2 interface.
Fabrication of TE/TM Mode Splitter Using Completely Buried GaAs/GaAlAs Waveguide
Authors: Okamoto Kazuya , Doi Masaaki , Irita Takeshi , Nakano Yoshiaki , Tada Kunio
Published: October 2002

A GaAs/GaAlAs-system TE/TM mode splitter using the mode interference principle is described. Single- and double-mode waveguides are patterned by reactive ion etching after the first molecular beam epitaxy. They are then completely buried by liquid-phase epitaxy, which enables low loss propagation due to side-wall smoothness, because of the thermal deformation effect. For achieving low loss characteristics in this mode splitter, the surface treatment process before crystal growth and S-bend waveguide mask formation procedure are also optimized. Propagation loss of the single-mode waveguide is less than 1.0 dB/cm. In order to secure birefringence of the waveguide for mode splitting, upper and lower GaAlAs-cladding mol fractions are different. Finally, the fabricated device achieves the TE/TM mode splitting ratio of 8.2 dB for both polarizations.